Mena-Ulecia, Karel; Gonzalez-Norambuena, Fabian; Vergara-Jaque, Ariela; Poblete, Horacio; Tiznado, William; Caballero, Julio
2018-02-05
Protein kinases (PKs) discriminate between closely related sequences that contain serine, threonine, and/or tyrosine residues. Such specificity is defined by the amino acid sequence surrounding the phosphorylatable residue, so that it is possible to identify an optimal recognition motif (ORM) for each PK. The ORM for the protein kinase A (PKA), a well-known member of the PK family, is the sequence RRX(S/T)X, where arginines at the -3 and -2 positions play a key role with respect to the primed phosphorylation site. In this work, differential affinities of PKA for the peptide substrate Kemptide (LRRASLG) and mutants that substitute the arginine residues by the unnatural peptide homoarginine were evaluated through molecular dynamics (MD) and free energy perturbation (FEP) calculations. The FEP study for the homoarginine mutants required previous elaboration of a CHARMM "arginine to homoarginine" (R2B) hybrid topology file which is available in this manuscript as Supporting Information. Mutants substituting the arginine residues by alanine, lysine, and histidine were also considered in the comparison by using the same protocol. FEP calculations allowed estimating the free energy changes from the free PKA to PKA-substrate complex (ΔΔG E→ES ) when Kemptide structure was mutated. Both ΔΔG S→ES values for homoarginine mutants were predicted with a difference below 1 kcal/mol. In addition, FEP correctly predicted that all the studied mutations decrease the catalytic efficiency of Kemptide for PKA. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.
Virtual substitution scan via single-step free energy perturbation.
Chiang, Ying-Chih; Wang, Yi
2016-02-05
With the rapid expansion of our computing power, molecular dynamics (MD) simulations ranging from hundreds of nanoseconds to microseconds or even milliseconds have become increasingly common. The majority of these long trajectories are obtained from plain (vanilla) MD simulations, where no enhanced sampling or free energy calculation method is employed. To promote the 'recycling' of these trajectories, we developed the Virtual Substitution Scan (VSS) toolkit as a plugin of the open-source visualization and analysis software VMD. Based on the single-step free energy perturbation (sFEP) method, VSS enables the user to post-process a vanilla MD trajectory for a fast free energy scan of substituting aryl hydrogens by small functional groups. Dihedrals of the functional groups are sampled explicitly in VSS, which improves the performance of the calculation and is found particularly important for certain groups. As a proof-of-concept demonstration, we employ VSS to compute the solvation free energy change upon substituting the hydrogen of a benzene molecule by 12 small functional groups frequently considered in lead optimization. Additionally, VSS is used to compute the relative binding free energy of four selected ligands of the T4 lysozyme. Overall, the computational cost of VSS is only a fraction of the corresponding multi-step FEP (mFEP) calculation, while its results agree reasonably well with those of mFEP, indicating that VSS offers a promising tool for rapid free energy scan of small functional group substitutions. This article is protected by copyright. All rights reserved. © 2016 Wiley Periodicals, Inc.
International Nuclear Information System (INIS)
Sakane, Shinichi; Yezdimer, Eric M.; Liu, Wenbin; Barriocanal, Jose A.; Doren, Douglas J.; Wood, Robert H.
2000-01-01
The ab initio/classical free energy perturbation (ABC-FEP) method proposed previously by Wood et al. [J. Chem. Phys. 110, 1329 (1999)] uses classical simulations to calculate solvation free energies within an empirical potential model, then applies free energy perturbation theory to determine the effect of changing the empirical solute-solvent interactions to corresponding interactions calculated from ab initio methods. This approach allows accurate calculation of solvation free energies using an atomistic description of the solvent and solute, with interactions calculated from first principles. Results can be obtained at a feasible computational cost without making use of approximations such as a continuum solvent or an empirical cavity formation energy. As such, the method can be used far from ambient conditions, where the empirical parameters needed for approximate theories of solvation may not be available. The sources of error in the ABC-FEP method are the approximations in the ab initio method, the finite sample of configurations, and the classical solvent model. This article explores the accuracy of various approximations used in the ABC-FEP method by comparing to the experimentally well-known free energy of hydration of water at two state points (ambient conditions, and 973.15 K and 600 kg/m3). The TIP4P-FQ model [J. Chem. Phys. 101, 6141 (1994)] is found to be a reliable solvent model for use with this method, even at supercritical conditions. Results depend strongly on the ab initio method used: a gradient-corrected density functional theory is not adequate, but a localized MP2 method yields excellent agreement with experiment. Computational costs are reduced by using a cluster approximation, in which ab initio pair interaction energies are calculated between the solute and up to 60 solvent molecules, while multi-body interactions are calculated with only a small cluster (5 to 12 solvent molecules). Sampling errors for the ab initio contribution to
Estimating Atomic Contributions to Hydration and Binding Using Free Energy Perturbation.
Irwin, Benedict W J; Huggins, David J
2018-05-08
We present a general method called atom-wise free energy perturbation (AFEP), which extends a conventional molecular dynamics free energy perturbation (FEP) simulation to give the contribution to a free energy change from each atom. AFEP is derived from an expansion of the Zwanzig equation used in the exponential averaging method by defining that the system total energy can be partitioned into contributions from each atom. A partitioning method is assumed and used to group terms in the expansion to correspond to individual atoms. AFEP is applied to six example free energy changes to demonstrate the method. Firstly, the hydration free energies of methane, methanol, methylamine, methanethiol, and caffeine in water. AFEP highlights the atoms in the molecules that interact favorably or unfavorably with water. Finally AFEP is applied to the binding free energy of human immunodeficiency virus type 1 protease to lopinavir, and AFEP reveals the contribution of each atom to the binding free energy, indicating candidate areas of the molecule to improve to produce a more strongly binding inhibitor. FEP gives a single value for the free energy change and is already a very useful method. AFEP gives a free energy change for each "part" of the system being simulated, where part can mean individual atoms, chemical groups, amino acids, or larger partitions depending on what the user is trying to measure. This method should have various applications in molecular dynamics studies of physical, chemical, or biochemical phenomena, specifically in the field of computational drug discovery.
FEPs and scenarios auditing of TVO-92 and TILA-96 against international FEP database
Energy Technology Data Exchange (ETDEWEB)
Vieno, T.; Nordman, H. [VTT Energy, Espoo (Finland)
1997-12-01
The NEA International Database of Features, Events and Processes (FEPs) relevant to the assessment of post-closure safety of radioactive waste repositories has been compiled by a working group within the Nuclear Energy Agency (NEA) of the OECD. The main parts of the database are a master list of 150 generalized FEPs and the original project-specific databases containing descriptions, comments and references on the FEPs. The first version of the database includes in total 1261 FEPs from seven national or international performance assessment projects. All project FEPs are mapped to one or more of the FEPs in the master list. The aim of the auditing was to discuss how the FEBs in the international database have been treated in the TVO-92 and TILA-96 safety assessments on spent fuel disposal (in Finland), where no formal methods were applied to develop scenarios. The auditing was made against all the 1261 projectspecific FEPs in the international database. The FEPs were discussed one by one and classified into categories according to their treatment in TVO-92 and TILA-96 or in the technical design of the disposal system. 37 refs.
FEPs and scenarios auditing of TVO-92 and TILA-96 against international FEP database
International Nuclear Information System (INIS)
Vieno, T.; Nordman, H.
1997-12-01
The NEA International Database of Features, Events and Processes (FEPs) relevant to the assessment of post-closure safety of radioactive waste repositories has been compiled by a working group within the Nuclear Energy Agency (NEA) of the OECD. The main parts of the database are a master list of 150 generalized FEPs and the original project-specific databases containing descriptions, comments and references on the FEPs. The first version of the database includes in total 1261 FEPs from seven national or international performance assessment projects. All project FEPs are mapped to one or more of the FEPs in the master list. The aim of the auditing was to discuss how the FEBs in the international database have been treated in the TVO-92 and TILA-96 safety assessments on spent fuel disposal (in Finland), where no formal methods were applied to develop scenarios. The auditing was made against all the 1261 projectspecific FEPs in the international database. The FEPs were discussed one by one and classified into categories according to their treatment in TVO-92 and TILA-96 or in the technical design of the disposal system
Energy Technology Data Exchange (ETDEWEB)
A. Schenker
2000-12-08
The US DOE must provide a reasonable assurance that the performance objectives for the Yucca Mountain Project (YMP) potential radioactive-waste repository can be achieved for a 10,000-year post-closure period. The guidance that mandates this direction is under the provisions of 10 CFR Part 63 and the US Department of Energy's ''Revised Interim Guidance Pending Issuance of New US Nuclear Regulatory Commission (NRC) Regulations (Revision 01, July 22, 1999), for Yucca Mountain, Nevada'' (Dyer 1999 and herein referred to as DOE's Interim Guidance). This assurance must be demonstrated in the form of a performance assessment that: (1) identifies the features, events, and processes (FEPs) that might affect the performance of the potential geologic repository; (2) examines the effects of such FEPs on the performance of the potential geologic repository; (3) estimates the expected annual dose to a specified receptor group; and (4) provides the technical basis for inclusion or exclusion of specific FEPs.
International Nuclear Information System (INIS)
Schenker, A.
2000-01-01
The US DOE must provide a reasonable assurance that the performance objectives for the Yucca Mountain Project (YMP) potential radioactive-waste repository can be achieved for a 10,000-year post-closure period. The guidance that mandates this direction is under the provisions of 10 CFR Part 63 and the US Department of Energy's ''Revised Interim Guidance Pending Issuance of New US Nuclear Regulatory Commission (NRC) Regulations (Revision 01, July 22, 1999), for Yucca Mountain, Nevada'' (Dyer 1999 and herein referred to as DOE's Interim Guidance). This assurance must be demonstrated in the form of a performance assessment that: (1) identifies the features, events, and processes (FEPs) that might affect the performance of the potential geologic repository; (2) examines the effects of such FEPs on the performance of the potential geologic repository; (3) estimates the expected annual dose to a specified receptor group; and (4) provides the technical basis for inclusion or exclusion of specific FEPs
CLAD DEGRADATION - FEPS SCREENING ARGUMENTS
International Nuclear Information System (INIS)
R. Schreiner
2004-01-01
The purpose of this report is to evaluate and document the screening of the clad degradation features, events, and processes (FEPs) with respect to modeling used to support the Total System Performance Assessment-License Application (TSPA-LA). This report also addresses the effect of certain FEPs on both the cladding and the commercial spent nuclear fuel (CSNF), DOE-owned spent nuclear fuel (DSNF), and defense high-level waste (DHLW) waste forms, as appropriate to address the effects on multiple materials and both components (FEPs 2.1.09.09.0A, 2.1.09.11.0A, 2.1.11.05.0A, 2.1.12.02.0A, and 2.1.12.03.0A). These FEPs are expected to affect the repository performance during the postclosure regulatory period of 10,000 years after permanent closure. Table 1-1 provides the list of cladding FEPs, including their screening decisions (include or exclude). The primary purpose of this report is to identify and document the analysis, screening decision, and TSPA-LA disposition (for included FEPs) or screening argument (for excluded FEPs) for these FEPs related to clad degradation. In some cases, where a FEP covers multiple technical areas and is shared with other FEP reports, this report may provide only a partial technical basis for the screening of the FEP. The full technical basis for shared FEPs is addressed collectively by the sharing FEP reports. The screening decisions and associated TSPA-LA dispositions or screening arguments from all of the FEP reports are cataloged in a project-specific FEPs database
Yucca Mountain Feature, Event, and Process (FEP) Analysis
International Nuclear Information System (INIS)
Freeze, G.
2005-01-01
A Total System Performance Assessment (TSPA) model was developed for the U.S. Department of Energy (DOE) Yucca Mountain Project (YMP) to help demonstrate compliance with applicable postclosure regulatory standards and support the License Application (LA). Two important precursors to the development of the TSPA model were (1) the identification and screening of features, events, and processes (FEPs) that might affect the Yucca Mountain disposal system (i.e., FEP analysis), and (2) the formation of scenarios from screened in (included) FEPs to be evaluated in the TSPA model (i.e., scenario development). YMP FEP analysis and scenario development followed a five-step process: (1) Identify a comprehensive list of FEPs potentially relevant to the long-term performance of the disposal system. (2) Screen the FEPs using specified criteria to identify those FEPs that should be included in the TSPA analysis and those that can be excluded from the analysis. (3) Form scenarios from the screened in (included) FEPs. (4) Screen the scenarios using the same criteria applied to the FEPs to identify any scenarios that can be excluded from the TSPA, as appropriate. (5) Specify the implementation of the scenarios in the computational modeling for the TSPA, and document the treatment of included FEPs. This paper describes the FEP analysis approach (Steps 1 and 2) for YMP, with a brief discussion of scenario formation (Step 3). Details of YMP scenario development (Steps 3 and 4) and TSPA modeling (Step 5) are beyond scope of this paper. The identification and screening of the YMP FEPs was an iterative process based on site-specific information, design, and regulations. The process was iterative in the sense that there were multiple evaluation and feedback steps (e.g., separate preliminary, interim, and final analyses). The initial YMP FEP list was compiled from an existing international list of FEPs from other radioactive waste disposal programs and was augmented by YMP site- and design
FEP report for the safety assessment SR-Site
Energy Technology Data Exchange (ETDEWEB)
2010-12-15
This report documents the analysis and processing of features, events and processes, FEPs, that has been carried out within the safety assessment SR-Site, and forms an important part of the reporting of the project. The main part of the work was conducted within the earlier safety assessment SR-Can, which was a preparatory stage for the SR-Site assessment. The overall objective of the FEP analysis and processing in both SR-Can and SR-Site included development of a database of features, events and processes, an SKB FEP database, in a format that facilitates both a systematic analysis of FEPs and documentation of that FEP analysis, as well as facilitating revisions and updates to be made in connection with new safety assessments. The primary objective in SR-Site was to establish an SR-Site FEP catalogue within the framework of the SKB FEP database. This FEP catalogue was required to contain all FEPs that needed to be handled in SR-Site and is an update of the corresponding SR-Can FEP catalogue that was established for the SR-Can assessment. The starting point for the handling of FEPs in SR-Site was the SR-Can version of the SKB FEP database and associated SR-Can reports. The SR-Can version of the SKB FEP database includes the SR-Can FEP catalogue, as well as the sources for the identification of FEPs in SR-Can, namely the SR 97 processes and variables, Project FEPs in the NEA International FEP database version 1.2 and matrix interactions in the Interaction matrices developed for a deep repository of the KBS-3 type. Since the completion of the FEP work within SR-Can, an updated electronic version, version 2.1, of the NEA FEP database has become available. Compared with version 1.2 of the NEA FEP database, version 2.1 contains FEPs from two more projects. As part of SR-Site, all new Project FEPs in version 2.1 of the NEA FEP database have been mapped according to the methodology adopted in SR-Can resulting in an SR-Site version of the SKB FEP database. The SKB FEP
FEP report for the safety assessment SR-Site
International Nuclear Information System (INIS)
2010-12-01
This report documents the analysis and processing of features, events and processes, FEPs, that has been carried out within the safety assessment SR-Site, and forms an important part of the reporting of the project. The main part of the work was conducted within the earlier safety assessment SR-Can, which was a preparatory stage for the SR-Site assessment. The overall objective of the FEP analysis and processing in both SR-Can and SR-Site included development of a database of features, events and processes, an SKB FEP database, in a format that facilitates both a systematic analysis of FEPs and documentation of that FEP analysis, as well as facilitating revisions and updates to be made in connection with new safety assessments. The primary objective in SR-Site was to establish an SR-Site FEP catalogue within the framework of the SKB FEP database. This FEP catalogue was required to contain all FEPs that needed to be handled in SR-Site and is an update of the corresponding SR-Can FEP catalogue that was established for the SR-Can assessment. The starting point for the handling of FEPs in SR-Site was the SR-Can version of the SKB FEP database and associated SR-Can reports. The SR-Can version of the SKB FEP database includes the SR-Can FEP catalogue, as well as the sources for the identification of FEPs in SR-Can, namely the SR 97 processes and variables, Project FEPs in the NEA International FEP database version 1.2 and matrix interactions in the Interaction matrices developed for a deep repository of the KBS-3 type. Since the completion of the FEP work within SR-Can, an updated electronic version, version 2.1, of the NEA FEP database has become available. Compared with version 1.2 of the NEA FEP database, version 2.1 contains FEPs from two more projects. As part of SR-Site, all new Project FEPs in version 2.1 of the NEA FEP database have been mapped according to the methodology adopted in SR-Can resulting in an SR-Site version of the SKB FEP database. The SKB FEP
FEP report for the safety assessment SR-Can
International Nuclear Information System (INIS)
Skagius, Kristina
2006-11-01
This report documents the analysis and processing of features, events and processes, FEPs, that has been carried out within the safety assessment SR-Can, and forms an important part of the reporting of the project. The SR-Can project is a preparatory stage for the SR-Site assessment, and the report from that project will be used in support of SKB's application to build a final repository. The overall objective of the FEP analysis and processing included development of a database of features, events and processes, an SKB FEP database, in a format that facilitates both a systematic analysis of FEPs and documentation of that FEP analysis, as well as facilitating revisions and updates to be made in connection with new safety assessments. The overall objective also extended to the development of procedures for such a systematic FEP analysis as well as the application of those procedures in order to establish an SR-Can FEP catalogue within the framework of the SKB FEP database. The work started by implementing the content of the SR 97 Process Report into a database format suitable for import and processing of FEP information from other sources. The SR 97 version of the database was systematically audited against the NEA database with Project FEPs, version 1.2. In addition, an earlier audit of the SR 97 process report against the interaction matrices developed for a deep repository of the KBS-3 type was revisited and updated. Relevant FEPs identified through the audit process were sorted into three main categories i) FEPs related to the initial states of the repository system, ii) FEPs related to internal processes of the repository system, and iii) FEPs related to external impacts on the repository system. This resulted in additions to the SR 97 list of processes and to the lists of initial state FEPs and external factors to be addressed in further processing. The further processing of the initial state FEPs revealed that those FEPs that are not covered by the
FEP report for the safety assessment SR-Can
Energy Technology Data Exchange (ETDEWEB)
Skagius, Kristina [Kemakta Konsult AB, Stockholm (Sweden)
2006-11-15
This report documents the analysis and processing of features, events and processes, FEPs, that has been carried out within the safety assessment SR-Can, and forms an important part of the reporting of the project. The SR-Can project is a preparatory stage for the SR-Site assessment, and the report from that project will be used in support of SKB's application to build a final repository. The overall objective of the FEP analysis and processing included development of a database of features, events and processes, an SKB FEP database, in a format that facilitates both a systematic analysis of FEPs and documentation of that FEP analysis, as well as facilitating revisions and updates to be made in connection with new safety assessments. The overall objective also extended to the development of procedures for such a systematic FEP analysis as well as the application of those procedures in order to establish an SR-Can FEP catalogue within the framework of the SKB FEP database. The work started by implementing the content of the SR 97 Process Report into a database format suitable for import and processing of FEP information from other sources. The SR 97 version of the database was systematically audited against the NEA database with Project FEPs, version 1.2. In addition, an earlier audit of the SR 97 process report against the interaction matrices developed for a deep repository of the KBS-3 type was revisited and updated. Relevant FEPs identified through the audit process were sorted into three main categories i) FEPs related to the initial states of the repository system, ii) FEPs related to internal processes of the repository system, and iii) FEPs related to external impacts on the repository system. This resulted in additions to the SR 97 list of processes and to the lists of initial state FEPs and external factors to be addressed in further processing. The further processing of the initial state FEPs revealed that those FEPs that are not covered by the
Overview description of the base scenario derived from FEP analysis
International Nuclear Information System (INIS)
Locke, J.; Bailey, L.
1998-01-01
This report forms part of a suite of documents describing the Nirex model development programme. The programme is designed to provide a clear audit trail from the identification of significant features, events and processes (FEPs) to the models and modelling processes employed within a detailed performance assessment. A scenario approach to performance assessment has been adopted. It is proposed that potential evolutions of a deep geological radioactive waste repository can be represented by a base scenario and a number of variant scenarios. It is intended that assessment of the base scenario would form the core of any future performance assessment. The base scenario is chosen to be broad-ranging and to represent the natural evolution of the repository system and its surrounding environment. The base scenario is defined to include all those FEPs which are certain to occur and those which are judged likely to occur for a significant period of the assessment - timescale. Variant scenarios are defined by FEPs which represent a significant perturbation to the natural system evolution, for example the occurrence of a large seismic event. The structuring of FEPs on a Master Directed Diagram (MDD), provides a systematic framework for identifying those FEPs which form part of the natural evolution of the system and those which may define alternative potential evolutions of the repository system. In order to construct a description of the base scenario, FEPs have been grouped into a series of conceptual models. Conceptual models are groups of FEPs, identified from the MDD, representing a specific component or process within the disposal system. It has been found appropriate to define conceptual models in terms of the three main components of the disposal system: the repository engineered system, the surrounding geosphere and the biosphere. For each of these components, conceptual models provide a description of the relevant subsystem in terms of its initial characteristics
Determination of partial molar volumes from free energy perturbation theory†
Vilseck, Jonah Z.; Tirado-Rives, Julian
2016-01-01
Partial molar volume is an important thermodynamic property that gives insights into molecular size and intermolecular interactions in solution. Theoretical frameworks for determining the partial molar volume (V°) of a solvated molecule generally apply Scaled Particle Theory or Kirkwood–Buff theory. With the current abilities to perform long molecular dynamics and Monte Carlo simulations, more direct methods are gaining popularity, such as computing V° directly as the difference in computed volume from two simulations, one with a solute present and another without. Thermodynamically, V° can also be determined as the pressure derivative of the free energy of solvation in the limit of infinite dilution. Both approaches are considered herein with the use of free energy perturbation (FEP) calculations to compute the necessary free energies of solvation at elevated pressures. Absolute and relative partial molar volumes are computed for benzene and benzene derivatives using the OPLS-AA force field. The mean unsigned error for all molecules is 2.8 cm3 mol−1. The present methodology should find use in many contexts such as the development and testing of force fields for use in computer simulations of organic and biomolecular systems, as a complement to related experimental studies, and to develop a deeper understanding of solute–solvent interactions. PMID:25589343
Determination of partial molar volumes from free energy perturbation theory.
Vilseck, Jonah Z; Tirado-Rives, Julian; Jorgensen, William L
2015-04-07
Partial molar volume is an important thermodynamic property that gives insights into molecular size and intermolecular interactions in solution. Theoretical frameworks for determining the partial molar volume (V°) of a solvated molecule generally apply Scaled Particle Theory or Kirkwood-Buff theory. With the current abilities to perform long molecular dynamics and Monte Carlo simulations, more direct methods are gaining popularity, such as computing V° directly as the difference in computed volume from two simulations, one with a solute present and another without. Thermodynamically, V° can also be determined as the pressure derivative of the free energy of solvation in the limit of infinite dilution. Both approaches are considered herein with the use of free energy perturbation (FEP) calculations to compute the necessary free energies of solvation at elevated pressures. Absolute and relative partial molar volumes are computed for benzene and benzene derivatives using the OPLS-AA force field. The mean unsigned error for all molecules is 2.8 cm(3) mol(-1). The present methodology should find use in many contexts such as the development and testing of force fields for use in computer simulations of organic and biomolecular systems, as a complement to related experimental studies, and to develop a deeper understanding of solute-solvent interactions.
The Enhanced Plan for Features, Events, and Processes (FEPs) at Yucca Mountain
International Nuclear Information System (INIS)
G. Freeze
2002-01-01
A performance assessment is required to demonstrate compliance with the post-closure performance objectives for the Yucca Mountain Project (YMP), as stated in 10 CFR Part 63.1 13 (66 FR 55732, p. 55807). A performance assessment is defined in 10 CFR 63.2 (66 FR 55732, p. 55794) as an analysis that: (1) identifies the features, events, and processes (FEPs) that might affect the potential geologic repository; (2) examines the effects of those FEPs upon the performance of the potential geologic repository; and (3) estimates the expected dose incurred by a specified reasonably maximally exposed individual as a result of releases caused by significant FEPs. The performance assessment must also provide the technical basis for inclusion or exclusion of specific FEPs in the performance assessment as stated in 10 CFR 63.114 (66 FR 55732, p. 55807). An initial approach for FEP development, in support of the Total System Performance Assessment for the Site Recommendation (TSPA-SR) (CRWMS M and O 2000e), was documented in Freeze et al. (2001). The development of a comprehensive list of FEPs potentially relevant to the post-closure performance of the potential Yucca Mountain repository is an ongoing, iterative process based on site-specific information, design, and regulations. Although comprehensiveness of the FEPs list cannot be proven with absolute certainty, confidence can be gained through a combination of formal and systematic reviews (both top-down and bottom-up), audits, and comparisons with other FEP lists and through the application of more than one classification scheme. To support TSPA-SR, DOE used a multi-step approach for demonstrating comprehensiveness of the initial list of FEPs. Input was obtained from other international radioactive waste disposal programs as compiled by the Nuclear Energy Agency (NEA) of the Organization for Economic Co-operation and Development (OECD) to establish a general list of FEPs. The list was subsequently refined to include YMP
The Enhanced Plan for Features, Events, and Processes (FEPS) at Yucca Mountain
Energy Technology Data Exchange (ETDEWEB)
G. Freeze
2002-03-25
A performance assessment is required to demonstrate compliance with the post-closure performance objectives for the Yucca Mountain Project (YMP), as stated in 10 CFR Part 63.1 13 (66 FR 55732, p. 55807). A performance assessment is defined in 10 CFR 63.2 (66 FR 55732, p. 55794) as an analysis that: (1) identifies the features, events, and processes (FEPs) that might affect the potential geologic repository; (2) examines the effects of those FEPs upon the performance of the potential geologic repository; and (3) estimates the expected dose incurred by a specified reasonably maximally exposed individual as a result of releases caused by significant FEPs. The performance assessment must also provide the technical basis for inclusion or exclusion of specific FEPs in the performance assessment as stated in 10 CFR 63.114 (66 FR 55732, p. 55807). An initial approach for FEP development, in support of the Total System Performance Assessment for the Site Recommendation (TSPA-SR) (CRWMS M&O 2000e), was documented in Freeze et al. (2001). The development of a comprehensive list of FEPs potentially relevant to the post-closure performance of the potential Yucca Mountain repository is an ongoing, iterative process based on site-specific information, design, and regulations. Although comprehensiveness of the FEPs list cannot be proven with absolute certainty, confidence can be gained through a combination of formal and systematic reviews (both top-down and bottom-up), audits, and comparisons with other FEP lists and through the application of more than one classification scheme. To support TSPA-SR, DOE used a multi-step approach for demonstrating comprehensiveness of the initial list of FEPs. Input was obtained from other international radioactive waste disposal programs as compiled by the Nuclear Energy Agency (NEA) of the Organization for Economic Co-operation and Development (OECD) to establish a general list of FEPs. The list was subsequently refined to include YMP
Interim FEP report for the safety assessment SR-Can
Energy Technology Data Exchange (ETDEWEB)
Skagius, Kristina (ed.) [Kemakta Konsult AB, Stockholm (Sweden)
2004-08-01
This report describes the work with identification and structuring of features, events and processes (FEPs) that has been carried out within the scope of the SR-Can safety assessment up to the time of the interim reporting of the project. The overall objective of the work is to develop a database of features, events and processes in a format that would facilitate both a systematic analysis of FEPs and documentation of the FEP analysis as well as facilitate revisions and updates to be made in connection with new safety assessments. This overall objective also includes the development of procedures for a systematic FEP analysis as well as to apply these procedures in order to arrive at an SR-Can version of the FEP database. The work started by implementing the content of the SR 97 Process report into a database format suitable for import and processing of FEP information from other sources. The SR 97 version of the database was systematically audited against the NEA database with Project FEPs, version 1.2. In addition, an earlier audit of the SR 97 process report against the interaction matrices developed for a deep repository of the KBS-3 type was revisited and updated. Relevant FEPs from the audit were sorted into three main categories in the SR-Can database i) FEPs related to the initial states of the repository system, ii) FEPs related to internal processes of the repository system, and iii) FEPs related to external impacts on the repository system. These groups of FEPs were further processed for making decisions on how to handle these FEPs in the assessment. Biosphere processes were not included in the SR 97 Process report and there is thus not the same basis for updating these descriptions as for the engineered barriers and the geosphere. All biosphere FEPs from the audit have therefore been compiled in a single category in the database, but remain to be further handled. FEPs were also categorised as irrelevant or as being related to methodology on a general
Interim FEP report for the safety assessment SR-Can
International Nuclear Information System (INIS)
Skagius, Kristina
2004-08-01
This report describes the work with identification and structuring of features, events and processes (FEPs) that has been carried out within the scope of the SR-Can safety assessment up to the time of the interim reporting of the project. The overall objective of the work is to develop a database of features, events and processes in a format that would facilitate both a systematic analysis of FEPs and documentation of the FEP analysis as well as facilitate revisions and updates to be made in connection with new safety assessments. This overall objective also includes the development of procedures for a systematic FEP analysis as well as to apply these procedures in order to arrive at an SR-Can version of the FEP database. The work started by implementing the content of the SR 97 Process report into a database format suitable for import and processing of FEP information from other sources. The SR 97 version of the database was systematically audited against the NEA database with Project FEPs, version 1.2. In addition, an earlier audit of the SR 97 process report against the interaction matrices developed for a deep repository of the KBS-3 type was revisited and updated. Relevant FEPs from the audit were sorted into three main categories in the SR-Can database i) FEPs related to the initial states of the repository system, ii) FEPs related to internal processes of the repository system, and iii) FEPs related to external impacts on the repository system. These groups of FEPs were further processed for making decisions on how to handle these FEPs in the assessment. Biosphere processes were not included in the SR 97 Process report and there is thus not the same basis for updating these descriptions as for the engineered barriers and the geosphere. All biosphere FEPs from the audit have therefore been compiled in a single category in the database, but remain to be further handled. FEPs were also categorised as irrelevant or as being related to methodology on a general
Clad Degradation - FEPs Screening Arguments
International Nuclear Information System (INIS)
E. Siegmann
2004-01-01
The purpose of this report is to document the screening of the cladding degradation features, events, and processes (FEPs) for commercial spent nuclear fuel (CSNF). This report also addresses the effect of some FEPs on both the cladding and the CSNF, DSNF, and HLW waste forms where it was considered appropriate to address the effects on both materials together. This report summarizes the work of others to screen clad degradation FEPs in a manner consistent with, and used in, the Total System Performance Assessment-License Application (TSPA-LA). This document was prepared according to ''Technical Work Plan for Waste Form Degradation Modeling, Testing, and Analyses in Support of LA'' (BSC 2004a [DIRS 167796])
On dark energy isocurvature perturbation
International Nuclear Information System (INIS)
Liu, Jie; Zhang, Xinmin; Li, Mingzhe
2011-01-01
Determining the equation of state of dark energy with astronomical observations is crucially important to understand the nature of dark energy. In performing a likelihood analysis of the data, especially of the cosmic microwave background and large scale structure data the dark energy perturbations have to be taken into account both for theoretical consistency and for numerical accuracy. Usually, one assumes in the global fitting analysis that the dark energy perturbations are adiabatic. In this paper, we study the dark energy isocurvature perturbation analytically and discuss its implications for the cosmic microwave background radiation and large scale structure. Furthermore, with the current astronomical observational data and by employing Markov Chain Monte Carlo method, we perform a global analysis of cosmological parameters assuming general initial conditions for the dark energy perturbations. The results show that the dark energy isocurvature perturbations are very weakly constrained and that purely adiabatic initial conditions are consistent with the data
XPS and surface resistivity measurements of plasma - treated FEP co-polymer
International Nuclear Information System (INIS)
Pitrus, R.K.; Brack, N.; Liesegang, J.; Pigram, P.J.
2002-01-01
Full text: Fluorinated polymers such as fluorinated ethylene propylene (FEP) and poly(tetrafluoroethylene) (PTFE) play an important role in many applications due to their many desirable properties such as chemical resistivity, inertness, electrical stability and low dielectric constant; however, one disadvantage of fluorinated polymers is their extreme surface hydrophobicity. Previous studies show that plasma treatment will modify the surface by increasing the surface free energy and also offer a rapid and convenient method for pre-treating the polymers for many purposes. This paper, through resistivity and XPS (x-ray photoelectron spectroscopy) measurements, attempts to discover basic effects of such plasma treatment. Fluorinated ethylene propylene (FEP) co-polymer film of (0.05) mm thickness (obtained commercially) and with the following structure (CF 2 -CF 2 )-(CF(CF 3 )CF 2 )- was used. A suitable cleaning procedure was used to remove adventitious carbon from the surface. XPS has been used to study FEP film properties. The spectra of XPS were analyzed with the main focus on carbon and fluorine as they compose the elemental component of FEP film. A value of 2.05 was obtained for the F/C ratio, which is slightly higher than the theoretical F/C value estimated from the chemical structure of FEP (F/C 2). The clean film was then air plasma treated (pressure 10 -1 torr and power 30W) for various treatment times to produce a higher energy fluoropolymer surface. XPS studies investigated changes to the polymer surface and determined that oxidation occurs on the FEP surface. The oxidation reactions on the FEP surface form oxygen functional groups such as C-O and C=O groups. The results also show that the percentage of CF 2 and CF 3 in the co-polymer surface decreased with exposure time and the percentage of CF, C-C, C-O and C=O increased. There is a sharp decrease in F/C ratio and increase in O/C ratio. In addition to XPS, the resistivity of FEP-film was measured by a
Evaluation of Features, Events, and Processes (FEP) for the Biosphere Model
International Nuclear Information System (INIS)
J. J. Tappen
2003-01-01
The purpose of this revision of ''Evaluation of the Applicability of Biosphere-Related Features, Events, and Processes (FEPs)'' (BSC 2001) is to document the screening analysis of biosphere-related primary FEPs, as identified in ''The Development of Information Catalogued in REV00 of the YMP FEP Database'' (Freeze et al. 2001), in accordance with the requirements of the final U.S. Nuclear Regulatory Commission (NRC) regulations at 10 CFR Part 63. This database is referred to as the Yucca Mountain Project (YMP) FEP Database throughout this document. Those biosphere-related primary FEPs that are screened as applicable will be used to develop the conceptual model portion of the biosphere model, which will in turn be used to develop the mathematical model portion of the biosphere model. As part of this revision, any reference to the screening guidance or criteria provided either by Dyer (1999) or by the proposed NRC regulations at 64 FR 8640 has been removed. The title of this revision has been changed to more accurately reflect the purpose of the analyses. In addition, this revision will address Item Numbers 19, 20, 21, 25, and 26 from Attachment 2 of ''U.S. Nuclear Regulatory Commission/U.S. Department of Energy Technical Exchange and Management Meeting on Total System Performance Assessment and Integration (August 6 through 10, 2001)'' (Reamer 2001). This Scientific Analysis Report (SAR) does not support the current revision to the YMP FEP Database (Freeze et al. 2001). Subsequent to the release of the YMP FEP Database (Freeze et al. 2001), a series of reviews was conducted on both the FEP processes used to support Total System Performance Assessment for Site Recommendation and to develop the YMP FEP Database. In response to observations and comments from these reviews, particularly the NRC/DOE TSPA Technical Exchange in August 2001 (Reamer 2001), several Key Technical Issue (KTI) Agreements were developed. ''The Enhanced Plan for Features, Events and Processes
Evaluation of Features, Events, and Processes (FEP) for the Biosphere Model
Energy Technology Data Exchange (ETDEWEB)
J. J. Tappen
2003-02-16
The purpose of this revision of ''Evaluation of the Applicability of Biosphere-Related Features, Events, and Processes (FEPs)'' (BSC 2001) is to document the screening analysis of biosphere-related primary FEPs, as identified in ''The Development of Information Catalogued in REV00 of the YMP FEP Database'' (Freeze et al. 2001), in accordance with the requirements of the final U.S. Nuclear Regulatory Commission (NRC) regulations at 10 CFR Part 63. This database is referred to as the Yucca Mountain Project (YMP) FEP Database throughout this document. Those biosphere-related primary FEPs that are screened as applicable will be used to develop the conceptual model portion of the biosphere model, which will in turn be used to develop the mathematical model portion of the biosphere model. As part of this revision, any reference to the screening guidance or criteria provided either by Dyer (1999) or by the proposed NRC regulations at 64 FR 8640 has been removed. The title of this revision has been changed to more accurately reflect the purpose of the analyses. In addition, this revision will address Item Numbers 19, 20, 21, 25, and 26 from Attachment 2 of ''U.S. Nuclear Regulatory Commission/U.S. Department of Energy Technical Exchange and Management Meeting on Total System Performance Assessment and Integration (August 6 through 10, 2001)'' (Reamer 2001). This Scientific Analysis Report (SAR) does not support the current revision to the YMP FEP Database (Freeze et al. 2001). Subsequent to the release of the YMP FEP Database (Freeze et al. 2001), a series of reviews was conducted on both the FEP processes used to support Total System Performance Assessment for Site Recommendation and to develop the YMP FEP Database. In response to observations and comments from these reviews, particularly the NRC/DOE TSPA Technical Exchange in August 2001 (Reamer 2001), several Key Technical Issue (KTI) Agreements were developed
Electron beam induced conductivity in 'PET' and 'FEP'
International Nuclear Information System (INIS)
Walzade, S.J.; Jog, J.P.; Dake, S.B.; Bhoraskar, S.V.
1983-01-01
Electron Beam Induced Conductivity (EBIC), classified into EBIC (bulk) and EBIC (surface) have been measured in PET and FEP respectively. The peculiar oscillatory nature of the induced gain versus beam energy variations is explained in terms of the spatial distributions of the trapping centres near the surface of the polymers. (author)
Directory of Open Access Journals (Sweden)
François Guérin
Full Text Available Whereas fluoroquinolone resistance mainly results from target modifications in gram-positive bacteria, it is primarily due to active efflux in Listeria monocytogenes. The aim of this study was to dissect a novel molecular mechanism of fluoroquinolone resistance in this important human pathogen. Isogenic L. monocytogenes clinical isolates BM4715 and BM4716, respectively susceptible and resistant to fluoroquinolones, were studied. MICs of norfloxacin and ciprofloxacin were determined in the presence or in the absence of reserpine (10 mg/L. Strain BM4715 was susceptible to norfloxacin (MIC, 4 mg/L and ciprofloxacin (MIC, 0.5 mg/L whereas BM4716 was highly resistant to both drugs (MICs 128 and 32 mg/L, respectively. Reserpine was responsible for a 16-fold decrease in both norfloxacin and ciprofloxacin MICs against BM4716 suggesting efflux associated resistance. Whole-genome sequencing of the strains followed by comparative genomic analysis revealed a single point mutation in the gene for a transcriptional regulator, designated fepR (for fluoroquinolone efflux protein regulator belonging to the TetR family. The frame-shift mutation was responsible for the introduction of a premature stop codon resulting in an inactive truncated protein. Just downstream from fepR, the structural gene for an efflux pump of the MATE family (named FepA was identified. Gene expression was quantified by qRT-PCR and demonstrated that fepA expression was more than 64-fold higher in BM4716 than in BM4715. The clean deletion of the fepR gene from BM4715 was responsible for an overexpression of fepA with resistance to norfloxacin and ciprofloxacin, confirming the role of FepR as a local repressor of fepA. In conclusion, we demonstrated that overexpression of the new MATE efflux pump FepA is responsible for fluoroquinolone resistance in L. monocytogenes and secondary to inactivation of the FepR repressor.
ADHESION AND SPREADING OF HUMAN FIBROBLASTS ON SUPERHYDROPHOBIC FEP-TEFLON
BUSSCHER, HJ; STOKROOS, [No Value; GOLVERDINGEN, JG; SCHAKENRAAD, JM
1991-01-01
Adhesion and spreading of human fibroblasts was studied on hydrophobized and hydrophilized FEP-Teflon, and compared with adhesion and spreading on untreated FEP-Teflon and Tissue culture polystyrene (TCPS). Superhydrophobic FEP-Teflon was prepared by ion etching followed by oxygen glow-discharge.
Evaluation of Features, Events, and Processes (FEP) for the Biosphere Model
International Nuclear Information System (INIS)
Wasiolek, M. A.
2003-01-01
The purpose of this report is to document the evaluation of biosphere features, events, and processes (FEPs) that relate to the license application (LA) process as required by the U.S. Nuclear Regulatory Commission (NRC) regulations at 10 CFR 63.114 (d, e, and f) [DIRS 156605]. The evaluation determines whether specific biosphere-related FEPs should be included or excluded from consideration in the Total System Performance Assessment (TSPA). This analysis documents the technical basis for screening decisions as required at 10 CFR 63.114 (d, e, and f) [DIRS 156605]. For FEPs that are included in the TSPA, this analysis provides a TSPA disposition, which summarizes how the FEP has been included and addressed in the TSPA model, and cites the analysis reports and model reports that provide the technical basis and description of its disposition. For FEPs that are excluded from the TSPA, this analysis report provides a screening argument, which identifies the basis for the screening decision (i.e., low probability, low consequence, or by regulation) and discusses the technical basis that supports that decision. In cases, where a FEP covers multiple technical areas and is shared with other FEP analysis reports, this analysis may provide only a partial technical basis for the screening of the FEP. The full technical basis for these shared FEPs is addressed collectively by all FEP analysis reports that cover technical disciplines sharing a FEP. FEPs must be included in the TSPA unless they can be excluded by low probability, low consequence, or regulation. A FEP can be excluded from the TSPA by low probability per 10 CFR 63.114(d) [DIRS 156605], by showing that it has less than one chance in 10,000 of occurring over 10,000 years (or an approximately equivalent annualized probability of 10 -8 ). A FEP can be excluded from the TSPA by low consequence per 10 CFR 63.114 (e or f) [DIRS 156605], by showing that omitting the FEP would not significantly change the magnitude and
FEPs Screening of Processes and Issues in Drip Shield and Waste Package Degradation
Energy Technology Data Exchange (ETDEWEB)
K.G. Mon; L.A. Rottinghaus
2004-03-26
As directed by a written development plan (BSC 2002 [DIRS 161132]), the primary purpose of this scientific analysis is to identify and document the analyses and resolution of the features, events, and processes (FEPs) affecting the waste package and drip shield performance in the repository. Thirty-three FEPs were identified that are associated with the waste package and drip shield performance. This scientific analysis has been prepared to document the screening methodology used in the process of FEP inclusion and exclusion. The scope of this scientific analysis is to identify the treatment of the FEPs affecting postclosure waste package and drip shield performance. It should be noted that seismic effects are not treated within this report. A full discussion of seismic effects is contained in the ''Engineered Barrier System Features, Events, and Processes'' report (BSC 2004 [DIRS 167253]). The FEPs that are deemed potentially important to repository postclosure performance are evaluated, either as components of the total system performance assessment (TSPA) or as a separate discussion in a scientific analysis report. The scope for this activity involves two tasks, namely: Task 1: Identify which FEPs are to be considered explicitly in the TSPA (called included FEPs) and in which scientific analyses these FEPs are addressed. Task 2: Identify FEPs not to be included in the TSPA (called excluded FEPs) and provide justification for why these FEPs do not need to be a part of the TSPA model. The analyses documented in this scientific analysis are for the license application (LA) base case design (BSC 2004 [DIRS 167040]). In this design, a drip shield is placed over the waste package and no backfill is placed over the drip shield (BSC 2004 [DIRS 167040]). Each FEP may include one or more specific issues that are collectively described by a FEP name, a FEP description, and descriptor phrases. The FEP Description may encompass a single feature, process
FEPs Screening of Processes and Issues in Drip Shield and Waste Package Degradation
International Nuclear Information System (INIS)
K.G. Mon; L.A. Rottinghaus
2004-01-01
As directed by a written development plan (BSC 2002 [DIRS 161132]), the primary purpose of this scientific analysis is to identify and document the analyses and resolution of the features, events, and processes (FEPs) affecting the waste package and drip shield performance in the repository. Thirty-three FEPs were identified that are associated with the waste package and drip shield performance. This scientific analysis has been prepared to document the screening methodology used in the process of FEP inclusion and exclusion. The scope of this scientific analysis is to identify the treatment of the FEPs affecting postclosure waste package and drip shield performance. It should be noted that seismic effects are not treated within this report. A full discussion of seismic effects is contained in the ''Engineered Barrier System Features, Events, and Processes'' report (BSC 2004 [DIRS 167253]). The FEPs that are deemed potentially important to repository postclosure performance are evaluated, either as components of the total system performance assessment (TSPA) or as a separate discussion in a scientific analysis report. The scope for this activity involves two tasks, namely: Task 1: Identify which FEPs are to be considered explicitly in the TSPA (called included FEPs) and in which scientific analyses these FEPs are addressed. Task 2: Identify FEPs not to be included in the TSPA (called excluded FEPs) and provide justification for why these FEPs do not need to be a part of the TSPA model. The analyses documented in this scientific analysis are for the license application (LA) base case design (BSC 2004 [DIRS 167040]). In this design, a drip shield is placed over the waste package and no backfill is placed over the drip shield (BSC 2004 [DIRS 167040]). Each FEP may include one or more specific issues that are collectively described by a FEP name, a FEP description, and descriptor phrases. The FEP Description may encompass a single feature, process or event, or a few
Guimarães, Cristiano R W
2011-07-12
MM-GB/SA scoring and free energy perturbation (FEP) calculations have emerged as reliable methodologies to understand structural and energetic relationships to binding. In spite of successful applications to elucidate the structure-activity relationships for few pairs of ligands, the reality is that the performance of FEP calculations has rarely been tested for more than a handful of compounds. In this work, a series of 13 benzene sulfonamide inhibitors of carbonic anhydrase with binding free energies determined by isothermal titration calorimetry was selected as a test case. R(2) values of 0.70, 0.71, and 0.49 with the experiment were obtained with MM-GB/SA and FEP simulations run with MCPRO+ and Desmond, respectively. All methods work well, but the results obtained with Desmond are inferior to MM-GB/SA and MCPRO+. The main contrast between the methods is the level of sampling, ranging from full to restricted flexibility to single conformation for the complexes in Desmond, MCPRO+, and MM-GB/SA, respectively. The current and historical results obtained with MM-GB/SA qualify this approach as a more attractive alternative for rank-ordering; it can achieve equivalent or superior predictive accuracy and handle more structurally dissimilar ligands at a fraction of the computational cost of the rigorous free-energy methods. As for the large theoretical dynamic range for the binding energies, that seems to be a direct result of the degree of sampling in the simulations since MCPRO+ as well as MM-GB/SA are plagued by this. Van't Hoff analysis for selected pairs of ligands suggests that the wider scoring spread is not only affected by missing entropic contributions due to restricted sampling but also exaggerated enthalpic separation between the weak and potent compounds caused by diminished shielding of electrostatic interactions, thermal effects, and protein relaxation/strain.
Evaluation of Features, Events, and Processes (FEP) for the Biosphere Model
Energy Technology Data Exchange (ETDEWEB)
M. A. Wasiolek
2003-10-09
The purpose of this report is to document the evaluation of biosphere features, events, and processes (FEPs) that relate to the license application (LA) process as required by the U.S. Nuclear Regulatory Commission (NRC) regulations at 10 CFR 63.114 (d, e, and f) [DIRS 156605]. The evaluation determines whether specific biosphere-related FEPs should be included or excluded from consideration in the Total System Performance Assessment (TSPA). This analysis documents the technical basis for screening decisions as required at 10 CFR 63.114 (d, e, and f) [DIRS 156605]. For FEPs that are included in the TSPA, this analysis provides a TSPA disposition, which summarizes how the FEP has been included and addressed in the TSPA model, and cites the analysis reports and model reports that provide the technical basis and description of its disposition. For FEPs that are excluded from the TSPA, this analysis report provides a screening argument, which identifies the basis for the screening decision (i.e., low probability, low consequence, or by regulation) and discusses the technical basis that supports that decision. In cases, where a FEP covers multiple technical areas and is shared with other FEP analysis reports, this analysis may provide only a partial technical basis for the screening of the FEP. The full technical basis for these shared FEPs is addressed collectively by all FEP analysis reports that cover technical disciplines sharing a FEP. FEPs must be included in the TSPA unless they can be excluded by low probability, low consequence, or regulation. A FEP can be excluded from the TSPA by low probability per 10 CFR 63.114(d) [DIRS 156605], by showing that it has less than one chance in 10,000 of occurring over 10,000 years (or an approximately equivalent annualized probability of 10{sup -8}). A FEP can be excluded from the TSPA by low consequence per 10 CFR 63.114 (e or f) [DIRS 156605], by showing that omitting the FEP would not significantly change the magnitude and
Non-adiabatic perturbations in Ricci dark energy model
International Nuclear Information System (INIS)
Karwan, Khamphee; Thitapura, Thiti
2012-01-01
We show that the non-adiabatic perturbations between Ricci dark energy and matter can grow both on superhorizon and subhorizon scales, and these non-adiabatic perturbations on subhorizon scales can lead to instability in this dark energy model. The rapidly growing non-adiabatic modes on subhorizon scales always occur when the equation of state parameter of dark energy starts to drop towards -1 near the end of matter era, except that the parameter α of Ricci dark energy equals to 1/2. In the case where α = 1/2, the rapidly growing non-adiabatic modes disappear when the perturbations in dark energy and matter are adiabatic initially. However, an adiabaticity between dark energy and matter perturbations at early time implies a non-adiabaticity between matter and radiation, this can influence the ordinary Sachs-Wolfe (OSW) effect. Since the amount of Ricci dark energy is not small during matter domination, the integrated Sachs-Wolfe (ISW) effect is greatly modified by density perturbations of dark energy, leading to a wrong shape of CMB power spectrum. The instability in Ricci dark energy is difficult to be alleviated if the effects of coupling between baryon and photon on dark energy perturbations are included
FEPs Screening of Processes and Issues in Drip Shield and Waste Package Degradation
International Nuclear Information System (INIS)
K. Mon
2004-01-01
The purpose of this report is to evaluate and document the inclusion or exclusion of features, events and processes (FEPs) with respect to drip shield and waste package modeling used to support the Total System Performance Assessment for License Application (TSPA-LA). Thirty-three FEPs associated with the waste package and drip shield performance have been identified (DTN: MO0407SEPFEPLA.000 [DIRS 170760]). A screening decision, either ''included'' or ''excluded,'' has been assigned to each FEP, with the technical bases for screening decisions, as required by the Nuclear Regulatory Commission (NRC) in 10 CFR 63.114 (d, e, and f) [DIRS 156605]. The FEPs analyses in this report address issues related to the degradation and potential failure of the drip shield and waste package over the post closure regulatory period of 10,000 years after permanent closure. For included FEPs, this report summarizes the disposition of the FEP in TSPA-LA. For excluded FEPs, this report provides the technical bases for the screening arguments for exclusion from TSPA-LA. The analyses are for the TSPA-LA base-case design (BSC 2004 [DIRS 168489]), where a drip shield is placed over the waste package without backfill over the drip shield (BSC 2004 [DIRS 168489]). Each FEP includes one or more specific issues, collectively described by a FEP name and description. The FEP description encompasses a single feature, event, or process, or a few closely related or coupled processes, provided the entire FEP can be addressed by a single specific screening argument or TSPA-LA disposition. The FEPs were assigned to associated Project reports, so the screening decisions reside with the relevant subject-matter experts
FEPs Screening of Processes and Issues in Drip Shield and Waste Package Degradation
Energy Technology Data Exchange (ETDEWEB)
K. Mon
2004-10-11
The purpose of this report is to evaluate and document the inclusion or exclusion of features, events and processes (FEPs) with respect to drip shield and waste package modeling used to support the Total System Performance Assessment for License Application (TSPA-LA). Thirty-three FEPs associated with the waste package and drip shield performance have been identified (DTN: MO0407SEPFEPLA.000 [DIRS 170760]). A screening decision, either ''included'' or ''excluded,'' has been assigned to each FEP, with the technical bases for screening decisions, as required by the Nuclear Regulatory Commission (NRC) in 10 CFR 63.114 (d, e, and f) [DIRS 156605]. The FEPs analyses in this report address issues related to the degradation and potential failure of the drip shield and waste package over the post closure regulatory period of 10,000 years after permanent closure. For included FEPs, this report summarizes the disposition of the FEP in TSPA-LA. For excluded FEPs, this report provides the technical bases for the screening arguments for exclusion from TSPA-LA. The analyses are for the TSPA-LA base-case design (BSC 2004 [DIRS 168489]), where a drip shield is placed over the waste package without backfill over the drip shield (BSC 2004 [DIRS 168489]). Each FEP includes one or more specific issues, collectively described by a FEP name and description. The FEP description encompasses a single feature, event, or process, or a few closely related or coupled processes, provided the entire FEP can be addressed by a single specific screening argument or TSPA-LA disposition. The FEPs were assigned to associated Project reports, so the screening decisions reside with the relevant subject-matter experts.
Nonlinear spherical perturbations in quintessence models of dark energy
Pratap Rajvanshi, Manvendra; Bagla, J. S.
2018-06-01
Observations have confirmed the accelerated expansion of the universe. The accelerated expansion can be modelled by invoking a cosmological constant or a dynamical model of dark energy. A key difference between these models is that the equation of state parameter w for dark energy differs from ‑1 in dynamical dark energy (DDE) models. Further, the equation of state parameter is not constant for a general DDE model. Such differences can be probed using the variation of scale factor with time by measuring distances. Another significant difference between the cosmological constant and DDE models is that the latter must cluster. Linear perturbation analysis indicates that perturbations in quintessence models of dark energy do not grow to have a significant amplitude at small length scales. In this paper we study the response of quintessence dark energy to non-linear perturbations in dark matter. We use a fully relativistic model for spherically symmetric perturbations. In this study we focus on thawing models. We find that in response to non-linear perturbations in dark matter, dark energy perturbations grow at a faster rate than expected in linear perturbation theory. We find that dark energy perturbation remains localised and does not diffuse out to larger scales. The dominant drivers of the evolution of dark energy perturbations are the local Hubble flow and a supression of gradients of the scalar field. We also find that the equation of state parameter w changes in response to perturbations in dark matter such that it also becomes a function of position. The variation of w in space is correlated with density contrast for matter. Variation of w and perturbations in dark energy are more pronounced in response to large scale perturbations in matter while the dependence on the amplitude of matter perturbations is much weaker.
Evaluation of Features, Events, and Processes (FEP) for the Biosphere Model
Energy Technology Data Exchange (ETDEWEB)
M. Wasiolek; P. Rogers
2004-10-27
The purpose of this analysis report is to evaluate and document the inclusion or exclusion of biosphere features, events, and processes (FEPs) with respect to modeling used to support the total system performance assessment (TSPA) for the license application (LA). A screening decision, either ''Included'' or ''Excluded'', is given for each FEP along with the corresponding technical basis for the excluded FEPs and the descriptions of how the included FEPs were incorporated in the biosphere model. This information is required by the U.S. Nuclear Regulatory Commission (NRC) regulations at 10 CFR 63.114 (d, e, and f) [DIRS 156605]. The FEPs addressed in this report concern characteristics of the reference biosphere, the receptor, and the environmental transport and receptor exposure pathways for the groundwater and volcanic ash exposure scenarios considered in biosphere modeling. This revision provides the summary of the implementation of included FEPs in TSPA-LA, (i.e., how the FEP is included); for excluded FEPs, this analysis provides the technical basis for exclusion from TSPA-LA (i.e., why the FEP is excluded). This report is one of the 10 documents constituting the biosphere model documentation suite. A graphical representation of the documentation hierarchy for the biosphere model is presented in Figure 1-1. This figure shows the interrelationships among the products (i.e., analysis and model reports) developed for biosphere modeling. The ''Biosphere Model Report'' describes in detail the biosphere conceptual model and mathematical model. The input parameter reports shown to the right of the ''Biosphere Model Report'' contain detailed descriptions of the model input parameters and their development. Outputs from these six reports are used in the ''Nominal Performance Biosphere Dose Conversion Factor Analysis and Disruptive Event Biosphere Dose Conversion Factor Analysis
Modelling requirements for future assessments based on FEP analysis
International Nuclear Information System (INIS)
Locke, J.; Bailey, L.
1998-01-01
This report forms part of a suite of documents describing the Nirex model development programme. The programme is designed to provide a clear audit trail from the identification of significant features, events and processes (FEPs) to the models and modelling processes employed within a detailed safety assessment. A scenario approach to performance assessment has been adopted. It is proposed that potential evolutions of a deep geological radioactive waste repository can be represented by a base scenario and a number of variant scenarios. The base scenario is chosen to be broad-ranging and to represent the natural evolution of the repository system and its surrounding environment. The base scenario is defined to include all those FEPs that are certain to occur and those which are judged likely to occur for a significant period of the assessment timescale. The structuring of FEPs on a Master Directed Diagram (MDD) provides a systematic framework for identifying those FEPs that form part of the natural evolution of the system and those, which may define alternative potential evolutions of the repository system. In order to construct a description of the base scenario, FEPs have been grouped into a series of conceptual models. Conceptual models are groups of FEPs, identified from the MDD, representing a specific component or process within the disposal system. It has been found appropriate to define conceptual models in terms of the three main components of the disposal system: the repository engineered system, the surrounding geosphere and the biosphere. For each of these components, conceptual models provide a description of the relevant subsystem in terms of its initial characteristics, subsequent evolution and the processes affecting radionuclide transport for the groundwater and gas pathways. The aim of this document is to present the methodology that has been developed for deriving modelling requirements and to illustrate the application of the methodology by
Overview of the FEP analysis approach to model development
International Nuclear Information System (INIS)
Bailey, L.
1998-01-01
This report heads a suite of documents describing the Nirex model development programme. The programme is designed to provide a clear audit trail from the identification of significant features, events and processes (FEPs) to the models and modelling processes employed within a detailed safety assessment. A five stage approach has been adopted, which provides a systematic framework for addressing uncertainty and for the documentation of all modelling decisions and assumptions. The five stages are as follows: Stage 1: EP Analysis - compilation and structuring of a FEP database; Stage 2: Scenario and Conceptual Model Development; Stage 3: Mathematical Model Development; Stage 4: Software Development; Stage 5: confidence Building. This report describes the development and structuring of a FEP database as a Master Directed Diagram (MDD) and explains how this may be used to identify different modelling scenarios, based upon the identification of scenario -defining FEPs. The methodology describes how the possible evolution of a repository system can be addressed in terms of a base scenario, a broad and reasonable representation of the 'natural' evolution of the system, and a number of variant scenarios, representing the effects of probabilistic events and processes. The MDD has been used to identify conceptual models to represent the base scenario and the interactions between these conceptual models have been systematically reviewed using a matrix diagram technique. This has led to the identification of modelling requirements for the base scenario, against which existing assessment software capabilities have been reviewed. A mechanism for combining probabilistic scenario-defining FEPs to construct multi-FEP variant scenarios has been proposed and trialled using the concept of a 'timeline', a defined sequence of events, from which consequences can be assessed. An iterative approach, based on conservative modelling principles, has been proposed for the evaluation of
Effect of Dark Energy Perturbation on Cosmic Voids Formation
Endo, Takao; Nishizawa, Atsushi J.; Ichiki, Kiyotomo
2018-05-01
In this paper, we present the effects of dark energy perturbation on the formation and abundance of cosmic voids. We consider dark energy to be a fluid with a negative pressure characterised by a constant equation of state w and speed of sound c_s^2. By solving fluid equations for two components, namely, dark matter and dark energy fluids, we quantify the effects of dark energy perturbation on the sizes of top-hat voids. We also explore the effects on the size distribution of voids based on the excursion set theory. We confirm that dark energy perturbation negligibly affects the size evolution of voids; c_s^2=0 varies the size only by 0.1% as compared to the homogeneous dark energy model. We also confirm that dark energy perturbation suppresses the void size when w -1 (Basse et al. 2011). In contrast to the negligible impact on the size, we find that the size distribution function on scales larger than 10 Mpc/h highly depends on dark energy perturbation; compared to the homogeneous dark energy model, the number of large voids of radius 30Mpc is 25% larger for the model with w = -0.9 and c_s^2=0 while they are 20% less abundant for the model with w = -1.3 and c_s^2=0.
THE DEVELOPMENT OF THE YUCCA MOUNTAIN PROJECT FEATURE, EVENT, AND PROCESS (FEP) DATABASE
International Nuclear Information System (INIS)
Freeze, G.; Swift, P.; Brodsky, N.
2000-01-01
A Total System Performance Assessment for Site Recommendation (TSPA-SR) has recently been completed (CRWMS M andO, 2000b) for the potential high-level waste repository at the Yucca Mountain site. The TSPA-SR is an integrated model of scenarios and processes relevant to the postclosure performance of the potential repository. The TSPA-SR scenarios and model components in turn include representations of all features, events, and processes (FEPs) identified as being relevant (i.e., screened in) for analysis. The process of identifying, classifying, and screening potentially relevant FEPs thus provides a critical foundation for scenario development and TSPA analyses for the Yucca Mountain site (Swift et al., 1999). The objectives of this paper are to describe (a) the identification and classification of the comprehensive list of FEPs potentially relevant to the postclosure performance of the potential Yucca Mountain repository, and (b) the development, structure, and use of an electronic database for storing and retrieving screening information about the inclusion and/or exclusion of these Yucca Mountain FEPs in TSPA-SR. The FEPs approach to scenario development is not unique to the Yucca Mountain Project (YMP). General systematic approaches are summarized in NEA (1992). The application of the FEPs approach in several other international radioactive waste disposal programs is summarized in NEA ( 1999)
deGroh, Kim; Gaier, James R.; Hall, Rachelle L.; Norris, Mary Jo; Espe, Matthew P.; Cato, Daveen R.
1999-01-01
Metallized Teflon(Registered Trademark) FEP (fluorinated ethylene propylene) thermal control material on the Hubble Space Telescope (HST) is degrading in the space environment. Teflon(Registered Trademark) FEP thermal control blankets (space-facing FEP) retrieved during the first servicing mission (SM1) were found to be embrittled on solar facing surfaces and contained microscopic cracks. During the second servicing mission (SM2) astronauts noticed that the FEP outer layer of the multi-layer insulation (MLI) covering the telescope was cracked in many locations around the telescope. Large cracks were observed on the light shield, forward shell and equipment bays. A tightly curled piece of cracked FEP from the light shield was retrieved during SM2 and was severely embrittled, as witnessed by ground testing. A Failure Review Board (FRB) was organized to determine the mechanism causing the MLI degradation. Density, x-ray crystallinity and solid state nuclear magnetic resonance (NMR) analyses of FEP retrieved during SM1 were inconsistent with results of FEP retrieved during SM2. Because the retrieved SM2 material curled while in space, it experienced a higher temperature extreme during thermal cycling, estimated at 200 C, than the SM1 material, estimated at 50 C. An investigation on the effects of heating pristine and FEP exposed on HST was therefore conducted. Samples of pristine. SM1, and SM2 FEP were heated to 200 C and evaluated for changes in density and morphology. Elevated temperature exposure was found to have a major impact on the density of the retrieved materials. Characterization of polymer morphology of as-received and heated FEP samples by NMR provided results that were consistent with the density results. These findings have provided insight to the damage mechanisms of FEP in the space environment.
Adams, Arvil
1975-01-01
This testimony, before a public hearing of the New York City Commission on Human Rights in May 1974, had three express focuses: (1) on urban poverty among blacks in the non-south; (2) on the enforcement of Fair Employment Practice (FEP) legislation and its effect on the economic position of blacks and other minority groups; and, (3) on guidelines…
Roles of dark energy perturbations in dynamical dark energy models: can we ignore them?
Park, Chan-Gyung; Hwang, Jai-chan; Lee, Jae-heon; Noh, Hyerim
2009-10-09
We show the importance of properly including the perturbations of the dark energy component in the dynamical dark energy models based on a scalar field and modified gravity theories in order to meet with present and future observational precisions. Based on a simple scaling scalar field dark energy model, we show that observationally distinguishable substantial differences appear by ignoring the dark energy perturbation. By ignoring it the perturbed system of equations becomes inconsistent and deviations in (gauge-invariant) power spectra depend on the gauge choice.
The iron uptake repressor Fep1 in the fission yeast binds Fe-S cluster through conserved cysteines
Energy Technology Data Exchange (ETDEWEB)
Kim, Hyo-Jin; Lee, Kang-Lok; Kim, Kyoung-Dong; Roe, Jung-Hye, E-mail: jhroe@snu.ac.kr
2016-09-09
Iron homeostasis is tightly regulated since iron is an essential but toxic element in the cell. The GATA-type transcription factor Fep1 and its orthologs contribute to iron homeostasis in many fungi by repressing genes for iron uptake when intracellular iron is high. Even though the function and interaction partners of Fep1 have been elucidated extensively In Schizosaccharomyces pombe, the mechanism behind iron-sensing by Fep1 remains elusive. It has been reported that Fep1 interacts with Fe-S-containing monothiol glutaredoxin Grx4 and Grx4-Fra2 complex. In this study, we demonstrate that Fep1 also binds iron, in the form of Fe-S cluster. Spectroscopic and biochemical analyses of as isolated and reconstituted Fep1 suggest that the dimeric Fep1 binds Fe-S clusters. The mutation study revealed that the cluster-binding depended on the conserved cysteines located between the two zinc fingers in the DNA binding domain. EPR analyses revealed [Fe-S]-specific peaks indicative of mixed presence of [2Fe-2S], [3Fe-4S], or [4Fe-4S]. The finding that Fep1 is an Fe-S protein fits nicely with the model that the Fe-S-trafficking Grx4 senses intracellular iron environment and modulates the activity of Fep1. - Highlights: • Fep1, a prototype fungal iron uptake regulator, was isolated stably from Schizosaccharomyces pombe. • Fep1 exhibits UV–visible absorption spectrum, characteristic of [Fe-S] proteins. • The iron and sulfide contents in purified or reconstituted Fep1 also support [Fe-S]. • The conserved cysteines are critical for [Fe-S]-binding. • EPR spectra at 5 K and 123 K suggest a mixed population of [Fe-S].
International Nuclear Information System (INIS)
Sakai, Ryutaro; Takeda, Seiji; Kimura, Hideo; Matsuba, Hisashi
2011-06-01
In the safety assessment for a geological disposal of radioactive waste such as high-level radioactive waste, it is necessary to estimate the hydrological environmental changes affected by external factors such as long-termed earthquake activity and volcanic activity. Therefore it is important to perform the informations including a wide range of future processes and conditions of engineered barriers and geosphere in a systematic manner and to construct scenarios considering external factors. Generation of geological and climatic disruptive events such as earthquake activity, volcanic activity, uplift, subsidence, climatic change and sea-level change and propagation process of their impacts and their types are needed to be clarified in order to understand the phenomena of their influence on a disposal system in case of our country. Japan Atomic Energy Agency started to develop FEP database including the correlation of FEPs and FEP data sheet. This paper presents the FEP data base of upheaval, submergence, earthquake activity and climate change in this study and also presents the results of the questionnaire survey to external experts to update the technical reliability and to keep the objective view in selecting the critical safety correlations. (author)
Moessbauer study of amorphous Fe-P alloys
International Nuclear Information System (INIS)
Takacs, L.; Toth-Kadar, E.
1981-01-01
Preliminary Moessbauer results are represented on electrodeposited Fe-P amorphous alloys. Very broad hyperfine field distributions and relatively large isomer shifts have been found. Problems worth of further investigation are discussed in details. (author)
Dever, Joyce A.; Townsend, Jacqueline A.; Gaier, James R.; Jalics, Alice I.
1999-01-01
Since the Hubble Space Telescope (HST) was deployed in low Earth orbit in April 1990, two servicing missions have been conducted to upgrade its scientific capabilities. Minor cracking of second-surface metalized Teflon FEP (DuPont; fluorinated ethylene propylene) surfaces from multilayer insulation (MLI) was first observed upon close examination of samples with high solar exposure retrieved during the first servicing mission, which was conducted 3.6 years after deployment. During the second HST servicing mission, 6.8 years after deployment, astronaut observations and photographic documentation revealed significant cracks in the Teflon FEP layer of the MLI on both the solar- and anti-solar-facing surfaces of the telescope. NASA Goddard Space Flight Center directed the efforts of the Hubble Space Telescope MLI Failure Review Board, whose goals included identifying the low-Earth-orbit environmental constituent(s) responsible for the cracking and embrittling of Teflon FEP which was observed during the second servicing mission. The NASA Lewis Research Center provided significant support to this effort. Because soft x-ray radiation from solar flares had been considered as a possible cause for the degradation of the mechanical properties of Teflon FEP (ref. 1), the effects of soft xray radiation and vacuum ultraviolet light on Teflon FEP were investigated. In this Lewisled effort, samples of Teflon FEP with a 100-nm layer of vapor-deposited aluminum (VDA) on the backside were exposed to synchrotron radiation of various vacuum ultraviolet and soft x-ray wavelengths between 18 nm (69 eV) and 0.65 nm (1900 eV). Synchrotron radiation exposures were conducted using the National Synchrotron Light Source at Brookhaven National Laboratory. Samples of FEP/VDA were exposed with the FEP surface facing the synchrotron beam. Doses and fluences were compared with those estimated for the 20-yr Hubble Space Telescope mission.
Athanasiou, Christina; Vasilakaki, Sofia; Dellis, Dimitris; Cournia, Zoe
2018-01-01
Computer-aided drug design has become an integral part of drug discovery and development in the pharmaceutical and biotechnology industry, and is nowadays extensively used in the lead identification and lead optimization phases. The drug design data resource (D3R) organizes challenges against blinded experimental data to prospectively test computational methodologies as an opportunity for improved methods and algorithms to emerge. We participated in Grand Challenge 2 to predict the crystallographic poses of 36 Farnesoid X Receptor (FXR)-bound ligands and the relative binding affinities for two designated subsets of 18 and 15 FXR-bound ligands. Here, we present our methodology for pose and affinity predictions and its evaluation after the release of the experimental data. For predicting the crystallographic poses, we used docking and physics-based pose prediction methods guided by the binding poses of native ligands. For FXR ligands with known chemotypes in the PDB, we accurately predicted their binding modes, while for those with unknown chemotypes the predictions were more challenging. Our group ranked #1st (based on the median RMSD) out of 46 groups, which submitted complete entries for the binding pose prediction challenge. For the relative binding affinity prediction challenge, we performed free energy perturbation (FEP) calculations coupled with molecular dynamics (MD) simulations. FEP/MD calculations displayed a high success rate in identifying compounds with better or worse binding affinity than the reference (parent) compound. Our studies suggest that when ligands with chemical precedent are available in the literature, binding pose predictions using docking and physics-based methods are reliable; however, predictions are challenging for ligands with completely unknown chemotypes. We also show that FEP/MD calculations hold predictive value and can nowadays be used in a high throughput mode in a lead optimization project provided that crystal structures of
Energy Technology Data Exchange (ETDEWEB)
Karacic, V.; Pripic-Majic, D.; Telis, S.
1980-11-01
The relationship between zinc protoporphyrin (ZPP) and total erythrozyte protoporphyrin, measured as free erythrozyte protoporphyrin (FEP), was determined in 194 adult subjects with different occupational and non-occupational lead exposures. Furthermore, the ZPP-FEP comparison was considered with respect to the dose-effect relationship of ZPP and FEP with blood lead (PbB) for males and females, Bilirubin (Bil.) interferences in ZPP analysis were taken into account. A very close and highly significant relationship was established between ZPP and FEP values. A significant correlation between log ZPP or log FEP and PbB was also found. It was established, by both in vitro and in vivo studies, that Bil. interferes with the ZPP fluorescence readings; the relationship between false positive ZPP concentrations and Bil. concentrations was highly significant. A small but highly significant influence of increased carboxyhemoglobin (COHb) concentrations on the decrease in hermatofluorometer ZPP readings, due to inadequate oxygenation of the blood, was found. The results obtained confirm the usefulness of ZPP determinations using hematofluorometers for surveillance of increased lead absorption but stress that the interfering effect of Bil. and to a lesser extent of COHb, cannot be ignored.
The accuracy of QCD perturbation theory at high energies
Dalla Brida, Mattia; Korzec, Tomasz; Ramos, Alberto; Sint, Stefan; Sommer, Rainer
2016-01-01
We discuss the determination of the strong coupling $\\alpha_\\mathrm{\\overline{MS}}^{}(m_\\mathrm{Z})$ or equivalently the QCD $\\Lambda$-parameter. Its determination requires the use of perturbation theory in $\\alpha_s(\\mu)$ in some scheme, $s$, and at some energy scale $\\mu$. The higher the scale $\\mu$ the more accurate perturbation theory becomes, owing to asymptotic freedom. As one step in our computation of the $\\Lambda$-parameter in three-flavor QCD, we perform lattice computations in a scheme which allows us to non-perturbatively reach very high energies, corresponding to $\\alpha_s = 0.1$ and below. We find that perturbation theory is very accurate there, yielding a three percent error in the $\\Lambda$-parameter, while data around $\\alpha_s \\approx 0.2$ is clearly insufficient to quote such a precision. It is important to realize that these findings are expected to be generic, as our scheme has advantageous properties regarding the applicability of perturbation theory.
Constraints on stress-energy perturbations in general relativity
International Nuclear Information System (INIS)
Traschen, J.
1985-01-01
Conditions are found for the existence of integral constraints on stress-energy perturbations in general relativity. The integral constraints can be thought of as a general-relativistic generalization of the conservation of energy and momentum of matter perturbations in special relativity. The constraints are stated in terms of a vector field V, and the Robertson-Walker spacetimes are shown to have such constraint vectors. Although in general V is not a Killing vector, in a vacuum spacetime the constraint vectors are precisely the Killing vectors
Synthesis of perm-selective membranes by grafting acrylic acid into air-irradiated Teflon-FEP films
Bozzi, Annick; Chapiro, Adolphe
Grafting acrylic acid into air-irradiated Teflon-FEP films was investigated. Pre-irradiation doses ranged from 0.5 to 10 kGy. Grafting occurred at 45 or 60°C. Homopolymerization inhibitors, ferrous ions or methylene blue, were added to the system. It was found that after completion of the reaction, within 40-100 min, membranes were obtained with very low electric resistivities. The influence of added inhibitors, pre-irradiation dose and grafting temperature was studied. From the results it is concluded that the initiating centers in air-irradiated Teflon-FEP are, on the one hand, peroxides of structure POOP', in which P is a polymeric radical and Pprime; a small fragment, and on the other trapped PO .2 radicals. The latter only react after losing their oxygen. In the presence of polymerization inhibitors, initiation involves a redox process which reduces the overall activation energy.
Synthesis of perm-selective membranes by grafting acrylic acid into air-irradiated Teflon-FEP films
International Nuclear Information System (INIS)
Bozzi, Annick; Chapiro, Adolphe
1988-01-01
Grafting acrylic acid into air-irradiated Teflon-FEP films was investigated. Pre-irradiation doses ranged from 0.5 to 10 kGy. Grafting occurred at 45 or 60 0 C. Homopolymerization inhibitors, ferrous ions or methylene blue, were added to the system. It was found that after completion of the reaction, within 40-100 min, membranes were obtained with very low electric resistivities. The influence of added inhibitors, pre-irradiation dose and grafting temperature was studied. From the results it is concluded that the initiating centers in air-irradiated Teflon-FEP are, on the one hand, peroxides of structure POOP', in which P is a polymeric radical and P' a small fragment, and on the other hand trapped PO 2 sup(·) radicals. The latter only react after losing their oxygen. In the presence of polymerization inhibitors, initiation involves a redox process which reduces the overall activation energy. (author)
Rebolini, Elisa; Teale, Andrew M.; Helgaker, Trygve; Savin, Andreas; Toulouse, Julien
2018-06-01
A Görling-Levy (GL)-based perturbation theory along the range-separated adiabatic connection is assessed for the calculation of electronic excitation energies. In comparison with the Rayleigh-Schrödinger (RS)-based perturbation theory this GL-based perturbation theory keeps the ground-state density constant at each order and thus gives the correct ionisation energy at each order. Excitation energies up to first order in the perturbation have been calculated numerically for the helium and beryllium atoms and the hydrogen molecule without introducing any density-functional approximations. In comparison with the RS-based perturbation theory, the present GL-based perturbation theory gives much more accurate excitation energies for Rydberg states but similar excitation energies for valence states.
Advancing Drug Discovery through Enhanced Free Energy Calculations.
Abel, Robert; Wang, Lingle; Harder, Edward D; Berne, B J; Friesner, Richard A
2017-07-18
A principal goal of drug discovery project is to design molecules that can tightly and selectively bind to the target protein receptor. Accurate prediction of protein-ligand binding free energies is therefore of central importance in computational chemistry and computer aided drug design. Multiple recent improvements in computing power, classical force field accuracy, enhanced sampling methods, and simulation setup have enabled accurate and reliable calculations of protein-ligands binding free energies, and position free energy calculations to play a guiding role in small molecule drug discovery. In this Account, we outline the relevant methodological advances, including the REST2 (Replica Exchange with Solute Temperting) enhanced sampling, the incorporation of REST2 sampling with convential FEP (Free Energy Perturbation) through FEP/REST, the OPLS3 force field, and the advanced simulation setup that constitute our FEP+ approach, followed by the presentation of extensive comparisons with experiment, demonstrating sufficient accuracy in potency prediction (better than 1 kcal/mol) to substantially impact lead optimization campaigns. The limitations of the current FEP+ implementation and best practices in drug discovery applications are also discussed followed by the future methodology development plans to address those limitations. We then report results from a recent drug discovery project, in which several thousand FEP+ calculations were successfully deployed to simultaneously optimize potency, selectivity, and solubility, illustrating the power of the approach to solve challenging drug design problems. The capabilities of free energy calculations to accurately predict potency and selectivity have led to the advance of ongoing drug discovery projects, in challenging situations where alternative approaches would have great difficulties. The ability to effectively carry out projects evaluating tens of thousands, or hundreds of thousands, of proposed drug candidates
High energy deep inelastic scattering in perturbative quantum chromodynamics
International Nuclear Information System (INIS)
Wallon, S.
1996-01-01
In this PhD thesis, we deal with high energy Deep Inelastic Scattering in Perturbative Quantum Chromodynamics (QCD). In this work, two main topics are emphasized: The first one deals with dynamics based on perturbative renormalization group, and on perturbative Regge approaches. We discuss the applicability of these predictions, the possibility of distinguishing them in the HERA experiments, and their unification. We prove that the perturbative Regge dynamic can be successfully applied to describe the HERA data. Different observables are proposed for distinguishing these two approaches. We show that these two predictions can be unified in a system of equations. In the second one, unitarization and saturation problems in high energy QCD are discussed. In the multi-Regge approach, equivalent to the integrable one-dimensional XXX Heisenberg spin chain, we develop methods in order to solve this system, based on the Functional Bethe Ansatz. In the dipole model context, we propose a new formulation of unitarity and saturation effects, using Wilson loops. (author)
Dynamics of entropy perturbations in assisted dark energy with mixed kinetic terms
International Nuclear Information System (INIS)
Karwan, Khamphee
2011-01-01
We study dynamics of entropy perturbations in the two-field assisted dark energy model. Based on the scenario of assisted dark energy, in which one scalar field is subdominant compared with the other in the early epoch, we show that the entropy perturbations in this two-field system tend to be constant on large scales in the early epoch and hence survive until the present era for a generic evolution of both fields during the radiation and matter eras. This behaviour of the entropy perturbations is preserved even when the fields are coupled via kinetic interaction. Since, for assisted dark energy, the subdominant field in the early epoch becomes dominant at late time, the entropy perturbations can significantly influence the dynamics of density perturbations in the universe. Assuming correlations between the entropy and curvature perturbations, the entropy perturbations can enhance the integrated Sachs-Wolfe (ISW) effect if the signs of the contributions from entropy perturbations and curvature perturbations are opposite after the matter era, otherwise the ISW contribution is suppressed. For canonical scalar field the effect of entropy perturbations on ISW effect is small because the initial value of the entropy perturbations estimated during inflation cannot be sufficiently large. However, in the case of k-essence, the initial value of the entropy perturbations can be large enough to affect the ISW effect to leave a significant imprint on the CMB power spectrum
Dark energy and dark matter perturbations in singular universes
International Nuclear Information System (INIS)
Denkiewicz, Tomasz
2015-01-01
We discuss the evolution of density perturbations of dark matter and dark energy in cosmological models which admit future singularities in a finite time. Up to now geometrical tests of the evolution of the universe do not differentiate between singular universes and ΛCDM scenario. We solve perturbation equations using the gauge invariant formalism. The analysis shows that the detailed reconstruction of the evolution of perturbations within singular cosmologies, in the dark sector, can exhibit important differences between the singular universes models and the ΛCDM cosmology. This is encouraging for further examination and gives hope for discriminating between those models with future galaxy weak lensing experiments like the Dark Energy Survey (DES) and Euclid or CMB observations like PRISM and CoRE
The NEA International FEP Database and its use in support of regulatory review
International Nuclear Information System (INIS)
Sumerling, T.
1999-01-01
A working group of the Nuclear Energy Agency has developed a database of features, events and processes (FEPs) relevant to the assessment of the long-term safety of radioactive waste disposal facilities. The Environment Agency participated in this work as described in a previous report, R and D Technical Report P97. This report describes work done in order to (i) provide an electronic version of the NEA International FEP Database in a convenient form suited to the Agency's needs; (ii) determine procedures for use of the Database in support of the Agency's review of an applicant's safety case for solid radioactive disposal, and in other appropriate Agency activities. Section 1 of the report outlines the objectives and work done. Section 2 gives an overview of the current status, development and international use of the NEA FEP Database. Alternative uses of the Database by the Agency, and procedures for use, are discussed in Section 3. Two alternative procedures for use of the Database in scientific and technical review of an applicant's safety case are outlined and compared; these provide a framework for orderly identification and discussion of technical issues within the review. It is concluded that the way in which the Database is used will depend on the circumstances and also the aims and preferences of the Agency. Detailed procedures for the use of the Database are best defined for the specific circumstances, taking account of the level of information available from the applicant, and the time and resources which the Agency may wish to devote to a given phase of review. The NEA FEP Database has been developed as a tool to assist in performing or reviewing safety assessments of radioactive waste disposal facilities. The principle of the Database, and also the software framework, may be equally applicable to other technical or scientific assessments, e.g. of landfill facilities or river catchment pollution studies. Since the Database is now available to the Agency
DETACHMENT OF HUMAN FIBROBLASTS FROM FEP-TEFLON SURFACES
VANKOOTEN, TG; SCHAKENRAAD, JM; VANDERMEI, HC; BUSSCHER, HJ
1991-01-01
In this study a comparison is made between the detachment behavior of human fibroblasts adhered to hydrophobic FEP-Teflon (water contact angle 109 degrees) and to hydrophilic glass (water contact angle smaller than 15 degrees) during exposure to a laminar, incrementally loaded flow. Detachment from
Energy Technology Data Exchange (ETDEWEB)
Miller, Bill; Savage, Dave; McEwen, Tim; White, Matt [QuantiSci Ltd, Melton Mowbray (United Kingdom)
2002-08-01
This is an 'Encyclopaedia' providing descriptions of Features, Events and Processes (FEPs) that are relevant to the Swedish repository for low and intermediate-level wastes (the SFR) and the proposed Swedish repository for spent fuel. Although the FEPs and their descriptions found in this encyclopaedia are specific to these two repository concepts, many of the descriptions will also be relevant to other repository designs and concepts, although they have not been written to be inclusive of the features of other repositories. As such, this encyclopaedia may be of interest to a wide range of individuals and organisations involved in repository safety assessment around the world. The purpose of this encyclopaedia is to describe, in qualitative terms, the various FEPs which have been identified as being relevant to the two Swedish repository designs. These descriptions may be used in a variety of ways. One important role will be to support quantitative performance assessments (PAs) by describing the conceptual understanding of the various components of the repository (e.g. the barriers, the rock and the groundwater) and their evolution: this conceptual understanding is crucial because it is the foundation upon which the mathematical analysis is based. The descriptions have been written at a level of detail appropriate for a scientifically literate reader without specialist knowledge of radioactive waste disposal technology or assessment procedures. As such, the descriptions avoid the use of specialist terms, acronyms and equations. Many of the FEP descriptions relate to issues which are the focus of ongoing research and, thus, they reflect the current state of knowledge and may require updating at regular intervals, either to include more recent technical information or procedures for treating the FEP in mathematical safety assessment. When attempting to predict the future behaviour of a repository for radioactive wastes, it is sensible to use a systematic
International Nuclear Information System (INIS)
Miller, Bill; Savage, Dave; McEwen, Tim; White, Matt
2002-08-01
This is an 'Encyclopaedia' providing descriptions of Features, Events and Processes (FEPs) that are relevant to the Swedish repository for low and intermediate-level wastes (the SFR) and the proposed Swedish repository for spent fuel. Although the FEPs and their descriptions found in this encyclopaedia are specific to these two repository concepts, many of the descriptions will also be relevant to other repository designs and concepts, although they have not been written to be inclusive of the features of other repositories. As such, this encyclopaedia may be of interest to a wide range of individuals and organisations involved in repository safety assessment around the world. The purpose of this encyclopaedia is to describe, in qualitative terms, the various FEPs which have been identified as being relevant to the two Swedish repository designs. These descriptions may be used in a variety of ways. One important role will be to support quantitative performance assessments (PAs) by describing the conceptual understanding of the various components of the repository (e.g. the barriers, the rock and the groundwater) and their evolution: this conceptual understanding is crucial because it is the foundation upon which the mathematical analysis is based. The descriptions have been written at a level of detail appropriate for a scientifically literate reader without specialist knowledge of radioactive waste disposal technology or assessment procedures. As such, the descriptions avoid the use of specialist terms, acronyms and equations. Many of the FEP descriptions relate to issues which are the focus of ongoing research and, thus, they reflect the current state of knowledge and may require updating at regular intervals, either to include more recent technical information or procedures for treating the FEP in mathematical safety assessment. When attempting to predict the future behaviour of a repository for radioactive wastes, it is sensible to use a systematic approach to
Fluoresceination of FepA during colicin B killing: effects of temperature, toxin and TonB.
Smallwood, Chuck R; Marco, Amparo Gala; Xiao, Qiaobin; Trinh, Vy; Newton, Salete M C; Klebba, Phillip E
2009-06-01
We studied the reactivity of 35 genetically engineered Cys sulphydryl groups at different locations in Escherichia coli FepA. Modification of surface loop residues by fluorescein maleimide (FM) was strongly temperature-dependent in vivo, whereas reactivity at other sites was much less affected. Control reactions with bovine serum albumin showed that the temperature dependence of loop residue reactivity was unusually high, indicating that conformational changes in multiple loops (L2, L3, L4, L5, L7, L8, L10) transform the receptor to a more accessible form at 37 degrees C. At 0 degrees C colicin B binding impaired or blocked labelling at 8 of 10 surface loop sites, presumably by steric hindrance. Overall, colicin B adsorption decreased the reactivity of more than half of the 35 sites, in both the N- and C- domains of FepA. However, colicin B penetration into the cell at 37 degrees C did not augment the chemical modification of any residues in FepA. The FM modification patterns were similarly unaffected by the tonB locus. FepA was expressed at lower levels in a tonB host strain, but when we accounted for this decrease its FM labelling was comparable whether TonB was present or absent. Thus we did not detect TonB-dependent structural changes in FepA, either alone or when it interacted with colicin B at 37 degrees C. The only changes in chemical modification were reductions from steric hindrance when the bacteriocin bound to the receptor protein. The absence of increases in the reactivity of N-domain residues argues against the idea that the colicin B polypeptide traverses the FepA channel.
Moessbauer and XRD study of pulse plated Fe-P and Fe-Ni thin layers
International Nuclear Information System (INIS)
Miko, Annamaria; Kuzmann, Erno; Lakatos-Varsanyi, Magda; Kakay, Attila; Nagy, Ferenc; Varga, Lajos Karoly
2005-01-01
57 Fe conversion electron Moessbauer spectroscopy, X-ray diffraction, electrochemical and magnetic measurements were used to study pulse electroplated Fe-P and Ni-Fe coatings. XRD and 57 Fe CEMS measurements revealed the amorphous character of the novel pulse plated Fe-P alloys. CEM spectra indicated significant differences in the short range order and in the magnetic anisotropy between the Fe-P deposits pulse plated at medium long deposition time (t on = 2 ms), with short relaxation time (t off = 9 ms) and low current density (I p = 0.05 Acm -2 ) or at short deposition time (t on = 1 ms) with long relaxation time (t off = 250 ms) and high current density (I p = 1.0 Acm -2 ). The broad peaks centred around the fcc reflections in XRD of the pulse plated Ni-22 wt.% Fe deposit reflected a microcrystalline Ni-Fe alloy with a very fine, 5-8 nm, grain size. The CEM spectrum of the pulse plated Ni-22 wt.% Fe coating corresponded to a highly disordered solid solution alloy containing a minute amount of ferrihydrite. Extreme favourable soft magnetic properties were observed with these Ni-Fe and Fe-P pulse plated thin layers.
Anisotropic perturbations due to dark energy
International Nuclear Information System (INIS)
Battye, Richard A.; Moss, Adam
2006-01-01
A variety of observational tests seem to suggest that the Universe is anisotropic. This is incompatible with the standard dogma based on adiabatic, rotationally invariant perturbations. We point out that this is a consequence of the standard decomposition of the stress-energy tensor for the cosmological fluids, and that rotational invariance need not be assumed, if there is elastic rigidity in the dark energy. The dark energy required to achieve this might be provided by point symmetric domain wall network with P/ρ=-2/3, although the concept is more general. We illustrate this with reference to a model with cubic symmetry and discuss various aspects of the model
Orgován, Zoltán; Ferenczy, György G.; Steinbrecher, Thomas; Szilágyi, Bence; Bajusz, Dávid; Keserű, György M.
2018-02-01
Optimization of fragment size d-amino acid oxidase (DAAO) inhibitors was investigated using a combination of computational and experimental methods. Retrospective free energy perturbation (FEP) calculations were performed for benzo[d]isoxazole derivatives, a series of known inhibitors with two potential binding modes derived from X-ray structures of other DAAO inhibitors. The good agreement between experimental and computed binding free energies in only one of the hypothesized binding modes strongly support this bioactive conformation. Then, a series of 1-H-indazol-3-ol derivatives formerly not described as DAAO inhibitors was investigated. Binding geometries could be reliably identified by structural similarity to benzo[d]isoxazole and other well characterized series and FEP calculations were performed for several tautomers of the deprotonated and protonated compounds since all these forms are potentially present owing to the experimental pKa values of representative compounds in the series. Deprotonated compounds are proposed to be the most important bound species owing to the significantly better agreement between their calculated and measured affinities compared to the protonated forms. FEP calculations were also used for the prediction of the affinities of compounds not previously tested as DAAO inhibitors and for a comparative structure-activity relationship study of the benzo[d]isoxazole and indazole series. Selected indazole derivatives were synthesized and their measured binding affinity towards DAAO was in good agreement with FEP predictions.
Moessbauer and XRD study of pulse plated Fe-P and Fe-Ni thin layers
Energy Technology Data Exchange (ETDEWEB)
Miko, Annamaria [Bay Zoltan Institute for Material Science (Hungary); Kuzmann, Erno, E-mail: kuzmann@para.chem.elte.hu [Eoetvoes Lorand University, Research Group for Nuclear Methods in Structural Chemistry, Hungarian Academy of Sciences, Department of Nuclear Chemistry (Hungary); Lakatos-Varsanyi, Magda [Bay Zoltan Institute for Material Science (Hungary); Kakay, Attila [Research Institute for Solid State Physics and Optics (Hungary); Nagy, Ferenc [Eoetvoes Lorand University, Research Group for Nuclear Methods in Structural Chemistry, Hungarian Academy of Sciences, Department of Nuclear Chemistry (Hungary); Varga, Lajos Karoly [Research Institute for Solid State Physics and Optics (Hungary)
2005-09-15
{sup 57}Fe conversion electron Moessbauer spectroscopy, X-ray diffraction, electrochemical and magnetic measurements were used to study pulse electroplated Fe-P and Ni-Fe coatings. XRD and {sup 57}Fe CEMS measurements revealed the amorphous character of the novel pulse plated Fe-P alloys. CEM spectra indicated significant differences in the short range order and in the magnetic anisotropy between the Fe-P deposits pulse plated at medium long deposition time (t{sub on} = 2 ms), with short relaxation time (t{sub off} = 9 ms) and low current density (I{sub p} = 0.05 Acm{sup -2}) or at short deposition time (t{sub on} = 1 ms) with long relaxation time (t{sub off} = 250 ms) and high current density (I{sub p} = 1.0 Acm{sup -2}). The broad peaks centred around the fcc reflections in XRD of the pulse plated Ni-22 wt.% Fe deposit reflected a microcrystalline Ni-Fe alloy with a very fine, 5-8 nm, grain size. The CEM spectrum of the pulse plated Ni-22 wt.% Fe coating corresponded to a highly disordered solid solution alloy containing a minute amount of ferrihydrite. Extreme favourable soft magnetic properties were observed with these Ni-Fe and Fe-P pulse plated thin layers.
Energy Technology Data Exchange (ETDEWEB)
Wolf, Jens [Gesellschaft fuer Anlagen- und Reaktorsicherheit mbH (GRS), Koeln (Germany); Behlau, Joachim [Bundesanstalt fuer Geowissenschaften und Rohstoffe, Hannover (Germany); Beuth, Thomas [Gesellschaft fuer Anlagen- und Reaktorsicherheit mbH (GRS), Koeln (Germany)] [and others
2012-06-15
The report is a compendium of the FEP (features, events, processes) data base that was developed in the frame of the preliminary safety analysis Gorleben (VSG). For each FEP issue the information includes the following subchapters: definition, general information and examples, status at the site, site-specific impacts, temporal restriction, conditional incidence rate, effects on subsidiary systems, adverse effects on the function of the initial barriers, justification, direct dependencies, open questions, references.
Internal wave energy flux from density perturbations in nonlinear stratifications
Lee, Frank M.; Allshouse, Michael R.; Swinney, Harry L.; Morrison, P. J.
2017-11-01
Tidal flow over the topography at the bottom of the ocean, whose density varies with depth, generates internal gravity waves that have a significant impact on the energy budget of the ocean. Thus, understanding the energy flux (J = p v) is important, but it is difficult to measure simultaneously the pressure and velocity perturbation fields, p and v . In a previous work, a Green's-function-based method was developed to calculate the instantaneous p, v , and thus J , given a density perturbation field for a constant buoyancy frequency N. Here we extend the previous analytic Green's function work to include nonuniform N profiles, namely the tanh-shaped and linear cases, because background density stratifications that occur in the ocean and some experiments are nonlinear. In addition, we present a finite-difference method for the general case where N has an arbitrary profile. Each method is validated against numerical simulations. The methods we present can be applied to measured density perturbation data by using our MATLAB graphical user interface EnergyFlux. PJM was supported by the U.S. Department of Energy Contract DE-FG05-80ET-53088. HLS and MRA were supported by ONR Grant No. N000141110701.
Yang, Xiulin
2015-05-25
There is a strong demand to replace expensive Pt catalysts with cheap metal sulfides or phosphides for hydrogen generation in water electrolysis. The earth-abundant Fe can be electroplated on carbon cloth (CC) to form high surface area rague-like FeOOH assembly. Subsequent gas phase phosphidation converts the FeOOH to FeP or FeP2 and the morphology of the crystal assembly is controlled by the phosphidation temperature. The FeP prepared at 250 oC presents lower crystallinity and those prepared at higher temperatures 400 oC and 500 oC possess higher crystallinity but lower surface area. The phosphidation at 300 oC produces nanocrystalline FeP and preserves the high-surface area morphology; thus it exhibits the highest HER efficiency in 0.5 M H2SO4; i.e. the required overpotential to reach 10 and 20 mA/cm2 is 34 and 43 mV respectively. These values are lowest among the reported non-precious metal phosphides on CC. The Tafel slope for the FeP prepared at 300 oC is around 29.2 mV/dec comparable to that of Pt/CC, indicating that the hydrogen evolution for our best FeP is limited by Tafel reaction (same as Pt). Importantly, the FeP/CC catalyst exhibits much better stability in a wide range working current density (up to 1 V/cm2), suggesting that it is a promising replacement of Pt for HER.
Yang, Xiulin; Lu, Ang-Yu; Zhu, Yihan; Min, Shixiong; Hedhili, Mohamed N.; Han, Yu; Huang, Kuo-Wei; Li, Lain-Jong
2015-01-01
There is a strong demand to replace expensive Pt catalysts with cheap metal sulfides or phosphides for hydrogen generation in water electrolysis. The earth-abundant Fe can be electroplated on carbon cloth (CC) to form high surface area rague-like FeOOH assembly. Subsequent gas phase phosphidation converts the FeOOH to FeP or FeP2 and the morphology of the crystal assembly is controlled by the phosphidation temperature. The FeP prepared at 250 oC presents lower crystallinity and those prepared at higher temperatures 400 oC and 500 oC possess higher crystallinity but lower surface area. The phosphidation at 300 oC produces nanocrystalline FeP and preserves the high-surface area morphology; thus it exhibits the highest HER efficiency in 0.5 M H2SO4; i.e. the required overpotential to reach 10 and 20 mA/cm2 is 34 and 43 mV respectively. These values are lowest among the reported non-precious metal phosphides on CC. The Tafel slope for the FeP prepared at 300 oC is around 29.2 mV/dec comparable to that of Pt/CC, indicating that the hydrogen evolution for our best FeP is limited by Tafel reaction (same as Pt). Importantly, the FeP/CC catalyst exhibits much better stability in a wide range working current density (up to 1 V/cm2), suggesting that it is a promising replacement of Pt for HER.
Perturbation approach to the self-energy of non-S hydrogenic states
International Nuclear Information System (INIS)
Le Bigot, Eric-Olivier; Jentschura, Ulrich D.; Mohr, Peter J.; Indelicato, Paul; Soff, Gerhard
2003-01-01
We present results on the self-energy correction to the energy levels of hydrogen and hydrogenlike ions. The self-energy represents the largest QED correction to the relativistic (Dirac-Coulomb) energy of a bound electron. We focus on the perturbation expansion of the self-energy of non-S states, and provide estimates of the so-called A 60 perturbation coefficient, which can be viewed as a relativistic Bethe logarithm. Precise values of A 60 are given for many P, D, F, and G states, while estimates are given for other states. These results can be used in high-precision spectroscopy experiments in hydrogen and hydrogenlike ions. They yield the best available estimate of the self-energy correction of many atomic states
International Nuclear Information System (INIS)
Du, Juan; Jiao, Lifang; Wu, Qiong; Liu, Yongchang; Zhao, Yanping; Guo, Lijing; Wang, Yijing; Yuan, Huatang
2013-01-01
Highlights: • Li 2 FeP 2 O 7 /C were prepared by a simple solid-state reaction. • Carbon coating and reducing particle size are adopted to improve the discharge capacity. • The detailed study about the electrochemical properties of Li 2 FeP 2 O 7 is scarce. • Li 2 FeP 2 O 7 /C show superior electrochemical properties. -- Abstract: The pristine Li 2 FeP 2 O 7 and Li 2 FeP 2 O 7 /C nanocomposites with different content of carbon have been successfully synthesized via a simple solid-state reaction, using cheap glucose as carbon source. XRD and EDS patterns demonstrate the high purity of the products. SEM images exhibit that the size of the particles is about 50–500 nm. Electrochemical measurements reveal that carbon coating and reducing particle size significantly enhance the electrochemical performances of Li 2 FeP 2 O 7 . Particularly, the Li 2 FeP 2 O 7 /C sample with a carbon content of 4.88 wt.% displays the best performance with a specific discharge capacity of 103.1 mAh g −1 at 0.1 C, which is 93.7% of its one-electron theoretical capacity, meaning 110 mAh g −1 . Meanwhile, it shows favorable cycling stability and excellent rate performance, indicating its potential applicability in Li-ion batteries in the long term
The energy of perturbations for Vlasov plasmas
International Nuclear Information System (INIS)
Morrison, P.J.
1994-02-01
The energy content of electrostatic perturbations about homogeneous equilibria is discussed. The calculation leading to the well-known dielectric (or as it is sometimes called the wave) energy is revisited and interpreted in light of Vlasov theory. It is argued that this quantity is deficient because resonant particles are not correctly handled. A linear integral transform is presented that solves the linear Vlasov-Poisson equation. This solution together with the Kruskal-Oberman energy [Phys. Fluids 1, 275 (1958)] is used to obtain an energy expression in terms of the electric field [Phys. Fluids B 4, 3038 (1992)]. It is described how the integral transform amounts to a change to normal coordinates in an infinite dimensional Hamiltonian system
Townsend, Jacqueline A.; Hansen, Patricia A.; Dever, J. A.; deGroh, K. K.; Banks, B.; Wang, L.; He, C.
1988-01-01
During the Hubble Space Telescope (HST) Second Servicing Mission (SM2), degradation of unsupported Teflon(Registered Trademark) FEP (fluorinated ethylene propylene), used as the outer layer of the multilayer insulation (MLI) blankets, was evident as large cracks on the telescope light shield. A sample of the degraded outer layer was retrieved during the mission and returned to Earth for ground testing and evaluation. The results of the Teflon(Registered Trademark) FEP sample evaluation and additional testing of pristine Teflon(Registered Trademark) FEP led the investigative team to theorize that the HST damage was caused by thermal cycling with deep-layer damage from electron and proton radiation which allowed the propagation of cracks along stress concentrations , and that the damage increased with the combined total dose of electrons, protons, UV and x-rays along with thermal cycling. This paper discusses the testing and evaluation of the retrieved Teflon(Registered Trademark) FEP.
Energy Technology Data Exchange (ETDEWEB)
Kim, Kyoung-Dong; Kim, Hyo-Jin; Lee, Kyung-Chang [Laboratory of Molecular Microbiology, School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 151-742 (Korea, Republic of); Roe, Jung-Hye, E-mail: jhroe@snu.ac.kr [Laboratory of Molecular Microbiology, School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 151-742 (Korea, Republic of)
2011-05-20
Research highlights: {yields} Monothiol glutaredoxin Grx4 allows Fep1-mediated de-repression of iron uptake genes at low iron. {yields} Grx4 directly interacts with Fep1 in vivo and in vitro. {yields} The Cys172 in the CGFS motif of Grx4 is necessary for cell proliferation and iron regulation. {yields} The Cys172 of Grx4 is required for normal interaction with Fep1. -- Abstract: The fission yeast Schizosaccharomyces pombe contains two CGFS-type monothiol glutaredoxins, Grx4 and Grx5, which are localized primarily in the nucleus and mitochondria, respectively. We observed involvement of Grx4 in regulating iron-responsive gene expression, which is modulated by a repressor Fep1. Lack of Grx4 caused defects not only in growth but also in the expression of both iron-uptake and iron-utilizing genes regardless of iron availability. In order to unravel how Grx4 is involved in Fep1-mediated regulation, interaction between them was investigated. Co-immunoprecipitation and bimolecular fluorescence complementation (BiFC) revealed that Grx4 physically interacts with Fep1 in vivo. BiFC revealed localized nuclear dots produced by interaction of Grx4 with Fep1. Mutation of cysteine-172 in the CGFS motif to serine (C172S) produced effects similarly observed under Grx4 depletion, such as the loss of iron-dependent gene regulation and the absence of nuclear dots in BiFC analysis. These results suggest that the ability of Grx4 to bind iron, most likely Fe-S cofactor, could be critical in interacting with and modulating the activity of Fep1.
Confined Mobility of TonB and FepA in Escherichia coli Membranes.
Directory of Open Access Journals (Sweden)
Yoriko Lill
Full Text Available The important process of nutrient uptake in Escherichia coli, in many cases, involves transit of the nutrient through a class of beta-barrel proteins in the outer membrane known as TonB-dependent transporters (TBDTs and requires interaction with the inner membrane protein TonB. Here we have imaged the mobility of the ferric enterobactin transporter FepA and TonB by tracking them in the membranes of live E. coli with single-molecule resolution at time-scales ranging from milliseconds to seconds. We employed simple simulations to model/analyze the lateral diffusion in the membranes of E.coli, to take into account both the highly curved geometry of the cell and artifactual effects expected due to finite exposure time imaging. We find that both molecules perform confined lateral diffusion in their respective membranes in the absence of ligand with FepA confined to a region [Formula: see text] μm in radius in the outer membrane and TonB confined to a region [Formula: see text] μm in radius in the inner membrane. The diffusion coefficient of these molecules on millisecond time-scales was estimated to be [Formula: see text] μm2/s and [Formula: see text] μm2/s for FepA and TonB, respectively, implying that each molecule is free to diffuse within its domain. Disruption of the inner membrane potential, deletion of ExbB/D from the inner membrane, presence of ligand or antibody to FepA and disruption of the MreB cytoskeleton was all found to further restrict the mobility of both molecules. Results are analyzed in terms of changes in confinement size and interactions between the two proteins.
Evolution of perturbations in distinct classes of canonical scalar field models of dark energy
International Nuclear Information System (INIS)
Jassal, H. K.
2010-01-01
Dark energy must cluster in order to be consistent with the equivalence principle. The background evolution can be effectively modeled by either a scalar field or by a barotropic fluid. The fluid model can be used to emulate perturbations in a scalar field model of dark energy, though this model breaks down at large scales. In this paper we study evolution of dark energy perturbations in canonical scalar field models: the classes of thawing and freezing models. The dark energy equation of state evolves differently in these classes. In freezing models, the equation of state deviates from that of a cosmological constant at early times. For thawing models, the dark energy equation of state remains near that of the cosmological constant at early times and begins to deviate from it only at late times. Since the dark energy equation of state evolves differently in these classes, the dark energy perturbations too evolve differently. In freezing models, since the equation of state deviates from that of a cosmological constant at early times, there is a significant difference in evolution of matter perturbations from those in the cosmological constant model. In comparison, matter perturbations in thawing models differ from the cosmological constant only at late times. This difference provides an additional handle to distinguish between these classes of models and this difference should manifest itself in the integrated Sachs-Wolfe effect.
Perturbation method for calculating impurity binding energy in an ...
Indian Academy of Sciences (India)
Nilanjan Sil
2017-12-18
Dec 18, 2017 ... Abstract. In the present paper, we have studied the binding energy of the shallow donor hydrogenic impurity, which is confined in an inhomogeneous cylindrical quantum dot (CQD) of GaAs-AlxGa1−xAs. Perturbation method is used to calculate the binding energy within the framework of effective mass ...
Supersingular quantum perturbations
International Nuclear Information System (INIS)
Detwiler, L.C.; Klauder, J.R.
1975-01-01
A perturbation potential is called supersingular whenever generally every matrix element of the perturbation in the unperturbed eigenstates is infinite. It follows that supersingular perturbations do not have conventional perturbation expansions, say for energy eigenvalues. By invoking variational arguments, we determine the asymptotic behavior of the energy eigenvalues for asymptotically small values of the coupling constant of the supersingular perturbation
Energy momentum tensor in local causal perturbation theory
International Nuclear Information System (INIS)
Prange, D.
2001-01-01
We study the energy momentum tensor in the Bogolyubov-Epstein-Glaser approach to perturbation theory. It is found to be locally conserved for a class of theories containing to derivated fields in the interaction. For the massless φ 4 -theory we derive the trace anomaly of the improved tensor. (orig.)
Energies and bounds from perturbative approximations to the Bloch-Horowitz effective Hamiltonian
International Nuclear Information System (INIS)
Darema-Rogers, F.; Vincent, C.M.
1978-01-01
Bloch-Horowitz perturbation theory is applied to the calculation of approximate energies and model-space eigenvectors, for the solvable large-matrix Hamiltonian H used by Pittel, Vincent, and Vergados. Two types of upper and lower bounds to the energies are discussed: moment-theory bounds, obtained by applying moment theory to the terms of perturbation theory, and norm bounds, derived from the expectation E-bar and variance sigma 2 of H with respect to an eigenvector approximated by nth order perturbation theory (n < or = 6). It is shown that lower bounds cannot be constructed unless some fourth-order quantity is known. The upper bounds are generally stricter than the lower bounds. All of the bounds apply even when back-door intruder states cause perturbation theory to diverge; but they lose their rigor and become ''quasibounds'' when there are physical intruders. The moment-theory and norm lower quasibounds always require estimation of a parameter. For the solvable Hamiltonians, it is shown that this can be done quite reliably, and that the resulting quasibounds are tight enough to have some practical utility. The energy-independent effective interaction V is constructed and its errors are displayed and discussed. Finally, a certain [1/2] pseudo-Pade approximant is empirically shown to give energies with a mean absolute error of less than 0.3 MeV in all cases
Baryon chiral perturbation theory extended beyond the low-energy region.
Epelbaum, E; Gegelia, J; Meißner, Ulf-G; Yao, De-Liang
We consider an extension of the one-nucleon sector of baryon chiral perturbation theory beyond the low-energy region. The applicability of this approach for higher energies is restricted to small scattering angles, i.e. the kinematical region, where the quark structure of hadrons cannot be resolved. The main idea is to re-arrange the low-energy effective Lagrangian according to a new power counting and to exploit the freedom of the choice of the renormalization condition for loop diagrams. We generalize the extended on-mass-shell scheme for the one-nucleon sector of baryon chiral perturbation theory by choosing a sliding scale, that is, we expand the physical amplitudes around kinematical points beyond the threshold. This requires the introduction of complex-valued renormalized coupling constants, which can be either extracted from experimental data, or calculated using the renormalization group evolution of coupling constants fixed in threshold region.
Baryon chiral perturbation theory extended beyond the low-energy region
International Nuclear Information System (INIS)
Epelbaum, E.; Gegelia, J.; Meissner, Ulf G.; Yao, De-Liang
2015-01-01
We consider an extension of the one-nucleon sector of baryon chiral perturbation theory beyond the low-energy region. The applicability of this approach for higher energies is restricted to small scattering angles, i.e. the kinematical region, where the quark structure of hadrons cannot be resolved. The main idea is to re-arrange the low-energy effective Lagrangian according to a new power counting and to exploit the freedom of the choice of the renormalization condition for loop diagrams. We generalize the extended on-mass-shell scheme for the one-nucleon sector of baryon chiral perturbation theory by choosing a sliding scale, that is, we expand the physical amplitudes around kinematical points beyond the threshold. This requires the introduction of complex-valued renormalized coupling constants, which can be either extracted from experimental data, or calculated using the renormalization group evolution of coupling constants fixed in threshold region. (orig.)
High-Pressure and High-Temperature in situ X-Ray Diffraction Study of FeP2 up to 70 GPa
International Nuclear Information System (INIS)
Gu Ting-Ting; Wu Xiang; Qin Shan; Liu Jing; Li Yan-Chun; Zhang Yu-Feng
2012-01-01
The high-pressure and high-temperature structural behavior of FeP 2 is investigated by means of synchrotron x-ray powder diffraction combined with a laser heating technique up to 70 GPa and at least 1800 K. No phase transition of FeP 2 occurs up to 68 GPa at room temperature. While a new phase of FeP 2 assigned to the CuAl 2 -type structure (I4/mcm, Z = 4) is observed at 70 GPa after laser-heating. This new phase presents a quenchable property on decompression to ambient conditions. Our results update previous experimental data and are consistent with theoretical studies. (condensed matter: structure, mechanical and thermal properties)
Determination of low-energy constants of Wilson chiral perturbation theory
International Nuclear Information System (INIS)
Herdoiza, Gregorio; Univ. Autonoma de Madrid, Contoblanco; Univ. Autonoma de Madrid; Jansen, Karl; Univ. Cyprus, Nicosia; Michael, Chris; Ottnad, Konstantin; Urbach, Carsten; Univ. Bonn
2013-03-01
By matching Wilson twisted mass lattice QCD determinations of pseudoscalar meson masses to Wilson Chiral Perturbation Theory we determine the low-energy constants W 6 ' , W 8 ' and their linear combination c 2 . We explore the dependence of these low-energy constants on the choice of the lattice action and on the number of dynamical flavours.
International Nuclear Information System (INIS)
Payne, T.E.; McGlinn, P.J.
2007-01-01
The Australian Nuclear Science and Technology Organisation (ANSTO) has established a project to undertake research relevant to the safety case for the proposed Australian radioactive waste facility. This facility will comprise a store for intermediate level radioactive waste, and either a store or a near-surface repository for low-level waste. In order to identify the research priorities for this project, a structured analysis of the features, events and processes (FEPs) relevant to the performance of the facility was undertaken. This analysis was based on the list of 137 FEPs developed by the IAEA project on 'Safety Assessment Methodologies for Near Surface Disposal Facilities' (ISAM). A number of key research issues were identified, and some factors which differ in significance for the store, compared to the repository concept, were highlighted. For example, FEPs related to long-term groundwater transport of radionuclides are considered to be of less significance for a store than a repository. On the other hand, structural damage from severe weather, accident or human interference is more likely for a store. The FEPs analysis has enabled the scientific research skills required for the inter-disciplinary project team to be specified. The outcomes of the research will eventually be utilised in developing the design, and assessing the performance, of the future facility. It is anticipated that a more detailed application of the FEPs methodology will be undertaken to develop the safety case for the proposed radioactive waste management facility. (authors)
Determination of low-energy constants of Wilson chiral perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Herdoiza, Gregorio [Mainz Univ. (Germany). Inst fuer Kernphysik, PRISMA Cluster of Excellence; Univ. Autonoma de Madrid, Contoblanco (Spain). Dept. de Fisica Teorica; Univ. Autonoma de Madrid (Spain). Inst. de Fisica Teorica UAM/CSIC; Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Univ. Cyprus, Nicosia (Cyprus). Dept. of Physics; Michael, Chris [Liverpool Univ. (United Kingdom). Theoretical Physics Division; Ottnad, Konstantin; Urbach, Carsten [Bonn Univ. (Germany). Helmholtz-Institut fuer Strahlen und Kernphysik; Univ. Bonn (Germany). Bethe Center for Theoretical Physics; Collaboration: European Twisted Mass Collaboration
2013-03-15
By matching Wilson twisted mass lattice QCD determinations of pseudoscalar meson masses to Wilson Chiral Perturbation Theory we determine the low-energy constants W{sub 6}{sup '}, W{sub 8}{sup '} and their linear combination c{sub 2}. We explore the dependence of these low-energy constants on the choice of the lattice action and on the number of dynamical flavours.
Faheem, Muhammad; Heyden, Andreas
2014-08-12
We report the development of a quantum mechanics/molecular mechanics free energy perturbation (QM/MM-FEP) method for modeling chemical reactions at metal-water interfaces. This novel solvation scheme combines planewave density function theory (DFT), periodic electrostatic embedded cluster method (PEECM) calculations using Gaussian-type orbitals, and classical molecular dynamics (MD) simulations to obtain a free energy description of a complex metal-water system. We derive a potential of mean force (PMF) of the reaction system within the QM/MM framework. A fixed-size, finite ensemble of MM conformations is used to permit precise evaluation of the PMF of QM coordinates and its gradient defined within this ensemble. Local conformations of adsorbed reaction moieties are optimized using sequential MD-sampling and QM-optimization steps. An approximate reaction coordinate is constructed using a number of interpolated states and the free energy difference between adjacent states is calculated using the QM/MM-FEP method. By avoiding on-the-fly QM calculations and by circumventing the challenges associated with statistical averaging during MD sampling, a computational speedup of multiple orders of magnitude is realized. The method is systematically validated against the results of ab initio QM calculations and demonstrated for C-C cleavage in double-dehydrogenated ethylene glycol on a Pt (111) model surface.
Determination of the QCD Λ-parameter and the accuracy of perturbation theory at high energies
International Nuclear Information System (INIS)
Dalla Brida, Mattia; Fritzsch, Patrick; Korzec, Tomasz; Ramos, Alberto; Sint, Stefan; Sommer, Rainer; Humboldt-Universitaet, Berlin
2016-04-01
We discuss the determination of the strong coupling α_M_S(m_Z) or equivalently the QCD Λ-parameter. Its determination requires the use of perturbation theory in α_s(μ) in some scheme, s, and at some energy scale μ. The higher the scale μ the more accurate perturbation theory becomes, owing to asymptotic freedom. As one step in our computation of the Λ-parameter in three-flavor QCD, we perform lattice computations in a scheme which allows us to non-perturbatively reach very high energies, corresponding to α_s=0.1 and below. We find that (continuum) perturbation theory is very accurate there, yielding a three percent error in the Λ-parameter, while data around α_s∼0.2 is clearly insufficient to quote such a precision. It is important to realize that these findings are expected to be generic, as our scheme has advantageous properties regarding the applicability of perturbation theory.
Determination of the QCD Λ-parameter and the accuracy of perturbation theory at high energies
Energy Technology Data Exchange (ETDEWEB)
Dalla Brida, Mattia [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Fritzsch, Patrick [Univ. Autonoma de Madrid (Spain). Inst. de Fisica Teorica UAM/CSIC; Korzec, Tomasz [Wuppertal Univ. (Germany). Dept. of Physics; Ramos, Alberto [CERN - European Organization for Nuclear Research, Geneva (Switzerland). Theory Div.; Sint, Stefan [Trinity College Dublin (Ireland). School of Mathematics; Sommer, Rainer [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Collaboration: ALPHA Collaboration
2016-04-15
We discuss the determination of the strong coupling α{sub MS}(m{sub Z}) or equivalently the QCD Λ-parameter. Its determination requires the use of perturbation theory in α{sub s}(μ) in some scheme, s, and at some energy scale μ. The higher the scale μ the more accurate perturbation theory becomes, owing to asymptotic freedom. As one step in our computation of the Λ-parameter in three-flavor QCD, we perform lattice computations in a scheme which allows us to non-perturbatively reach very high energies, corresponding to α{sub s}=0.1 and below. We find that (continuum) perturbation theory is very accurate there, yielding a three percent error in the Λ-parameter, while data around α{sub s}∼0.2 is clearly insufficient to quote such a precision. It is important to realize that these findings are expected to be generic, as our scheme has advantageous properties regarding the applicability of perturbation theory.
Su, Jun; Zhu, Long; Guo, Chenchen
2018-05-01
Background: Special attention has been paid to study the shell effect and odd-even staggering (OES) in the nuclear spallation. Purpose: In this paper, we investigate the influence of the nuclear level density on the OES in the 56Fe+p spallations at energies from 300 to 1500 MeV/nucleon. Method: The isospin-dependent quantum molecular dynamics (IQMD) model is applied to produce the highly excited and equilibrium remnants, which is then de-excited using the statistical model gemini. The excitation energy of the heaviest hot fragments is applied to match the IQMD model with the gemini model. In the gemini model, the statistical description of the evaporation are based on the Hauser-Feshbach formalism, in which level density prescriptions are applied. Results: By investigating the OES of the excited pre-fragments, it is found that the OES originates at the end of the decay process when the excitation energy is close to the nucleon-emission threshold energy, i.e., the smaller value of the neutron separation energy and proton separation energy. The strong influence of level density on the OES is noticed. Two types of the nuclear level densities, the discrepancy of which is only about 7% near the nucleon emission threshold energy, are used in the model. However, the calculated values of the OES differ by the factor of 3 for the relevant nuclei. Conclusions: It is suggested that, although the particle-separation energies play a key role in determining the OES, the level density at excitation energy lower than the particle-separation energies should be taken into consideration
Geometric scaling in ultrahigh energy neutrinos and nonlinear perturbative QCD
International Nuclear Information System (INIS)
Machado, Magno V.T.
2011-01-01
The ultrahigh energy neutrino cross section is a crucial ingredient in the calculation of the event rate in high energy neutrino telescopes. Currently there are several approaches which predict different behaviors for its magnitude for ultrahigh energies. In this contribution is presented a summary of current predictions based on the non-linear QCD evolution equations, the so-called perturbative saturation physics. In particular, predictions are shown based on the parton saturation approaches and the consequences of geometric scaling property at high energies are discussed. The scaling property allows an analytical computation of the neutrino scattering on nucleon/nucleus at high energies, providing a theoretical parameterization. (author)
Statistical mechanical perturbation theory of solid-vapor interfacial free energy
Kalikmanov, Vitalij Iosifovitsj; Hagmeijer, Rob; Venner, Cornelis H.
2017-01-01
The solid–vapor interfacial free energy γsv plays an important role in a number of physical phenomena, such as adsorption, wetting, and adhesion. We propose a closed form expression for the orientation averaged value of this quantity using a statistical mechanical perturbation approach developed in
Statistical Mechanical Perturbation Theory of Solid−Vapor Interfacial Free Energy
Kalikmanov, V.I.; Hagmeijer, R.; Venner, C.H.
2017-01-01
The solid–vapor interfacial free energy γsv plays an important role in a number of physical phenomena, such as adsorption, wetting, and adhesion. We propose a closed form expression for the orientation averaged value of this quantity using a statistical mechanical perturbation approach developed in
Low CMB quadrupole from dark energy isocurvature perturbations
International Nuclear Information System (INIS)
Gordon, Christopher; Hu, Wayne
2004-01-01
We explicate the origin of the temperature quadrupole in the adiabatic dark energy model and explore the mechanism by which scale invariant isocurvature dark energy perturbations can lead to its sharp suppression. The model requires anticorrelated curvature and isocurvature fluctuations and is favored by the Wilkinson Microwave Anisotropy Probe data at about the 95% confidence level in a flat scale invariant model. In an inflationary context, the anticorrelation may be established if the curvature fluctuations originate from a variable decay rate of the inflaton; such models however tend to overpredict gravitational waves. This isocurvature model can in the future be distinguished from alternatives involving a reduction in large scale power or modifications to the sound speed of the dark energy through the polarization and its cross correlation with the temperature. The isocurvature model retains the same polarization fluctuations as its adiabatic counterpart but reduces the correlated temperature fluctuations. We present a pedagogical discussion of dark energy fluctuations in a quintessence and k-essence context in the Appendix
Measuring the speed of dark: Detecting dark energy perturbations
International Nuclear Information System (INIS)
Putter, Roland de; Huterer, Dragan; Linder, Eric V.
2010-01-01
The nature of dark energy can be probed not only through its equation of state but also through its microphysics, characterized by the sound speed of perturbations to the dark energy density and pressure. As the sound speed drops below the speed of light, dark energy inhomogeneities increase, affecting both cosmic microwave background and matter power spectra. We show that current data can put no significant constraints on the value of the sound speed when dark energy is purely a recent phenomenon, but can begin to show more interesting results for early dark energy models. For example, the best fit model for current data has a slight preference for dynamics [w(a)≠-1], degrees of freedom distinct from quintessence (c s ≠1), and early presence of dark energy [Ω de (a<<1)≠0]. Future data may open a new window on dark energy by measuring its spatial as well as time variation.
International Nuclear Information System (INIS)
Dominguez, Fabio; Marquet, C.; Mueller, A.H.; Wu Bin; Xiao, Bo-Wen
2008-01-01
We compare medium induced energy loss and p perpendicular -broadening in perturbative QCD with that of the trailing string picture of SYM theory. We consider finite and infinite extent matter as well as relativistic heavy quarks which correspond to those being produced in the medium or external to it. When expressed in terms of the appropriate saturation momentum, we find identical parametric forms for energy loss in perturbative QCD and SYM theory. We find simple correspondences between p perpendicular -broadening in QCD and in SYM theory although p perpendicular -broadening is radiation dominated in SYM theory and multiple scattering dominated in perturbative QCD
Pivetal, Jeremy; Pereira, Filipa M; Barbosa, Ana I; Castanheira, Ana P; Reis, Nuno M; Edwards, Alexander D
2017-03-13
This study reports for the first time the sensitive colorimetric and fluorescence detection of clinically relevant protein biomarkers by sandwich immunoassays using the covalent immobilisation of antibodies onto the fluoropolymer surface inside Teflon®-FEP microfluidic devices. Teflon®-FEP has outstanding optical transparency ideal for high-sensitivity colorimetric and fluorescence bioassays, however this thermoplastic is regarded as chemically inert and very hydrophobic. Covalent immobilisation can offer benefits over passive adsorption to plastic surfaces by allowing better control over antibody density, orientation and analyte binding capacity, and so we tested a range of different and novel covalent immobilisation strategies. We first functionalised the inner surface of a 10-bore, 200 μm internal diameter FEP microcapillary film with high-molecular weight polyvinyl alcohol (PVOH) without changing the outstanding optical transparency of the device delivered by the matched refractive index of FEP and water. Glutaraldehyde immobilisation was compared with the use of photoactivated linkers and NHS-ester crosslinkers for covalently immobilising capture antibodies onto PVOH. Three clinically relevant sandwich ELISAs were tested against the cytokine IL-1β, the myocardial infarct marker cardiac troponin I (cTnI), and the chronic heart failure marker brain natriuretic peptide (BNP). Overall, glutaraldehyde immobilisation was effective for BNP assays, but yielded unacceptable background for IL-1β and cTnI assays caused by direct binding of the biotinylated detection antibody to the modified PVOH surface. We found NHS-ester groups reacted with APTES-treated PVOH coated fluoropolymers. This facilitated a novel method for capture antibody immobilisation onto fluoropolymer devices using a bifunctional NHS-maleimide crosslinker. The density of covalently immobilised capture antibodies achieved using PVOH/APTES/NHS/maleimide approached levels seen with passive adsorption
Low energy pion-pion phase shifts from chiral perturbation theory
International Nuclear Information System (INIS)
Borges, J. Sa; Barbosa, J. Soares; Oguri, V.
1997-01-01
The low energy pion-pion S- and P- experimental phase-shifts are fitted with chiral perturbation theory (Ch PT) amplitude. The low energy pion-pion S- and P- experimental phase-shifts. The parameters l 1 and l 2 of the one loop corrected amplitude are fixed and the corresponding values of the scattering lengths are calculated. We propose that the present method is the best way to fix Ch P T parameters. The unitarization program of current algebra is also discussed. (author)
Wafer-scale fabrication of glass-FEP-glass microfluidic devices for lipid bilayer experiments
Bomer, Johan G.; Prokofyev, A.V.; van den Berg, Albert; le Gac, Severine
2014-01-01
We report a wafer-scale fabrication process for the production of glass-FEP-glass microdevices using UV-curable adhesive (NOA81) as gluing material, which is applied using a novel "spin & roll" approach. Devices are characterized for the uniformity of the gluing layer, presence of glue in the
Bacalhau, Anna Paula; Pinto-Neto, Nelson; Vitenti, Sandro Dias Pinto
2018-04-01
We investigate cosmological scenarios containing one canonical scalar field with an exponential potential in the context of bouncing models, in which the bounce happens due to quantum cosmological effects. The only possible bouncing solutions in this scenario (discarding an infinitely fine-tuned exception) must have one and only one dark energy phase, occurring either in the contracting era or in the expanding era. Hence, these bounce solutions are necessarily asymmetric. Naturally, the more convenient solution is the one in which the dark energy phase happens in the expanding era, in order to be a possible explanation for the current accelerated expansion indicated by cosmological observations. In this case, one has the picture of a Universe undergoing a classical dust contraction from very large scales, the initial repeller of the model, moving to a classical stiff-matter contraction near the singularity, which is avoided due to the quantum bounce. The Universe is then launched to a dark energy era, after passing through radiation- and dust-dominated phases, finally returning to the dust expanding phase, the final attractor of the model. We calculate the spectral indices and amplitudes of scalar and tensor perturbations numerically, considering the whole history of the model, including the bounce phase itself, without making any approximation nor using any matching condition on the perturbations. As the background model is necessarily dust dominated in the far past, the usual adiabatic vacuum initial conditions can be easily imposed in this era. Hence, this is a cosmological model in which the presence of dark energy behavior in the Universe does not turn the usual vacuum initial conditions prescription for cosmological perturbation in bouncing models problematic. Scalar and tensor perturbations end up being almost scale invariant, as expected. The background parameters can be adjusted, without fine-tunings, to yield the observed amplitude for scalar
International Nuclear Information System (INIS)
Vieno, T.; Hautojaervi, A.; Raiko, H.; Ahonen, L.; Salo, J.P.
1994-12-01
Rock Engineering Systems (RES) is an approach to discover the important characteristics and interactions of a complex problem. Recently RES has been applied to identify features, events and processes (FEPs) for performance analysis of nuclear waste repositories. The RES methodology was applied to identify FEPs for the near-field analysis of the copper-steel canister for spent fuel disposal. The aims of the exercise were to learn and test the RES methodology and, secondly, to find out how much the results differ when RES is applied by two different groups on the same problem. A similar exercise was previously carried out by a SKB group. A total of 90 potentially significant FEPs were identified. The exercise showed that the RES methodology is a practicable tool to get a comprehensive and transparent picture of a complex problem. The approach is easy to learn and use. It reveals the important characteristics and interactions and organizes them in a format easy to understand. (9 refs., 5 figs., 3 tabs.)
Energy correlations in perturbative quantum chromodynamics: a conjecture for all orders
International Nuclear Information System (INIS)
Basham, C.L.; Brown, L.S.; Ellis, S.D.; Love, S.T.
1979-01-01
The hadronic energy produced in high-energy electron-positron annihilation has an angular correlation which can be computed by the asymptotically free perturbation theory of quantum chromodynamics. In finite orders, the correlation is not well behaved as the detectors become anti-collinear. The leading behaviour has been calculated to fourth order and an exponential expression for the sum of all orders is discussed. This expression obeys a non-trivial sum rule which lends support for its validity. (Auth.)
The effect of the initial exciton numbers on 54,56Fe(p, xp) Pre-Equilibrium Reactions
International Nuclear Information System (INIS)
Bölükdemir, M. H.; Tel, E.; Aydın, A.; Okuducu, S.; Kaplan, A.
2011-01-01
In pre-equilibrium nuclear reactions, the geometry-dependent hybrid model is applied with the use of the neutron and proton densities to investigate the effect of initial exciton numbers on the nucleon emission spectra. The initial exciton numbers calculated with the theoretical neutron and proton densities have been obtained within the Skryme-Hartree-Fock method with SKM* and SLy4 forces on target nuclei in the 54,56 Fe(p, xp) reaction at 61.5-MeV incident proton energy by using a new calculationmethod of Tel et al. Also, the differences between the initial exciton numbers for protons and neutrons as a function of nuclear radius, focusing on systematic discrepancies correlated to differences in the proton and neutron densities have been investigated.
Energy Technology Data Exchange (ETDEWEB)
Nho, Y -C; Shin, J; Sohn, J -Y; Fei, G [Radiation Research Division for Industry and Environment, Korea Atomic Energy Research Institute, 1266 Sinjeong-dong, Jeongeup-si, Jeollabuk-do 580-185 (Korea, Republic of)
2012-09-15
In this study, a novel polymer electrolyte membrane, poly(vinylbenzyl sulfonic acid)-grafted poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP-g-PVBSA), has been successfully prepared by simultaneous irradiation grafting of vinylbenzyl chloride(VBC) monomer onto a FEP film and taking subsequent chemical modification steps to modify the benzyl chloride moiety to the benzyl sulfonic acid moiety. The chemical reactions for the sulfonation were carried out via the formation of thiouronium salt with thiourea, base-catalyzed hydrolysis for the formation of thiol, and oxidation with hydrogen peroxide. Each chemical conversion process was confirmed by FTIR, elemental analysis, and SEM-EDX. A chemical stability study performed with Fenton's reagent (3% H{sub 2}O{sub 2} solution containing 4 ppm of Fe{sup 2+}) at 70 deg. C revealed that FEP-g-PVBSA has a higher chemical stability than the poly(styrene sulfonic acid)-grafted membranes (FEP-g-PSSA). An EDX analysis was also used to observe the cross-sectional distribution behaviors of the hydrophilic sulfonic acid groups and hydrophobic fluorine groups. The characteristics of an ion-exchange capacity (IEC), water and methanol uptake, methanol permeability, and proton conductivity as a function of the degree of grafting were also studied. The IECs and water uptakes of membranes with different degrees of grafting (36-102%) were measured to be in the range of 0.8-1.62 meq/g, and 10-30%, respectively. When the degree of grafting reached 60% the proton conductivity was higher than that of a Nafion (registered) 212 membrane (6.1E-02 S/cm). The methanol permeability and uptake of the FEP-g-PVBSA membrane was significantly lower than that of the Nafion (registered) 212 membrane, and even the degree of grafting reached 102%. (author)
2015-01-01
The reliability of free energy simulations (FES) is limited by two factors: (a) the need for correct sampling and (b) the accuracy of the computational method employed. Classical methods (e.g., force fields) are typically used for FES and present a myriad of challenges, with parametrization being a principle one. On the other hand, parameter-free quantum mechanical (QM) methods tend to be too computationally expensive for adequate sampling. One widely used approach is a combination of methods, where the free energy difference between the two end states is computed by, e.g., molecular mechanics (MM), and the end states are corrected by more accurate methods, such as QM or hybrid QM/MM techniques. Here we report two new approaches that significantly improve the aforementioned scheme; with a focus on how to compute corrections between, e.g., the MM and the more accurate QM calculations. First, a molecular dynamics trajectory that properly samples relevant conformational degrees of freedom is generated. Next, potential energies of each trajectory frame are generated with a QM or QM/MM Hamiltonian. Free energy differences are then calculated based on the QM or QM/MM energies using either a non-Boltzmann Bennett approach (QM-NBB) or non-Boltzmann free energy perturbation (NB-FEP). Both approaches are applied to calculate relative and absolute solvation free energies in explicit and implicit solvent environments. Solvation free energy differences (relative and absolute) between ethane and methanol in explicit solvent are used as the initial test case for QM-NBB. Next, implicit solvent methods are employed in conjunction with both QM-NBB and NB-FEP to compute absolute solvation free energies for 21 compounds. These compounds range from small molecules such as ethane and methanol to fairly large, flexible solutes, such as triacetyl glycerol. Several technical aspects were investigated. Ultimately some best practices are suggested for improving methods that seek to connect
Isaksen, Geir Villy; Andberg, Tor Arne Heim; Åqvist, Johan; Brandsdal, Bjørn Olav
2015-07-01
Structural information and activity data has increased rapidly for many protein targets during the last decades. In this paper, we present a high-throughput interface (Qgui) for automated free energy and empirical valence bond (EVB) calculations that use molecular dynamics (MD) simulations for conformational sampling. Applications to ligand binding using both the linear interaction energy (LIE) method and the free energy perturbation (FEP) technique are given using the estrogen receptor (ERα) as a model system. Examples of free energy profiles obtained using the EVB method for the rate-limiting step of the enzymatic reaction catalyzed by trypsin are also shown. In addition, we present calculation of high-precision Arrhenius plots to obtain the thermodynamic activation enthalpy and entropy with Qgui from running a large number of EVB simulations. Copyright © 2015 Elsevier Inc. All rights reserved.
Bistafa, Carlos; Kitamura, Yukichi; Martins-Costa, Marilia T C; Nagaoka, Masataka; Ruiz-López, Manuel F
2018-05-22
We describe a method to locate stationary points in the free-energy hypersurface of complex molecular systems using high-level correlated ab initio potentials. In this work, we assume a combined QM/MM description of the system although generalization to full ab initio potentials or other theoretical schemes is straightforward. The free-energy gradient (FEG) is obtained as the mean force acting on relevant nuclei using a dual level strategy. First, a statistical simulation is carried out using an appropriate, low-level quantum mechanical force-field. Free-energy perturbation (FEP) theory is then used to obtain the free-energy derivatives for the target, high-level quantum mechanical force-field. We show that this composite FEG-FEP approach is able to reproduce the results of a standard free-energy minimization procedure with high accuracy, while simultaneously allowing for a drastic reduction of both computational and wall-clock time. The method has been applied to study the structure of the water molecule in liquid water at the QCISD/aug-cc-pVTZ level of theory, using the sampling from QM/MM molecular dynamics simulations at the B3LYP/6-311+G(d,p) level. The obtained values for the geometrical parameters and for the dipole moment of the water molecule are within the experimental error, and they also display an excellent agreement when compared to other theoretical estimations. The developed methodology represents therefore an important step toward the accurate determination of the mechanism, kinetics, and thermodynamic properties of processes in solution, in enzymes, and in other disordered chemical systems using state-of-the-art ab initio potentials.
Yang, Li; Liu, Danni; Hao, Shuai; Qu, Fengli; Ge, Ruixiang; Ma, Yongjun; Du, Gu; Asiri, Abdullah M; Chen, Liang; Sun, Xuping
2017-02-21
Nanostructures possess distinct quenching ability toward fluorophores with different emission frequencies and have been intensively used as nanoquenchers for homogeneous nucleic acid detection. Complete understanding of such a sensing system will provide significant guidance for the design of superior sensing materials, which is still lacking. In this Letter, we demonstrate the development of FeP nanowires as a nanoquencher for high-performance fluorescent nucleic acid detection with much superior performance to α-Fe 2 O 3 counterparts. The whole detection process is complete within 1 min, and this fluorosensor presents a detection limit as low as 4 pM with strong discrimination of single-point mutation. Electrochemical tests and density functional theory calculations reveal that FeP NWs are superior in both conductivity for facilitated electron diffusion and hydrogen-evolving catalytic activity for favorable electron depletion, providing further experimental and theoretical insights into the enhanced sensing performance of the FeP nanosensor. Both faster electron transfer kinetics and stronger electron-consuming ability via catalyzed proton reduction enable FeP nanowires to be a superb nucleic acid nanosensor for applications.
Trottier, H. D.; Shakespeare, N. H.; Lepage, G. P.; MacKenzie, P. B.
2002-05-01
Perturbative coefficients for Wilson loops and the static-quark self-energy are extracted from Monte Carlo simulations at weak coupling. The lattice volumes and couplings are chosen to ensure that the lattice momenta are all perturbative. Twisted boundary conditions are used to eliminate the effects of lattice zero modes and to suppress nonperturbative finite-volume effects due to Z(3) phases. Simulations of the Wilson gluon action are done with both periodic and twisted boundary conditions, and over a wide range of lattice volumes (from 34 to 164) and couplings (from β~9 to β~60). A high precision comparison is made between the simulation data and results from finite-volume lattice perturbation theory. The Monte Carlo results are shown to be in excellent agreement with perturbation theory through second order. New results for third-order coefficients for a number of Wilson loops and the static-quark self-energy are reported.
Perturbations in electromagnetic dark energy
International Nuclear Information System (INIS)
Jiménez, Jose Beltrán; Maroto, Antonio L.; Koivisto, Tomi S.; Mota, David F.
2009-01-01
It has been recently proposed that the presence of a temporal electromagnetic field on cosmological scales could explain the phase of accelerated expansion that the universe is currently undergoing. The field contributes as a cosmological constant and therefore, the homogeneous cosmology produced by such a model is exactly the same as that of ΛCDM. However, unlike a cosmological constant term, electromagnetic fields can acquire perturbations which in principle could affect CMB anisotropies and structure formation. In this work, we study the evolution of inhomogeneous scalar perturbations in this model. We show that provided the initial electromagnetic fluctuations generated during inflation are small, the model is perfectly compatible with both CMB and large scale structure observations at the same level of accuracy as ΛCDM
Base case and perturbation scenarios
Energy Technology Data Exchange (ETDEWEB)
Edmunds, T
1998-10-01
This report describes fourteen energy factors that could affect electricity markets in the future (demand, process, source mix, etc.). These fourteen factors are believed to have the most influence on the State's energy environment. A base case, or most probable, characterization is given for each of these fourteen factors over a twenty year time horizon. The base case characterization is derived from quantitative and qualitative information provided by State of California government agencies, where possible. Federal government databases are nsed where needed to supplement the California data. It is envisioned that a initial selection of issue areas will be based upon an evaluation of them under base case conditions. For most of the fourteen factors, the report identities possible perturbations from base case values or assumptions that may be used to construct additional scenarios. Only those perturbations that are plausible and would have a significant effect on energy markets are included in the table. The fourteen factors and potential perturbations of the factors are listed in Table 1.1. These perturbations can be combined to generate internally consist.ent. combinations of perturbations relative to the base case. For example, a low natural gas price perturbation should be combined with a high natural gas demand perturbation. The factor perturbations are based upon alternative quantitative forecasts provided by other institutions (the Department of Energy - Energy Information Administration in some cases), changes in assumptions that drive the quantitative forecasts, or changes in assumptions about the structure of the California energy markets. The perturbations are intended to be used for a qualitative reexamination of issue areas after an initial evaluation under the base case. The perturbation information would be used as a "tiebreaker;" to make decisions regarding those issue areas that were marginally accepted or rejected under the base case. Hf a
Disformal transformation of cosmological perturbations
Directory of Open Access Journals (Sweden)
Masato Minamitsuji
2014-10-01
Full Text Available We investigate the gauge-invariant cosmological perturbations in the gravity and matter frames in the general scalar–tensor theory where two frames are related by the disformal transformation. The gravity and matter frames are the extensions of the Einstein and Jordan frames in the scalar–tensor theory where two frames are related by the conformal transformation, respectively. First, it is shown that the curvature perturbation in the comoving gauge to the scalar field is disformally invariant as well as conformally invariant, which gives the predictions from the cosmological model where the scalar field is responsible both for inflation and cosmological perturbations. Second, in case that the disformally coupled matter sector also contributes to curvature perturbations, we derive the evolution equations of the curvature perturbation in the uniform matter energy density gauge from the energy (nonconservation in the matter sector, which are independent of the choice of the gravity sector. While in the matter frame the curvature perturbation in the uniform matter energy density gauge is conserved on superhorizon scales for the vanishing nonadiabatic pressure, in the gravity frame it is not conserved even if the nonadiabatic pressure vanishes. The formula relating two frames gives the amplitude of the curvature perturbation in the matter frame, once it is evaluated in the gravity frame.
Disformal transformation of cosmological perturbations
International Nuclear Information System (INIS)
Minamitsuji, Masato
2014-01-01
We investigate the gauge-invariant cosmological perturbations in the gravity and matter frames in the general scalar–tensor theory where two frames are related by the disformal transformation. The gravity and matter frames are the extensions of the Einstein and Jordan frames in the scalar–tensor theory where two frames are related by the conformal transformation, respectively. First, it is shown that the curvature perturbation in the comoving gauge to the scalar field is disformally invariant as well as conformally invariant, which gives the predictions from the cosmological model where the scalar field is responsible both for inflation and cosmological perturbations. Second, in case that the disformally coupled matter sector also contributes to curvature perturbations, we derive the evolution equations of the curvature perturbation in the uniform matter energy density gauge from the energy (non)conservation in the matter sector, which are independent of the choice of the gravity sector. While in the matter frame the curvature perturbation in the uniform matter energy density gauge is conserved on superhorizon scales for the vanishing nonadiabatic pressure, in the gravity frame it is not conserved even if the nonadiabatic pressure vanishes. The formula relating two frames gives the amplitude of the curvature perturbation in the matter frame, once it is evaluated in the gravity frame
Wafer-scale fabrication of glass-FEP-glass microfluidic devices for lipid bilayer experiments.
Bomer, Johan G; Prokofyev, Alexander V; van den Berg, Albert; Le Gac, Séverine
2014-12-07
We report a wafer-scale fabrication process for the production of glass-FEP-glass microdevices using UV-curable adhesive (NOA81) as gluing material, which is applied using a novel "spin & roll" approach. Devices are characterized for the uniformity of the gluing layer, presence of glue in the microchannels, and alignment precision. Experiments on lipid bilayers with electrophysiological recordings using a model pore-forming polypeptide are demonstrated.
International Nuclear Information System (INIS)
Trottier, H.D.; Shakespeare, N.H.; Lepage, G.P.; Mackenzie, P.B.
2002-01-01
Perturbative coefficients for Wilson loops and the static-quark self-energy are extracted from Monte Carlo simulations at weak coupling. The lattice volumes and couplings are chosen to ensure that the lattice momenta are all perturbative. Twisted boundary conditions are used to eliminate the effects of lattice zero modes and to suppress nonperturbative finite-volume effects due to Z(3) phases. Simulations of the Wilson gluon action are done with both periodic and twisted boundary conditions, and over a wide range of lattice volumes (from 3 4 to 16 4 ) and couplings (from β≅9 to β≅60). A high precision comparison is made between the simulation data and results from finite-volume lattice perturbation theory. The Monte Carlo results are shown to be in excellent agreement with perturbation theory through second order. New results for third-order coefficients for a number of Wilson loops and the static-quark self-energy are reported
/sup 54/Fe(p vector,d)/sup 53/Fe and /sup 140/Ce(p vector,d)/sup 139/Ce reactions at 122 MeV
Energy Technology Data Exchange (ETDEWEB)
Dickey, S A; Kraushaar, J J; Shepard, J R [Colorado Univ., Boulder (USA). Nuclear Physics Lab.; Miller, D W; Jacobs, W W; Jones, W P [Indiana Univ., Bloomington (USA). Dept. of Physics
1985-08-05
The /sup 54/Fe(p vector,d)/sup 53/Fe and /sup 140/Ce(p vector,d)/sup 139/Ce reactions have been studied at a proton energy of 122 MeV. Analyzing powers and angular distributions were obtained for outgoing deuterons to the strong low-lying single-particle states in both nuclei. These data along with the data of others at 26, 29, 41, 52 and 24, 35, 55 MeV for /sup 54/Fe and /sup 140/Ce respectively, have been compared with exact-finite-range DWBA calculations carried out in a consistent fashion to determine the energy dependence of the spectroscopic factors. A strong energy dependence was noticed for the spectroscopic factors when the l-values were large.
Energy Technology Data Exchange (ETDEWEB)
Boehmer, M.
2006-09-25
In this work the spallation reaction {sup 56}Fe+p was investigated in inverse kinematics with regard to complete identification of the heavy residues. A ring imaging Cerenkov counter was used for velocity measurements in the experimental setup located at GSI in Darmstadt. A new fast readout electronic was developed and has been operated successfully in the experiment. Momentum reconstruction was carried out with the ALADiN spectrometer and a new software package written for this purpose. Cross sections and velocity distributions for more than 100 mass separated isotopes could be extracted from the dataset and compared with empirical models and other spallation experiments. The experiences gained in this experiment will be used for systematic improvements in the setup of the new spectrometer R3B at FAIR. (orig.)
Symmetry-adapted perturbation theory interaction energy decomposition for some noble gas complexes
Cukras, Janusz; Sadlej, Joanna
2008-06-01
This Letter contains a study of the interaction energy in HArF⋯N 2 and HArF⋯P 2 complexes. Symmetry-adapted perturbation theory (SAPT) has been applied to analyze the electrostatic, induction, dispersion and exchange contributions to the total interaction energy. The interaction energy has also been obtained by supermolecular method at the MP2, MP4, CCSD, CCSD(T) levels. The interaction energy for the studied complexes results from a partial cancelation of large attractive electrostatic, induction, dispersion terms by a strong repulsive exchange contribution. The induction and dispersion effects proved to be crucial in establishing the preference for the colinear HArF⋯N 2 and HArF⋯P 2 structures and shift direction of νHAr stretching vibrations.
Stochastic evaluation of second-order many-body perturbation energies.
Willow, Soohaeng Yoo; Kim, Kwang S; Hirata, So
2012-11-28
With the aid of the Laplace transform, the canonical expression of the second-order many-body perturbation correction to an electronic energy is converted into the sum of two 13-dimensional integrals, the 12-dimensional parts of which are evaluated by Monte Carlo integration. Weight functions are identified that are analytically normalizable, are finite and non-negative everywhere, and share the same singularities as the integrands. They thus generate appropriate distributions of four-electron walkers via the Metropolis algorithm, yielding correlation energies of small molecules within a few mE(h) of the correct values after 10(8) Monte Carlo steps. This algorithm does away with the integral transformation as the hotspot of the usual algorithms, has a far superior size dependence of cost, does not suffer from the sign problem of some quantum Monte Carlo methods, and potentially easily parallelizable and extensible to other more complex electron-correlation theories.
Energy Technology Data Exchange (ETDEWEB)
Herbert, John M. [Kansas State Univ., Manhattan, KS (United States). Dept. of Chemistry
1997-01-01
Rayleigh-Schroedinger perturbation theory is an effective and popular tool for describing low-lying vibrational and rotational states of molecules. This method, in conjunction with ab initio techniques for computation of electronic potential energy surfaces, can be used to calculate first-principles molecular vibrational-rotational energies to successive orders of approximation. Because of mathematical complexities, however, such perturbation calculations are rarely extended beyond the second order of approximation, although recent work by Herbert has provided a formula for the nth-order energy correction. This report extends that work and furnishes the remaining theoretical details (including a general formula for the Rayleigh-Schroedinger expansion coefficients) necessary for calculation of energy corrections to arbitrary order. The commercial computer algebra software Mathematica is employed to perform the prohibitively tedious symbolic manipulations necessary for derivation of generalized energy formulae in terms of universal constants, molecular constants, and quantum numbers. As a pedagogical example, a Hamiltonian operator tailored specifically to diatomic molecules is derived, and the perturbation formulae obtained from this Hamiltonian are evaluated for a number of such molecules. This work provides a foundation for future analyses of polyatomic molecules, since it demonstrates that arbitrary-order perturbation theory can successfully be applied with the aid of commercially available computer algebra software.
Within-day energy deficiency and metabolic perturbation in male endurance athletes
DEFF Research Database (Denmark)
Torstveit, Monica K; Fahrenholtz, Ida Lysdahl; Stenqvist, Thomas B
2018-01-01
) or normal RMR (RMRratio> 0.90, n=11). Despite no observed differences in 24-hour EB or EA between the groups, subjects with suppressed RMR spent more time in an energy deficit exceeding 400 kcal (20.9 [18.8 - 21.8] hours vs. 10.8 [2.5 - 16.4], P=0.023), and had larger single-hour energy deficits compared......Endurance athletes are at increased risk of relative energy deficiency associated with metabolic perturbation and impaired health. We aimed to estimate and compare within-day energy balance (WDEB) in male athletes with suppressed and normal resting metabolic rate (RMR) and explore if within...... to subjects with normal RMR (3265 ± 1963 kcal vs. -1340 ± 2439, P=0.023). Larger single-hour energy deficits were associated with higher cortisol levels (r = -0.499, P=0.004) and a lower testosterone:cortisol ratio (r = 0.431, P=0.015), but no associations with T3or fasting blood glucose were observed...
Kerr-CFT and gravitational perturbations
International Nuclear Information System (INIS)
Dias, Oscar J.C.; Reall, Harvey S.; Santos, Jorge E.
2009-01-01
Motivated by the Kerr-CFT conjecture, we investigate perturbations of the near-horizon extreme Kerr spacetime. The Teukolsky equation for a massless field of arbitrary spin is solved. Solutions fall into two classes: normal modes and traveling waves. Imposing suitable (outgoing) boundary conditions, we find that there are no unstable modes. The explicit form of metric perturbations is obtained using the Hertz potential formalism, and compared with the Kerr-CFT boundary conditions. The energy and angular momentum associated with scalar field and gravitational normal modes are calculated. The energy is positive in all cases. The behaviour of second order perturbations is discussed.
Third-Order Density Perturbation and One-Loop Power Spectrum in Dark-Energy-Dominated Universe
Takahashi, Ryuichi
2008-01-01
We investigate the third-order density perturbation and the one-loop correction to the linear power spectrum in the dark-energy cosmological model. Our main interest is to understand the dark-energy effect on baryon acoustic oscillations in a quasi-nonlinear regime ($k \\approx 0.1h$/Mpc). Analytical solutions and simple fitting formulae are presented for the dark-energy model with the general time-varying equation of state $w(a)$. It turns out that the power spectrum coincides with the approx...
Fox, Stephen J; Pittock, Chris; Tautermann, Christofer S; Fox, Thomas; Christ, Clara; Malcolm, N O J; Essex, Jonathan W; Skylaris, Chris-Kriton
2013-08-15
Schemes of increasing sophistication for obtaining free energies of binding have been developed over the years, where configurational sampling is used to include the all-important entropic contributions to the free energies. However, the quality of the results will also depend on the accuracy with which the intermolecular interactions are computed at each molecular configuration. In this context, the energy change associated with the rearrangement of electrons (electronic polarization and charge transfer) upon binding is a very important effect. Classical molecular mechanics force fields do not take this effect into account explicitly, and polarizable force fields and semiempirical quantum or hybrid quantum-classical (QM/MM) calculations are increasingly employed (at higher computational cost) to compute intermolecular interactions in free-energy schemes. In this work, we investigate the use of large-scale quantum mechanical calculations from first-principles as a way of fully taking into account electronic effects in free-energy calculations. We employ a one-step free-energy perturbation (FEP) scheme from a molecular mechanical (MM) potential to a quantum mechanical (QM) potential as a correction to thermodynamic integration calculations within the MM potential. We use this approach to calculate relative free energies of hydration of small aromatic molecules. Our quantum calculations are performed on multiple configurations from classical molecular dynamics simulations. The quantum energy of each configuration is obtained from density functional theory calculations with a near-complete psinc basis set on over 600 atoms using the ONETEP program.
Block diagrams and the cancellation of divergencies in energy-level perturbation theory
International Nuclear Information System (INIS)
Michels, M.A.J.; Suttorp, L.G.
1979-01-01
The effective Hamiltonian for the degenerate energy-eigenvalue problem in adiabatic perturbation theory is cast in a form that permits an expansion in Feynman diagrams. By means of a block representation a resummation of these diagrams is carried out such that in the adiabatic limit no divergencies are encountered. The resummed form of the effective Hamiltonian is used to establish a connexion with the S matrix. (Auth.)
Directory of Open Access Journals (Sweden)
Sri Utami
2017-02-01
Full Text Available Energi yang dihasilkan oleh sel surya sangat bervariasi dan sangat tergantung pada kondisi cuaca. Untuk mengoptimasinya digunakan maximum power point. Penelitian ini mengimplementasikan algoritma Perturb and Observe pada Maximum Power Point Tracker (MPPT sebagai kontroller untuk pembangkitan energi surya. Sistem dibangun menggunakan Arduino Uno R3 untuk mengekstraksi daya maksimum panel surya. Microcontroller ini mengontrol DC buck converter dan digunakan untuk charging baterai 6V. Metode ini beroperasi dengan memberi perturbing tegangan atau arus terminal array dan membandingkan daya yang dihasilkan dengan output panel surya. Diperlukan perturbing yang sesuai untuk mendapatkan nilai optimasi yang tepat. Validasi dari panel surya menggunakan metode yang diusulkan pada MPPT-nya memberikan performansi yang lebih baik dibuktikan pada nilai daya dan tegangannya. Menggunakan parameter perturbation 0.1, MPPT mampu mengoptimasi daya ouput panel surya sebesar 24.49 W dengan beban 5 ? dan nilai irradiasi 523 W/m2 dibandingkan dengan metode konvensional dengan beban sama dan nilai irradiasi sebesar 527 W/m2 yang menghasilkan daya keluaran 15.37 W
International Nuclear Information System (INIS)
McKay, M.K.; Skinner, N.L.; Wood, S.T.
1994-07-01
The Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) refers to a set of several microcomputer programs that were developed to create and analyze probabilistic risk assessments (PRAs), primarily for nuclear power plants. The Fault Tree, Event Tree, and Piping and Instrumentation Diagram (FEP) editors allow the user to graphically build and edit fault trees, and event trees, and piping and instrumentation diagrams (P and IDs). The software is designed to enable the independent use of the graphical-based editors found in the Integrated Reliability and Risk Assessment System (IRRAS). FEP is comprised of three separate editors (Fault Tree, Event Tree, and Piping and Instrumentation Diagram) and a utility module. This reference manual provides a screen-by-screen guide of the entire FEP System
Relative binding affinity prediction of farnesoid X receptor in the D3R Grand Challenge 2 using FEP+
Schindler, Christina; Rippmann, Friedrich; Kuhn, Daniel
2018-01-01
Physics-based free energy simulations have increasingly become an important tool for predicting binding affinity and the recent introduction of automated protocols has also paved the way towards a more widespread use in the pharmaceutical industry. The D3R 2016 Grand Challenge 2 provided an opportunity to blindly test the commercial free energy calculation protocol FEP+ and assess its performance relative to other affinity prediction methods. The present D3R free energy prediction challenge was built around two experimental data sets involving inhibitors of farnesoid X receptor (FXR) which is a promising anticancer drug target. The FXR binding site is predominantly hydrophobic with few conserved interaction motifs and strong induced fit effects making it a challenging target for molecular modeling and drug design. For both data sets, we achieved reasonable prediction accuracy (RMSD ≈ 1.4 kcal/mol, rank 3-4 according to RMSD out of 20 submissions) comparable to that of state-of-the-art methods in the field. Our D3R results boosted our confidence in the method and strengthen our desire to expand its applications in future in-house drug design projects.
Relative binding affinity prediction of farnesoid X receptor in the D3R Grand Challenge 2 using FEP.
Schindler, Christina; Rippmann, Friedrich; Kuhn, Daniel
2018-01-01
Physics-based free energy simulations have increasingly become an important tool for predicting binding affinity and the recent introduction of automated protocols has also paved the way towards a more widespread use in the pharmaceutical industry. The D3R 2016 Grand Challenge 2 provided an opportunity to blindly test the commercial free energy calculation protocol FEP+ and assess its performance relative to other affinity prediction methods. The present D3R free energy prediction challenge was built around two experimental data sets involving inhibitors of farnesoid X receptor (FXR) which is a promising anticancer drug target. The FXR binding site is predominantly hydrophobic with few conserved interaction motifs and strong induced fit effects making it a challenging target for molecular modeling and drug design. For both data sets, we achieved reasonable prediction accuracy (RMSD ≈ 1.4 kcal/mol, rank 3-4 according to RMSD out of 20 submissions) comparable to that of state-of-the-art methods in the field. Our D3R results boosted our confidence in the method and strengthen our desire to expand its applications in future in-house drug design projects.
Energy Technology Data Exchange (ETDEWEB)
Moenig, Joerg; Beuth, Thomas; Wolf, Jens [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Theodor-Heuss-Str. 4, D-38122 Braunschweig (Germany); Lommerzheim, Andre [DBE TECHNOLOGY GmbH, Eschenstr. 55, D-31224 Peine (Germany); Mrugalla, Sabine [Federal Institute for Geosciences and Natural Resources (BGR), Stilleweg 2, D-30655 Hannover (Germany)
2013-07-01
Based upon the German safety criteria, released in 2010 by the Federal Ministry of the Environment (BMU), a safety concept and a safety assessment concept for the disposal of heat-generating high-level waste have both been developed in the framework of the preliminary safety case for the Gorleben site (Project VSG). The main objective of the disposal is to contain the radioactive waste inside a defined rock zone, which is called containment-providing rock zone. The radionuclides shall remain essentially at the emplacement site, and at the most, a small defined quantity of material shall be able to leave this rock zone. This shall be accomplished by the geological barrier and a technical barrier system, which is required to seal the inevitable penetration of the geological barrier by the construction of the mine. The safe containment has to be demonstrated for probable and less probable evolutions of the site, while evolutions with very low probability (less than 1 % over the demonstration period of 1 million years) need not to be considered. Owing to the uncertainty in predicting the real evolution of the site, plausible scenarios have been derived in a systematic manner. Therefore, a comprehensive site-specific features, events and processes (FEP) data base for the Gorleben site has been developed. The safety concept was directly taken into account, e.g. by identification of FEP with direct influence on the barriers that provide the containment. No effort was spared to identify the interactions of the FEP, their probabilities of occurrence, and their characteristics (values). The information stored in the data base provided the basis for the development of scenarios. The scenario development methodology is based on FEP related to an impairment of the functionality of a subset of barriers, called initial barriers. By taking these FEP into account in their probable characteristics the reference scenario is derived. Thus, the reference scenario describes a
Targeted Energy Transfer Phenomena in Vibro-Impact Oscillators
International Nuclear Information System (INIS)
Lee, Young S.; McFarland, D. Michael; Bergman, Lawrence A.; Nucera, Francesco; Vakakis, Alexander F.
2008-01-01
We study targeted energy transfer (TET) in a coupled oscillator, consisting of a single-degree-of-freedom primary linear oscillator coupled to a vibro-impact nonlinear energy sink (VI NES). For this purpose, we first compute the VI periodic orbits of the underlying hamiltonian VI system, and construct the corresponding frequency-energy plot (FEP). Then, considering inelastic impacts and viscous dissipation, we examine VI damped transitions on the FEP to identify a TET phenomenon by exciting a VI impulsive orbit, which is the most efficient mechanism for TET. Not only can the VI TET involve passive absorption and local dissipation of significant portions of the energy from the primary systems, but it occurs at sufficiently fast time scales. This renders VI NESs suitable for applications, like seismic mitigation, where shock elimination in the early, highly energetic regime of the motion is a critical requirement
Z-1 perturbation theory applied to the correlation energy problem of atoms
International Nuclear Information System (INIS)
Robinson, B.H.
1975-01-01
Rayleigh--Schroedinger Perturbation Theory is applied to obtain directly exact and explicit analytic formulas for the electron correlation energies of N electron systems in terms of their pairwise interactions through second order in Z -1 , where Z is the nucleus of the atom. It is demonstrated that the second order correlation energy may be expressed as exactly the sum of pairwise correlation energies. In the case of no zeroth order degeneracy, the zeroth and first order terms vanish. The expression for the pairwise energies is an infinite sum, all terms of which are of the same sign. There is no numerical differencing. In the case of zeroth order degeneracy it is shown that the above statement concerning the second order energy still holds, but the expressions are a bit more complicated. It is shown that they ''almost'' reduce to a much simpler form. Also, the computation of the first order correlation energy is considered
Scalar cosmological perturbations
International Nuclear Information System (INIS)
Uggla, Claes; Wainwright, John
2012-01-01
Scalar perturbations of Friedmann-Lemaitre cosmologies can be analyzed in a variety of ways using Einstein's field equations, the Ricci and Bianchi identities, or the conservation equations for the stress-energy tensor, and possibly introducing a timelike reference congruence. The common ground is the use of gauge invariants derived from the metric tensor, the stress-energy tensor, or from vectors associated with a reference congruence, as basic variables. Although there is a complication in that there is no unique choice of gauge invariants, we will show that this can be used to advantage. With this in mind our first goal is to present an efficient way of constructing dimensionless gauge invariants associated with the tensors that are involved, and of determining their inter-relationships. Our second goal is to give a unified treatment of the various ways of writing the governing equations in dimensionless form using gauge-invariant variables, showing how simplicity can be achieved by a suitable choice of variables and normalization factors. Our third goal is to elucidate the connection between the metric-based approach and the so-called 1 + 3 gauge-invariant approach to cosmological perturbations. We restrict our considerations to linear perturbations, but our intent is to set the stage for the extension to second-order perturbations. (paper)
CERN. Geneva
2013-01-01
Perturbative QCD is the general theoretical framework for describing hard scattering processes yielding multiparticle production at hadron colliders. In these lectures, we shall introduce fundamental features of perturbative QCD and describe its application to several high energy collider processes, including jet production in electron-positron annihilation, deep inelastic scattering, Higgs boson and gauge boson production at the LHC.
International Nuclear Information System (INIS)
Mohamed Mahmoud Nasef; Hamdani Saidi; Hussin Mohd Nor
1999-01-01
Radiation grafted and sulfonated FEP membranes were prepared by radiation-induced grafting of styrene onto poly(tetrafluoroethylene-co-hexafluoropropylene) films at room temperature and subsequently sulfonated. The membrane composition was controlled via variation of the grafting conditions such as type of diluent, irradiation dose, dose rate and monomer concentration. The membrane properties such as water uptake, ion exchange capacity and ionic conductivity were found to be strongly dependent upon the degree of grafting. The membranes were shown to have a good combination of physico-chemical properties, which made them promising for development of low cost proton exchange membranes
International Nuclear Information System (INIS)
Ecker, G.
1996-06-01
After a general introduction to the structure of effective field theories, the main ingredients of chiral perturbation theory are reviewed. Applications include the light quark mass ratios and pion-pion scattering to two-loop accuracy. In the pion-nucleon system, the linear σ model is contrasted with chiral perturbation theory. The heavy-nucleon expansion is used to construct the effective pion-nucleon Lagrangian to third order in the low-energy expansion, with applications to nucleon Compton scattering. (author)
Preparation of membranes by radiation grafting of acrylic acid onto Teflon-FEP film
International Nuclear Information System (INIS)
Gupta, B.D.
1991-01-01
The grafting of acrylic acid on radiation-peroxidised Teflon-FEP film provides an effective technique to prepare ion-exchange membranes. It was found that the grafted membranes have very high degree of swelling in aqueous KOH. The electric resistance of the film decreases considerably by grafting. An electric resistance of 0.2Ω cm 2 was obtained for a graft level beyond 58%. The hydrophilicity of the film was evaluated in terms of contact angle which shows a decreasing trend with the increasing degree of grafting. (author). 8 refs
Effect of perturbation of convective energy transport on the luminosity and radius of the sun
International Nuclear Information System (INIS)
Endal, A.S.; Twigg, L.W.
1982-01-01
The response of solar models to perturbations of the efficiency of convective energy transport is studied for a number of cases. Such perturbations primarily affect the shallow superadiabatic layer of the convective envelope (at depths 3 km below the photosphere). Independent of the details of the perturbation scheme, the resulting change in the solar radius (ΔR/R) is always very small compared to the change in luminosity (ΔL/L). This appears to be true for any physical mechanism of solar variability which operates in the outer layers of the convection zone. Changes of the solar radius have been inferred by Dunham et al. from historical observations of solar eclipses in 1715 and 1925. Considering the constraints on concurrent luminosity changes, this type of solar variability must be indicative of changes in the solar structure at substantial depths below the superadiabatic layer of the convective envelope
Transport of energetic ions by low-n magnetic perturbations
International Nuclear Information System (INIS)
Mynick, H.E.
1992-10-01
The stochastic transport of MeV ions induced by low-n magnetic perturbations is studied, focussing chiefly on the stochastic mechanism operative for passing particles in low frequency perturbations. Beginning with a single-harmonic form for the perturbing field, it iii first shown numerically and analytically that the stochastic threshold of energetic particles can be much lower than that of the magnetic field, contrary to earlier expectations, so that MHD perturbations could cause appreciable loss of energetic ions without destroying the bulk confinement. The analytic theory is then extended in a number of directions, to darity the relation of the present stochaistic mechanism to instances already found, to allow for more complex perturbations, and to consider the more general relationship between the stochasticity of magnetic fields, and that of particles of differing energies (and pitch angles) moving in those fields. It is shown that the stochastic threshold is in general a nonmonotonic function of energy, whose form can to some extent be tailored to achieve desired goals (e.g., burn control or ash removal) by a judicious choice of the perturbation. Illustrative perturbations are exhibited which are stochastic for low but not for high-energy ions, for high but not for low-energy ions, and for intermediate-energy ions, but not for low or high energy. The second possibility is the behavior needed for burn control; the third provides a possible mechanism for ash removal
Project SFR 1 SAR-08. Update of priority of FEPs from Project SAFE
International Nuclear Information System (INIS)
Gordon, Anna; Loefgren, Martin; Lindgren, Maria
2008-03-01
SFR 1 is a repository for final disposal of low and intermediate level radioactive waste produced at Swedish nuclear power plants, as well as at Swedish industrial, research, and medical treatment facilities. The repository obtained operational license in March 1988. The aim of Project SFR 1 SAR-08 is to perform an updated safety analysis, according to requirements in the regulations. A major difference between this and previous safety analyses is that repository safety should be demonstrated for 100,000 years after repository closure. This should be compared with the time frame of the safety assessment in Project SAFE that was 10,000 years. Due to the extended time frame, permafrost and glaciation have to be considered in the reference evolution of Project SFR 1 SAR-08. Other rationales for the update are recent input from the authorities concerning SAFE documents and the SFR 1 repository, as well as new data concerning the SFR 1 inventory. This report describes the outcome of revisiting the qualitative FEP (Features, Events and Processes) analysis carried out within Project SAFE for the SFR 1 repository. Each and every interaction definition, as defined in SAFE, has been examined with the aim at assuring that the SAFE interaction matrices are also applicable for SAR-08. It was found that this is generally the case, but seven new interactions were defined in order to make the interaction matrices more applicable for SAR-08. The priority of all interactions assigned priority 1 and many interactions assigned priority 2 in SAFE have been carefully examined. The examination has been made in the context of the general initial and boundary conditions that should also form the basis for the SAR-08 main scenario and less probable scenarios. In 48 cases, the priority of the interaction needed upgrading, compared to in SAFE. In a majority of these cases, the upgrade is due to the extended time frame of the safety assessment, from 10,000 years in SAFE to 100,000 years in SAR
Project SFR 1 SAR-08. Update of priority of FEPs from Project SAFE
Energy Technology Data Exchange (ETDEWEB)
Gordon, Anna (Swedish Nuclear Fuel and Waste Management Co., Stockholm (SE)); Loefgren, Martin; Lindgren, Maria (Kemakta Konsult AB, Stockholm (SE)) (eds.)
2008-03-15
SFR 1 is a repository for final disposal of low and intermediate level radioactive waste produced at Swedish nuclear power plants, as well as at Swedish industrial, research, and medical treatment facilities. The repository obtained operational license in March 1988. The aim of Project SFR 1 SAR-08 is to perform an updated safety analysis, according to requirements in the regulations. A major difference between this and previous safety analyses is that repository safety should be demonstrated for 100,000 years after repository closure. This should be compared with the time frame of the safety assessment in Project SAFE that was 10,000 years. Due to the extended time frame, permafrost and glaciation have to be considered in the reference evolution of Project SFR 1 SAR-08. Other rationales for the update are recent input from the authorities concerning SAFE documents and the SFR 1 repository, as well as new data concerning the SFR 1 inventory. This report describes the outcome of revisiting the qualitative FEP (Features, Events and Processes) analysis carried out within Project SAFE for the SFR 1 repository. Each and every interaction definition, as defined in SAFE, has been examined with the aim at assuring that the SAFE interaction matrices are also applicable for SAR-08. It was found that this is generally the case, but seven new interactions were defined in order to make the interaction matrices more applicable for SAR-08. The priority of all interactions assigned priority 1 and many interactions assigned priority 2 in SAFE have been carefully examined. The examination has been made in the context of the general initial and boundary conditions that should also form the basis for the SAR-08 main scenario and less probable scenarios. In 48 cases, the priority of the interaction needed upgrading, compared to in SAFE. In a majority of these cases, the upgrade is due to the extended time frame of the safety assessment, from 10,000 years in SAFE to 100,000 years in SAR
Project SFR 1 SAR-08. Update of priority of FEPs from Project SAFE
Energy Technology Data Exchange (ETDEWEB)
Gordon, Anna [Swedish Nuclear Fuel and Waste Management Co., Stockholm (SE); Loefgren, Martin; Lindgren, Maria [Kemakta Konsult AB, Stockholm (SE); eds.
2008-03-15
SFR 1 is a repository for final disposal of low and intermediate level radioactive waste produced at Swedish nuclear power plants, as well as at Swedish industrial, research, and medical treatment facilities. The repository obtained operational license in March 1988. The aim of Project SFR 1 SAR-08 is to perform an updated safety analysis, according to requirements in the regulations. A major difference between this and previous safety analyses is that repository safety should be demonstrated for 100,000 years after repository closure. This should be compared with the time frame of the safety assessment in Project SAFE that was 10,000 years. Due to the extended time frame, permafrost and glaciation have to be considered in the reference evolution of Project SFR 1 SAR-08. Other rationales for the update are recent input from the authorities concerning SAFE documents and the SFR 1 repository, as well as new data concerning the SFR 1 inventory. This report describes the outcome of revisiting the qualitative FEP (Features, Events and Processes) analysis carried out within Project SAFE for the SFR 1 repository. Each and every interaction definition, as defined in SAFE, has been examined with the aim at assuring that the SAFE interaction matrices are also applicable for SAR-08. It was found that this is generally the case, but seven new interactions were defined in order to make the interaction matrices more applicable for SAR-08. The priority of all interactions assigned priority 1 and many interactions assigned priority 2 in SAFE have been carefully examined. The examination has been made in the context of the general initial and boundary conditions that should also form the basis for the SAR-08 main scenario and less probable scenarios. In 48 cases, the priority of the interaction needed upgrading, compared to in SAFE. In a majority of these cases, the upgrade is due to the extended time frame of the safety assessment, from 10,000 years in SAFE to 100,000 years in SAR
International Nuclear Information System (INIS)
Caswell, W.E.
1979-01-01
We introduce a generalization of Wick-ordering which maps the anharmonic oscillator (AO) Hamiltonian for mass m and coupling lambda exactly into a ''Wick-ordered'' Hamiltonian with an effective mass M which is a simple analytic function of lambda and m. The effective coupling Λ=lambda/M 3 is bounded. We transform the AO perturbation series in lambda into one in Λ. This series may then be summed using Borel summation methods. We also introduce a new summation method for the AO series (which is a practical necessity to obtain accurate energy levels of the excited states). We obtain a numerical accuracy for (E/sub P/T--E/sub e/xact)/ E/sub e/xact of at least 10 -7 (using 20 orders of perturbation theory) and 10 -3 (using only 2 orders of perturbation theory) for all couplings and all energy levels of the anharmonic oscillator. The methods are applicable also to the double-well potential (DWP, the AO with a negative mass-squared). The only change is that now the effective coupling is unbounded as lambda→0. The series in Λ is, however, still summable. The relative accuracy in the energy levels for 20 orders of perturbation theory varies from 10 -7 for large coupling to 1% at lambda=0.1 and to 10% at lambda=.05. We also present results for the sextic oscillator
Massive states in chiral perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Mallik, S [Saha Inst. of Nuclear Physics, Calcutta (India)
1995-08-01
It is shown that the chiral nonanalytic terms generated by {Delta}{sub 33} resonance in the nucleon self-energy is reproduced in chiral perturbation theory by perturbing appropriate local operators contained in the pion-nucleon effective Lagrangian itself. (orig.)
Kaus, Joseph W; Harder, Edward; Lin, Teng; Abel, Robert; McCammon, J Andrew; Wang, Lingle
2015-06-09
Recent advances in improved force fields and sampling methods have made it possible for the accurate calculation of protein–ligand binding free energies. Alchemical free energy perturbation (FEP) using an explicit solvent model is one of the most rigorous methods to calculate relative binding free energies. However, for cases where there are high energy barriers separating the relevant conformations that are important for ligand binding, the calculated free energy may depend on the initial conformation used in the simulation due to the lack of complete sampling of all the important regions in phase space. This is particularly true for ligands with multiple possible binding modes separated by high energy barriers, making it difficult to sample all relevant binding modes even with modern enhanced sampling methods. In this paper, we apply a previously developed method that provides a corrected binding free energy for ligands with multiple binding modes by combining the free energy results from multiple alchemical FEP calculations starting from all enumerated poses, and the results are compared with Glide docking and MM-GBSA calculations. From these calculations, the dominant ligand binding mode can also be predicted. We apply this method to a series of ligands that bind to c-Jun N-terminal kinase-1 (JNK1) and obtain improved free energy results. The dominant ligand binding modes predicted by this method agree with the available crystallography, while both Glide docking and MM-GBSA calculations incorrectly predict the binding modes for some ligands. The method also helps separate the force field error from the ligand sampling error, such that deviations in the predicted binding free energy from the experimental values likely indicate possible inaccuracies in the force field. An error in the force field for a subset of the ligands studied was identified using this method, and improved free energy results were obtained by correcting the partial charges assigned to the
2016-01-01
Recent advances in improved force fields and sampling methods have made it possible for the accurate calculation of protein–ligand binding free energies. Alchemical free energy perturbation (FEP) using an explicit solvent model is one of the most rigorous methods to calculate relative binding free energies. However, for cases where there are high energy barriers separating the relevant conformations that are important for ligand binding, the calculated free energy may depend on the initial conformation used in the simulation due to the lack of complete sampling of all the important regions in phase space. This is particularly true for ligands with multiple possible binding modes separated by high energy barriers, making it difficult to sample all relevant binding modes even with modern enhanced sampling methods. In this paper, we apply a previously developed method that provides a corrected binding free energy for ligands with multiple binding modes by combining the free energy results from multiple alchemical FEP calculations starting from all enumerated poses, and the results are compared with Glide docking and MM-GBSA calculations. From these calculations, the dominant ligand binding mode can also be predicted. We apply this method to a series of ligands that bind to c-Jun N-terminal kinase-1 (JNK1) and obtain improved free energy results. The dominant ligand binding modes predicted by this method agree with the available crystallography, while both Glide docking and MM-GBSA calculations incorrectly predict the binding modes for some ligands. The method also helps separate the force field error from the ligand sampling error, such that deviations in the predicted binding free energy from the experimental values likely indicate possible inaccuracies in the force field. An error in the force field for a subset of the ligands studied was identified using this method, and improved free energy results were obtained by correcting the partial charges assigned to the
International Nuclear Information System (INIS)
Lyubovitskij, V.E.; Gutsche, Th.; Faessler, Amand; Mau, R. Vinh
2002-01-01
We apply the perturbative chiral quark model to the study of the low-energy πN interaction. Using an effective chiral Lagrangian we reproduce the Weinberg-Tomozawa result for the S-wave πN scattering lengths. After inclusion of the photon field we give predictions for the electromagnetic O(p 2 ) low-energy couplings of the chiral perturbation theory effective Lagrangian that define the electromagnetic mass shifts of nucleons and first-order (e 2 ) radiative corrections to the πN scattering amplitude. Finally, we estimate the leading isospin-breaking correction to the strong energy shift of the π - p atom in the 1s state, which is relevant for the experiment 'pionic hydrogen' at PSI
Degenerate RS perturbation theory. [Rayleigh-Schroedinger energies and wave functions
Hirschfelder, J. O.; Certain, P. R.
1974-01-01
A concise, systematic procedure is given for determining the Rayleigh-Schroedinger energies and wave functions of degenerate states to arbitrarily high orders even when the degeneracies of the various states are resolved in arbitrary orders. The procedure is expressed in terms of an iterative cycle in which the energy through the (2n + 1)-th order is expressed in terms of the partially determined wave function through the n-th order. Both a direct and an operator derivation are given. The two approaches are equivalent and can be transcribed into each other. The direct approach deals with the wave functions (without the use of formal operators) and has the advantage that it resembles the usual treatment of nondegenerate perturbations and maintains close contact with the basic physics. In the operator approach, the wave functions are expressed in terms of infinite-order operators which are determined by the successive resolution of the space of the zeroth-order functions.
International Nuclear Information System (INIS)
Jaworski, F.B.
1978-01-01
The effective quasiparticle recombination time in Pb superconductors was experimentally measured by optically perturbing Pb-oxide-Pb tunnel junctions. Analysis by carefully studying the optically modulated energy gap as a function of temperature determined the effective recombination time to be 2.06 x 10 - 10 T - 1/2e/sup δ//sup kT/ +- 30%. Careful studies on optically perturbed Sn-oxide-Sn tunnel junctions provide information on the quasiparticle nonequilibrium energy distribution function. Initial data compared closer with a modified heating model describing the photo-excited quasi particles rather than with an effective chemical potential model. However, an analysis of the IV characteristic of voltage-biased Sn junctions numerically unfolded the exact energy distribution from an integral equation. The results compare favorably to the theory of Chang and Scalapino, who calculate from the coupled Boltzmann kinetic equations the phonon and quasiparticle energy distributions. Lastly, a brief study describes Inelastic Electron Tunneling Spectroscopy as applied to the problem of the identification of altered DNA bases. The technique demonstrates an exciting potential application of physics to a contemporary problem in molecular biology
Perturbed soliton excitations in inhomogeneous DNA
International Nuclear Information System (INIS)
Daniel, M.; Vasumathi, V.
2005-05-01
We study nonlinear dynamics of inhomogeneous DNA double helical chain under dynamic plane-base rotator model by considering angular rotation of bases in a plane normal to the helical axis. The DNA dynamics in this case is found to be governed by a perturbed sine-Gordon equation when taking into account the interstrand hydrogen bonding energy and intrastrand inhomogeneous stacking energy and making an analogy with the Heisenberg model of the Hamiltonian for an inhomogeneous anisotropic spin ladder with ferromagnetic legs and antiferromagentic rung coupling. In the homogeneous limit the dynamics is governed by the kink-antikink soliton of the sine-Gordon equation which represents the formation of open state configuration in DNA double helix. The effect of inhomogeneity in stacking energy in the form of localized and periodic variations on the formation of open states in DNA is studied under perturbation. The perturbed soliton is obtained using a multiple scale soliton perturbation theory by solving the associated linear eigen value problem and constructing the complete set of eigen functions. The inhomogeneity in stacking energy is found to modulate the width and speed of the soliton depending on the nature of inhomogeneity. Also it introduces fluctuations in the form of train of pulses or periodic oscillation in the open state configuration (author)
Ajustes al framework de evaluación de productos de software MyFEPS
Angeleri, Paula; Titiosky, Rolando; Sorgen, Amos; Wuille Bille, Jaquelina; Oliveros, Alejandro
2014-01-01
El objetivo de este artículo es presentar la situación actual del proyecto de investigación MyFEPS Metodologías y Framework para la Evaluación de Productos de Software, basados en normas internacionales, en desarrollo en la Facultad de Ingeniería y Tecnología Informática de la Universidad de Belgrano, cuyo propósito es diseñar e implementar un framework que de apoyo al proceso de evaluación de software completo: desde la determinación de los objetivos de la evaluación, su planificación, ejecu...
Secondary isocurvature perturbations from acoustic reheating
Ota, Atsuhisa; Yamaguchi, Masahide
2018-06-01
The superhorizon (iso)curvature perturbations are conserved if the following conditions are satisfied: (i) (each) non adiabatic pressure perturbation is zero, (ii) the gradient terms are ignored, that is, at the leading order of the gradient expansion (iii) (each) total energy momentum tensor is conserved. We consider the case with the violation of the last two requirements and discuss the generation of secondary isocurvature perturbations during the late time universe. Second order gradient terms are not necessarily ignored even if we are interested in the long wavelength modes because of the convolutions which may pick products of short wavelength perturbations up. We then introduce second order conserved quantities on superhorizon scales under the conditions (i) and (iii) even in the presence of the gradient terms by employing the full second order cosmological perturbation theory. We also discuss the violation of the condition (iii), that is, the energy momentum tensor is conserved for the total system but not for each component fluid. As an example, we explicitly evaluate second order heat conduction between baryons and photons due to the weak Compton scattering, which dominates during the period just before recombination. We show that such secondary effects can be recast into the isocurvature perturbations on superhorizon scales if the local type primordial non Gaussianity exists a priori.
Generalized chiral perturbation theory
International Nuclear Information System (INIS)
Knecht, M.; Stern, J.
1994-01-01
The Generalized Chiral Perturbation Theory enlarges the framework of the standard χPT (Chiral Perturbation Theory), relaxing certain assumptions which do not necessarily follow from QCD or from experiment, and which are crucial for the usual formulation of the low energy expansion. In this way, experimental tests of the foundations of the standard χPT become possible. Emphasis is put on physical aspects rather than on formal developments of GχPT. (author). 31 refs
International Nuclear Information System (INIS)
Scholz, H.
1986-01-01
The radiation-initiated grafting copolymerisation of hydrophil monomers to FEP, a copolymer of tetrafluorethene and hexafluorpropene and to polyacryl nitrile (PAN) was examined in this dissertation. The grafted products were used as diaphragms for the separation of water-ethanol mixtures by pervaporation. Water was separated through the diaphragm from the mixture in the pervaporation experiments. It was shown how the mechanical properties of the basic polymer affect the interaction between basic polymer and grafted polymer and how the grafting conditions affect the diaphragm properties. By grafting acrylic acid on to the basic polymers FEP and PAN, very good results were achieved for the water-ethanol separation, if the diaphragms were used in the K form. The selectivity of PAN-g-acrylic acid-K for water reached values of α > 1000. (orig./RB) [de
Within-Day Energy Deficiency and Metabolic Perturbation in Male Endurance Athletes.
Torstveit, Monica Klungland; Fahrenholtz, Ida; Stenqvist, Thomas B; Sylta, Øystein; Melin, Anna
2018-06-26
Endurance athletes are at increased risk of relative energy deficiency associated with metabolic perturbation and impaired health. We aimed to estimate and compare within-day energy balance in male athletes with suppressed and normal resting metabolic rate (RMR) and explore whether within-day energy deficiency is associated with endocrine markers of energy deficiency. A total of 31 male cyclists, triathletes, and long-distance runners recruited from regional competitive sports clubs were included. The protocol comprised measurements of RMR by ventilated hood and energy intake and energy expenditure to predict RMR ratio (measured RMR/predicted RMR), energy availability, 24-hr energy balance and within-day energy balance in 1-hr intervals, assessment of body composition by dual-energy X-ray absorptiometry, and blood plasma analysis. Subjects were categorized as having suppressed (RMR ratio 0.90, n = 11) RMR. Despite there being no observed differences in 24-hr energy balance or energy availability between the groups, subjects with suppressed RMR spent more time in an energy deficit exceeding 400 kcal (20.9 [18.8-21.8] hr vs. 10.8 [2.5-16.4], p = .023) and had larger single-hour energy deficits compared with subjects with normal RMR (3,265 ± 1,963 kcal vs. -1,340 ± 2,439, p = .023). Larger single-hour energy deficits were associated with higher cortisol levels (r = -.499, p = .004) and a lower testosterone:cortisol ratio (r = .431, p = .015), but no associations with triiodothyronine or fasting blood glucose were observed. In conclusion, within-day energy deficiency was associated with suppressed RMR and catabolic markers in male endurance athletes.
Pan, Albert C; Cuello, Luis G; Perozo, Eduardo; Roux, Benoît
2011-12-01
The amount of ionic current flowing through K(+) channels is determined by the interplay between two separate time-dependent processes: activation and inactivation gating. Activation is concerned with the stimulus-dependent opening of the main intracellular gate, whereas inactivation is a spontaneous conformational transition of the selectivity filter toward a nonconductive state occurring on a variety of timescales. A recent analysis of multiple x-ray structures of open and partially open KcsA channels revealed the mechanism by which movements of the inner activation gate, formed by the inner helices from the four subunits of the pore domain, bias the conformational changes at the selectivity filter toward a nonconductive inactivated state. This analysis highlighted the important role of Phe103, a residue located along the inner helix, near the hinge position associated with the opening of the intracellular gate. In the present study, we use free energy perturbation molecular dynamics simulations (FEP/MD) to quantitatively elucidate the thermodynamic basis for the coupling between the intracellular gate and the selectivity filter. The results of the FEP/MD calculations are in good agreement with experiments, and further analysis of the repulsive, van der Waals dispersive, and electrostatic free energy contributions reveals that the energetic basis underlying the absence of inactivation in the F103A mutation in KcsA is the absence of the unfavorable steric interaction occurring with the large Ile100 side chain in a neighboring subunit when the intracellular gate is open and the selectivity filter is in a conductive conformation. Macroscopic current analysis shows that the I100A mutant indeed relieves inactivation in KcsA, but to a lesser extent than the F103A mutant.
Measurement of the spallation reaction 56Fe+p in inverse kinematics
International Nuclear Information System (INIS)
Boehmer, M.
2006-01-01
In this work the spallation reaction 56 Fe+p was investigated in inverse kinematics with regard to complete identification of the heavy residues. A ring imaging Cerenkov counter was used for velocity measurements in the experimental setup located at GSI in Darmstadt. A new fast readout electronic was developed and has been operated successfully in the experiment. Momentum reconstruction was carried out with the ALADiN spectrometer and a new software package written for this purpose. Cross sections and velocity distributions for more than 100 mass separated isotopes could be extracted from the dataset and compared with empirical models and other spallation experiments. The experiences gained in this experiment will be used for systematic improvements in the setup of the new spectrometer R3B at FAIR. (orig.)
Equation-of-motion coupled cluster perturbation theory revisited
DEFF Research Database (Denmark)
Eriksen, Janus Juul; Jørgensen, Poul; Olsen, Jeppe
2014-01-01
The equation-of-motion coupled cluster (EOM-CC) framework has been used for deriving a novel series of perturbative corrections to the coupled cluster singles and doubles energy that formally con- verges towards the full configuration interaction energy limit. The series is based on a Møller-Ples......-Plesset partitioning of the Hamiltonian and thus size extensive at any order in the perturbation, thereby rem- edying the major deficiency inherent to previous perturbation series based on the EOM-CC ansatz. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4873138]...
Shiozaki, Toru; Győrffy, Werner; Celani, Paolo; Werner, Hans-Joachim
2011-08-01
The extended multireference quasi-degenerate perturbation theory, proposed by Granovsky [J. Chem. Phys. 134, 214113 (2011)], is combined with internally contracted multi-state complete active space second-order perturbation theory (XMS-CASPT2). The first-order wavefunction is expanded in terms of the union of internally contracted basis functions generated from all the reference functions, which guarantees invariance of the theory with respect to unitary rotations of the reference functions. The method yields improved potentials in the vicinity of avoided crossings and conical intersections. The theory for computing nuclear energy gradients for MS-CASPT2 and XMS-CASPT2 is also presented and the first implementation of these gradient methods is reported. A number of illustrative applications of the new methods are presented.
International Nuclear Information System (INIS)
Logrado, P.G.; Vianna, J.D.M.
Upper and lower bounds for the energy eigenvalues is Schoenberg's perturbation-theory ground state are studied. After a review of the characteristic features of the partitioning techniques the perturbative expansion proposed by Schoenberg is generated from an exact operator equation. The upper and lower bounds for the ground state eigenvalue are derived by using reaction and wave operators concepts, the bracketing function and operator inequalities. (Author) [pt
Non-adiabatic perturbations in multi-component perfect fluids
Energy Technology Data Exchange (ETDEWEB)
Koshelev, N.A., E-mail: koshna71@inbox.ru [Ulyanovsk State University, Leo Tolstoy str 42, 432970 (Russian Federation)
2011-04-01
The evolution of non-adiabatic perturbations in models with multiple coupled perfect fluids with non-adiabatic sound speed is considered. Instead of splitting the entropy perturbation into relative and intrinsic parts, we introduce a set of symmetric quantities, which also govern the non-adiabatic pressure perturbation in models with energy transfer. We write the gauge invariant equations for the variables that determine on a large scale the non-adiabatic pressure perturbation and the rate of changes of the comoving curvature perturbation. The analysis of evolution of the non-adiabatic pressure perturbation has been made for several particular models.
Non-adiabatic perturbations in multi-component perfect fluids
International Nuclear Information System (INIS)
Koshelev, N.A.
2011-01-01
The evolution of non-adiabatic perturbations in models with multiple coupled perfect fluids with non-adiabatic sound speed is considered. Instead of splitting the entropy perturbation into relative and intrinsic parts, we introduce a set of symmetric quantities, which also govern the non-adiabatic pressure perturbation in models with energy transfer. We write the gauge invariant equations for the variables that determine on a large scale the non-adiabatic pressure perturbation and the rate of changes of the comoving curvature perturbation. The analysis of evolution of the non-adiabatic pressure perturbation has been made for several particular models
Trivedi, Shefali; Ravi Kumar, D.; Aravindan, S.
2016-10-01
Phosphorus in steel is known to increase strength and hardness and decrease ductility. Higher phosphorus content (more than 0.05%), however, promotes brittle behavior due to segregation of Fe3P along the grain boundaries which makes further mechanical working of these alloys difficult. In this work, thin sheets of Fe-P alloys (with phosphorus in range of 0.1-0.35%) have been developed through processing by powder metallurgy followed by hot rolling and cold rolling. The effect of phosphorus content and annealing parameters (temperature and time) on microstructure, mechanical properties, formability in biaxial stretching and fracture behavior of the cold rolled and annealed sheets has been studied. A comparison has also been made between the properties of the sheets made through P/M route and the conventional cast route with similar phosphorus content. It has been shown that thin sheets of Fe-P alloys with phosphorous up to 0.35% possessing a good combination of strength and formability can be produced through rolling of billets of these alloys made through powder metallurgy technique without the problem of segregation.
Ryuichi, TAKAHASHI; Department of Physics and Astrophysics, Nagoya University
2008-01-01
We investigate the third-order density perturbation and the one-loop correction to the linear power spectrum in the dark-energy cosmological model. Our main interest is to understand the dark-energy effect on baryon acoustic oscillations in a quasi-nonlinear regime (k≈0.1h/Mpc). Analytical solutions and simple fitting formulae are presented for the dark-energy model with the general time-varying equation of state w(a). It turns out that the power spectrum coincides with the approximate res...
DEFF Research Database (Denmark)
Forsmann, Ditte M.; Kjærgaard, Charlotte
2014-01-01
soils (TOC from 5 to 39%) with a gradient in Fe:P molar ratio (molar ratio between bicarbonate dithionite extractable Fe and P (FeBD:PBD) from 3 to 112) and degree of non-equilibrium (preferential) flow. Short-term batch incubation experiments (21 days) indicated that concurrent Fe and P release...
New Approaches and Applications for Monte Carlo Perturbation Theory
Energy Technology Data Exchange (ETDEWEB)
Aufiero, Manuele; Bidaud, Adrien; Kotlyar, Dan; Leppänen, Jaakko; Palmiotti, Giuseppe; Salvatores, Massimo; Sen, Sonat; Shwageraus, Eugene; Fratoni, Massimiliano
2017-02-01
This paper presents some of the recent and new advancements in the extension of Monte Carlo Perturbation Theory methodologies and application. In particular, the discussed problems involve Brunup calculation, perturbation calculation based on continuous energy functions, and Monte Carlo Perturbation Theory in loosely coupled systems.
Effective field theory of cosmological perturbations
International Nuclear Information System (INIS)
Piazza, Federico; Vernizzi, Filippo
2013-01-01
The effective field theory of cosmological perturbations stems from considering a cosmological background solution as a state displaying spontaneous breaking of time translations and (adiabatic) perturbations as the related Nambu–Goldstone modes. With this insight, one can systematically develop a theory for the cosmological perturbations during inflation and, with minor modifications, also describe in full generality the gravitational interactions of dark energy, which are relevant for late-time cosmology. The formalism displays a unique set of Lagrangian operators containing an increasing number of cosmological perturbations and derivatives. We give an introductory description of the unitary gauge formalism for theories with broken gauge symmetry—that allows us to write down the most general Lagrangian—and of the Stückelberg ‘trick’—that allows to recover gauge invariance and to make the scalar field explicit. We show how to apply this formalism to gravity and cosmology and we reproduce the detailed analysis of the action in the ADM variables. We also review some basic applications to inflation and dark energy. (paper)
Effective field theory of cosmological perturbations
Piazza, Federico; Vernizzi, Filippo
2013-11-01
The effective field theory of cosmological perturbations stems from considering a cosmological background solution as a state displaying spontaneous breaking of time translations and (adiabatic) perturbations as the related Nambu-Goldstone modes. With this insight, one can systematically develop a theory for the cosmological perturbations during inflation and, with minor modifications, also describe in full generality the gravitational interactions of dark energy, which are relevant for late-time cosmology. The formalism displays a unique set of Lagrangian operators containing an increasing number of cosmological perturbations and derivatives. We give an introductory description of the unitary gauge formalism for theories with broken gauge symmetry—that allows us to write down the most general Lagrangian—and of the Stückelberg ‘trick’—that allows to recover gauge invariance and to make the scalar field explicit. We show how to apply this formalism to gravity and cosmology and we reproduce the detailed analysis of the action in the ADM variables. We also review some basic applications to inflation and dark energy.
Collective behaviour of linear perturbation waves observed through the energy density spectrum
Energy Technology Data Exchange (ETDEWEB)
Scarsoglio, S [Department of Water Engineering, Politecnico di Torino (Italy); De Santi, F; Tordella, D, E-mail: stefania.scarsoglio@polito.it [Department of Aeronautics and Space Engineering, Politecnico di Torino (Italy)
2011-12-22
We consider the collective behaviour of small three-dimensional transient perturbations in sheared flows. In particular, we observe their varied life history through the temporal evolution of the amplification factor. The spectrum of wave vectors considered fills the range from the size of the external flow scale to the size of the very short dissipative waves. We observe that the amplification factor distribution is scale-invariant. In the condition we analyze, the system is subject to all the physical processes included in the linearized Navier-Stokes equations. With the exception of the nonlinear interaction, these features are the same as those characterizing the turbulent state. The linearized perturbative system offers a great variety of different transient behaviours associated to the parameter combination present in the initial conditions. For the energy spectrum computed by freezing each wave at the instant where its asymptotic condition is met, we ask whether this system is able to show a power-law scaling analogous to the Kolmogorov argument. At the moment, for at least two typical shear flows, the bluff-body wake and the plane Poiseuille flow, the answer is yes.
Minimal Self-Models and the Free Energy Principle
Directory of Open Access Journals (Sweden)
Jakub eLimanowski
2013-09-01
Full Text Available The term "minimal phenomenal selfhood" describes the basic, pre-reflective experience of being a self (Blanke & Metzinger, 2009. Theoretical accounts of the minimal self have long recognized the importance and the ambivalence of the body as both part of the physical world, and the enabling condition for being in this world (Gallagher, 2005; Grafton, 2009. A recent account of minimal phenomenal selfhood (MPS, Metzinger, 2004a centers on the consideration that minimal selfhood emerges as the result of basic self-modeling mechanisms, thereby being founded on pre-reflective bodily processes. The free energy principle (FEP, Friston, 2010 is a novel unified theory of cortical function that builds upon the imperative that self-organizing systems entail hierarchical generative models of the causes of their sensory input, which are optimized by minimizing free energy as an approximation of the log-likelihood of the model. The implementation of the FEP via predictive coding mechanisms and in particular the active inference principle emphasizes the role of embodiment for predictive self-modeling, which has been appreciated in recent publications. In this review, we provide an overview of these conceptions and illustrate thereby the potential power of the FEP in explaining the mechanisms underlying minimal selfhood and its key constituents, multisensory integration, interoception, agency, perspective, and the experience of mineness. We conclude that the conceptualization of MPS can be well mapped onto a hierarchical generative model furnished by the free energy principle and may constitute the basis for higher-level, cognitive forms of self-referral, as well as the understanding of other minds.
Streamer properties and associated x-rays in perturbed air
Köhn, C.; Chanrion, O.; Babich, L. P.; Neubert, T.
2018-01-01
Streamers are ionization waves in electric discharges. One of the key ingredients of streamer propagation is an ambient gas that serves as a source of free electrons. Here, we explore the dependence of streamer dynamics on different spatial distributions of ambient air molecules. We vary the spatial profile of air parallel and perpendicular to the ambient electric field. We consider local sinusoidal perturbations of 5%-100%, as induced from discharge shock waves. We use a cylindrically symmetric particle-in-cell code to simulate the evolution of bidirectional streamers and compare the electron density, electric field, streamer velocity and electron energy of streamers in uniform air and in perturbed air. In all considered cases, the motion is driven along in decreasing air density and damped along increasing air density. Perturbations of at most 5%-10% change the velocity differences by up to approximately 40%. Perturbations perpendicular to the electric field additionally squeeze or branch streamers. Air variations can thus partly explain the difference of velocities and morphologies of streamer discharges. In cases with large perturbations, electrons gain energies of up to 30 keV compared to 100 eV in uniformly distributed air. For such perturbations parallel to the ambient electric field, we see the spontaneous initiation of a negative streamer; for perpendicular perturbations, x-rays with energies of up to 20 keV are emitted within 0.17 ns.
Directory of Open Access Journals (Sweden)
Patrick Connolly
2017-09-01
Full Text Available The present paper argues that a systems theory epistemology (and particularly the notion of hierarchical recursive organization provides the critical theoretical context within which the significance of Friston's (2010a Free Energy Principle (FEP for both evolution and psychoanalysis is best understood. Within this perspective, the FEP occupies a particular level of the hierarchical organization of the organism, which is the level of biological self-organization. This form of biological self-organization is in turn understood as foundational and pervasive to the higher levels of organization of the human organism that are of interest to both neuroscience as well as psychoanalysis. Consequently, central psychoanalytic claims should be restated, in order to be located in their proper place within a hierarchical recursive organization of the (situated organism. In light of the FEP the realization of the psychoanalytic mind by the brain should be seen in terms of the evolution of different levels of systematic organization where the concepts of psychoanalysis describe a level of hierarchical recursive organization superordinate to that of biological self-organization and the FEP. The implication of this formulation is that while “psychoanalytic” mental processes are fundamentally subject to the FEP, they nonetheless also add their own principles of process over and above that of the FEP. A model found in Grobbelaar (1989 offers a recursive bottom-up description of the self-organization of the psychoanalytic ego as dependent on the organization of language (and affect, which is itself founded upon the tendency toward autopoiesis (self-making within the organism, which is in turn described as formally similar to the FEP. Meaningful consilience between Grobbelaar's model and the hierarchical recursive description available in Friston's (2010a theory is described. The paper concludes that the valuable contribution of the FEP to psychoanalysis
International Nuclear Information System (INIS)
Mueller, A.H.
1986-03-01
A brief review of some of the recent progress in perturbative QCD is given (heavy quark production, small-x physics, minijets and related topics, classical simulations in high energy reactions, coherence and the string effect)
International Nuclear Information System (INIS)
West, G.
1990-01-01
The main thrust of this talk is to review and discuss various topics in both perturbative and non-perturbative QCD that are, by and large, model independent. This inevitably means that we shall rely heavily on the renormalization group and asymptotic freedom. Although this usually means that one has to concentrate on high energy phenomena, there are some physical processes even involving bound states which are certainly highly non-perturbative, where one can make some progress without becoming overly model independent. Experience with the EMC effect, where there are about as many ''explanations'' as authors, has surely taught us that it may well be worth returning to ''basics'' and thinking about general properties of QCD rather than guessing, essentially arbitrarily, what we think is its low energy structure. No doubt we shall have to await further numerical progress or for some inspired theoretical insight before we can, with confidence, attack these extremely difficult problems. So, with this in mine, I shall review a smattering of problems which do have a non-perturbative component and where some rather modest progress can actually be made; I emphasize the adjective ''modest''exclamation point
Gonthier, Jérôme F.; Corminboeuf, Clémence
2014-04-01
Non-covalent interactions occur between and within all molecules and have a profound impact on structural and electronic phenomena in chemistry, biology, and material science. Understanding the nature of inter- and intramolecular interactions is essential not only for establishing the relation between structure and properties, but also for facilitating the rational design of molecules with targeted properties. These objectives have motivated the development of theoretical schemes decomposing intermolecular interactions into physically meaningful terms. Among the various existing energy decomposition schemes, Symmetry-Adapted Perturbation Theory (SAPT) is one of the most successful as it naturally decomposes the interaction energy into physical and intuitive terms. Unfortunately, analogous approaches for intramolecular energies are theoretically highly challenging and virtually nonexistent. Here, we introduce a zeroth-order wavefunction and energy, which represent the first step toward the development of an intramolecular variant of the SAPT formalism. The proposed energy expression is based on the Chemical Hamiltonian Approach (CHA), which relies upon an asymmetric interpretation of the electronic integrals. The orbitals are optimized with a non-hermitian Fock matrix based on two variants: one using orbitals strictly localized on individual fragments and the other using canonical (delocalized) orbitals. The zeroth-order wavefunction and energy expression are validated on a series of prototypical systems. The computed intramolecular interaction energies demonstrate that our approach combining the CHA with strictly localized orbitals achieves reasonable interaction energies and basis set dependence in addition to producing intuitive energy trends. Our zeroth-order wavefunction is the primary step fundamental to the derivation of any perturbation theory correction, which has the potential to truly transform our understanding and quantification of non
International Nuclear Information System (INIS)
Gonthier, Jérôme F.; Corminboeuf, Clémence
2014-01-01
Non-covalent interactions occur between and within all molecules and have a profound impact on structural and electronic phenomena in chemistry, biology, and material science. Understanding the nature of inter- and intramolecular interactions is essential not only for establishing the relation between structure and properties, but also for facilitating the rational design of molecules with targeted properties. These objectives have motivated the development of theoretical schemes decomposing intermolecular interactions into physically meaningful terms. Among the various existing energy decomposition schemes, Symmetry-Adapted Perturbation Theory (SAPT) is one of the most successful as it naturally decomposes the interaction energy into physical and intuitive terms. Unfortunately, analogous approaches for intramolecular energies are theoretically highly challenging and virtually nonexistent. Here, we introduce a zeroth-order wavefunction and energy, which represent the first step toward the development of an intramolecular variant of the SAPT formalism. The proposed energy expression is based on the Chemical Hamiltonian Approach (CHA), which relies upon an asymmetric interpretation of the electronic integrals. The orbitals are optimized with a non-hermitian Fock matrix based on two variants: one using orbitals strictly localized on individual fragments and the other using canonical (delocalized) orbitals. The zeroth-order wavefunction and energy expression are validated on a series of prototypical systems. The computed intramolecular interaction energies demonstrate that our approach combining the CHA with strictly localized orbitals achieves reasonable interaction energies and basis set dependence in addition to producing intuitive energy trends. Our zeroth-order wavefunction is the primary step fundamental to the derivation of any perturbation theory correction, which has the potential to truly transform our understanding and quantification of non
Systematic approach to scenario development using FEP analysis
International Nuclear Information System (INIS)
Bailey, L.E.E.; Lever, D.A.
2001-01-01
UK regulatory requirements require that the 'assessed radiological risk ... to a representative member of the potentially exposed group at greatest risk should be consistent with a risk target of 10 -6 per year' and that risks should be 'summed over all situations that could give rise to exposure to the group'. It is a further requirement that a repository performance assessment provides a 'comprehensive record of the judgements and assumptions on which the risk assessments are based'. In order to meet these requirements, Nirex, working with AEA Technology, has developed an approach to performance assessment based on the identification and analysis of features, events and processes (FEPs). The objectives of the approach are to provide a comprehensive, traceable and clear presentation of a performance assessment for a deep geological radioactive waste repository. The approach to scenario development is fundamental to the overall Nirex strategy for performance assessment, eventually leading to a repository safety case for regulatory submission. This paper outlines the main concepts of the approach, illustrated with examples of work undertaken by Nirex to demonstrate its practicality. Due to the current status of the Nirex repository programme, the approach has not yet been used to conduct a full performance assessment of a repository located at a specific site. (authors)
The use of perturbation theory in density-functional theory
International Nuclear Information System (INIS)
Goerling, A.
1996-01-01
Perturbation theory with respect to the electron-electron interaction leads to expressions for the exchange and correlation energies and potentials in terms of Kohn-Sham orbitals and Kohn-Sham eigenvalues. An exact open-quote exchange-only close-quote procedure for solids is introduced. Results for several semiconductors are presented. Perturbation theory expansions for the hardness of molecules and the bad gap of solids are given. Density-functional exchange and correlation energies for excited states are defined and a perturbation theory based Kohn-Sham formalism to treat excited states within density-functional theory is introduced
Production of transverse energy from minijets in next-to-leading order perturbative QCD
Eskola, Kari J
2000-01-01
We compute in next-to-leading order (NLO) perturbative QCD the transverse energy carried into the central rapidity unit of hadron or nuclear collisions by the partons freed in the few-GeV subcollisions. The formulation is based on a rapidity window and a measurement function of a new type. The behaviour of the NLO results as a function of the minimum transverse momentum and as a function of the scale choice is studied. The NLO results are found to be stable relative to the leading-order ones even in the few-GeV domain.
Singular perturbation theory for interacting fermions in two dimensions
International Nuclear Information System (INIS)
Chubukov, A.V.; Maslov, D.L.; Gangadharaiah, S.; Glazman, L.I.
2004-11-01
We consider a system of interacting fermions in two dimensions beyond the second-order perturbation theory in the interaction. It is shown that the mass-shell singularities in the self-energy, arising already at the second order of the perturbation theory, manifest a nonperturbative effect: an interaction with the zero-sound mode. Resuming the perturbation theory for a weak, short-range interaction and accounting for a finite curvature of the fermion spectrum, we eliminate the singularities and obtain the results for the quasi-particle self-energy and the spectral function to all orders in the interaction with the zero-sound mode. A threshold for emission of zero-sound waves leads a non-monotonic variation of the self-energy with energy (or momentum) near the mass shell. Consequently, the spectral function has a kink-like feature. We also study in detail a non-analytic temperature dependence of the specific heat, C(T) ∝T 2 . It turns out that although the interaction with the collective mode results in an enhancement of the fermion self-energy, this interaction does not affect the non-analytic term in C(T) due to a subtle cancellation between the contributions from the real and imaginary parts of the self-energy. For a short-range and weak interaction, this implies that the second-order perturbation theory suffices to determine the non-analytic part of C(T). We also obtain a general form of the non-analytic term in C(T), valid for the case of a generic Fermi liquid, i.e., beyond the perturbation theory. (author)
Dorman, L. I.
2005-11-01
We show that an exact forecast of great radiation hazard in space, in the magnetosphere, in the atmosphere and on the ground can be made by using high-energy particles (few GeV/nucleon and higher) whose transportation from the Sun is characterized by a much bigger diffusion coefficient than for small and middle energy particles. Therefore, high energy particles come from the Sun much earlier (8-20 min after acceleration and escaping into solar wind) than the main part of smaller energy particles (more than 30-60 min later), causing radiation hazard for electronics and personal health, as well as spacecraft and aircrafts. We describe here principles of an automatic set of programs that begin with "FEP-Search", used to determine the beginning of a large FEP event. After a positive signal from "FEP-Search", the following programs start working: "FEP-Research/Spectrum", and then "FEP-Research/Time of Ejection", "FEP-Research /Source" and "FEP-Research/Diffusion", which online determine properties of FEP generation and propagation. On the basis of the obtained information, the next set of programs immediately start to work: "FEP-Forecasting/Spacecrafts", "FEP-Forecasting/Aircrafts", "FEP-Forecasting/Ground", which determine the expected differential and integral fluxes and total fluency for spacecraft on different orbits, aircrafts on different airlines, and on the ground, depending on altitude and cutoff rigidity. If the level of radiation hazard is expected to be dangerous for high level technology or/and personal health, the following programs will be used "FEP-Alert/Spacecrafts", "FEP-Alert/ Aircrafts", "FEP-Alert/Ground".
Directory of Open Access Journals (Sweden)
L. I. Dorman
2005-11-01
Full Text Available We show that an exact forecast of great radiation hazard in space, in the magnetosphere, in the atmosphere and on the ground can be made by using high-energy particles (few GeV/nucleon and higher whose transportation from the Sun is characterized by a much bigger diffusion coefficient than for small and middle energy particles. Therefore, high energy particles come from the Sun much earlier (8-20 min after acceleration and escaping into solar wind than the main part of smaller energy particles (more than 30-60 min later, causing radiation hazard for electronics and personal health, as well as spacecraft and aircrafts. We describe here principles of an automatic set of programs that begin with "FEP-Search", used to determine the beginning of a large FEP event. After a positive signal from "FEP-Search", the following programs start working: "FEP-Research/Spectrum", and then "FEP-Research/Time of Ejection", "FEP-Research /Source" and "FEP-Research/Diffusion", which online determine properties of FEP generation and propagation. On the basis of the obtained information, the next set of programs immediately start to work: "FEP-Forecasting/Spacecrafts", "FEP-Forecasting/Aircrafts", "FEP-Forecasting/Ground", which determine the expected differential and integral fluxes and total fluency for spacecraft on different orbits, aircrafts on different airlines, and on the ground, depending on altitude and cutoff rigidity. If the level of radiation hazard is expected to be dangerous for high level technology or/and personal health, the following programs will be used "FEP-Alert/Spacecrafts", "FEP-Alert/ Aircrafts", "FEP-Alert/Ground".
International Nuclear Information System (INIS)
Cohen, M.; Feldmann, T.
1981-01-01
The energy function of a perturbed quantum system is derived directly as a quotient of the form N(lambda)/D(lambda). The Taylor series coefficients of N(lambda) and D(lambda) are found to satisfy certain relations, but there remain many unspecified degrees of freedom which may be freely exploited. Certain choices of coefficients lead to well known Pade and lesser known Levin approximants, but the general formalism includes many other rational function forms. In particular, the present procedure allows information other than the Taylor series coefficients to be included naturally, and is shown to lead to low-order approximants of high accuracy. (author)
International Nuclear Information System (INIS)
Piattella, O.F.; Martins, D.L.A.; Casarini, L.
2014-01-01
We consider a cosmological model of the late universe constituted by standard cold dark matter plus a dark energy component with constant equation of state w and constant effective speed of sound. By neglecting fluctuations in the dark energy component, we obtain an equation describing the evolution of sub-horizon cold dark matter perturbations through the epoch of dark matter-dark energy equality. We explore its analytic solutions and calculate an exact w-dependent correction for the dark matter growth function, logarithmic growth function and growth index parameter through the epoch considered. We test our analytic approximation with the numerical solution and find that the discrepancy is less than 1% for 0k = during the cosmic evolution up to a = 100
Modified potentials in many-body perturbation theory
International Nuclear Information System (INIS)
Silver, D.M.; Bartlett, R.J.
1976-01-01
Many-body perturbation-theory calculations of the pair-correlation energy within the regime of various finite expansions in two-center Slater-type basis sets are performed using a wide variety of modified potentials for the determination of unoccupied orbitals. To achieve meaningful convergence, it appears that the perturbation series must be carried through third order, using shifted denominators to include contributions from various higher-order diagrams. Moreover, certain denominator shifts are found necessary to ensure that a negative-definite resolvent accompanies the perturbation scheme when an arbitrary modified potential is employed. Through third order with denominator shifts, well-behaved modified potentials are found to give results that are equivalent, within 1 kcal/mole, to those obtained for pair-correlation energies with the standard self-consistent-field-V/sup N/ potential
International Nuclear Information System (INIS)
Astashenok, Artyom V.; Odintsov, Sergei D.
2013-01-01
We confront dark energy models which are currently similar to ΛCDM theory with observational data which include the SNe data, matter density perturbations and baryon acoustic oscillations data. DE cosmology under consideration may evolve to Big Rip, type II or type III future singularity, or to Little Rip or Pseudo-Rip universe. It is shown that matter perturbations data define more precisely the possible deviation from ΛCDM model than consideration of SNe data only. The combined data analysis proves that DE models under consideration are as consistent as ΛCDM model. We demonstrate that growth of matter density perturbations may occur at sufficiently small background density but still before the possible disintegration of bound objects (like clusters of galaxies, galaxies, etc.) in Big Rip, type III singularity, Little Rip or Pseudo-Rip universe. This new effect may bring the future universe to chaotic state well before disintegration or Rip.
Tension perturbations of black brane spacetimes
International Nuclear Information System (INIS)
Traschen, Jennie; Fox, Daniel
2004-01-01
We consider black brane spacetimes that have at least one spatial translation Killing field that is tangent to the brane. A new parameter, the tension of a spacetime, is defined. The tension parameter is associated with spatial translations in much the same way that the ADM mass is associated with the time translation Killing field. In this work, we explore the implications of the spatial translation symmetry for small perturbations around a background black brane. For static-charged black branes we derive a law which relates the tension perturbation to the surface gravity times the change in the horizon area, plus terms that involve variations in the charges and currents. We find that as a black brane evaporates the tension decreases. We also give a simple derivation of a first law for black brane spacetimes. These constructions hold when the background stress-energy is governed by a Hamiltonian, and the results include arbitrary perturbative stress-energy sources
Ortiz, Néstor; Sarbach, Olivier
2018-01-01
We analyze the stability of the Cauchy horizon associated with a globally naked, shell-focussing singularity arising from the complete gravitational collapse of a spherical dust cloud. In a previous work, we have studied the dynamics of spherical test scalar fields on such a background. In particular, we proved that such fields cannot develop any divergences which propagate along the Cauchy horizon. In the present work, we extend our analysis to the more general case of test fields without symmetries and to linearized gravitational perturbations with odd parity. To this purpose, we first consider test fields possessing a divergence-free stress-energy tensor satisfying the dominant energy condition, and we prove that a suitable energy norm is uniformly bounded in the domain of dependence of the initial slice. In particular, this result implies that free-falling observers co-moving with the dust particles measure a finite energy of the field, even as they cross the Cauchy horizon at points lying arbitrarily close to the central singularity. Next, for the case of Klein–Gordon fields, we derive point-wise bounds from our energy estimates which imply that the scalar field cannot diverge at the Cauchy horizon, except possibly at the central singular point. Finally, we analyze the behaviour of odd-parity, linear gravitational and dust perturbations of the collapsing spacetime. Similarly to the scalar field case, we prove that the relevant gauge-invariant combinations of the metric perturbations stay bounded away from the central singularity, implying that no divergences can propagate in the vacuum region. Our results are in accordance with previous numerical studies and analytic work in the self-similar case.
Answering Schrödinger's question: A free-energy formulation
Ramstead, Maxwell James Désormeau; Badcock, Paul Benjamin; Friston, Karl John
2018-03-01
The free-energy principle (FEP) is a formal model of neuronal processes that is widely recognised in neuroscience as a unifying theory of the brain and biobehaviour. More recently, however, it has been extended beyond the brain to explain the dynamics of living systems, and their unique capacity to avoid decay. The aim of this review is to synthesise these advances with a meta-theoretical ontology of biological systems called variational neuroethology, which integrates the FEP with Tinbergen's four research questions to explain biological systems across spatial and temporal scales. We exemplify this framework by applying it to Homo sapiens, before translating variational neuroethology into a systematic research heuristic that supplies the biological, cognitive, and social sciences with a computationally tractable guide to discovery.
Perturbation theory in large order
International Nuclear Information System (INIS)
Bender, C.M.
1978-01-01
For many quantum mechanical models, the behavior of perturbation theory in large order is strikingly simple. For example, in the quantum anharmonic oscillator, which is defined by -y'' + (x 2 /4 + ex 4 /4 - E) y = 0, y ( +- infinity) = 0, the perturbation coefficients, A/sub n/, in the expansion for the ground-state energy, E(ground state) approx. EPSILON/sub n = 0//sup infinity/ A/sub n/epsilon/sup n/, simplify dramatically as n → infinity: A/sub n/ approx. (6/π 3 )/sup 1/2/(-3)/sup n/GAMMA(n + 1/2). Methods of applied mathematics are used to investigate the nature of perturbation theory in quantum mechanics and show that its large-order behavior is determined by the semiclassical content of the theory. In quantum field theory the perturbation coefficients are computed by summing Feynman graphs. A statistical procedure in a simple lambda phi 4 model for summing the set of all graphs as the number of vertices → infinity is presented. Finally, the connection between the large-order behavior of perturbation theory in quantum electrodynamics and the value of α, the charge on the electron, is discussed. 7 figures
Energy Technology Data Exchange (ETDEWEB)
Fanelli, Fabrizio; Orgera, Gianluigi; Bezzi, Mario; Rossi, Plinio; Allegritti, Massimiliano; Passariello, Roberto [University of Rome, Department of Radiological Sciences, Rome (Italy)
2008-05-15
To evaluate the efficacy and safety of an expanded polytetrafluoroethylene-fluorinated ethylene-propylene (ePTFE/FEP)-covered metallic stent in the management of malignant biliary obstruction. Eighty consecutive patients with malignant common bile duct strictures were treated by placement of 83 covered metallic stents. The stent-graft consists of an inner ePTFE/FEP lining and an outer supporting structure of nitinol wire. Clinical evaluation, assessment of serum bilirubin and liver enzyme levels were analyzed before biliary drainage, before stent-graft placement and during the follow-up period at 1, 3, 6, 9 and 12 months. Technical success was obtained in all cases. After a mean follow-up of 6.9{+-}4.63 months, the 30-day mortality rate was 14.2%. Survival rates were 40% and 20.2% at 6 and 12 months, respectively. Stent-graft patency rates were 95.5%, 92.6% and 85.7% at 3, 6 and 12 months, respectively. Complications occurred in five patients (6.4%); among these, acute cholecystitis was observed in three patients (3.8%). A stent-graft occlusion rate of 9% was observed. The percentage of patients undergoing lifetime palliation (91%) and the midterm patency rate suggest that placement of this ePTFE/FEP-covered stent-graft is safe and highly effective in achieving biliary drainage in patients with malignant strictures of the common bile duct. (orig.)
Kanai, Takahiro; Shiizaki, Kazuhiro; Betsui, Hiroyuki; Aoyagi, Jun; Yamagata, Takanori
2018-05-16
Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disorder. ADPKD is characterized clinically by the presence of multiple bilateral renal cysts that lead to chronic renal failure. The cysts evolve from renal tubular epithelial cells that express the Klotho gene. Notably, Klotho acts as a co-receptor for fibroblast growth factor 23 (FGF23); in this context, it induces phosphaturia and maintains serum phosphate at a normal level. Many reports have shown that decreases in the soluble Klotho level and increases in the FGF23 level are associated with glomerular filtration rate (GFR) decline, but a recent study observed these changes in patient with normal eGFR. It remains unclear whether the decrease in the Klotho level precedes the increase in FGF23. Here, we present an ADPKD patient with enlarged kidneys due to multiple cysts who had a decreased soluble Klotho level but a normal eGFR and a normal FGF23 level. The patient's serum phosphate level was normal, as was the fractional excretion of phosphate (FEP). This appears to be the first reported case to show a decreased soluble Klotho level plus normal eGFR, FGF23, and FEP. These results suggest that Klotho decreases before FGF23 increases and further suggest that Klotho is not required to maintain normal serum phosphate levels in ADPKD if the FEP and serum phosphate levels are normal.
Evolution of curvature perturbation in generalized gravity theories
International Nuclear Information System (INIS)
Matsuda, Tomohiro
2009-01-01
Using the cosmological perturbation theory in terms of the δN formalism, we find the simple formulation of the evolution of the curvature perturbation in generalized gravity theories. Compared with the standard gravity theory, a crucial difference appears in the end-boundary of the inflationary stage, which is due to the non-ideal form of the energy-momentum tensor that depends explicitly on the curvature scalar. Recent study shows that ultraviolet-complete quantum theory of gravity (Horava-Lifshitz gravity) can be approximated by using a generalized gravity action. Our paper may give an important step in understanding the evolution of the curvature perturbation during inflation, where the energy-momentum tensor may not be given by the ideal form due to the corrections from the fundamental theory.
Manzoni, Francesco; Ryde, Ulf
2018-03-01
We have calculated relative binding affinities for eight tetrafluorophenyl-triazole-thiogalactoside inhibitors of galectin-3 with the alchemical free-energy perturbation approach. We obtain a mean absolute deviation from experimental estimates of only 2-3 kJ/mol and a correlation coefficient (R 2) of 0.5-0.8 for seven relative affinities spanning a range of up to 11 kJ/mol. We also studied the effect of using different methods to calculate the charges of the inhibitor and different sizes of the perturbed group (the atoms that are described by soft-core potentials and are allowed to have differing coordinates). However, the various approaches gave rather similar results and it is not possible to point out one approach as consistently and significantly better than the others. Instead, we suggest that such small and reasonable variations in the computational method can be used to check how stable the calculated results are and to obtain a more accurate estimate of the uncertainty than if performing only one calculation with a single computational setup.
Odd-parity perturbations of the self-similar LTB spacetime
Energy Technology Data Exchange (ETDEWEB)
Duffy, Emily M; Nolan, Brien C, E-mail: emilymargaret.duffy27@mail.dcu.ie, E-mail: brien.nolan@dcu.ie [School of Mathematical Sciences, Dublin City University, Glasnevin, Dublin 9 (Ireland)
2011-05-21
We consider the behaviour of odd-parity perturbations of those self-similar LemaItre-Tolman-Bondi spacetimes which admit a naked singularity. We find that a perturbation which evolves from initially regular data remains finite on the Cauchy horizon. Finiteness is demonstrated by considering the behaviour of suitable energy norms of the perturbation (and pointwise values of these quantities) on natural spacelike hypersurfaces. This result holds for a general choice of initial data and initial data surface. Finally, we examine the perturbed Weyl scalars in order to provide a physical interpretation of our results. Taken on its own, this result does not support cosmic censorship; however, a full perturbation of this spacetime would include even-parity perturbations, so we cannot conclude that this spacetime is stable to all linear perturbations.
Perturbation expansions generated by an approximate propagator
International Nuclear Information System (INIS)
Znojil, M.
1987-01-01
Starting from a knowledge of an approximate propagator R at some trial energy guess E 0 , a new perturbative prescription for p-plet of bound states and of their energies is proposed. It generalizes the Rayleigh-Schroedinger (RS) degenerate perturbation theory to the nondiagonal operators R (eliminates a RS need of their diagnolisation) and defines an approximate Hamiltonian T by mere inversion. The deviation V of T from the exact Hamiltonian H is assumed small only after a substraction of a further auxiliary Hartree-Fock-like separable ''selfconsistent'' potential U of rank p. The convergence is illustrated numerically on the anharmonic oscillator example
International Nuclear Information System (INIS)
Fox, D.J.
1983-10-01
Analytic derivatives of the potential energy for Self-Consistent-Field (SCF) wave functions have been developed in recent years and found to be useful tools. The first derivative for configuration interaction (CI) wave functions is also available. This work details the extension of analytic methods to energy second derivatives for CI wave functions. The principal extension required for second derivatives is evaluation of the first order change in the CI wave function with respect to a nuclear perturbation. The shape driven graphical unitary group approach (SDGUGA) direct CI program was adapted to evaluate this term via the coupled-perturbed CI equations. Several iterative schemes are compared for use in solving these equations. The pilot program makes no use of molecular symmetry but the timing results show that utilization of molecular symmetry is desirable. The principles for defining and solving a set of symmetry adapted equations are discussed. Evaluation of the second derivative also requires the solution of the second order coupled-perturbed Hartree-Fock equations to obtain the correction to the molecular orbitals due to the nuclear perturbation. This process takes a consistently higher percentage of the computation time than for the first order equations alone and a strategy for its reduction is discussed
Non-hard sphere thermodynamic perturbation theory.
Zhou, Shiqi
2011-08-21
A non-hard sphere (HS) perturbation scheme, recently advanced by the present author, is elaborated for several technical matters, which are key mathematical details for implementation of the non-HS perturbation scheme in a coupling parameter expansion (CPE) thermodynamic perturbation framework. NVT-Monte Carlo simulation is carried out for a generalized Lennard-Jones (LJ) 2n-n potential to obtain routine thermodynamic quantities such as excess internal energy, pressure, excess chemical potential, excess Helmholtz free energy, and excess constant volume heat capacity. Then, these new simulation data, and available simulation data in literatures about a hard core attractive Yukawa fluid and a Sutherland fluid, are used to test the non-HS CPE 3rd-order thermodynamic perturbation theory (TPT) and give a comparison between the non-HS CPE 3rd-order TPT and other theoretical approaches. It is indicated that the non-HS CPE 3rd-order TPT is superior to other traditional TPT such as van der Waals/HS (vdW/HS), perturbation theory 2 (PT2)/HS, and vdW/Yukawa (vdW/Y) theory or analytical equation of state such as mean spherical approximation (MSA)-equation of state and is at least comparable to several currently the most accurate Ornstein-Zernike integral equation theories. It is discovered that three technical issues, i.e., opening up new bridge function approximation for the reference potential, choosing proper reference potential, and/or using proper thermodynamic route for calculation of f(ex-ref), chiefly decide the quality of the non-HS CPE TPT. Considering that the non-HS perturbation scheme applies for a wide variety of model fluids, and its implementation in the CPE thermodynamic perturbation framework is amenable to high-order truncation, the non-HS CPE 3rd-order or higher order TPT will be more promising once the above-mentioned three technological advances are established. © 2011 American Institute of Physics
Winter, Thomas G.; Alston, Steven G.
1992-02-01
Cross sections have been determined for electron transfer and ionization in collisions between protons and He+ ions at proton energies from several hundred kilo-electron-volts to 2 MeV. A coupled-Sturmian approach is taken, extending the work of Winter [Phys. Rev. A 35, 3799 (1987)] and Stodden et al. [Phys. Rev. A 41, 1281 (1990)] to high energies where perturbative approaches are expected to be valid. An explicit connection is made with the first-order Born approximation for ionization and the impulse version of the distorted, strong-potential Born approximation for electron transfer. The capture cross section is shown to be affected by the presence of target basis functions of positive energy near v2/2, corresponding to the Thomas mechanism.
International Nuclear Information System (INIS)
Winter, T.G.; Alston, S.G.
1992-01-01
Cross sections have been determined for electron transfer and ionization in collisions between protons and He + ions at proton energies from several hundred kilo-electron-volts to 2 MeV. A coupled-Sturmian approach is taken, extending the work of Winter [Phys. Rev. A 35, 3799 (1987)] and Stodden et al. [Phys. Rev. A 41, 1281 (1990)] to high energies where perturbative approaches are expected to be valid. An explicit connection is made with the first-order Born approximation for ionization and the impulse version of the distorted, strong-potential Born approximation for electron transfer. The capture cross section is shown to be affected by the presence of target basis functions of positive energy near v 2 /2, corresponding to the Thomas mechanism
Density perturbations in a braneworld universe with dark radiation
International Nuclear Information System (INIS)
Gumjudpai, Burin; Maartens, Roy; Gordon, Christopher
2003-01-01
We investigate the effects on cosmological density perturbations of dark radiation in a Randall-Sundrum 2-type braneworld. Dark radiation in the background is limited by observational constraints to be a small fraction of the radiation energy density, but it has an interesting qualitative effect in the radiation era. On large scales, it serves to slightly suppress the radiation density perturbations at late times, while boosting the perturbations in dark radiation. In a kinetic (stiff) era, the suppression is much stronger, and drives the density perturbations to zero
Variational Perturbation Treatment of the Confined Hydrogen Atom
Montgomery, H. E., Jr.
2011-01-01
The Schrodinger equation for the ground state of a hydrogen atom confined at the centre of an impenetrable cavity is treated using variational perturbation theory. Energies calculated from variational perturbation theory are comparable in accuracy to the results from a direct numerical solution. The goal of this exercise is to introduce the…
International Nuclear Information System (INIS)
McCoy, B.M.; Wu, T.T.
1976-01-01
Our previous study of Yang-Mills fields is extended by calculating the high-energy behavior of the boson-fermion and of the boson-boson amplitude in sixth-order perturbation theory. In the isovector and isoscalar channels of both these processes the behavior of the amplitude is the same as that found in fermion-fermion scattering
Mercier Franco, Luís Fernando; Castier, Marcelo; Economou, Ioannis G
2017-12-07
We show that the Zwanzig first-order perturbation theory can be obtained directly from a truncated Taylor series expansion of a two-body perturbation theory and that such truncation provides a more accurate prediction of thermodynamic properties than the full two-body perturbation theory. This unexpected result is explained by the quality of the resulting approximation for the fluid radial distribution function. We prove that the first-order and the two-body perturbation theories are based on different approximations for the fluid radial distribution function. To illustrate the calculations, the square-well fluid is adopted. We develop an analytical expression for the two-body perturbed Helmholtz free energy for the square-well fluid. The equation of state obtained using such an expression is compared to the equation of state obtained from the first-order approximation. The vapor-liquid coexistence curve and the supercritical compressibility factor of a square-well fluid are calculated using both equations of state and compared to Monte Carlo simulation data. Finally, we show that the approximation for the fluid radial distribution function given by the first-order perturbation theory provides closer values to the ones calculated via Monte Carlo simulations. This explains why such theory gives a better description of the fluid thermodynamic behavior.
Salah, W
2003-01-01
The influence of the photo-injector exit hall on the energy loss for an accelerated electron beam is investigated, by calculating the total energy transferred from the electrons to the wakefields, which are driven by the beam. The obtained energy loss is compared to those previously obtained for a 'pill-box' cavity. This comparison shows that the influence of this hall, in terms of energy loss, varies over the beam length. It is strongest in the middle of the beam and decreases towards both ends. In consequence of this perturbation, the center of the beam is displaced from its initial position during the first phase (t < 200 ps) where the exit aperture has no effect to a new equilibrium position which takes place at 200 < t < 250 ps. (author)
Energy momentum tensor and operator product expansion in local causal perturbation theory
International Nuclear Information System (INIS)
Prange, D.
2000-09-01
We derive new examples for algebraic relations of interacting fields in local perturbative quantum field theory. The fundamental building blocks in this approach are time ordered products of free (composed) fields. We give explicit formulas for the construction of Poincare covariant ones, which were already known to exist through cohomological arguments. For a large class of theories the canonical energy momentum tensor is shown to be conserved. Classical theories without dimensionful couplings admit an improved tensor that is additionally traceless. On the example of φ 4 -theory we discuss the improved tensor in the quantum theory. Its trace receives an anomalous contribution due to its conservation. Moreover, we define an interacting bilocal normal product for scalar theories. This leads to an operator product expansion of two time ordered fields. (orig.) [de
Coupling-parameter expansion in thermodynamic perturbation theory.
Ramana, A Sai Venkata; Menon, S V G
2013-02-01
An approach to the coupling-parameter expansion in the liquid state theory of simple fluids is presented by combining the ideas of thermodynamic perturbation theory and integral equation theories. This hybrid scheme avoids the problems of the latter in the two phase region. A method to compute the perturbation series to any arbitrary order is developed and applied to square well fluids. Apart from the Helmholtz free energy, the method also gives the radial distribution function and the direct correlation function of the perturbed system. The theory is applied for square well fluids of variable ranges and compared with simulation data. While the convergence of perturbation series and the overall performance of the theory is good, improvements are needed for potentials with shorter ranges. Possible directions for further developments in the coupling-parameter expansion are indicated.
Nonperturbative perturbation theory
International Nuclear Information System (INIS)
Bender, C.M.
1989-01-01
In this talk we describe a recently proposed graphical perturbative calculational scheme for quantum field theory. The basic idea is to expand in the power of the interaction term. For example, to solve a λφ 4 theory in d-dimensional space-time, we introduce a small parameter δ and consider a λ(φ 2 ) 1+δ field theory. We show how to expand such a theory as a series in powers of δ. The resulting perturbation series appears to have a finite radius of convergence and numerical results for low-dimensional models are good. We have computed the two-point and four-point Green's functions to second order in powers of δ and the 2n-point Green's functions (n>2) to order δ. We explain how to renormalize the theory and show that, to first order in powers of δ, when δ>0 and d≥4 the theory is free. This conclusion remains valid to second order in powers of δ, and we believe that it remains valid to all orders in powers of δ. The new perturbative scheme is consistent with global supersymmetry invariance. We examine a two-dimensional supersymmetric quantum field theory in which we do not know of any other means for doing analytical calculations. We illustrate the power of this new technique by computing the ground-state energy density E to second order in this new perturbation theory. We show that there is a beautiful and delicate cancellation between infinite classes of graphs which leads to the result that E=0. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Egan, M J; Maul, P R; Watkins, B M; Venter, A [QuantiSci Ltd., Henley-on-Thames (United Kingdom)
2001-10-01
In order to assist SSI in its reappraisal of the SFR safety case, QuantiSci has been appointed to develop a systematic framework within which to conduct the review of SKB's post-closure performance assessment (PA). The biosphere FEP list presented here was developed for use as reference material in conducting the review. SSI wishes to develop an independent PA capability for a time-dependent biosphere in preparation for the examination of the revised SFR safety case. This report documents the model development that has been undertaken by QuantiSci using the Amber computer code.
International Nuclear Information System (INIS)
Egan, M.J.; Maul, P.R.; Watkins, B.M.; Venter, A.
2001-10-01
In order to assist SSI in its reappraisal of the SFR safety case, QuantiSci has been appointed to develop a systematic framework within which to conduct the review of SKB's post-closure performance assessment (PA). The biosphere FEP list presented here was developed for use as reference material in conducting the review. SSI wishes to develop an independent PA capability for a time-dependent biosphere in preparation for the examination of the revised SFR safety case. This report documents the model development that has been undertaken by QuantiSci using the Amber computer code
International Nuclear Information System (INIS)
Gómez-Valent, Adrià; Karimkhani, Elahe; Solà, Joan
2015-01-01
We determine the Hubble expansion and the general cosmic perturbation equations for a general system consisting of self-conserved matter, ρ m , and self-conserved dark energy (DE), ρ D . While at the background level the two components are non-interacting, they do interact at the perturbations level. We show that the coupled system of matter and DE perturbations can be transformed into a single, third order, matter perturbation equation, which reduces to the (derivative of the) standard one in the case that the DE is just a cosmological constant. As a nontrivial application we analyze a class of dynamical models whose DE density ρ D (H) consists of a constant term, C 0 , and a series of powers of the Hubble rate. These models were previously analyzed from the point of view of dynamical vacuum models, but here we treat them as self-conserved DE models with a dynamical equation of state. We fit them to the wealth of expansion history and linear structure formation data and compare their fit quality with that of the concordance ΛCDM model. Those with C 0 =0 include the so-called ''entropic-force'' and ''QCD-ghost'' DE models, as well as the pure linear model ρ D ∼H, all of which appear strongly disfavored. The models with C 0 ≠0 , in contrast, emerge as promising dynamical DE candidates whose phenomenological performance is highly competitive with the rigid Λ-term inherent to the ΛCDM
Energy Technology Data Exchange (ETDEWEB)
Gómez-Valent, Adrià; Karimkhani, Elahe; Solà, Joan, E-mail: adriagova@ecm.ub.edu, E-mail: e.karimkhani91@basu.ac.ir, E-mail: sola@ecm.ub.edu [High Energy Physics Group, Dept. ECM, and Institut de Ciències del Cosmos (ICC), Universitat de Barcelona, Av. Diagonal 647, E-08028 Barcelona, Catalonia (Spain)
2015-12-01
We determine the Hubble expansion and the general cosmic perturbation equations for a general system consisting of self-conserved matter, ρ{sub m}, and self-conserved dark energy (DE), ρ{sub D}. While at the background level the two components are non-interacting, they do interact at the perturbations level. We show that the coupled system of matter and DE perturbations can be transformed into a single, third order, matter perturbation equation, which reduces to the (derivative of the) standard one in the case that the DE is just a cosmological constant. As a nontrivial application we analyze a class of dynamical models whose DE density ρ{sub D}(H) consists of a constant term, C{sub 0}, and a series of powers of the Hubble rate. These models were previously analyzed from the point of view of dynamical vacuum models, but here we treat them as self-conserved DE models with a dynamical equation of state. We fit them to the wealth of expansion history and linear structure formation data and compare their fit quality with that of the concordance ΛCDM model. Those with C{sub 0}=0 include the so-called ''entropic-force'' and ''QCD-ghost'' DE models, as well as the pure linear model ρ{sub D}∼H, all of which appear strongly disfavored. The models with C{sub 0}≠0 , in contrast, emerge as promising dynamical DE candidates whose phenomenological performance is highly competitive with the rigid Λ-term inherent to the ΛCDM.
Energy Technology Data Exchange (ETDEWEB)
Franceschini, V.; Grecchi, V.; Silverstone, H.J.
1985-09-01
The resonance energies for the hydrogen atom in an electric field, both the real and imaginary parts, have been calculated together from the real Rayleigh-Schroedinger perturbation series by Borel summation. Pade approximants were used to evaluate the Borel transform. The numerical results compare well with values obtained by the complex-coordinate variational method and by sequential use of Pade approximants.
Duchko, A N; Bykov, A D
2015-10-21
Large-order Rayleigh-Schrödinger perturbation theory (RSPT) is applied to the calculation of anharmonic vibrational energy levels of H2CO molecule. We use the model of harmonic oscillators perturbed by anharmonic terms of potential energy. Since the perturbation series typically diverge due to strong couplings, we apply the algebraic approximation technique because of its effectiveness shown earlier by Goodson and Sergeev [J. Chem. Phys. 110, 8205 (1999); ibid. 124, 094111 (2006)] and in our previous articles [A. D. Bykov et al. Opt. Spectrosc. 114, 396 (2013); ibid. 116, 598 (2014)]. To facilitate the resummation of terms contributing to perturbed states, when resonance mixing between states is especially strong and perturbation series diverge very quick, we used repartition of the Hamiltonian by shifting the normal mode frequencies. Energy levels obtained by algebraic approximants were compared with the results of variational calculation. It was found that for low energy states (up to ∼5000 cm(-1)), algebraic approximants gave accurate values of energy levels, which were in excellent agreement with the variational method. For highly excited states, strong and multiple resonances complicate series resummation, but a suitable change of normal mode frequencies allows one to reduce the resonance mixing and to get accurate energy levels. The theoretical background of the problem of RSPT series divergence is discussed along with its numerical analysis. For these purposes, the vibrational energy is considered as a function of a complex perturbation parameter. Layout and classification of its singularities allow us to model the asymptotic behavior of the perturbation series and prove the robustness of the algorithm.
Quasi-degenerate perturbation theory using matrix product states
International Nuclear Information System (INIS)
Sharma, Sandeep; Jeanmairet, Guillaume; Alavi, Ali
2016-01-01
In this work, we generalize the recently proposed matrix product state perturbation theory (MPSPT) for calculating energies of excited states using quasi-degenerate (QD) perturbation theory. Our formulation uses the Kirtman-Certain-Hirschfelder canonical Van Vleck perturbation theory, which gives Hermitian effective Hamiltonians at each order, and also allows one to make use of Wigner’s 2n + 1 rule. Further, our formulation satisfies Granovsky’s requirement of model space invariance which is important for obtaining smooth potential energy curves. Thus, when we use MPSPT with the Dyall Hamiltonian, we obtain a model space invariant version of quasi-degenerate n-electron valence state perturbation theory (NEVPT), a property that the usual formulation of QD-NEVPT2 based on a multipartitioning technique lacked. We use our method on the benchmark problems of bond breaking of LiF which shows ionic to covalent curve crossing and the twist around the double bond of ethylene where significant valence-Rydberg mixing occurs in the excited states. In accordance with our previous work, we find that multi-reference linearized coupled cluster theory is more accurate than other multi-reference theories of similar cost
Quasi-degenerate perturbation theory using matrix product states
Energy Technology Data Exchange (ETDEWEB)
Sharma, Sandeep, E-mail: sanshar@gmail.com; Jeanmairet, Guillaume [Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart (Germany); Alavi, Ali, E-mail: a.alavi@fkf.mpg.de [Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom)
2016-01-21
In this work, we generalize the recently proposed matrix product state perturbation theory (MPSPT) for calculating energies of excited states using quasi-degenerate (QD) perturbation theory. Our formulation uses the Kirtman-Certain-Hirschfelder canonical Van Vleck perturbation theory, which gives Hermitian effective Hamiltonians at each order, and also allows one to make use of Wigner’s 2n + 1 rule. Further, our formulation satisfies Granovsky’s requirement of model space invariance which is important for obtaining smooth potential energy curves. Thus, when we use MPSPT with the Dyall Hamiltonian, we obtain a model space invariant version of quasi-degenerate n-electron valence state perturbation theory (NEVPT), a property that the usual formulation of QD-NEVPT2 based on a multipartitioning technique lacked. We use our method on the benchmark problems of bond breaking of LiF which shows ionic to covalent curve crossing and the twist around the double bond of ethylene where significant valence-Rydberg mixing occurs in the excited states. In accordance with our previous work, we find that multi-reference linearized coupled cluster theory is more accurate than other multi-reference theories of similar cost.
Quasi-degenerate perturbation theory using matrix product states
Sharma, Sandeep; Jeanmairet, Guillaume; Alavi, Ali
2016-01-01
In this work, we generalize the recently proposed matrix product state perturbation theory (MPSPT) for calculating energies of excited states using quasi-degenerate (QD) perturbation theory. Our formulation uses the Kirtman-Certain-Hirschfelder canonical Van Vleck perturbation theory, which gives Hermitian effective Hamiltonians at each order, and also allows one to make use of Wigner's 2n + 1 rule. Further, our formulation satisfies Granovsky's requirement of model space invariance which is important for obtaining smooth potential energy curves. Thus, when we use MPSPT with the Dyall Hamiltonian, we obtain a model space invariant version of quasi-degenerate n-electron valence state perturbation theory (NEVPT), a property that the usual formulation of QD-NEVPT2 based on a multipartitioning technique lacked. We use our method on the benchmark problems of bond breaking of LiF which shows ionic to covalent curve crossing and the twist around the double bond of ethylene where significant valence-Rydberg mixing occurs in the excited states. In accordance with our previous work, we find that multi-reference linearized coupled cluster theory is more accurate than other multi-reference theories of similar cost.
One dimensional systems with singular perturbations
International Nuclear Information System (INIS)
Alvarez, J J; Gadella, M; Nieto, L M; Glasser, L M; Lara, L P
2011-01-01
This paper discusses some one dimensional quantum models with singular perturbations. Eventually, a mass discontinuity is added at the points that support the singular perturbations. The simplest model includes an attractive singular potential with a mass jump both located at the origin. We study the form of the only bound state. Another model exhibits a hard core at the origin plus one or more repulsive deltas with mass jumps at the points supporting these deltas. We study the location and the multiplicity of these resonances for the case of one or two deltas and settle the basis for a generalization. Finally, we consider the harmonic oscillator and the infinite square well plus a singular potential at the origin. We see how the energy of bound states is affected by the singular perturbation.
Adiabatic perturbation theory for atoms and molecules in the low-frequency regime.
Martiskainen, Hanna; Moiseyev, Nimrod
2017-12-14
There is an increasing interest in the photoinduced dynamics in the low frequency, ω, regime. The multiphoton absorptions by molecules in strong laser fields depend on the polarization of the laser and on the molecular structure. The unique properties of the interaction of atoms and molecules with lasers in the low-frequency regime imply new concepts and directions in strong-field light-matter interactions. Here we represent a perturbational approach for the calculations of the quasi-energy spectrum in the low-frequency regime, which avoids the construction of the Floquet operator with extremely large number of Floquet channels. The zero-order Hamiltonian in our perturbational approach is the adiabatic Hamiltonian where the atoms/molecules are exposed to a dc electric field rather than to ac-field. This is in the spirit of the first step in the Corkum three-step model. The second-order perturbation correction terms are obtained when iℏω∂∂τ serves as a perturbation and τ is a dimensionless variable. The second-order adiabatic perturbation scheme is found to be an excellent approach for calculating the ac-field Floquet solutions in our test case studies of a simple one-dimensional time-periodic model Hamiltonian. It is straightforward to implement the perturbation approach presented here for calculating atomic and molecular energy shifts (positions) due to the interaction with low-frequency ac-fields using high-level electronic structure methods. This is enabled since standard quantum chemistry packages allow the calculations of atomic and molecular energy shifts due to the interaction with dc-fields. In addition to the shift of the energy positions, the energy widths (inverse lifetimes) can be obtained at the same level of theory. These energy shifts are functions of the laser parameters (low frequency, intensity, and polarization).
Geometry of perturbed Gaussian states and quantum estimation
International Nuclear Information System (INIS)
Genoni, Marco G; Giorda, Paolo; Paris, Matteo G A
2011-01-01
We address the non-Gaussianity (nG) of states obtained by weakly perturbing a Gaussian state and investigate the relationships with quantum estimation. For classical perturbations, i.e. perturbations to eigenvalues, we found that the nG of the perturbed state may be written as the quantum Fisher information (QFI) distance minus a term depending on the infinitesimal energy change, i.e. it provides a lower bound to statistical distinguishability. Upon moving on isoenergetic surfaces in a neighbourhood of a Gaussian state, nG thus coincides with a proper distance in the Hilbert space and exactly quantifies the statistical distinguishability of the perturbations. On the other hand, for perturbations leaving the covariance matrix unperturbed, we show that nG provides an upper bound to the QFI. Our results show that the geometry of non-Gaussian states in the neighbourhood of a Gaussian state is definitely not trivial and cannot be subsumed by a differential structure. Nevertheless, the analysis of perturbations to a Gaussian state reveals that nG may be a resource for quantum estimation. The nG of specific families of perturbed Gaussian states is analysed in some detail with the aim of finding the maximally non-Gaussian state obtainable from a given Gaussian one. (fast track communication)
Non-perturbative materialization of ghosts
International Nuclear Information System (INIS)
Emparan, Roberto; Garriga, Jaume
2006-01-01
In theories with a hidden ghost sector that couples to visible matter through gravity only, empty space can decay into ghosts and ordinary matter by graviton exchange. Perturbatively, such processes can be very slow provided that the gravity sector violates Lorentz invariance above some cut-off scale. Here, we investigate non-perturbative decay processes involving ghosts, such as the spontaneous creation of self-gravitating lumps of ghost matter, as well as pairs of Bondi dipoles (i.e. lumps of ghost matter chasing after positive energy objects). We find the corresponding instantons and calculate their Euclidean action. In some cases, the instantons induce topology change or have negative Euclidean action. To shed some light on the meaning of such peculiarities, we also consider the nucleation of concentrical domain walls of ordinary and ghost matter, where the Euclidean calculation can be compared with the canonical (Lorentzian) description of tunneling. We conclude that non-perturbative ghost nucleation processes can be safely suppressed in phenomenological scenarios
Numerical studies of QCD renormalons in high-order perturbative expansions
International Nuclear Information System (INIS)
Bauer, Clemens
2013-01-01
Perturbative expansions in four-dimensional non-Abelian gauge theories such as Quantum Chromodynamics (QCD) are expected to be divergent, at best asymptotic. One reason is that it is impossible to strictly exclude from the relevant Feynman diagrams those energy regions in which a perturbative treatment is inapplicable. The divergent nature of the series is then signaled by a rapid (factorial) growth of the perturbative expansion coefficients, commonly referred to as a renormalon. In QCD, the most severe divergences occur in the infrared (IR) limit and therefore they are classified as IR renormalons. Their appearance can be understood within the well-accepted Operator Product Expansion (OPE) framework. According to the OPE, the perturbative calculation of a physical observable must be amended by non-perturbative power corrections that come in the form of condensates, universal characteristics of the rich QCD vacuum structure. Adding up perturbative and non-perturbative contributions, the ambiguity due to the renormalon cancels and the physical observable is well-defined. Although the field has made considerable progress in the last twenty years, a proof of renormalon existence is still pending. It has only been tested assuming strong simplifications or in toy models. The aim of this thesis is to provide the first numerical evidence for renormalon existence in the gauge sector of QCD. We use Numerical Stochastic Perturbation Theory (NSPT) to directly obtain perturbative coefficients within lattice regularization, a means to replace continuum spacetime by a four-dimensional hypercubic lattice. A peculiar feature of NSPT are comparatively low simulation costs when reaching high expansion orders. We examine two distinct observables: the static self-energy of an isolated quark and the elementary plaquette. Following the OPE classification, the static quark self-energy is ideally suited for a renormalon study. Taking into account peculiarities of the lattice approach such
Nonperturbative Quantum Physics from Low-Order Perturbation Theory.
Mera, Héctor; Pedersen, Thomas G; Nikolić, Branislav K
2015-10-02
The Stark effect in hydrogen and the cubic anharmonic oscillator furnish examples of quantum systems where the perturbation results in a certain ionization probability by tunneling processes. Accordingly, the perturbed ground-state energy is shifted and broadened, thus acquiring an imaginary part which is considered to be a paradigm of nonperturbative behavior. Here we demonstrate how the low order coefficients of a divergent perturbation series can be used to obtain excellent approximations to both real and imaginary parts of the perturbed ground state eigenenergy. The key is to use analytic continuation functions with a built-in singularity structure within the complex plane of the coupling constant, which is tailored by means of Bender-Wu dispersion relations. In the examples discussed the analytic continuation functions are Gauss hypergeometric functions, which take as input fourth order perturbation theory and return excellent approximations to the complex perturbed eigenvalue. These functions are Borel consistent and dramatically outperform widely used Padé and Borel-Padé approaches, even for rather large values of the coupling constant.
High-order perturbations of a spherical collapsing star
International Nuclear Information System (INIS)
Brizuela, David; Martin-Garcia, Jose M.; Sperhake, Ulrich; Kokkotas, Kostas D.
2010-01-01
A formalism to deal with high-order perturbations of a general spherical background was developed in earlier work [D. Brizuela, J. M. Martin-Garcia, and G. A. Mena Marugan, Phys. Rev. D 74, 044039 (2006); D. Brizuela, J. M. Martin-Garcia, and G. A. Mena Marugan, Phys. Rev. D 76, 024004 (2007)]. In this paper, we apply it to the particular case of a perfect fluid background. We have expressed the perturbations of the energy-momentum tensor at any order in terms of the perturbed fluid's pressure, density, and velocity. In general, these expressions are not linear and have sources depending on lower-order perturbations. For the second-order case we make the explicit decomposition of these sources in tensor spherical harmonics. Then, a general procedure is given to evolve the perturbative equations of motions of the perfect fluid for any value of the harmonic label. Finally, with the problem of a spherical collapsing star in mind, we discuss the high-order perturbative matching conditions across a timelike surface, in particular, the surface separating the perfect fluid interior from the exterior vacuum.
The mass and angular momentum of reconstructed metric perturbations
van de Meent, Maarten
2017-06-01
We prove a key result regarding the mass and angular momentum content of linear vacuum perturbations of the Kerr metric obtained through the formalism developed by Chrzarnowski, Cohen, and Kegeles (CCK). More precisely, we prove that the Abbott-Deser mass and angular momentum integrals of any such perturbation vanish when that perturbation was obtained from a regular Fourier mode of the Hertz potential. As a corollary we obtain a generalization of previous results on the completion of the ‘no string’ radiation gauge metric perturbation generated by a point particle. We find that for any bound orbit around a Kerr black hole, the mass and angular momentum perturbations completing the CCK metric are simply the energy and angular momentum of the particle ‘outside’ the orbit and vanish ‘inside’ the orbit.
Dimensional perturbation theory for the two-electron atom
International Nuclear Information System (INIS)
Goodson, D.Z.
1987-01-01
Perturbation theory in δ = 1/D, where D is the dimensionality of space, is applied to the two-electron atom. In Chapter 1 an efficient procedure for calculating the coefficients of the perturbation series for the ground-state energy is developed using recursion relations between the moments of the coordinate operators. Results through tenth order are presented. The series is divergent, but Pade summation gives results comparable in accuracy to the best configuration-interaction calculations. The singularity structure of the Pade approximants confirms the hypothesis that the energy as a function of δ has an infinite sequence of poles on the negative real axis that approaches an essential singularity at δ = O. The essential singularity causes the divergence of the perturbation series. There are also two poles at δ = 1 that slow the asymptotic convergence of the low-order terms. In Chapter 2, various techniques are demonstrated for removing the effect of these poles, and accurate results are thereby obtained, even at very low order. In Chapter 3, the large D limit of the correlation energy (CE) is investigated. In the limit D → infinity it is only 35% smaller than at D = 3. It can be made to vanish in the limit by modifying the Hartree-Fock (HF) wavefunction. In Chapter 4, perturbation theory is applied to the Hooke's-law model of the atom. Prospects for treating more-complicated systems are briefly discussed
Application of linear and higher perturbation theory in reactor physics
International Nuclear Information System (INIS)
Woerner, D.
1978-01-01
For small perturbations in the material composition of a reactor according to the first approximation of perturbation theory the eigenvalue perturbation is proportional to the perturbation of the system. This assumption is true for the neutron flux not influenced by the perturbance. The two-dimensional code LINESTO developed for such problems in this paper on the basis of diffusion theory determines the relative change of the multiplication constant. For perturbations varying the neutron flux in the space of energy and position the eigenvalue perturbation is also influenced by this changed neutron flux. In such cases linear perturbation theory yields larger errors. Starting from the methods of calculus of variations there is additionally developed in this paper a perturbation method of calculation permitting in a quick and simple manner to assess the influence of flux perturbation on the eigenvalue perturbation. While the source of perturbations is evaluated in isotropic approximation of diffusion theory the associated inhomogeneous equation may be used to determine the flux perturbation by means of diffusion or transport theory. Possibilities of application and limitations of this method are studied in further systematic investigations on local perturbations. It is shown that with the integrated code system developed in this paper a number of local perturbations may be checked requiring little computing time. With it flux perturbations in first approximation and perturbations of the multiplication constant in second approximation can be evaluated. (orig./RW) [de
Resummation of divergent perturbation series: Application to the vibrational states of H2CO molecule
International Nuclear Information System (INIS)
Duchko, A. N.; Bykov, A. D.
2015-01-01
Large-order Rayleigh–Schrödinger perturbation theory (RSPT) is applied to the calculation of anharmonic vibrational energy levels of H 2 CO molecule. We use the model of harmonic oscillators perturbed by anharmonic terms of potential energy. Since the perturbation series typically diverge due to strong couplings, we apply the algebraic approximation technique because of its effectiveness shown earlier by Goodson and Sergeev [J. Chem. Phys. 110, 8205 (1999); ibid. 124, 094111 (2006)] and in our previous articles [A. D. Bykov et al. Opt. Spectrosc. 114, 396 (2013); ibid. 116, 598 (2014)]. To facilitate the resummation of terms contributing to perturbed states, when resonance mixing between states is especially strong and perturbation series diverge very quick, we used repartition of the Hamiltonian by shifting the normal mode frequencies. Energy levels obtained by algebraic approximants were compared with the results of variational calculation. It was found that for low energy states (up to ∼5000 cm −1 ), algebraic approximants gave accurate values of energy levels, which were in excellent agreement with the variational method. For highly excited states, strong and multiple resonances complicate series resummation, but a suitable change of normal mode frequencies allows one to reduce the resonance mixing and to get accurate energy levels. The theoretical background of the problem of RSPT series divergence is discussed along with its numerical analysis. For these purposes, the vibrational energy is considered as a function of a complex perturbation parameter. Layout and classification of its singularities allow us to model the asymptotic behavior of the perturbation series and prove the robustness of the algorithm
Elliptic CY3folds and non-perturbative modular transformation
International Nuclear Information System (INIS)
Iqbal, Amer; Shabbir, Khurram
2016-01-01
We study the refined topological string partition function of a class of toric elliptically fibered Calabi-Yau threefolds. These Calabi-Yau threefolds give rise to five dimensional quiver gauge theories and are dual to configurations of M5-M2-branes. We determine the Gopakumar-Vafa invariants for these threefolds and show that the genus g free energy is given by the weight 2 g Eisenstein series. We also show that although the free energy at all genera are modular invariant, the full partition function satisfies the non-perturbative modular transformation property discussed by Lockhart and Vafa in arXiv:1210.5909 and therefore the modularity of free energy is up to non-perturbative corrections. (orig.)
Elliptic CY3folds and non-perturbative modular transformation
Energy Technology Data Exchange (ETDEWEB)
Iqbal, Amer [Government College University, Abdus Salam School of Mathematical Sciences, Lahore (Pakistan); Shabbir, Khurram [Government College University, Department of Mathematics, Lahore (Pakistan)
2016-03-15
We study the refined topological string partition function of a class of toric elliptically fibered Calabi-Yau threefolds. These Calabi-Yau threefolds give rise to five dimensional quiver gauge theories and are dual to configurations of M5-M2-branes. We determine the Gopakumar-Vafa invariants for these threefolds and show that the genus g free energy is given by the weight 2 g Eisenstein series. We also show that although the free energy at all genera are modular invariant, the full partition function satisfies the non-perturbative modular transformation property discussed by Lockhart and Vafa in arXiv:1210.5909 and therefore the modularity of free energy is up to non-perturbative corrections. (orig.)
Level density approach to perturbation theory and inverse-energy-weighted sum-rules
International Nuclear Information System (INIS)
Halemane, T.R.
1983-01-01
The terms in the familiar Rayleigh-Schroedinger perturbation series involve eigenvalues and eigenfunctions of the unperturbed operator. A level density formalism, that does not involve computation of eigenvalues and eigenfunctions, is given here for the perturbation series. In the CLT (central limit theorem) limit the expressions take very simple linear forms. The evaluation is in terms of moments and traces of operators and operator products. 3 references
Modeling Small-Amplitude Perturbations in Inertial Confinement Fusion Pellets
Zalesak, Steven; Metzler, N.; Velikovich, A. L.; Gardner, J. H.; Manheimer, W.
2005-10-01
Recent advances in inertial confinement fusion (ICF) technology serve to ensure that imploding laser-driven ICF pellets will spend a significantly larger portion of their time in what is regarded as the ``linear'' portion of their perturbation evolution, i.e., in the presence of small-amplitude but nonetheless evolving perturbations. Since the evolution of these linear perturbations collectively form the initial conditions for the subsequent nonlinear evolution of the pellet, which in turn determines the energy yield of the pellet, the accurate numerical modeling of these small-amplitude perturbations has taken on an increased importance. This modeling is difficult despite the expected linear evolution of the perturbations themselves, because these perturbations are embedded in a highly nonlinear, strongly-shocked, and highly complex flow field which in and of itself stresses numerical computation capabilities, and whose simulation often employs numerical techniques which were not designed with the proper treatment of small-amplitude perturbations in mind. In this paper we will review some of the techniques that we have recently found to be of use toward this end.
Olsson, Martin A.; García-Sosa, Alfonso T.; Ryde, Ulf
2018-01-01
We have studied the binding of 102 ligands to the farnesoid X receptor within the D3R Grand Challenge 2016 blind-prediction competition. First, we employed docking with five different docking software and scoring functions. The selected docked poses gave an average root-mean-squared deviation of 4.2 Å. Consensus scoring gave decent results with a Kendall's τ of 0.26 ± 0.06 and a Spearman's ρ of 0.41 ± 0.08. For a subset of 33 ligands, we calculated relative binding free energies with free-energy perturbation. Five transformations between the ligands involved a change of the net charge and we implemented and benchmarked a semi-analytic correction (Rocklin et al., J Chem Phys 139:184103, 2013) for artifacts caused by the periodic boundary conditions and Ewald summation. The results gave a mean absolute deviation of 7.5 kJ/mol compared to the experimental estimates and a correlation coefficient of R 2 = 0.1. These results were among the four best in this competition out of 22 submissions. The charge corrections were significant (7-8 kJ/mol) and always improved the results. By employing 23 intermediate states in the free-energy perturbation, there was a proper overlap between all states and the precision was 0.1-0.7 kJ/mol. However, thermodynamic cycles indicate that the sampling was insufficient in some of the perturbations.
Optimized Perturbation Theory for Wave Functions of Quantum Systems
International Nuclear Information System (INIS)
Hatsuda, T.; Tanaka, T.; Kunihiro, T.
1997-01-01
The notion of the optimized perturbation, which has been successfully applied to energy eigenvalues, is generalized to treat wave functions of quantum systems. The key ingredient is to construct an envelope of a set of perturbative wave functions. This leads to a condition similar to that obtained from the principle of minimal sensitivity. Applications of the method to the quantum anharmonic oscillator and the double well potential show that uniformly valid wave functions with correct asymptotic behavior are obtained in the first-order optimized perturbation even for strong couplings. copyright 1997 The American Physical Society
Effects of Time-Dependent Inflow Perturbations on Turbulent Flow in a Street Canyon
Duan, G.; Ngan, K.
2017-12-01
Urban flow and turbulence are driven by atmospheric flows with larger horizontal scales. Since building-resolving computational fluid dynamics models typically employ steady Dirichlet boundary conditions or forcing, the accuracy of numerical simulations may be limited by the neglect of perturbations. We investigate the sensitivity of flow within a unit-aspect-ratio street canyon to time-dependent perturbations near the inflow boundary. Using large-eddy simulation, time-periodic perturbations to the streamwise velocity component are incorporated via the nudging technique. Spatial averages of pointwise differences between unperturbed and perturbed velocity fields (i.e., the error kinetic energy) show a clear dependence on the perturbation period, though spatial structures are largely insensitive to the time-dependent forcing. The response of the error kinetic energy is maximized for perturbation periods comparable to the time scale of the mean canyon circulation. Frequency spectra indicate that this behaviour arises from a resonance between the inflow forcing and the mean motion around closed streamlines. The robustness of the results is confirmed using perturbations derived from measurements of roof-level wind speed.
Virial theorem and the Born-Oppenheimer approximation at different orders of perturbation
International Nuclear Information System (INIS)
Olivier, Gabriel; Weislinger, Edmond
1977-01-01
The link between the virial theorem and the adiabatic approximation is studied for a few orders of perturbation. It is shown that the total energy of the system is distributed between the mean values of kinetic and potential energy of the nuclei and the electrons in each order of perturbation. No static approximation connected with the Hellmann-Feynman theorem is made [fr
Perturbative instabilities in Horava gravity
International Nuclear Information System (INIS)
Bogdanos, Charalampos; Saridakis, Emmanuel N
2010-01-01
We investigate the scalar and tensor perturbations in Horava gravity, with and without detailed balance, around a flat background. Once both types of perturbations are taken into account, it is revealed that the theory is plagued by ghost-like scalar instabilities in the range of parameters which would render it power-counting renormalizable, that cannot be overcome by simple tricks such as analytic continuation. Implementing a consistent flow between the UV and IR limits seems thus more challenging than initially presumed, regardless of whether the theory approaches general relativity at low energies or not. Even in the phenomenologically viable parameter space, the tensor sector leads to additional potential problems, such as fine-tunings and super-luminal propagation.
Scalar perturbations on Lemaitre-Tolman-Bondi spacetimes
International Nuclear Information System (INIS)
Zibin, J. P.
2008-01-01
In recent years there has been growing interest in verifying the horizon-scale homogeneity of the Universe that follows from applying the Copernican principle to the observed isotropy. This program has been stimulated by the discovery that a very large void, centered near us, can explain supernova luminosity distance measurements without dark energy. It is crucial to confront such models with as wide a variety of data as possible. With this application in mind, we develop the relativistic theory of linear scalar perturbations on spherically symmetric dust (Lemaitre-Tolman-Bondi) spacetimes, using the covariant 1+1+2 formalism. We show that the evolution of perturbations is determined by a small set of new linear transfer functions. If decaying modes are ignored (to be consistent with the standard inflationary paradigm), the standard techniques of perturbation theory on homogeneous backgrounds, such as harmonic expansion, can be applied, and results closely paralleling those of familiar cosmological perturbation theory can be obtained.
Non-perturbative effects and the refined topological string
Energy Technology Data Exchange (ETDEWEB)
Hatsuda, Yasuyuki [DESY Hamburg (Germany). Theory Group; Tokyo Institute of Technology (Japan). Dept. of Physics; Marino, Marcos [Geneve Univ. (Switzerland). Dept. de Physique Theorique et Section de Mathematiques; Moriyama, Sanefumi [Nagoya Univ. (Japan). Kobayashi Maskawa Inst.; Nagoya Univ. (Japan). Graduate School of Mathematics; Okuyama, Kazumi [Shinshu Univ., Matsumoto, Nagano (Japan). Dept. of Physics
2013-06-15
The partition function of ABJM theory on the three-sphere has non-perturbative corrections due to membrane instantons in the M-theory dual. We show that the full series of membrane instanton corrections is completely determined by the refined topological string on the Calabi-Yau manifold known as local P{sup 1} x P{sup 1}, in the Nekrasov-Shatashvili limit. Our result can be interpreted as a first-principles derivation of the full series of non-perturbative effects for the closed topological string on this Calabi-Yau background. Based on this, we make a proposal for the non-perturbative free energy of topological strings on general, local Calabi-Yau manifolds.
Shielding of External Magnetic Perturbations By Torque In Rotating Tokamak Plasmas
International Nuclear Information System (INIS)
Park, Jong-Kyu; Boozer, Allen H.; Menard, Jonathan E.; Gerhardt, Stefan P.; Sabbagh, Steve A.
2009-01-01
The imposition of a nonaxisymmetric magnetic perturbation on a rotating tokamak plasma requires energy and toroidal torque. Fundamental electrodynamics implies that the torque is essentially limited and must be consistent with the external response of a plasma equilibrium (rvec f) = (rvec j) x (rvec B). Here magnetic measurements on National Spherical Torus eXperiment (NSTX) device are used to derive the energy and the torque, and these empirical evaluations are compared with theoretical calculations based on perturbed scalar pressure equilibria (rvec f) = (rvec (del))p coupled with the theory of nonambipolar transport. The measurement and the theory are consistent within acceptable uncertainties, but can be largely inconsistent when the torque is comparable to the energy. This is expected since the currents associated with the torque are ignored in scalar pressure equilibria, but these currents tend to shield the perturbation.
Martyushev, Leonid M.
2018-03-01
The paper [1] is certainly very useful and important for understanding living systems (e.g. brain) as adaptive, self-organizing patterns. There is no need to enumerate all advantages of the paper, they are obvious. The purpose of my brief comment is to discuss one issue which, as I see it, was not thought out by the authors well enough. As a consequence, their ideas do not find as wide distribution as they otherwise could have found. This issue is related to the name selected for the principle forming the basis of their approach: free-energy principle (FEP). According to the sec. 2.1 [1]: "It asserts that all biological systems maintain their integrity by actively reducing the disorder or dispersion (i.e., entropy) of their sensory and physiological states by minimizing their variational free energy." Let us note that the authors suggested different names for the principle in their earlier works (an objective function, a function of the ensemble density encoded by the organism's configuration and the sensory data to which it is exposed, etc.), and explicitly and correctly mentioned that the free energy and entropy considered by them had nothing in common with the quantities employed in physics [2,3]. It is also obvious that a purely information-theoretic approach used by the authors with regard to the problems under study allows many other wordings and interpretations. However, in spite of this fact, in their last papers as well as in the present paper, the authors choose specifically FEP. Apparently, it may be explained by the intent to additionally base their approach on the foundation of statistical thermodynamics and therefore to demonstrate the universality of the described method. However, this is exactly what might cause misunderstandings specifically among physicists and consequently in their rejection and ignoring of FEP. The physical analogy employed by the authors has the following fundamental inconsistencies: In physics, free energy is used to describe
Higher order alchemical derivatives from coupled perturbed self-consistent field theory.
Lesiuk, Michał; Balawender, Robert; Zachara, Janusz
2012-01-21
We present an analytical approach to treat higher order derivatives of Hartree-Fock (HF) and Kohn-Sham (KS) density functional theory energy in the Born-Oppenheimer approximation with respect to the nuclear charge distribution (so-called alchemical derivatives). Modified coupled perturbed self-consistent field theory is used to calculate molecular systems response to the applied perturbation. Working equations for the second and the third derivatives of HF/KS energy are derived. Similarly, analytical forms of the first and second derivatives of orbital energies are reported. The second derivative of Kohn-Sham energy and up to the third derivative of Hartree-Fock energy with respect to the nuclear charge distribution were calculated. Some issues of practical calculations, in particular the dependence of the basis set and Becke weighting functions on the perturbation, are considered. For selected series of isoelectronic molecules values of available alchemical derivatives were computed and Taylor series expansion was used to predict energies of the "surrounding" molecules. Predicted values of energies are in unexpectedly good agreement with the ones computed using HF/KS methods. Presented method allows one to predict orbital energies with the error less than 1% or even smaller for valence orbitals. © 2012 American Institute of Physics
Energy Technology Data Exchange (ETDEWEB)
Egan, M.J.; Maul, P.R.; Watkins, B.M.; Venter, A. [QuantiSci Ltd., Henley-on-Thames (United Kingdom)
2001-10-01
In order to assist SSI in its reappraisal of the SFR safety case, QuantiSci has been appointed to develop a systematic framework within which to conduct the review of SKB's post-closure performance assessment (PA). The biosphere FEP list presented here was developed for use as reference material in conducting the review. SSI wishes to develop an independent PA capability for a time-dependent biosphere in preparation for the examination of the revised SFR safety case. This report documents the model development that has been undertaken by QuantiSci using the Amber computer code.
On the resolvents methods in quantum perturbation calculations
International Nuclear Information System (INIS)
Burzynski, A.
1979-01-01
This paper gives a systematic review of resolvent methods in quantum perturbation calculations. The case of discrete spectrum of hamiltonian is considered specially (in the literature this is the fewest considered case). The topics of calculations of quantum transitions by using of the resolvent formalism, quantum transitions between states from particular subspaces, the shifts of energy levels, are shown. The main ideas of stationary perturbation theory developed by Lippmann and Schwinger are considered too. (author)
Gas hydrate inhibition by perturbation of liquid water structure
Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Lee, Kun-Hong
2015-06-01
Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates.
Energy Technology Data Exchange (ETDEWEB)
Duchko, A. N. [National Research Tomsk Polytechnic University, Tomsk (Russian Federation); V.E. Zuev Institute of Atmospheric Optics, Tomsk (Russian Federation); Bykov, A. D., E-mail: adbykov@rambler.ru [V.E. Zuev Institute of Atmospheric Optics, Tomsk (Russian Federation)
2015-10-21
Large-order Rayleigh–Schrödinger perturbation theory (RSPT) is applied to the calculation of anharmonic vibrational energy levels of H{sub 2}CO molecule. We use the model of harmonic oscillators perturbed by anharmonic terms of potential energy. Since the perturbation series typically diverge due to strong couplings, we apply the algebraic approximation technique because of its effectiveness shown earlier by Goodson and Sergeev [J. Chem. Phys. 110, 8205 (1999); ibid. 124, 094111 (2006)] and in our previous articles [A. D. Bykov et al. Opt. Spectrosc. 114, 396 (2013); ibid. 116, 598 (2014)]. To facilitate the resummation of terms contributing to perturbed states, when resonance mixing between states is especially strong and perturbation series diverge very quick, we used repartition of the Hamiltonian by shifting the normal mode frequencies. Energy levels obtained by algebraic approximants were compared with the results of variational calculation. It was found that for low energy states (up to ∼5000 cm{sup −1}), algebraic approximants gave accurate values of energy levels, which were in excellent agreement with the variational method. For highly excited states, strong and multiple resonances complicate series resummation, but a suitable change of normal mode frequencies allows one to reduce the resonance mixing and to get accurate energy levels. The theoretical background of the problem of RSPT series divergence is discussed along with its numerical analysis. For these purposes, the vibrational energy is considered as a function of a complex perturbation parameter. Layout and classification of its singularities allow us to model the asymptotic behavior of the perturbation series and prove the robustness of the algorithm.
Supersymmetry restoration in superstring perturbation theory
International Nuclear Information System (INIS)
Sen, Ashoke
2015-01-01
Superstring perturbation theory based on the 1PI effective theory approach has been useful for addressing the problem of mass renormalization and vacuum shift. We derive Ward identities associated with space-time supersymmetry transformation in this approach. This leads to a proof of the equality of renormalized masses of bosons and fermions and identities relating fermionic amplitudes to bosonic amplitudes after taking into account the effect of mass renormalization. This also relates unbroken supersymmetry to a given order in perturbation theory to absence of tadpoles of massless scalars to higher order. The results are valid at the perturbative vacuum as well as in the shifted vacuum when the latter describes the correct ground state of the theory. We apply this to SO(32) heterotic string theory on Calabi-Yau 3-folds where a one loop Fayet-Iliopoulos term apparently breaks supersymmetry at one loop, but analysis of the low energy effective field theory indicates that there is a nearby vacuum where supersymmetry is restored. We explicitly prove that the perturbative amplitudes of this theory around the shifted vacuum indeed satisfy the Ward identities associated with unbroken supersymmetry. We also test the general arguments by explicitly verifying the equality of bosonic and fermionic masses at one loop order in the shifted vacuum, and the appearance of two loop dilaton tadpole in the perturbative vacuum where supersymmetry is expected to be broken.
Supersymmetry restoration in superstring perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Sen, Ashoke [Harish-Chandra Research Institute,Chhatnag Road, Jhusi, Allahabad 211019 (India)
2015-12-14
Superstring perturbation theory based on the 1PI effective theory approach has been useful for addressing the problem of mass renormalization and vacuum shift. We derive Ward identities associated with space-time supersymmetry transformation in this approach. This leads to a proof of the equality of renormalized masses of bosons and fermions and identities relating fermionic amplitudes to bosonic amplitudes after taking into account the effect of mass renormalization. This also relates unbroken supersymmetry to a given order in perturbation theory to absence of tadpoles of massless scalars to higher order. The results are valid at the perturbative vacuum as well as in the shifted vacuum when the latter describes the correct ground state of the theory. We apply this to SO(32) heterotic string theory on Calabi-Yau 3-folds where a one loop Fayet-Iliopoulos term apparently breaks supersymmetry at one loop, but analysis of the low energy effective field theory indicates that there is a nearby vacuum where supersymmetry is restored. We explicitly prove that the perturbative amplitudes of this theory around the shifted vacuum indeed satisfy the Ward identities associated with unbroken supersymmetry. We also test the general arguments by explicitly verifying the equality of bosonic and fermionic masses at one loop order in the shifted vacuum, and the appearance of two loop dilaton tadpole in the perturbative vacuum where supersymmetry is expected to be broken.
Daunizeau, Jean
2018-03-01
What is life? According to Erwin Schrödinger [13], the living cell departs from other physical systems in that it - apparently - resists the second law of thermodynamics by restricting the dynamical repertoire (minimizing the entropy) of its physiological states. This is a physical rephrasing of Claude Bernard's biological notion of homeostasis, namely: the capacity of living systems to self-organize in order to maintain the stability of their internal milieu despite uninterrupted exchanges with an ever-altering external environment [2]. The important point here is that physical systems can neither identify nor prevent a state of high entropy. The Free Energy Principle or FEP was originally proposed as a mathematical description of how the brain actually solves this issue [4]. In line with the Bayesian brain hypothesis, the FEP views the brain as a hierarchical statistical learning machine, endowed with the imperative of minimizing Free Energy, i.e. prediction error. Action prescription under the FEP, however, does not follow standard Bayesian decision theory. Rather, action is assumed to further minimize Free Energy, which makes the active brain a self-fulfilling prophecy machine [6]. This is adaptive, under the assumption that evolution has equipped the brain with innate priors centered on homeostatic set points. In turn, avoiding (surprising) violations of such prior predictions implements homeostatic regulation [10], which becomes increasingly anticipatory as learning unfolds over the course of ontological development [5].
Controlling quark mass determinations non-perturbatively in three-flavour QCD
Campos, Isabel
2017-01-01
The determination of quark masses from lattice QCD simulations requires a non-perturbative renormalization procedure and subsequent scale evolution to high energies, where a conversion to the commonly used MS-bar scheme can be safely established. We present our results for the non-perturbative running of renormalized quark masses in Nf=3 QCD between the electroweak and a hadronic energy scale, where lattice simulations are at our disposal. Recent theoretical advances in combination with well-established techniques allows to follow the scale evolution to very high statistical accuracy, and full control of systematic effects.
Energy Technology Data Exchange (ETDEWEB)
Kamerlin, Shina C. L.; Haranczyk, Maciej; Warshel, Arieh
2009-05-01
Phosphate hydrolysis is ubiquitous in biology. However, despite intensive research on this class of reactions, the precise nature of the reaction mechanism remains controversial. In this work, we have examined the hydrolysis of three homologous phosphate diesters. The solvation free energy was simulated by means of either an implicit solvation model (COSMO), hybrid quantum mechanical / molecular mechanical free energy perturbation (QM/MM-FEP) or a mixed solvation model in which N water molecules were explicitly included in the ab initio description of the reacting system (where N=1-3), with the remainder of the solvent being implicitly modelled as a continuum. Here, both COSMO and QM/MM-FEP reproduce Delta Gobs within an error of about 2kcal/mol. However, we demonstrate that in order to obtain any form of reliable results from a mixed model, it is essential to carefully select the explicit water molecules from short QM/MM runs that act as a model for the true infinite system. Additionally, the mixed models tend to be increasingly inaccurate the more explicit water molecules are placed into the system. Thus, our analysis indicates that this approach provides an unreliable way for modelling phosphate hydrolysis in solution.
Perturbations of the Yang-Mills field in the universe
International Nuclear Information System (INIS)
Zhao Wen
2009-01-01
It has been suggested that the Yang-Mills (YM) field can be a kind of candidate for the inflationary field at high energy scales or dark energy at very low energy scales, which can naturally give the equation of state -1 -2 , from which it follows that the equation of state of the YM field always goes to -1, independent of the initial conditions. By solving the first order Einstein equations and the YM field equations, we find that in the YM field inflationary models, the scale-invariant primordial perturbation power spectrum cannot be generated. Therefore, only using this kind of YM field is not enough to account for inflationary sources. However, as a kind of candidate for dark energy, the YM field has the 'sound speed' cs 2 S = -1/3 < 0, which makes the perturbation oe have a damping behavior at large scales. This provides a way to distinguish the YM field dark energy models from other kinds of models. (research papers)
Growth of matter perturbation in quintessence cosmology
Mulki, Fargiza A. M.; Wulandari, Hesti R. T.
2017-01-01
Big bang theory states that universe emerged from singularity with very high temperature and density, then expands homogeneously and isotropically. This theory gives rise standard cosmological principle which declares that universe is homogeneous and isotropic on large scales. However, universe is not perfectly homogeneous and isotropic on small scales. There exist structures starting from clusters, galaxies even to stars and planetary system scales. Cosmological perturbation theory is a fundamental theory that explains the origin of structures. According to this theory, the structures can be regarded as small perturbations in the early universe, which evolves as the universe expands. In addition to the problem of inhomogeneities of the universe, observations of supernovae Ia suggest that our universe is being accelerated. Various models of dark energy have been proposed to explain cosmic acceleration, one of them is cosmological constant. Because of several problems arise from cosmological constant, the alternative models have been proposed, one of these models is quintessence. We reconstruct growth of structure model following quintessence scenario at several epochs of the universe, which is specified by the effective equation of state parameters for each stage. Discussion begins with the dynamics of quintessence, in which exponential potential is analytically derived, which leads to various conditions of the universe. We then focus on scaling and quintessence dominated solutions. Subsequently, we review the basics of cosmological perturbation theory and derive formulas to investigate how matter perturbation evolves with time in subhorizon scales which leads to structure formation, and also analyze the influence of quintessence to the structure formation. From analytical exploration, we obtain the growth rate of matter perturbation and the existence of quintessence as a dark energy that slows down the growth of structure formation of the universe.
Lacroix, Frederic; Guillot, Mathieu; McEwen, Malcolm; Gingras, Luc; Beaulieu, Luc
2011-10-01
This work presents the experimental extraction of the perturbation factor in megavoltage electron beams for three models of silicon diodes (IBA Dosimetry, EFD and SFD, and the PTW 60012 unshielded) using a plastic scintillation detector (PSD). The authors used a single scanning PSD mounted on a high-precision scanning tank to measure depth-dose curves in 6-, 12-, and 18-MeV clinical electron beams. They also measured depth-dose curves using the IBA Dosimetry, EFD and SFD, and the PTW 60012 unshielded diodes. The authors used the depth-dose curves measured with the PSD as a perturbation-free reference to extract the perturbation factors of the diodes. The authors found that the perturbation factors for the diodes increased substantially with depth, especially for low-energy electron beams. The experimental results show the same trend as published Monte Carlo simulation results for the EFD diode; however, the perturbations measured experimentally were greater. They found that using an effective point of measurement (EPOM) placed slightly away from the source reduced the variation of perturbation factors with depth and that the optimal EPOM appears to be energy dependent. The manufacturer recommended EPOM appears to be incorrect at low electron energy (6 MeV). In addition, the perturbation factors for diodes may be greater than predicted by Monte Carlo simulations.
International Nuclear Information System (INIS)
Lacroix, Frederic; Guillot, Mathieu; McEwen, Malcolm; Gingras, Luc; Beaulieu, Luc
2011-01-01
Purpose: This work presents the experimental extraction of the perturbation factor in megavoltage electron beams for three models of silicon diodes (IBA Dosimetry, EFD and SFD, and the PTW 60012 unshielded) using a plastic scintillation detector (PSD). Methods: The authors used a single scanning PSD mounted on a high-precision scanning tank to measure depth-dose curves in 6-, 12-, and 18-MeV clinical electron beams. They also measured depth-dose curves using the IBA Dosimetry, EFD and SFD, and the PTW 60012 unshielded diodes. The authors used the depth-dose curves measured with the PSD as a perturbation-free reference to extract the perturbation factors of the diodes. Results: The authors found that the perturbation factors for the diodes increased substantially with depth, especially for low-energy electron beams. The experimental results show the same trend as published Monte Carlo simulation results for the EFD diode; however, the perturbations measured experimentally were greater. They found that using an effective point of measurement (EPOM) placed slightly away from the source reduced the variation of perturbation factors with depth and that the optimal EPOM appears to be energy dependent. Conclusions: The manufacturer recommended EPOM appears to be incorrect at low electron energy (6 MeV). In addition, the perturbation factors for diodes may be greater than predicted by Monte Carlo simulations.
Gauge invariance of the Rayleigh--Schroedinger time-independent perturbation theory
International Nuclear Information System (INIS)
Yang, K.H.
1977-08-01
It is shown that the Rayleigh-Schroedinger time-independent perturbation theory is gauge invariant when the operator concerned is the particle's instantaneous energy operator H/sub B/ = (1/2m)[vector p - (e/c) vector A] 2 + eV 0 . More explicitly, it is shown that the energy perturbation corrections of each individual order of every state is gauge invariant. When the vector potential is curlless, the energy corrections of all orders are shown to vanish identically regardless of the explicit form of the vector potential. The relation between causality and gauge invariance is investigated. It is shown that gauge invariance guarantees conformity with causality and violation of gauge invariance implies violation of causality
A modified variation-perturbation approach to zero-point vibrational motion
DEFF Research Database (Denmark)
Åstrand, Per-Olof; Ruud, K.; Sundholm, D.
2000-01-01
We present a detailed investigation of the perturbation approach for calculating zero-point vibrational contributions to molecular properties. It is demonstrated that if the sum of the potential energy and the zero-point vibrational energy is regarded as an effective potential energy, the leading...
Non-perturbative QCD Effect on K-Factor of Drell-Yan Process
International Nuclear Information System (INIS)
Hou Zhaoyu; Zhi Haisu; Chen Junxiao
2006-01-01
By using a non-perturbative quark propagator with the lowest-dimensional condensate contributions from the QCD vacuum, the non-perturbative effect to K-factor of the Drell-Yan process is numerically investigated for 12 6 C- 12 6 C collision at the center-of-mass energy (s) 1/2 = 200 GeV, 630 GeV respectively. Calculated results show that the non-perturbative QCD effect has just a weak influence on K-factor in the two cases.
Non-perturbative versus perturbative renormalization of lattice operators
International Nuclear Information System (INIS)
Goeckeler, M.; Technische Hochschule Aachen; Horsley, R.; Ilgenfritz, E.M.; Oelrich, H.; Forschungszentrum Juelich GmbH; Schierholz, G.; Forschungszentrum Juelich GmbH; Perlt, H.; Schiller, A.; Rakow, P.
1995-09-01
Our objective is to compute the moments of the deep-inelastic structure functions of the nucleon on the lattice. A major source of uncertainty is the renormalization of the lattice operators that enter the calculation. In this talk we compare the renormalization constants of the most relevant twist-two bilinear quark operators which we have computed non-perturbatively and perturbatively to one loop order. Furthermore, we discuss the use of tadpole improved perturbation theory. (orig.)
A view on coupled cluster perturbation theory using a bivariational Lagrangian formulation.
Kristensen, Kasper; Eriksen, Janus J; Matthews, Devin A; Olsen, Jeppe; Jørgensen, Poul
2016-02-14
We consider two distinct coupled cluster (CC) perturbation series that both expand the difference between the energies of the CCSD (CC with single and double excitations) and CCSDT (CC with single, double, and triple excitations) models in orders of the Møller-Plesset fluctuation potential. We initially introduce the E-CCSD(T-n) series, in which the CCSD amplitude equations are satisfied at the expansion point, and compare it to the recently developed CCSD(T-n) series [J. J. Eriksen et al., J. Chem. Phys. 140, 064108 (2014)], in which not only the CCSD amplitude, but also the CCSD multiplier equations are satisfied at the expansion point. The computational scaling is similar for the two series, and both are term-wise size extensive with a formal convergence towards the CCSDT target energy. However, the two series are different, and the CCSD(T-n) series is found to exhibit a more rapid convergence up through the series, which we trace back to the fact that more information at the expansion point is utilized than for the E-CCSD(T-n) series. The present analysis can be generalized to any perturbation expansion representing the difference between a parent CC model and a higher-level target CC model. In general, we demonstrate that, whenever the parent parameters depend upon the perturbation operator, a perturbation expansion of the CC energy (where only parent amplitudes are used) differs from a perturbation expansion of the CC Lagrangian (where both parent amplitudes and parent multipliers are used). For the latter case, the bivariational Lagrangian formulation becomes more than a convenient mathematical tool, since it facilitates a different and faster convergent perturbation series than the simpler energy-based expansion.
Screening of Coulomb interaction and many-body perturbation theory in atoms
International Nuclear Information System (INIS)
Dzyuba, V.A.; Flambaum, V.V.; Sil'vestrov, P.G.; Sushkov, O.P.
1988-01-01
Taking into account the electron Coulomb interaction screening considerably improves the convergence of perturbation theory in residual interaction. The developed technique allows to take into account screening diagrams in all orders of perturbation theory. Calculation of the correlation corrections to the thallium energy levels is carried out as an example
Adiabatic perturbations in pre-big bang models: Matching conditions and scale invariance
International Nuclear Information System (INIS)
Durrer, Ruth; Vernizzi, Filippo
2002-01-01
At low energy, the four-dimensional effective action of the ekpyrotic model of the universe is equivalent to a slightly modified version of the pre-big bang model. We discuss cosmological perturbations in these models. In particular we address the issue of matching the perturbations from a collapsing to an expanding phase. We show that, under certain physically motivated and quite generic assumptions on the high energy corrections, one obtains n=0 for the spectrum of scalar perturbations in the original pre-big bang model (with a vanishing potential). With the same assumptions, when an exponential potential for the dilaton is included, a scale invariant spectrum (n=1) of adiabatic scalar perturbations is produced under very generic matching conditions, both in a modified pre-big bang and ekpyrotic scenario. We also derive the resulting spectrum for arbitrary power law scale factors matched to a radiation-dominated era
Influence of resonant magnetic perturbations on transient heat load deposition and fast ion losses
International Nuclear Information System (INIS)
Rack, Michael Thomas
2014-01-01
Thermonuclear fusion is the energy conversion process which keeps the sun shining. For the last six decades, researchers have been investigating the physics involved in order to enable the usage of this energy supply on Earth. The most promising candidates for fusion power plants are based on magnetic confinement of plasma to provide the ideal conditions for efficient thermonuclear fusion in well controlled surroundings. One important aspect is the control of instabilities that occur in the edge region of the plasma and lead to an ejection of huge amounts of energy. Magnetic perturbation fields which are resonant in the plasma edge are found to modify the plasma favourably and reduce the impact of these instabilities. This dissertation focuses on the effects of resonant magnetic perturbation fields on the ejected energy as well as on the drawbacks of these perturbation fields. The transient energy ejection which is triggered by the instabilities causes extreme heat loads on the wall components in fusion devices. Therefore, it is crucial to understand how resonant magnetic perturbation fields affect the heat load deposition. Furthermore, the impact of resonant magnetic perturbation fields on the confinement of fast ions is an important aspect as fast ions are still required to be well confined in order to avoid additional wall loads and increase the fusion efficiency. Recent upgrades on the Joint European Torus allow for a detailed study of the heat load deposition profiles caused by transient events. Throughout this work, the new features are used for the study of the modifications of the transient heat load depositions that occur if resonant magnetic perturbation fields are applied. This leads to a further understanding of the processes involved during the plasma edge instabilities. Additionally, an alternative method using lower hybrid waves for applying resonant magnetic perturbations is investigated. Furthermore, a new diagnostic, capable of detecting fast ion
Influence of resonant magnetic perturbations on transient heat load deposition and fast ion losses
Energy Technology Data Exchange (ETDEWEB)
Rack, Michael Thomas
2014-07-11
Thermonuclear fusion is the energy conversion process which keeps the sun shining. For the last six decades, researchers have been investigating the physics involved in order to enable the usage of this energy supply on Earth. The most promising candidates for fusion power plants are based on magnetic confinement of plasma to provide the ideal conditions for efficient thermonuclear fusion in well controlled surroundings. One important aspect is the control of instabilities that occur in the edge region of the plasma and lead to an ejection of huge amounts of energy. Magnetic perturbation fields which are resonant in the plasma edge are found to modify the plasma favourably and reduce the impact of these instabilities. This dissertation focuses on the effects of resonant magnetic perturbation fields on the ejected energy as well as on the drawbacks of these perturbation fields. The transient energy ejection which is triggered by the instabilities causes extreme heat loads on the wall components in fusion devices. Therefore, it is crucial to understand how resonant magnetic perturbation fields affect the heat load deposition. Furthermore, the impact of resonant magnetic perturbation fields on the confinement of fast ions is an important aspect as fast ions are still required to be well confined in order to avoid additional wall loads and increase the fusion efficiency. Recent upgrades on the Joint European Torus allow for a detailed study of the heat load deposition profiles caused by transient events. Throughout this work, the new features are used for the study of the modifications of the transient heat load depositions that occur if resonant magnetic perturbation fields are applied. This leads to a further understanding of the processes involved during the plasma edge instabilities. Additionally, an alternative method using lower hybrid waves for applying resonant magnetic perturbations is investigated. Furthermore, a new diagnostic, capable of detecting fast ion
(Non)perturbative gravity, nonlocality, and nice slices
International Nuclear Information System (INIS)
Giddings, Steven B.
2006-01-01
Perturbative dynamics of gravity is investigated for high-energy scattering and in black hole backgrounds. In the latter case, a straightforward perturbative analysis fails, in a close parallel to the failure of the former when the impact parameter reaches the Schwarzschild radius. This suggests a flaw in a semiclassical description of physics on spatial slices that intersect both outgoing Hawking radiation and matter that has carried information into a black hole; such slices are instrumental in a general argument for black hole information loss. This indicates a possible role for the proposal that nonperturbative gravitational physics is intrinsically nonlocal
A primer for chiral perturbation theory
Scherer, Stefan
2012-01-01
Chiral Perturbation Theory, as effective field theory, is a commonly accepted and well established working tool, approximating quantum chromodynamics at energies well below typical hadron masses. This volume, based on a number of lectures and supplemented with additional material, provides a pedagogical introduction for graduate students and newcomers entering the field from related areas of nuclear and particle physics. Starting with the the Lagrangian of the strong interactions and general symmetry principles, the basic concepts of Chiral Perturbation Theory in the mesonic and baryonic sectors are developed. The application of these concepts is then illustrated with a number of examples. A large number of exercises (81, with complete solutions) are included to familiarize the reader with helpful calculational techniques.
Wong, Kin-Yiu; Gao, Jiali
2008-09-09
In this paper, we describe an automated integration-free path-integral (AIF-PI) method, based on Kleinert's variational perturbation (KP) theory, to treat internuclear quantum-statistical effects in molecular systems. We have developed an analytical method to obtain the centroid potential as a function of the variational parameter in the KP theory, which avoids numerical difficulties in path-integral Monte Carlo or molecular dynamics simulations, especially at the limit of zero-temperature. Consequently, the variational calculations using the KP theory can be efficiently carried out beyond the first order, i.e., the Giachetti-Tognetti-Feynman-Kleinert variational approach, for realistic chemical applications. By making use of the approximation of independent instantaneous normal modes (INM), the AIF-PI method can readily be applied to many-body systems. Previously, we have shown that in the INM approximation, the AIF-PI method is accurate for computing the quantum partition function of a water molecule (3 degrees of freedom) and the quantum correction factor for the collinear H(3) reaction rate (2 degrees of freedom). In this work, the accuracy and properties of the KP theory are further investigated by using the first three order perturbations on an asymmetric double-well potential, the bond vibrations of H(2), HF, and HCl represented by the Morse potential, and a proton-transfer barrier modeled by the Eckart potential. The zero-point energy, quantum partition function, and tunneling factor for these systems have been determined and are found to be in excellent agreement with the exact quantum results. Using our new analytical results at the zero-temperature limit, we show that the minimum value of the computed centroid potential in the KP theory is in excellent agreement with the ground state energy (zero-point energy) and the position of the centroid potential minimum is the expectation value of particle position in wave mechanics. The fast convergent property
GENP-2, Program System for Integral Reactor Perturbation
International Nuclear Information System (INIS)
Boioli, A.; Cecchini, G.P.
1975-01-01
1 - Description of problem or function: GENP-2 is a system of programs that use 'generalized perturbation theory' to calculate the perturbations of reactor integral characteristics which can be expressed by means of ratios between linear or bilinear functionals of the real and/or adjoint fluxes (e.g. reaction rate ratios), due to cross section perturbations. 2 - Method of solution: GENP-2 consists of the following codes: DDV, SORCI, CIAP-PMN and GLOBP-2D. DDV calculates the real or adjoint fluxes and power distribution using multigroup diffusion theory in 2-dimensions. SORCI uses the fluxes from DDV to calculate the real and/or adjoint general perturbation sources. CIAP-PMN reads the sources from SORCI and uses them in the real or adjoint generalised importance calculations (2 dimensions, multi- group diffusion). GLOBP-2D uses the importance calculated by CIAP-PMN, and the fluxes calculated by DDV, in generalised perturbation expressions to calculate the perturbation in the quantity of interest. 3 - Restrictions on the complexity of the problem: DDV although variably dimensioned has the following restrictions: - max. number of mesh points 6400; - max. number of mesh points in 1-dimension 81; - max. number of regions 6400; - max. number of energy groups 100; - if power distribution calculated, product of number of groups and number of regions 2500. The other programs have the same restrictions if applicable
Perturbations of ultralight vector field dark matter
Energy Technology Data Exchange (ETDEWEB)
Cembranos, J.A.R.; Maroto, A.L.; Jareño, S.J. Núñez [Departamento de Física Teórica I, Universidad Complutense de Madrid, E-28040 Madrid (Spain)
2017-02-13
We study the dynamics of cosmological perturbations in models of dark matter based on ultralight coherent vector fields. Very much as for scalar field dark matter, we find two different regimes in the evolution: for modes with k{sup 2}≪Hma, we have a particle-like behaviour indistinguishable from cold dark matter, whereas for modes with k{sup 2}≫Hma, we get a wave-like behaviour in which the sound speed is non-vanishing and of order c{sub s}{sup 2}≃k{sup 2}/m{sup 2}a{sup 2}. This implies that, also in these models, structure formation could be suppressed on small scales. However, unlike the scalar case, the fact that the background evolution contains a non-vanishing homogeneous vector field implies that, in general, the evolution of the three kinds of perturbations (scalar, vector and tensor) can no longer be decoupled at the linear level. More specifically, in the particle regime, the three types of perturbations are actually decoupled, whereas in the wave regime, the three vector field perturbations generate one scalar-tensor and two vector-tensor perturbations in the metric. Also in the wave regime, we find that a non-vanishing anisotropic stress is present in the perturbed energy-momentum tensor giving rise to a gravitational slip of order (Φ−Ψ)/Φ∼c{sub s}{sup 2}. Moreover in this regime the amplitude of the tensor to scalar ratio of the scalar-tensor modes is also h/Φ∼c{sub s}{sup 2}. This implies that small-scale density perturbations are necessarily associated to the presence of gravity waves in this model. We compare their spectrum with the sensitivity of present and future gravity waves detectors.
A general-model-space diagrammatic perturbation theory
International Nuclear Information System (INIS)
Hose, G.; Kaldor, U.
1980-01-01
A diagrammatic many-body perturbation theory applicable to arbitrary model spaces is presented. The necessity of having a complete model space (all possible occupancies of the partially-filled shells) is avoided. This requirement may be troublesome for systems with several well-spaced open shells, such as most atomic and molecular excited states, as a complete model space spans a very broad energy range and leaves out states within that range, leading to poor or no convergence of the perturbation series. The method presented here would be particularly useful for such states. The solution of a model problem (He 2 excited Σ + sub(g) states) is demonstrated. (Auth.)
A primer for Chiral Perturbative Theory
International Nuclear Information System (INIS)
Scherer, Stefan; Schindler, Matthias R.; George Washington Univ., Washington, DC
2012-01-01
Chiral Perturbation Theory, as effective field theory, is a commonly accepted and well established working tool, approximating quantum chromodynamics at energies well below typical hadron masses. This volume, based on a number of lectures and supplemented with additional material, provides a pedagogical introduction for graduate students and newcomers entering the field from related areas of nuclear and particle physics. Starting with the the Lagrangian of the strong interactions and general symmetry principles, the basic concepts of Chiral Perturbation Theory in the mesonic and baryonic sectors are developed. The application of these concepts is then illustrated with a number of examples. A large number of exercises (81, with complete solutions) are included to familiarize the reader with helpful calculational techniques. (orig.)
Perturbative quantum chromodynamics
1989-01-01
This book will be of great interest to advanced students and researchers in the area of high energy theoretical physics. Being the most complete and updated review volume on Perturbative QCD, it serves as an extremely useful textbook or reference book. Some of the reviews in this volume are the best that have been written on the subject anywhere. Contents: Factorization of Hard Processes in QCD (J C Collins, D E Soper & G Sterman); Exclusive Processes in Quantum Chromodynamics (S J Brodsky & G P Lepage); Coherence and Physics of QCD Jets (Yu L Dokshitzer, V A Khoze & S I Troyan); Pomeron in Qu
Interacting fermions in two dimensions: Beyond the perturbation theory
International Nuclear Information System (INIS)
Gangadharaiah, S.; Maslov, D.L.; Chubukov, A.V.; Glazman, L.I.
2005-05-01
We consider a system of 2D fermions with short-range interaction. A straightforward perturbation theory is shown to be ill-defined even for an infinitesimally weak interaction, as the perturbative series for the self-energy diverges near the mass shell. We show that the divergences result from the interaction of fermions with the zero-sound collective mode. By re-summing the most divergent diagrams, we obtain a closed form of the self-energy near the mass shell. The spectral function exhibits a threshold feature at the onset of the emission of the zero-sound waves. We also show that the interaction with the zero sound does not affect a non- analytic, T 2 -part of the specific heat. (author)
Scenario development and analysis in JNC'S second progress report
International Nuclear Information System (INIS)
Umeki, H.; Makino, H.; Miyahara, K.; Naito, M.
2001-01-01
Scenario development and analysis is an integral part of the performance assessment in the JNC's second progress report which will be issued by the end of November 1999. A systematic approach has been elaborated to ensure traceability and transparency in overall context of the scenario development and set up of calculation cases for assessment of the repository performance. In this approach, the hierarchical FEP matrix was designed to flexibly identify FEPs at different level of detail. The reasoned argument with clearly defined criteria was then applied for screening and grouping of FEPs to define scenarios in the form of influence diagrams. Scenarios and calculation cases were developed based on the expected safety functions of disposal system and relationships with potential detrimental/favorable factors and perturbation factors. The process to develop scenarios and calculation cases are recorded and managed in a computer system. (authors)
Quasipotential in the fourth order of perturbation theory
International Nuclear Information System (INIS)
Bojkova, N.A.; Dvoeglazov, V.V.; Tyukhtyaev, Yu.N.; Faustov, R.N.
1992-01-01
The quasipotential in the fourth order of perturbation theory is calculated in the Coulomb gauge for the unequal mass particles. It could be used for the future calculations of energy spectra in two-body systems. 15 refs.; 1 fig
A nanowire based triboelectric nanogenerator for harvesting water wave energy and its applications
Li, Xiaoyi; Tao, Juan; Zhu, Jing; Pan, Caofeng
2017-07-01
The ocean wave energy is one of the most promising renewable and clean energy sources for human life, which is the so-called "Blue energy." In this work, a nanowire based triboelectric nanogenerator was designed for harvesting wave energy. The nanowires on the surface of FEP largely raise the contacting area with water and also make the polymer film hydrophobic. The output can reach 10 μ A and 200 V. When combined with a capacitor, an infrared emitter, and a receiver, a self-powered wireless infrared system is fabricated, which can be used in the fields of communication and detecting.
Vlaisavljevich, Bess; Shiozaki, Toru
2016-08-09
We report the development of the theory and computer program for analytical nuclear energy gradients for (extended) multistate complete active space perturbation theory (CASPT2) with full internal contraction. The vertical shifts are also considered in this work. This is an extension of the fully internally contracted CASPT2 nuclear gradient program recently developed for a state-specific variant by us [MacLeod and Shiozaki, J. Chem. Phys. 2015, 142, 051103]; in this extension, the so-called λ equation is solved to account for the variation of the multistate CASPT2 energies with respect to the change in the amplitudes obtained in the preceding state-specific CASPT2 calculations, and the Z vector equations are modified accordingly. The program is parallelized using the MPI3 remote memory access protocol that allows us to perform efficient one-sided communication. The optimized geometries of the ground and excited states of a copper corrole and benzophenone are presented as numerical examples. The code is publicly available under the GNU General Public License.
Non-perturbative inputs for gluon distributions in the hadrons
International Nuclear Information System (INIS)
Ermolaev, B.I.; Troyan, S.I.
2017-01-01
Description of hadronic reactions at high energies is conventionally done in the framework of QCD factorization. All factorization convolutions comprise non-perturbative inputs mimicking non-perturbative contributions and perturbative evolution of those inputs. We construct inputs for the gluon-hadron scattering amplitudes in the forward kinematics and, using the optical theorem, convert them into inputs for gluon distributions in the hadrons, embracing the cases of polarized and unpolarized hadrons. In the first place, we formulate mathematical criteria which any model for the inputs should obey and then suggest a model satisfying those criteria. This model is based on a simple reasoning: after emitting an active parton off the hadron, the remaining set of spectators becomes unstable and therefore it can be described through factors of the resonance type, so we call it the resonance model. We use it to obtain non-perturbative inputs for gluon distributions in unpolarized and polarized hadrons for all available types of QCD factorization: basic, K_T-and collinear factorizations. (orig.)
Non-perturbative inputs for gluon distributions in the hadrons
Energy Technology Data Exchange (ETDEWEB)
Ermolaev, B.I. [Ioffe Physico-Technical Institute, Saint Petersburg (Russian Federation); Troyan, S.I. [St. Petersburg Institute of Nuclear Physics, Gatchina (Russian Federation)
2017-03-15
Description of hadronic reactions at high energies is conventionally done in the framework of QCD factorization. All factorization convolutions comprise non-perturbative inputs mimicking non-perturbative contributions and perturbative evolution of those inputs. We construct inputs for the gluon-hadron scattering amplitudes in the forward kinematics and, using the optical theorem, convert them into inputs for gluon distributions in the hadrons, embracing the cases of polarized and unpolarized hadrons. In the first place, we formulate mathematical criteria which any model for the inputs should obey and then suggest a model satisfying those criteria. This model is based on a simple reasoning: after emitting an active parton off the hadron, the remaining set of spectators becomes unstable and therefore it can be described through factors of the resonance type, so we call it the resonance model. We use it to obtain non-perturbative inputs for gluon distributions in unpolarized and polarized hadrons for all available types of QCD factorization: basic, K{sub T}-and collinear factorizations. (orig.)
Extended Møller-Plesset perturbation theory for dynamical and static correlations
International Nuclear Information System (INIS)
Tsuchimochi, Takashi; Van Voorhis, Troy
2014-01-01
We present a novel method that appropriately handles both dynamical and static electron correlations in a balanced manner, using a perturbation theory on a spin-extended Hartree-Fock (EHF) wave function reference. While EHF is a suitable candidate for degenerate systems where static correlation is ubiquitous, it is known that most of dynamical correlation is neglected in EHF. In this work, we derive a perturbative correction to a fully spin-projected self-consistent wave function based on second-order Møller-Plesset perturbation theory (MP2). The proposed method efficiently captures the ability of EHF to describe static correlation in degeneracy, combined with MP2's ability to treat dynamical correlation effects. We demonstrate drastic improvements on molecular ground state and excited state potential energy curves and singlet-triplet splitting energies over both EHF and MP2 with similar computational effort to the latter
Giner, Emmanuel; Angeli, Celestino; Garniron, Yann; Scemama, Anthony; Malrieu, Jean-Paul
2017-06-01
The present paper introduces a new multi-reference perturbation approach developed at second order, based on a Jeziorski-Mokhorst expansion using individual Slater determinants as perturbers. Thanks to this choice of perturbers, an effective Hamiltonian may be built, allowing for the dressing of the Hamiltonian matrix within the reference space, assumed here to be a CAS-CI. Such a formulation accounts then for the coupling between the static and dynamic correlation effects. With our new definition of zeroth-order energies, these two approaches are strictly size-extensive provided that local orbitals are used, as numerically illustrated here and formally demonstrated in the Appendix. Also, the present formalism allows for the factorization of all double excitation operators, just as in internally contracted approaches, strongly reducing the computational cost of these two approaches with respect to other determinant-based perturbation theories. The accuracy of these methods has been investigated on ground-state potential curves up to full dissociation limits for a set of six molecules involving single, double, and triple bond breaking together with an excited state calculation. The spectroscopic constants obtained with the present methods are found to be in very good agreement with the full configuration interaction results. As the present formalism does not use any parameter or numerically unstable operation, the curves obtained with the two methods are smooth all along the dissociation path.
Compact perturbative expressions for neutrino oscillations in matter
Energy Technology Data Exchange (ETDEWEB)
Denton, Peter B. [Theoretical Physics Department, Fermi National Accelerator Laboratory,P.O. Box 500, Batavia, IL 60510 (United States); Physics & Astronomy Department, Vanderbilt University,PMB 401807, 2301 Vanderbilt Place, Nashville, TN 37235 (United States); Minakata, Hisakazu [Instituto de Física, Universidade de São Paulo,C.P. 66.318, 05315-970 São Paulo (Brazil); Department of Physics, Yachay Tech University,San Miguel de Urcuquí 100119 (Ecuador); Parke, Stephen J. [Theoretical Physics Department, Fermi National Accelerator Laboratory,P.O. Box 500, Batavia, IL 60510 (United States)
2016-06-08
We further develop and extend a recent perturbative framework for neutrino oscillations in uniform matter density so that the resulting oscillation probabilities are accurate for the complete matter potential versus baseline divided by neutrino energy plane. This extension also gives the exact oscillation probabilities in vacuum for all values of baseline divided by neutrino energy. The expansion parameter used is related to the ratio of the solar to the atmospheric Δm{sup 2} scales but with a unique choice of the atmospheric Δm{sup 2} such that certain first-order effects are taken into account in the zeroth-order Hamiltonian. Using a mixing matrix formulation, this framework has the exceptional feature that the neutrino oscillation probability in matter has the same structure as in vacuum, to all orders in the expansion parameter. It also contains all orders in the matter potential and sin θ{sub 13}. It facilitates immediate physical interpretation of the analytic results, and makes the expressions for the neutrino oscillation probabilities extremely compact and very accurate even at zeroth order in our perturbative expansion. The first and second order results are also given which improve the precision by approximately two or more orders of magnitude per perturbative order.
Analytic continuation and perturbative expansions in QCD
Czech Academy of Sciences Publication Activity Database
Caprini, I.; Fischer, Jan
2002-01-01
Roč. 24, - (2002), s. 127-135 ISSN 1434-6044 R&D Projects: GA MPO RP-4210/69 Institutional research plan: CEZ:AV0Z1010920 Keywords : perturbative expansion * quantum chromodynamics * infrared ambiguity * essential singularities Subject RIV: BF - Elementary Particles and High Energy Physics Impact factor: 6.162, year: 2002
Perturbative two- and three-loop coefficients from large β Monte Carlo
Lepage, G. P.; Mackenzie, P. B.; Shakespeare, N. H.; Trottier, H. D.
Perturbative coefficients for Wilson loops and the static quark self-energy are extracted from Monte Carlo simulations at large β on finite volumes, where all the lattice momenta are large. The Monte Carlo results are in excellent agreement with perturbation theory through second order. New results for third order coefficients are reported. Twisted boundary conditions are used to eliminate zero modes and to suppress Z3 tunneling.
Perturbative two- and three-loop coefficients from large b Monte Carlo
International Nuclear Information System (INIS)
Lepage, G.P.; Mackenzie, P.B.; Shakespeare, N.H.; Trottier, H.D.
1999-01-01
Perturbative coefficients for Wilson loops and the static quark self-energy are extracted from Monte Carlo simulations at large β on finite volumes, where all the lattice momenta are large. The Monte Carlo results are in excellent agreement with perturbation theory through second order. New results for third order coefficients are reported. Twisted boundary conditions are used to eliminate zero modes and to suppress Z 3 tunneling
Perturbative two- and three-loop coefficients from large β Monte Carlo
International Nuclear Information System (INIS)
Lepage, G.P.; Mackenzie, P.B.; Shakespeare, N.H.; Trottier, H.D.
2000-01-01
Perturbative coefficients for Wilson loops and the static quark self-energy are extracted from Monte Carlo simulations at large β on finite volumes, where all the lattice momenta are large. The Monte Carlo results are in excellent agreement with perturbation theory through second order. New results for third order coefficients are reported. Twisted boundary conditions are used to eliminate zero modes and to suppress Z 3 tunneling
Perturbative Universality in Soft Particle Production
Khoze, V A; Ochs, Wolfgang; Khoze, Valery A.; Lupia, Sergio; Ochs, Wolfgang
1998-01-01
The spectrum of partons in a QCD jet becomes independent of the primary energy in the low momentum limit. This follows within the perturbative QCD from the colour coherence in soft gluon branching. Remarkably, the hadrons follow such behaviour closely, suggesting the parton hadron duality picture to be appropriate also for the low momentum particles. More generally, this scaling property holds for particles of low transverse and arbitrary longitudinal momentum, which explains an old experimental observation (``fan invariance''). Further tests of the perturbatively based picture for soft particle production are proposed for three-jet events in e+e- annihilation and di-jet production events in gamma p, gamma-gamma and p\\bar p collisions. They are based upon the difference in the intensity of the soft radiation from primary q\\bar q and gg antennae.
Cosmological perturbations in a family of deformations of general relativity
International Nuclear Information System (INIS)
Krasnov, Kirill; Shtanov, Yuri
2010-01-01
We study linear cosmological perturbations in a previously introduced family of deformations of general relativity characterized by the absence of new degrees of freedom. The homogeneous and isotropic background in this class of theories is unmodified and is described by the usual Friedmann equations. The theory of cosmological perturbations is modified and the relevant deformation parameter has the dimension of length. Gravitational perturbations of the scalar type can be described by a certain relativistic potential related to the matter perturbations just as in general relativity. A system of differential equations describing the evolution of this potential and of the stress-energy density perturbations is obtained. We find that the evolution of scalar perturbations proceeds with a modified effective time-dependent speed of sound, which, contrary to the case of general relativity, does not vanish even at the matter-dominated stage. In a broad range of values of the length parameter controlling the deformation, a specific transition from the regime of modified gravity to the regime of general relativity in the evolution of scalar perturbations takes place during the radiation domination. In this case, the resulting power spectrum of perturbations in radiation and dark matter is suppressed on the comoving spatial scales that enter the Hubble radius before this transition. We estimate the bounds on the deformation parameter for which this suppression does not lead to observable consequences. Evolution of scalar perturbations at the inflationary stage is modified but very slightly and the primordial spectrum generated during inflation is not noticeably different from the one obtained in general relativity
International Nuclear Information System (INIS)
Wright, H.L.; Meason, J.L.; Wolf, M.; Harvey, J.T.
1976-01-01
Measurements have been performed on the perturbing effect of a number of scattering materials by the 'free-field' neutron leakage spectrum from a Godiva Type Critical Assembly (White Sands Missile Range Fast Burst Reactor). The results of these measurements are interpreted in relation to some of the general parameters characterizing a neutron environment, namely, the average neutron energy >10 KeV, the spectral index and the hardness parameter. Three neutron spectrum measurements have been performed, each under different experimental configurations of scattering materials. Results from these measurements show the following with relation to the spectral index: (1) The neutron environment on the core surface and at 12-inches from the core surface (free-field) yield a spectral index of 6.8, (2) The neutron environment behind a 4.75-inch Plexiglas plate yield 4.6 for the spectral index and (3) The neutron environment behind a 2-inch aluminum plate yield 6.7 for the spectral index. It is concluded that the core surface and the 12-inch from core surface neutron environment are identical with the 'free-field' neutron environment at 20-inches when considering only those neutrons with energy >10 KeV. On the other hand, it appears that the 4.75 inches of Plexiglas severely perturbs the 'free-field' neutron environment, i.e., a much harder neutron spectrum >10 KeV. In the situation where 2-inches of aluminum is used as the perturbing medium, essentially no change in the neutron spectrum >10 KeV is noted
Calculation of the Odderon intercept in perturbative QCD
International Nuclear Information System (INIS)
Gauron, P.; Lipatov, L.; Nicolescu, B.; Paris-6 Univ., 75
1993-01-01
The question of the equality of hadron-hadron and hadron-antihadron cross sections at very high energies is investigated. By using a variational method combined with conformal invariant techniques it is shown that the Odderon J-plane singularity in the leading logarithmic approximation of QCD lies above 1. Therefore, in the perturbative theory the difference between hadron-hadron and antihadron-hadron interactions grows with energy. (K.A.) 11 refs
Perturbation theory of low-dimensional quantum liquids. I. The pseudoparticle-operator basis
International Nuclear Information System (INIS)
Carmelo, J.M.P.; Castro Neto, A.H.; Campbell, D.K.
1994-01-01
We introduce an operator algebra for the description of the low-energy physics of one-dimensional, integrable, multicomponent quantum liquids. Considering the particular case of the Hubbard chain in a magnetic field and chemical potential, we show that at low energy its Bethe-ansatz solution can be interpreted in terms of a pseudoparticle-operator algebra. Our algebraic approach provides a concise interpretation of, and justification for, several recent studies of low-energy excitations and trasnport which have been based on detailed analyses of specific Bethe-ansatz eigenfunctions and eigenenergies. A central point is that the exact ground state of the interacting many-electron problem is the noninteracting pseudoparticle ground state. Furthermore, in the pseudoparticle basis, the quantum problem becomes perturbative, i.e., the two-pseudoparticle forward-scattering vertices and amplitudes do not diverge, and one can define a many-pseudoparticle perturbation theory. We write the general quantum-liquid Hamiltonian in the pseudoparticle basis and show that the pseudoparticle-perturbation theory leads, in a natural way, to the generalized Landau-liquid approach
Variational configuration interaction methods and comparison with perturbation theory
International Nuclear Information System (INIS)
Pople, J.A.; Seeger, R.; Krishnan, R.
1977-01-01
A configuration interaction (CI) procedure which includes all single and double substitutions from an unrestricted Hartree-Fock single determinant is described. This has the feature that Moller-Plesset perturbation results to second and third order are obtained in the first CI iterative cycle. The procedure also avoids the necessity of a full two-electron integral transformation. A simple expression for correcting the final CI energy for lack of size consistency is proposed. Finally, calculations on a series of small molecules are presented to compare these CI methods with perturbation theory
International Nuclear Information System (INIS)
Nagashima, Keisuke; Fukuda, Takeshi
1991-12-01
Evidence of temperature gradient driven particle flux was observed from the sawtooth induced density propagation phenomenon in JT-60. This off-diagonal particle flux was confirmed using the numerical calculation of measured chord integrated electron density. It was shown that the discrepancies between thermal and particle diffusivities estimated from the perturbation method and energy/particle balance analysis can be explained by considering the flux equations with off-diagonal transport terms. These flux equations were compared with the E x B convective fluxes in an electro-static drift wave instability and it was found that the E x B fluxes are consistent with several experimental observations. (author)
Perturbed effects at radiation physics
International Nuclear Information System (INIS)
Külahcı, Fatih; Şen, Zekâi
2013-01-01
Perturbation methodology is applied in order to assess the linear attenuation coefficient, mass attenuation coefficient and cross-section behavior with random components in the basic variables such as the radiation amounts frequently used in the radiation physics and chemistry. Additionally, layer attenuation coefficient (LAC) and perturbed LAC (PLAC) are proposed for different contact materials. Perturbation methodology provides opportunity to obtain results with random deviations from the average behavior of each variable that enters the whole mathematical expression. The basic photon intensity variation expression as the inverse exponential power law (as Beer–Lambert's law) is adopted for perturbation method exposition. Perturbed results are presented not only in terms of the mean but additionally the standard deviation and the correlation coefficients. Such perturbation expressions provide one to assess small random variability in basic variables. - Highlights: • Perturbation methodology is applied to Radiation Physics. • Layer attenuation coefficient (LAC) and perturbed LAC are proposed for contact materials. • Perturbed linear attenuation coefficient is proposed. • Perturbed mass attenuation coefficient (PMAC) is proposed. • Perturbed cross-section is proposed
Perturbative two- and three-loop coefficients from large {beta} Monte Carlo
Energy Technology Data Exchange (ETDEWEB)
Lepage, G.P.; Mackenzie, P.B.; Shakespeare, N.H.; Trottier, H.D
2000-03-01
Perturbative coefficients for Wilson loops and the static quark self-energy are extracted from Monte Carlo simulations at large {beta} on finite volumes, where all the lattice momenta are large. The Monte Carlo results are in excellent agreement with perturbation theory through second order. New results for third order coefficients are reported. Twisted boundary conditions are used to eliminate zero modes and to suppress Z{sub 3} tunneling.
International Nuclear Information System (INIS)
Yuan Lin; Zhou Ben-Hu; Zhao Yun-Hui; Xu Jun; Hai Wen-Hua
2012-01-01
A variational-integral perturbation method (VIPM) is established by combining the variational perturbation with the integral perturbation. The first-order corrected wave functions are constructed, and the second-order energy corrections for the ground state and several lower excited states are calculated by applying the VIPM to the hydrogen atom in a strong uniform magnetic field. Our calculations demonstrated that the energy calculated by the VIPM only shows a negative value, which indicates that the VIPM method is more accurate than the other methods. Our study indicated that the VIPM can not only increase the accuracy of the results but also keep the convergence of the wave functions
von Voigts-Rhetz, P; Anton, M; Vorwerk, H; Zink, K
2016-02-07
In modern radiotherapy the verification of complex treatments plans is often performed in inhomogeneous or even anthropomorphic phantoms. For dose verification small detectors are necessary and therefore alanine detectors are most suitable. Though the response of alanine for a wide range of clinical photon energies in water is well know, the knowledge about the influence of the surrounding phantom material on the response of alanine is sparse. Therefore we investigated the influence of twenty different surrounding/phantom materials for alanine dosimeters in clinical photon fields via Monte Carlo simulations. The relative electron density of the used materials was in the range [Formula: see text] up to 1.69, covering almost all materials appearing in inhomogeneous or anthropomorphic phantoms used in radiotherapy. The investigations were performed for three different clinical photon spectra ranging from 6 to 25 MV-X and Co-60 and as a result a perturbation correction [Formula: see text] depending on the environmental material was established. The Monte Carlo simulation show, that there is only a small dependence of [Formula: see text] on the phantom material and the photon energy, which is below ±0.6%. The results confirm the good suitability of alanine detectors for in-vivo dosimetry.
Rey, David M.
Energy and water are connected through the water-use cycle (e.g. obtaining, transporting, and treating water) and thermoelectric energy generation, which converts heat to electricity via steam-driven turbines. As the United States implements more renewable energy technologies, quantifying the relationships between energy, water, and land-surface impacts of these implementations will provide policy makers the strengths and weaknesses of different renewable energy options. In this study, a MODFLOW model of the Indian Wells Valley (IWV), in California, was developed to capture the water, energy, and land-surface impacts of potential proposed 1) solar, 2) wind, and 3) biofuel implementations. The model was calibrated to pre-existing groundwater head data from 1985 to present to develop a baseline model before running two-year predictive scenarios for photovoltaic (PV), concentrating solar power (CSP), wind, and biofuel implementations. Additionally, the baseline model was perturbed by decreasing mountain front recharge values by 5%, 10%, and 15%, simulating potential future system perturbations under a changing climate. These potential future conditions were used to re-run each implementation scenario. Implementation scenarios were developed based on population, typical energy use per person, existing land-use and land-cover type within the IWV, and previously published values for water use, surface-area use, and energy-generation potential for each renewable fuel type. The results indicate that the quantity of water needed, localized drawdown from pumping water to meet implementation demands, and generation efficiency are strongly controlled by the fuel type, as well as the energy generating technology and thermoelectric technologies implemented. Specifically, PV and wind-turbine (WT) implementations required less than 1% of the estimated annual aquifer recharge, while technologies such as biofuels and CSP, which rely on thermoelectric generation, ranged from 3% to 20
Quantum instability in the kicked rotator with rank-one perturbation
International Nuclear Information System (INIS)
Milek, B.; Seba, P.
1990-03-01
We show that the quasi-energy spectrum of the kicked quantum rotator with rank-one perturbation is singularly continous under certain conditions. The exotic quasi-energy eigenstates, given analytically within this model, are calculated in a basis of 2x10 6 rotator states and their self-similarity property is demonstrated. (orig.)
Three-nucleon scattering by using chiral perturbation theory potential
International Nuclear Information System (INIS)
Kamata, Hiroyuki
2003-01-01
Three-nucleon scattering problems are studied by using two-nucleon and three-nucleon potentials derived from chiral perturbation theory. The three-nucleon term is shown to appear in the effective potential of the rank of next-to-next-to-leading order (NNLO). New three-nucleon forces are taken into consideration in addition to the conventional Fujita-Miyazawa (FM) type three-nucleon potential. Two-nucleon potential of the chiral perturbation theory is as precise as the conventional ones in low energy region. The FM type three-nucleon force which explains Sagara discrepancy in high energy region is introduced automatically. Concerning the Ay puzzle, the results seems to behave as if the puzzle has been solved at the level of NLO, but at the NNLO (without three-nucleon force) level the result is similar to the cases of conventional potential indicating the need of three-nucleon force. In contrast to the FM type three-nucleon force, five free parameters exist in the new D and E type three-nucleon forces introduced by the NNLO, but they are reduced to two independent parameters by antisymmetrization, which are found to be sensitive to the coupling energy of tritons and to the nd scattering length (spin doublet state). Parameters determined from them cannot give satisfactory answer to the A y puzzle. It seems, however, too hasty to conclude that A y puzzle cannot be solved by the chiral perturbation theory. (S. Funahashi)
Modified perturbation theory for strongly correlated electron systems
International Nuclear Information System (INIS)
Takagi, Osamu; Saso, Tetsuro
1999-01-01
We propose a modified scheme for calculating the single-particle excitation spectrum of the impurity Anderson model. It is based on the second order perturbation theory, but modifies the self-energy so as to reproduce the correct atomic limit and to fulfill the Friedel sum rule. Therefore, it offers a simple scheme valid over wide range of excitation energy and parameters, and would be useful also for potential application to the lattice problems. (author)
Perturbation theory of intermolecular interactions: What is the problem, are there solutions?
International Nuclear Information System (INIS)
Adams, W.H.
1990-01-01
We review the nature of the problem in the framework of Rayleigh-Schroedinger perturbation theory (the polarization approximation) considering explicitly two examples: the interaction of two hydrogen atoms and the interaction of Li with H. We show, in agreement with the work of Claverie and of Morgan and Simon, that the LiH problem is dramatically different from the H 2 problem. In particular, the physical states of LiH are higher in energy than an infinite number of discrete, unphysical states and they are buried in a continuum of unbound, unphysical states, which starts well below the lowest physical state. Clavrie has shown that the perturbation expansion, under these circumstances, is likely to converge to an unphysical state of lower energy than the physical ground state, if it converges at all. We review, also, the application of two classes of exchange perturbation theory to LiH and larger systems. We show that the spectra of three Eisenschitz-London (EL) class, exchange perturbation theories have no continuum of unphysical states overlaying the physical states and no discrete, unphysical states below the lowest physical state. In contrast, the spectra of two Hirschfelder-Silbey class theories differ hardly at all from that found with the polarization approximation. Not one of the EL class of perturbation theories, however, eliminates all of the discrete unphysical states
International Nuclear Information System (INIS)
Dasnieres de Veigy, A.; Ouvry, S.; Paris-6 Univ., 75
1992-06-01
The problem of the statistical mechanics of an anyon gas is addressed. A perturbative analysis in the anyonic coupling constant α is reviewed, and the thermodynamical potential is computed at first and second order. An adequate second quantized formalism (field theory at finite temperature) is proposed. At first order in perturbation theory, the results are strikingly simple: only the second virial coefficient close to bosonic statistics is corrected. At second order, however, the complexity of the anyon model appears. One can compute exactly the perturbative correction to each cluster coefficient. However, and contrary to first order, a closed expression for the equation of state seems out of reach. As an illustration, the perturbative expressions of a 3 , a 4 , a 5 and a 6 are given at second order. Finally, using the same formalism, the equation of state of an anyon gas in a constant magnetic field is analyzed at first order in perturbation theory. (K.A.) 16 refs.; 3 figs.; 7 tabs
International Nuclear Information System (INIS)
Bartlett, R.; Kirtman, B.; Davidson, E.R.
1978-01-01
After noting some advantages of using perturbation theory some of the various types are related on a chart and described, including many-body nonlinear summations, quartic force-field fit for geometry, fourth-order correlation approximations, and a survey of some recent work. Alternative initial approximations in perturbation theory are also discussed. 25 references
A nanowire based triboelectric nanogenerator for harvesting water wave energy and its applications
Directory of Open Access Journals (Sweden)
Xiaoyi Li
2017-07-01
Full Text Available The ocean wave energy is one of the most promising renewable and clean energy sources for human life, which is the so-called “Blue energy.” In this work, a nanowire based triboelectric nanogenerator was designed for harvesting wave energy. The nanowires on the surface of FEP largely raise the contacting area with water and also make the polymer film hydrophobic. The output can reach 10 μ A and 200 V. When combined with a capacitor, an infrared emitter, and a receiver, a self-powered wireless infrared system is fabricated, which can be used in the fields of communication and detecting.
Relative Free Energies for Hydration of Monovalent Ions from QM and QM/MM Simulations.
Lev, Bogdan; Roux, Benoît; Noskov, Sergei Yu
2013-09-10
Methods directly evaluating the hydration structure and thermodynamics of physiologically relevant cations (Na(+), K(+), Cl(-), etc.) have wide ranging applications in the fields of inorganic, physical, and biological chemistry. All-atom simulations based on accurate potential energy surfaces appear to offer a viable option for assessing the chemistry of ion solvation. Although MD and free energy simulations of ion solvation with classical force fields have proven their usefulness, a number of challenges still remain. One of them is the difficulty of force field benchmarking and validation against structural and thermodynamic data obtained for a condensed phase. Hybrid quantum mechanical/molecular mechanical (QM/MM) models combined with sampling algorithms have the potential to provide an accurate solvation model and to incorporate the effects from the surrounding, which is often missing in gas-phase ab initio computations. Herein, we report the results from QM/MM free energy simulations of Na(+)/K(+) and Cl(-)/Br(-) hydration where we simultaneously characterized the relative thermodynamics of ion solvation and changes in the solvation structure. The Flexible Inner Region Ensemble Separator (FIRES) method was used to impose a spatial separation between QM region and the outer sphere of solvent molecules treated with the CHARMM27 force field. FEP calculations based on QM/MM simulations utilizing the CHARMM/deMon2k interface were performed with different basis set combinations for K(+)/Na(+) and Cl(-)/Br(-) perturbations to establish the dependence of the computed free energies on the basis set level. The dependence of the computed relative free energies on the size of the QM and MM regions is discussed. The current methodology offers an accurate description of structural and thermodynamic aspects of the hydration of alkali and halide ions in neat solvents and can be used to obtain thermodynamic data on ion solvation in condensed phase along with underlying
International Nuclear Information System (INIS)
Martel, Karl; Poisson, Eric
2005-01-01
We present a formalism to study the metric perturbations of the Schwarzschild spacetime. The formalism is gauge invariant, and it is also covariant under two-dimensional coordinate transformations that leave the angular coordinates unchanged. The formalism is applied to the typical problem of calculating the gravitational waves produced by material sources moving in the Schwarzschild spacetime. We examine the radiation escaping to future null infinity as well as the radiation crossing the event horizon. The waveforms, the energy radiated, and the angular-momentum radiated can all be expressed in terms of two gauge-invariant scalar functions that satisfy one-dimensional wave equations. The first is the Zerilli-Moncrief function, which satisfies the Zerilli equation, and which represents the even-parity sector of the perturbation. The second is the Cunningham-Price-Moncrief function, which satisfies the Regge-Wheeler equation, and which represents the odd-parity sector of the perturbation. The covariant forms of these wave equations are presented here, complete with covariant source terms that are derived from the stress-energy tensor of the matter responsible for the perturbation
International Nuclear Information System (INIS)
Hubbard, W.B.; Dewitt, H.E.
1985-01-01
A model free energy is presented which accurately represents results from 45 high-precision Monte Carlo calculations of the thermodynamics of hydrogen-helium mixtures at pressures of astrophysical and planetophysical interest. The free energy is calculated using free-electron perturbation theory (dielectric function theory), and is an extension of the expression given in an earlier paper in this series. However, it fits the Monte Carlo results more accurately, and is valid for the full range of compositions from pure hydrogen to pure helium. Using the new free energy, the phase diagram of mixtures of liquid metallic hydrogen and helium is calculated and compared with earlier results. Sample results for mixing volumes are also presented, and the new free energy expression is used to compute a theoretical Jovian adiabat and compare the adiabat with results from three-dimensional Thomas-Fermi-Dirac theory. The present theory gives slightly higher densities at pressures of about 10 megabars. 20 references
Hubbard, W. B.; Dewitt, H. E.
1985-01-01
A model free energy is presented which accurately represents results from 45 high-precision Monte Carlo calculations of the thermodynamics of hydrogen-helium mixtures at pressures of astrophysical and planetophysical interest. The free energy is calculated using free-electron perturbation theory (dielectric function theory), and is an extension of the expression given in an earlier paper in this series. However, it fits the Monte Carlo results more accurately, and is valid for the full range of compositions from pure hydrogen to pure helium. Using the new free energy, the phase diagram of mixtures of liquid metallic hydrogen and helium is calculated and compared with earlier results. Sample results for mixing volumes are also presented, and the new free energy expression is used to compute a theoretical Jovian adiabat and compare the adiabat with results from three-dimensional Thomas-Fermi-Dirac theory. The present theory gives slightly higher densities at pressures of about 10 megabars.
International Nuclear Information System (INIS)
Truchet, G.; Leconte, P.; Peneliau, Y.; Santamarina, A.
2013-01-01
The first goal of this paper is to present an exact method able to precisely evaluate very small reactivity effects with a Monte Carlo code (<10 pcm). it has been decided to implement the exact perturbation theory in TRIPOLI-4 and, consequently, to calculate a continuous-energy adjoint flux. The Iterated Fission Probability (IFP) method was chosen because it has shown great results in some other Monte Carlo codes. The IFP method uses a forward calculation to compute the adjoint flux, and consequently, it does not rely on complex code modifications but on the physical definition of the adjoint flux as a phase-space neutron importance. In the first part of this paper, the IFP method implemented in TRIPOLI-4 is described. To illustrate the efficiency of the method, several adjoint fluxes are calculated and compared with their equivalent obtained by the deterministic code APOLLO-2. The new implementation can calculate angular adjoint flux. In the second part, a procedure to carry out an exact perturbation calculation is described. A single cell benchmark has been used to test the accuracy of the method, compared with the 'direct' estimation of the perturbation. Once again the method based on the IFP shows good agreement for a calculation time far more inferior to the 'direct' method. The main advantage of the method is that the relative accuracy of the reactivity variation does not depend on the magnitude of the variation itself, which allows us to calculate very small reactivity perturbations with high precision. It offers the possibility to split reactivity contributions on both isotopes and reactions. Other applications of this perturbation method are presented and tested like the calculation of exact kinetic parameters (βeff, Λeff) or sensitivity parameters
Adaptation to sensory-motor reflex perturbations is blind to the source of errors.
Hudson, Todd E; Landy, Michael S
2012-01-06
In the study of visual-motor control, perhaps the most familiar findings involve adaptation to externally imposed movement errors. Theories of visual-motor adaptation based on optimal information processing suppose that the nervous system identifies the sources of errors to effect the most efficient adaptive response. We report two experiments using a novel perturbation based on stimulating a visually induced reflex in the reaching arm. Unlike adaptation to an external force, our method induces a perturbing reflex within the motor system itself, i.e., perturbing forces are self-generated. This novel method allows a test of the theory that error source information is used to generate an optimal adaptive response. If the self-generated source of the visually induced reflex perturbation is identified, the optimal response will be via reflex gain control. If the source is not identified, a compensatory force should be generated to counteract the reflex. Gain control is the optimal response to reflex perturbation, both because energy cost and movement errors are minimized. Energy is conserved because neither reflex-induced nor compensatory forces are generated. Precision is maximized because endpoint variance is proportional to force production. We find evidence against source-identified adaptation in both experiments, suggesting that sensory-motor information processing is not always optimal.
Spectral zeta function and non-perturbative effects in ABJM Fermi-gas
International Nuclear Information System (INIS)
Hatsuda, Yasuyuki
2015-03-01
The exact partition function in ABJM theory on three-sphere can be regarded as a canonical partition function of a non-interacting Fermi-gas with an unconventional Hamiltonian. All the information on the partition function is encoded in the discrete spectrum of this Hamiltonian. We explain how (quantum mechanical) non-perturbative corrections in the Fermi-gas system appear from a spectral consideration. Basic tools in our analysis are a Mellin-Barnes type integral representation and a spectral zeta function. From a consistency with known results, we conjecture that the spectral zeta function in the ABJM Fermi-gas has an infinite number of ''non-perturbative'' poles, which are invisible in the semi-classical expansion of the Planck constant. We observe that these poles indeed appear after summing up perturbative corrections. As a consequence, the perturbative resummation of the spectral zeta function causes non-perturbative corrections to the grand canonical partition function. We also present another example associated with a spectral problem in topological string theory. A conjectured non-perturbative free energy on the resolved conifold is successfully reproduced in this framework.
Perturbation theory of the quark-gluon plasma at finite temperature and baryon number density
International Nuclear Information System (INIS)
Anon.
1984-01-01
At very high energy densities, hadronic matter becomes an almost ideal gas of quarks and gluons. In these circumstances, the effects of particle interactions are small, and to some order in perturbation theory are computable by methods involving weak coupling expansions. To illustrate the perturbative methods which may be used to compute the thermodynamic potential, the results and methods which are employed to compute to first order in α/sub s/ are reviewed. The problem of the plasmon effect, and the necessity of using non-perturbative methods when going beyond first order in α/sub s/ in evaluating the thermodynamic potential are discussed. The results at zero temperature and finite baryon number density to second order in α/sub s/ are also reviewed. The method of renormalization group improving the weak coupling expansions by replacing the expansion by an expansion in a temperature and baryon number density dependent coupling which approaches zero at high energy densities is discussed. Non-perturbative effects such as instantons are briefly mentioned and the breakdown of perturbation theory for the thermodynamical at order α/sub s/ 3 for finite temperature is presented
Pezzulo, Giovanni; Levin, Michael
2018-03-01
The free-energy principle (FEP) has been initially proposed as a theory of brain structure and function [1], but its scope is rapidly extending to explain biological phenomena at multiple levels of complexity, from simple life forms and their morphology [2] to complex societal and cultural dynamics [3].
Thoughts on non-perturbative thermalization and jet quenching in heavy ion collisions
International Nuclear Information System (INIS)
Kovchegov, Yuri V.
2006-01-01
We start by presenting physical arguments for the impossibility of perturbative thermalization leading to (non-viscous) Bjorken hydrodynamic description of heavy ion collisions. These arguments are complimentary to our more formal argument presented in [Yu.V. Kovchegov, hep-ph/0503038]. We argue that the success of hydrodynamic models in describing the quark-gluon system produced in heavy ion collisions could only be due to non-perturbative strong coupling effects. We continue by studying non-perturbative effects in heavy ion collisions at high energies. We model non-perturbative phenomena by an instanton ensemble. We show that non-perturbative instanton vacuum fields may significantly contribute to jet quenching in nuclear collisions. At the same time, the instanton ensemble contribution to thermalization is likely to be rather weak, leading to non-perturbative thermalization time comparable to the time of hadronization. This example illustrates that jet quenching is not necessarily a signal of a thermalized medium. Indeed, since the instanton models do not capture all the effects of QCD vacuum (e.g., they do not account for confinement), there may be other non-perturbative effects facilitating thermalization of the system
International Nuclear Information System (INIS)
Iyer, S.V.; Vafai, K.
1999-01-01
The study of natural convection flow and heat transfer within a cylindrical annulus has received considerable attention because of its numerous applications, such as in nuclear reactor design, electronic component cooling, thermal storage systems, energy conservation, energy storage, and energy transmission. Here, the effects of multiple geometric perturbations on the inner and outer cylinders of an annulus with impermeable end walls are investigated in this work. A three-dimensional study was done using a numerical scheme based on a Galerkin method of finite element formulation. The nature of the buoyancy-induced flow field has been analyzed in detail. The flow fields for the cases considered were found to be qualitatively similar, and the introduction of each additional perturbation altered the flow field in a regular and recurring manner. The introduction of each perturbation on the outer cylinder causes clockwise and counterclock-wise rotating patterns on either side of the perturbation in the upper circumferential regions of the annulus. The motion of the fluid entrained by these circulatory patterns constitutes the key features of the flow pattern observed in the annulus. It is observed that the presence of multiple perturbations on the inner and outer cylinders substantially increases the overall heat transfer rate as compared to the regular annulus without any perturbation. Key qualitative and quantitative effects of the introduction of perturbations on both the inner and outer cylinders of the annulus are discussed
Jet fragmentation and predictions of the resummed perturbative QCD
Energy Technology Data Exchange (ETDEWEB)
Safonov, Alexei Nikolayevich [Univ. of Florida, Gainesville, FL (United States)
2001-01-01
This dissertation is dedicated to the experimental analysis of jet fragmentation, the process of formation of jets of particles produced in high-energy collisions, and to the comparison of the results to the predictions of resummed perturbative calculations within Quantum Chromodynamics.
Carbaryl and propoxur are N-methyl carbamate pesticides (NMCs) which are part of the EPA’s cumulative risk assessments for NMCs. These NMCs inhibit cholinesterase (ChE) activity and may lead to cholinergic disruption of CNS function. We used decreases in the PhAD of FEPs to indic...
Perturbed Partial Cavity Drag Reduction at High Reynolds Numbers
Makiharju, Simo; Elbing, Brian; Wiggins, Andrew; Dowling, David; Perlin, Marc; Ceccio, Steven
2010-11-01
Ventilated partial cavities were investigated at Reynolds numbers to 80 million. These cavities could be suitable for friction drag reduction on ocean going vessels and thereby lead to environmental and economical benefits. The test model was a 3.05 m wide by 12.9 m long flat plate, with a 0.18 m backward-facing step and a cavity-terminating beach, which had an adjustable slope, tilt and height. The step and beach trapped a ventilated partial cavity over the longitudinal mid-section of the model. Large-scale flow perturbations, mimicking the effect of ambient ocean waves were investigated. For the conditions tested a cavity could be maintained under perturbed flow conditions when the gas flux supplied was greater than the minimum required to maintain a cavity under steady conditions, with larger perturbations requiring more excess gas flux to maintain the cavity. High-speed video was used to observe the unsteady three dimensional cavity closure, the overall cavity shape, and the cavity oscillations. Cavities with friction drag reduction exceeding 95% were attained at optimal conditions. A simplified energy cost-benefit analysis of partial cavity drag reduction was also performed. The results suggest that PCDR could potentially lead to energy savings.
Analytic perturbation theory in analyzing some QCD observables
International Nuclear Information System (INIS)
Shirkov, D.V.
2001-01-01
The paper is devoted to application of recently devised ghost-free Analytic Perturbation Theory (APT) for analysis of some QCD observables. We start with the discussion of the main problem of the perturbative QCD - ghost singularities and with the resume of this trouble solution within the APT. By a few examples in the various energy and momentum transfer regions (with the flavor number f = 3, 4 and 5) we demonstrate the effect of improved convergence of the APT modified perturbative QCD expansion. Our first observation is that in the APT analysis the three-loop contribution (of an order of α s 3 ) is as a rule numerically inessential. This raises hope for practical solving the well-known problem of asymptotic nature of common QFT perturbation series. The second conclusion is that a common perturbative analysis of time-like events with the big π 2 term in the π 2 coefficient is not adequate at s ≤ 2 GeV 2 . In particular, this relates to τ decay. Then, for the 'high' (f = 5) region it is shown that the common two-loop (NLO, NLLA) perturbation approximation widely used there (at 10 GeV ≤ √s ≤ 170 GeV) for analysis of shape/events data contains a systematic negative error of a 1 - 2 per cent level for the extracted α bar s (2) values. Our physical conclusion is that the α bar s (M Z 2 ) value averaged over the f = 5 data s (M Z 2 )> APT; f= 5 ≅ 0.124 appreciably differs from the currently accepted 'world average' (= 0.118)
Developments in perturbation theory
International Nuclear Information System (INIS)
Greenspan, E.
1976-01-01
Included are sections dealing with perturbation expressions for reactivity, methods for the calculation of perturbed fluxes, integral transport theory formulations for reactivity, generalized perturbation theory, sensitivity and optimization studies, multigroup calculations of bilinear functionals, and solution of inhomogeneous Boltzmann equations with singular operators
Li, Fei; Li, Peng; Xu, Wenjian; Peng, Yuxing; Bo, Xiaochen; Wang, Shengqi
2010-01-15
The propagation of perturbations in protein concentration through a protein interaction network (PIN) can shed light on network dynamics and function. In order to facilitate this type of study, PerturbationAnalyzer, which is an open source plugin for Cytoscape, has been developed. PerturbationAnalyzer can be used in manual mode for simulating user-defined perturbations, as well as in batch mode for evaluating network robustness and identifying significant proteins that cause large propagation effects in the PINs when their concentrations are perturbed. Results from PerturbationAnalyzer can be represented in an intuitive and customizable way and can also be exported for further exploration. PerturbationAnalyzer has great potential in mining the design principles of protein networks, and may be a useful tool for identifying drug targets. PerturbationAnalyzer can be accessed from the Cytoscape web site http://www.cytoscape.org/plugins/index.php or http://biotech.bmi.ac.cn/PerturbationAnalyzer. Supplementary data are available at Bioinformatics online.
Green's functions in quantum chemistry II - Improving the Σ perturbation approach
International Nuclear Information System (INIS)
Sebastian, K.L.; Narayanan, P.; Rama Varma, K.T.
1978-01-01
Two methods, which are expected to lead to results better than those of the Σ perturbation approach given earlier are investigated. Within the algebraic approximation, the methods are applied to the hydrogen molecule and to ethylene in the Pariser-Parr-Pople (PPP) approximation. Both the methods are seen to suffer from the defect of not conserving the number of particles in the system. The methods are (a) the use of a partitioning other than Hartree-Fock. Due to the non-conservation of particle number, the method does not seem to be suited for the calculation of the ground state energy, but it gives good results for ionisation potentials. The investigation reveals that the only partitioning which conserves the number of particles is the Hartree-Fock partitioning (b) the renormalised Σ perturbation method, suggested by Csnak and others. For ethylene in the PPP approximation, the method does conserve the number of particles (but not in general). However, the energy obtained is not as good as that in the Σ perturbation method. This method therefore seems to be of limited applicability in molecular calculations. (author)
Infrared problems in field perturbation theory
International Nuclear Information System (INIS)
David, Francois.
1982-12-01
The work presented mainly covers questions related to the presence of ''infrared'' divergences in perturbation expansions of the Green functions of certain massless field theories. It is important to determine the mathematical status of perturbation expansions in field theory in order to define the region in which they are valid. Renormalization and the symmetry of a theory are important factors in infrared problems. The main object of this thesis resides in the mathematical techniques employed: integral representations of the Feynman amplitudes; methods for desingularization, regularization and dimensional renormalization. Nonlinear two dimensional space-time sigma models describing Goldstone's low energy boson dynamics associated with a breaking of continuous symmetry are studied. Random surface models are then investigated followed by infrared divergences in super-renormalizable theories. Finally, nonperturbation effects in massless theories are studied by expanding the two-dimensional nonlinear sigma model in 1/N [fr
Shishkin, G. I.
2015-11-01
An initial-boundary value problem is considered for a singularly perturbed parabolic convection-diffusion equation with a perturbation parameter ɛ (ɛ ∈ (0, 1]) multiplying the highest order derivative. The stability of a standard difference scheme based on monotone approximations of the problem on a uniform mesh is analyzed, and the behavior of discrete solutions in the presence of perturbations is examined. The scheme does not converge ɛ-uniformly in the maximum norm as the number of its grid nodes is increased. When the solution of the difference scheme converges, which occurs if N -1 ≪ ɛ and N -1 0 ≪ 1, where N and N 0 are the numbers of grid intervals in x and t, respectively, the scheme is not ɛ-uniformly well conditioned or stable to data perturbations in the grid problem and to computer perturbations. For the standard difference scheme in the presence of data perturbations in the grid problem and/or computer perturbations, conditions on the "parameters" of the difference scheme and of the computer (namely, on ɛ, N, N 0, admissible data perturbations in the grid problem, and admissible computer perturbations) are obtained that ensure the convergence of the perturbed solutions. Additionally, the conditions are obtained under which the perturbed numerical solution has the same order of convergence as the solution of the unperturbed standard difference scheme.
Perturbativity in the seesaw mechanism
International Nuclear Information System (INIS)
Asaka, Takehiko; Tsuyuki, Takanao
2016-01-01
We consider the Standard Model extended by right-handed neutrinos to explain massive neutrinos through the seesaw mechanism. The new fermion can be observed when it has a sufficiently small mass and large mixings to left-handed neutrinos. If such a particle is the lightest right-handed neutrino, its contribution to the mass matrix of active neutrinos needs to be canceled by that of a heavier one. Yukawa couplings of the heavier one are then larger than those of the lightest one. We show that the perturbativity condition gives a severe upper bound on the mixing of the lightest right-handed neutrino, depending on the masses of heavier ones. Models of high energy phenomena, such as leptogenesis, can be constrained by low energy experiments.
Non-Perturbative Asymptotic Improvement of Perturbation Theory and Mellin-Barnes Representation
Directory of Open Access Journals (Sweden)
Samuel Friot
2010-10-01
Full Text Available Using a method mixing Mellin-Barnes representation and Borel resummation we show how to obtain hyperasymptotic expansions from the (divergent formal power series which follow from the perturbative evaluation of arbitrary ''N-point'' functions for the simple case of zero-dimensional φ4 field theory. This hyperasymptotic improvement appears from an iterative procedure, based on inverse factorial expansions, and gives birth to interwoven non-perturbative partial sums whose coefficients are related to the perturbative ones by an interesting resurgence phenomenon. It is a non-perturbative improvement in the sense that, for some optimal truncations of the partial sums, the remainder at a given hyperasymptotic level is exponentially suppressed compared to the remainder at the preceding hyperasymptotic level. The Mellin-Barnes representation allows our results to be automatically valid for a wide range of the phase of the complex coupling constant, including Stokes lines. A numerical analysis is performed to emphasize the improved accuracy that this method allows to reach compared to the usual perturbative approach, and the importance of hyperasymptotic optimal truncation schemes.
A new perturbative approximation applied to supersymmetric quantum field theory
International Nuclear Information System (INIS)
Bender, C.M.; Milton, K.A.; Pinsky, S.S.; Simmons, L.M. Jr.; Los Alamos National Lab.
1988-01-01
We show that a recently proposed graphical perturbative calculational scheme in quantum field theory is consistent with global supersymmetry invariance. We examine a two-dimensional supersymmetric quantum field theory in which we do not known of any other means for doing analytical calculations. We illustrate the power of this new technique by computing the ground-state energy density E to second order in this new perturbation theory. We show that there is a beautiful and delicate cancellation between infinite classes of graphs which leads to the result that E=0. (orig.)
International Nuclear Information System (INIS)
Last, George V.; Rohay, Virginia J.; Schelling, F J.; Bunn, Amoret L.; Delamare, Michael A.; Dirkes, Roger L.; Hildebrand, R D.; Morse, John G.; Napier, Bruce A.; Riley, Robert G.; Soler, Luis; Thorne, Paul D.
2004-01-01
The U. S. Department of Energy?s Richland Operations Office has initiated efforts to adapt and implement the Features, Events, and Processes (FEPs) methodology (used in scenario development for nuclear waste disposal programs) to the environmental management and remediation problems facing the Hanford Site. These efforts have shown that modification of the FEPs methodology to incorporate the use of Process Relationship Diagrams (PRD) is effective in facilitating the development of conceptual models and selection of potentially relevant factors to be incorporated into a specific performance assessment. In developing this methodology for Hanford, a master PRD was created to provide an organization structure for identifying the potentially relevant factors (i.e. FEPs) and for illustrating the relationships between these factors. This organizational framework was developed to match the organization of current Hanford site-wide performance assessment activities and to facilitate screening of the FEPs relevant to the problems (and conceptual models) that need to be addressed at the site. However, the link between Hanford specific FEPs and the international list of FEPs was maintained to demonstrate completeness and perhaps to expand the usefulness of the international list for other environmental programs
Adiabatic CMB perturbations in pre-big bang string cosmology
DEFF Research Database (Denmark)
Enqvist, Kari; Sloth, Martin Snoager
2001-01-01
We consider the pre-big bang scenario with a massive axion field which starts to dominate energy density when oscillating in an instanton-induced potential and subsequently reheats the universe as it decays into photons, thus creating adiabatic CMB perturbations. We find that the fluctuations...
Xu, Enhua; Zhao, Dongbo; Li, Shuhua
2015-10-13
A multireference second order perturbation theory based on a complete active space configuration interaction (CASCI) function or density matrix renormalized group (DMRG) function has been proposed. This method may be considered as an approximation to the CAS/A approach with the same reference, in which the dynamical correlation is simplified with blocked correlated second order perturbation theory based on the generalized valence bond (GVB) reference (GVB-BCPT2). This method, denoted as CASCI-BCPT2/GVB or DMRG-BCPT2/GVB, is size consistent and has a similar computational cost as the conventional second order perturbation theory (MP2). We have applied it to investigate a number of problems of chemical interest. These problems include bond-breaking potential energy surfaces in four molecules, the spectroscopic constants of six diatomic molecules, the reaction barrier for the automerization of cyclobutadiene, and the energy difference between the monocyclic and bicyclic forms of 2,6-pyridyne. Our test applications demonstrate that CASCI-BCPT2/GVB can provide comparable results with CASPT2 (second order perturbation theory based on the complete active space self-consistent-field wave function) for systems under study. Furthermore, the DMRG-BCPT2/GVB method is applicable to treat strongly correlated systems with large active spaces, which are beyond the capability of CASPT2.
Győrffy, Werner; Knizia, Gerald; Werner, Hans-Joachim
2017-12-01
We present the theory and algorithms for computing analytical energy gradients for explicitly correlated second-order Møller-Plesset perturbation theory (MP2-F12). The main difficulty in F12 gradient theory arises from the large number of two-electron integrals for which effective two-body density matrices and integral derivatives need to be calculated. For efficiency, the density fitting approximation is used for evaluating all two-electron integrals and their derivatives. The accuracies of various previously proposed MP2-F12 approximations [3C, 3C(HY1), 3*C(HY1), and 3*A] are demonstrated by computing equilibrium geometries for a set of molecules containing first- and second-row elements, using double-ζ to quintuple-ζ basis sets. Generally, the convergence of the bond lengths and angles with respect to the basis set size is strongly improved by the F12 treatment, and augmented triple-ζ basis sets are sufficient to closely approach the basis set limit. The results obtained with the different approximations differ only very slightly. This paper is the first step towards analytical gradients for coupled-cluster singles and doubles with perturbative treatment of triple excitations, which will be presented in the second part of this series.
DEFF Research Database (Denmark)
Li, Xue; Zhao, Yang; Li, Weiwei
2017-01-01
In order to study the microstructure of the prepared potential proton exchange membrane (PEM), molecular dynamics (MD) simulations were used to lucubrate the transport behavior of water molecules and hydronium ions inside the hydrated sulfonated styrene grafted fluorinated ethylene propylene (FEP...... whereas larger water clusters formed. The results of the mean square displacements (MSDs) show that the proton conductivities of the membranes with the proposed side chain lengths were about three fifths of the experimental data, of which the membrane with side chain length of 7 sulfonic styrene units...... was supposed to exhibit the highest proton conductivity, that is 115.69 mS cm-1. All of the supposed membrane models presented good proton conductivity that could definitely meet the application requirements of the proton exchange membranes. The MD simulations can provide an insight to the chain structure...
International Nuclear Information System (INIS)
Alexander, W.R.; Neall, F.B.
2007-06-01
Although the site of the proposed spent fuel repository at Olkiluoto in southwest Finland has been extensively investigated over the last fifteen years, Posiva decided to construct a rock characterisation facility (RCF) at the site to collect more detailed information on the host rock. The data provided by the ONKALO RCF will support the detailed repository design and safety assessment (SA) and will allow construction and disposal methods to be tested under relevant in situ conditions. ONKALO has been so designed that it can act as access routes and auxiliary rooms for the SF repository and so may be in use for the entire operational phase of the repository (currently up to 100 years). Extensive experience from deep mining suggests that such an extended period of operation could have a major impact on both the host rock formation and any nearby facilities, such as the SF repository, and, consequently, Posiva decided to investigate potential perturbations to the repository caused by the existence of ONKALO. A preliminary assessment was carried out in 2003, before construction of the RCF began, and this was recently partially updated in early 2006. This current report represents the most recent update of these reports and has the primary aims of: checking if the previous reports have missed any essential issues; evaluating whether the identified issues have been treated in an appropriate manner; updating the reports in the light of new information. This is carried out based on data from ONKALO itself and on improved understanding of some of the perturbation mechanisms identified in the original studies along with a consideration of newly identified processes. This report differs from the previous studies in addressing the issues in a more SA-oriented manner (for example, focussing the examination of potential perturbations on a re-worked FEP list), allowing the work reported here to be more easily dovetailed with future SA studies on the Olkiluoto repository
Commutator perturbation method in the study of vibrational-rotational spectra of diatomic molecules
International Nuclear Information System (INIS)
Matamala-Vasquez, A.; Karwowski, J.
2000-01-01
The commutator perturbation method, an algebraic version of the Van Vleck-Primas perturbation method, expressed in terms of ladder operators, has been applied to solving the eigenvalue problem of the Hamiltonian describing the vibrational-rotational motion of a diatomic molecule. The physical model used in this work is based on Dunham's approach. The method facilitates obtaining both energies and eigenvectors in an algebraic way
Energy Technology Data Exchange (ETDEWEB)
Demianski, M [California Inst. of Tech., Pasadena (USA)
1976-07-01
A stationary axially symmetric perturbation of a rotating black hole due to a distribution of test matter is investigated. The Newman-Penrose spin coefficient formalism is used to derive a general set of equations describing the perturbed space-time. In a linear approximation it is shown that the mass and angular momentum of a rotating black hole is not affected by the perturbation. The metric perturbations near the horizon are given. It is concluded that given a perturbing test fluid distribution, one can always find a corresponding metric perturbation such that the mass and angular momentum of the black hole are not changed. It was also noticed that when a tends to M, those perturbed spin coefficients and components of the Weyl tensor which determine the intrinsic properties of the incoming null cone near the horizon grow indefinitely.
International Nuclear Information System (INIS)
Harada, Masayasu
2009-01-01
Chiral perturbation theory has been used for great number of phenomenological analyses in low energy QCD as well as the lattice QCD analyses since the creation of the theory by Weinberg in 1979 followed by its consolidation by Gasser and Leutwyler in 1984 and 85. The theory is now the highly established one as the approach based on the effective field theory to search for Green function including quantum correlations in the frame of the systematic expansion technique using Lagrangian which includes all of the terms allowed by the symmetry. This review has been intended to describe how systematically physical quantities are calculated in the framework of the chiral symmetry. Consequently many of the various phenomenological analyses are not taken up here for which other reports are to be referred. Further views are foreseen to be developed based on the theory in addition to numbers of results reported up to the present. Finally π-π scattering is taken up to discuss to what energy scale the theory is available. (S. Funahashi)
Zheng, Zhong-liang; Ye, Mao-qing; Zuo, Zhen-yu; Liu, Zhi-gang; Tai, Keng-chang; Zou, Guo-lin
2006-05-01
Hydrogen bonds occurring in the catalytic triad (Asp32, His64 and Ser221) and the oxyanion hole (Asn155) are very important to the catalysis of peptide bond hydrolysis by serine proteases. For the subtilisin NK (nattokinase), a bacterial serine protease, construction and analysis of a three-dimensional structural model suggested that several hydrogen bonds formed by four residues function to stabilize the transition state of the hydrolysis reaction. These four residues are Ser33, Asp60, Ser62 and Thr220. In order to remove the effect of these hydrogen bonds, four mutants (Ser33-->Ala33, Asp60-->Ala60, Ser62-->Ala62, and Thr220-->Ala220) were constructed by site-directed mutagenesis. The results of enzyme kinetics indicated that removal of these hydrogen bonds increases the free-energy of the transition state (DeltaDeltaG(T)). We concluded that these hydrogen bonds are more important for catalysis than for binding the substrate, because removal of these bonds mainly affects the kcat but not the K(m) values. A substrate, SUB1 (succinyl-Ala-Ala-Pro-Phe-p-nitroanilide), was used during enzyme kinetics experiments. In the present study we have also shown the results of FEP (free-energy perturbation) calculations with regard to the binding and catalysis reactions for these mutant subtilisins. The calculated difference in FEP also suggested that these four residues are more important for catalysis than binding of the substrate, and the simulated values compared well with the experimental values from enzyme kinetics. The results of MD (molecular dynamics) simulations further demonstrated that removal of these hydrogen bonds partially releases Asp32, His64 and Asn155 so that the stability of the transition state decreases. Another substrate, SUB2 (H-D-Val-Leu-Lys-p-nitroanilide), was used for FEP calculations and MD simulations.
Meson-baryon scattering in manifestly Lorentz invariant chiral perturbation theory
International Nuclear Information System (INIS)
Mai, Maxim; Bruns, Peter C.; Kubis, Bastian; Meissner, Ulf-G.
2011-01-01
We analyze meson-baryon scattering lengths in the framework of covariant baryon chiral perturbation theory at leading one-loop order. We compute the complete set of matching relations between the dimension-two low-energy constants in the two- and three-flavor formulations of the theory. We derive new two-flavor low-energy theorems for pion-hyperon scattering that can be tested in lattice simulations.
Nonperturbative calculations in the framework of variational perturbation theory in QCD
Solovtsova, O. P.
2017-07-01
We discuss applications of the method based on the variational perturbation theory to perform calculations down to the lowest energy scale. The variational series is different from the conventional perturbative expansion and can be used to go beyond the weak-coupling regime. We apply this method to investigate the Borel representation of the light Adler function constructed from the τ data and to determine the residual condensates. It is shown that within the method suggested the optimal values of these lower dimension condensates are close to zero.
Inflationary perturbations in no-scale theories
Energy Technology Data Exchange (ETDEWEB)
Salvio, Alberto [CERN, Theoretical Physics Department, Geneva (Switzerland)
2017-04-15
We study the inflationary perturbations in general (classically) scale-invariant theories. Such scenario is motivated by the hierarchy problem and provides natural inflationary potentials and dark matter candidates. We analyse in detail all sectors (the scalar, vector and tensor perturbations) giving general formulae for the potentially observable power spectra, as well as for the curvature spectral index n{sub s} and the tensor-to-scalar ratio r. We show that the conserved Hamiltonian for all perturbations does not feature negative energies even in the presence of the Weyl-squared term if the appropriate quantisation is performed and argue that this term does not lead to phenomenological problems at least in some relevant setups. The general formulae are then applied to a concrete no-scale model, which includes the Higgs and a scalar, ''the planckion'', whose vacuum expectation value generates the Planck mass. Inflation can be triggered by a combination of the planckion and the Starobinsky scalar and we show that no tension with observations is present even in the case of pure planckion inflation, if the coefficient of the Weyl-squared term is large enough. In general, even quadratic inflation is allowed in this case. Moreover, the Weyl-squared term leads to an isocurvature mode, which currently satisfies the observational bounds, but it may be detectable with future experiments. (orig.)
Regular perturbation theory for two-electron atoms
International Nuclear Information System (INIS)
Feranchuk, I.D.; Triguk, V.V.
2011-01-01
Regular perturbation theory (RPT) for the ground and excited states of two-electron atoms or ions is developed. It is shown for the first time that summation of the matrix elements from the electron-electron interaction operator over all intermediate states can be calculated in a closed form by means of the two-particle Coulomb Green's function constructed in the Letter. It is shown that the second order approximation of RPT includes the main part of the correlation energy both for the ground and excited states. This approach can be also useful for description of two-electron atoms in external fields. -- Highlights: → We develop regular perturbation theory for the two-electron atoms or ions. → We calculate the sum of the matrix elements over all intermediate states. → We construct the two-particle Coulomb Green's function.
International Nuclear Information System (INIS)
Pahl, Christoph Johannes
2008-01-01
In hadron production data of the e + e - annihilation experiments JADE and OPAL we measure the first five moments of twelve hadronic-event-shape variables at c.m. energies from 14 to 207 GeV. From the comparison of the QCD NLO prediction with the data corrected by means of MC models about hadronization we obtain the reference value of the strong coupling α s (M Z 0 )=0.1254±0.0007(stat.)±0.0010(exp.) +0.0009 -0.0 0 23 (had.) +0.0069 -0.0053 (theo.). For some, especially higher moments, systematic unsufficiencies in the QCD NLO prediction are recognizable. Simultaneous fits to two moments under assumption of identical renormalization scales yield scale values from x μ =0.057 to x μ =0.196. We check predictions of different non-perturbative models. From the single-dressed-gluon approximation a perturbative prediction in O(α 5 s ) results with neglegible energy power correction, which describes the thrust average on hadron level well with α s (M Z 0 )=0.1186±0,0017(exp.) -0.0028 +0.0033 (theo.). The variance of the event-shape variable is measured and compared with models as well as predictions. [de
Extended Krenciglowa-Kuo method and perturbation expansion of Q-box
International Nuclear Information System (INIS)
Shimizu, Genki; Otsuka, Takaharu; Takayanagi, Kazuo
2015-01-01
The Extended Krenciglowa-Kuo (EKK) method is a microscopic method to construct the energy-independent effective Hamiltonian H eff ; provided with an exact Q-box of the system, we can show which eigenstates are described by H eff given by the EKK method. In actual calculations, however, we can calculate the Q-box only up to a finite order in the perturbation theory. In this work, we examine the EKK method with the approximate Q-box, and show that the perturbative calculation of the Q-box does not harm the convergence properties of the EKK iterative method. (author)
Challenges in the extraction of TMDs from SIDIS data: perturbative vs non-perturbative aspects
Energy Technology Data Exchange (ETDEWEB)
Boglione, Mariaelena [aDipartimento di Fisica Teorica, Università di Torino, Via P. Giuria 1, I-10125 Torino, Italy; Gonzalez Hernandez, Jose O. [INFN, Sezione di Torino, and Dipartimento di Fisica Teorica, Università di Torino, Via P. Giuria 1, I-10125 Torino, Italy; Melis, Stefano [Univ. Torino, Torino, Italy; Prokudin, Alexey [Jefferson Laboratory, 12000 Jeerson Avenue, Newport News, VA 23606, USA
2015-09-01
We present our recent results on the study of the Semi-Inclusive Deep Inelastic Scattering (SIDIS) cross section as a function of the transverse momentum, q_{T}. Using the Collins-Soper-Sterman (CSS) formalism, we study the matching between the region where fixed-order perturbative QCD can successfully be applied and the region where soft gluon resummation is necessary. We find that the commonly used prescription of matching through the so-called Y-factor cannot be applied in the SIDIS kinematical configurations we examine. We comment on the impact that the nonperturbative component has even at relatively high energies.
Perturbative and constructive renormalization
International Nuclear Information System (INIS)
Veiga, P.A. Faria da
2000-01-01
These notes are a survey of the material treated in a series of lectures delivered at the X Summer School Jorge Andre Swieca. They are concerned with renormalization in Quantum Field Theories. At the level of perturbation series, we review classical results as Feynman graphs, ultraviolet and infrared divergences of Feynman integrals. Weinberg's theorem and Hepp's theorem, the renormalization group and the Callan-Symanzik equation, the large order behavior and the divergence of most perturbation series. Out of the perturbative regime, as an example of a constructive method, we review Borel summability and point out how it is possible to circumvent the perturbation diseases. These lectures are a preparation for the joint course given by professor V. Rivasseau at the same school, where more sophisticated non-perturbative analytical methods based on rigorous renormalization group techniques are presented, aiming at furthering our understanding about the subject and bringing field theoretical models to a satisfactory mathematical level. (author)
Correlation effects of third-order perturbation in the extended Hubbard model
International Nuclear Information System (INIS)
Wei, G.Z.; Nie, H.Q.; Li, L.; Zhang, K.Y.
1989-01-01
Using the local approach, a third-order perturbation calculation has been performed to investigate the effects of intra-atomic electron correlation and electron and spin correlation between nearest neighbour sites in the extended Hubbard model. It was found that significant correction of the third order over the second order results and, in comparison with the results of the third-order perturbation where only the intra-atomic electron correlation is included, the influence of the electron and spin correlation between nearest neighbour sites on the correlation energy is non-negligible. 17 refs., 3 figs
Relativistic many-body perturbation-theory calculations based on Dirac-Fock-Breit wave functions
International Nuclear Information System (INIS)
Ishikawa, Y.; Quiney, H.M.
1993-01-01
A relativistic many-body perturbation theory based on the Dirac-Fock-Breit wave functions has been developed and implemented by employing analytic basis sets of Gaussian-type functions. The instantaneous Coulomb and low-frequency Breit interactions are treated using a unified formalism in both the construction of the Dirac-Fock-Breit self-consistent-field atomic potential and in the evaluation of many-body perturbation-theory diagrams. The relativistic many-body perturbation-theory calculations have been performed on the helium atom and ions of the helium isoelectronic sequence up to Z=50. The contribution of the low-frequency Breit interaction to the relativistic correlation energy is examined for the helium isoelectronic sequence
Evaluating results from the Relativistic Heavy Ion Collider with perturbative QCD and hydrodynamics
Energy Technology Data Exchange (ETDEWEB)
Fries, R.J.; Nonaka, C.
2011-07-01
We review the basic concepts of perturbative quantum chromodynamics (QCD) and relativistic hydrodynamics, and their applications to hadron production in high energy nuclear collisions. We discuss results from the Relativistic Heavy Ion Collider (RHIC) in light of these theoretical approaches. Perturbative QCD and hydrodynamics together explain a large amount of experimental data gathered during the first decade of RHIC running, although some questions remain open. We focus primarily on practical aspects of the calculations, covering basic topics like perturbation theory, initial state nuclear effects, jet quenching models, ideal hydrodynamics, dissipative corrections, freeze-out and initial conditions. We conclude by comparing key results from RHIC to calculations.
Directory of Open Access Journals (Sweden)
Monika Hrubovčáková
2016-01-01
Full Text Available Iron and iron-phosphorus open-cell foams were manufactured by a replica method based on a powder metallurgical approach to serve as a temporary biodegradable bone replacement material. Iron foams alloyed with phosphorus were prepared with the aim of enhancing the mechanical properties and manipulating the corrosion rate. Two different types of Fe-P foams containing 0.5 wt.% of P were prepared: Fe-P(I foams from a phosphated carbonyl iron powder and Fe-P(II foams from a mixture of carbonyl iron and commercial Fe3P. The microstructure of foams was analyzed using scanning electron microscopy. The mechanical properties and the corrosion behaviour were studied by compression tests and potentiodynamic polarization in Hank’s solution and a physiological saline solution. The results showed that the manufactured foams exhibited an open, interconnected, microstructure similar to that of a cancellous bone. The presence of phosphorus improved the mechanical properties of the foams and decreased the corrosion rate as compared to pure iron foams.
Multiphoton transitions in semiconductors in the non-perturbative approach
International Nuclear Information System (INIS)
Iqbal, M.Z.; Hassan, A.R.
1987-09-01
Transition rates for multiphoton absorption via direct band-to-band excitation have been calculated using a non-perturbative approach due to Jones and Reiss, based on the Volkov type final state wave functions. Both cases of parabolic and non-parabolic energy bands have been included in our calculations. Absorption coefficients have been obtained for the cases of plane polarized and circularly polarized light. In particular, two-photon absorption coefficients are derived for the two cases of polarization for the parabolic band approximation as well as for non-parabolic bands and compared with the results based on perturbation theory. Numerical estimates of the two photon absorption coefficients resulting from our calculations are also provided. (author). 10 refs, 1 tab
New Methods in Non-Perturbative QCD
Energy Technology Data Exchange (ETDEWEB)
Unsal, Mithat [North Carolina State Univ., Raleigh, NC (United States)
2017-01-31
In this work, we investigate the properties of quantum chromodynamics (QCD), by using newly developing mathematics and physics formalisms. Almost all of the mass in the visible universe emerges from a quantum chromodynamics (QCD), which has a completely negligible microscopic mass content. An intimately related issue in QCD is the quark confinement problem. Answers to non-perturbative questions in QCD remained largely elusive despite much effort over the years. It is also believed that the usual perturbation theory is inadequate to address these kinds of problems. Perturbation theory gives a divergent asymptotic series (even when the theory is properly renormalized), and there are non-perturbative phenomena which never appear at any order in perturbation theory. Recently, a fascinating bridge between perturbation theory and non-perturbative effects has been found: a formalism called resurgence theory in mathematics tells us that perturbative data and non-perturbative data are intimately related. Translating this to the language of quantum field theory, it turns out that non-perturbative information is present in a coded form in perturbation theory and it can be decoded. We take advantage of this feature, which is particularly useful to understand some unresolved mysteries of QCD from first principles. In particular, we use: a) Circle compactifications which provide a semi-classical window to study confinement and mass gap problems, and calculable prototypes of the deconfinement phase transition; b) Resurgence theory and transseries which provide a unified framework for perturbative and non-perturbative expansion; c) Analytic continuation of path integrals and Lefschetz thimbles which may be useful to address sign problem in QCD at finite density.
Campbell, John O.
2018-03-01
In 2006 Karl Friston introduced the free energy principle (FEP) to neuroscience as a unifying concept [1]. This proposal, along with its use in developing the 'Bayesian Brain' formulation quickly gained traction and a 2008 feature article in New Scientist heralded it as providing a promising unified theory of the brain [2]:
Cosmological perturbation theory and quantum gravity
Energy Technology Data Exchange (ETDEWEB)
Brunetti, Romeo [Dipartimento di Matematica, Università di Trento,Via Sommarive 14, 38123 Povo TN (Italy); Fredenhagen, Klaus [II Institute für Theoretische Physik, Universität Hamburg,Luruper Chaussee 149, 22761 Hamburg (Germany); Hack, Thomas-Paul [Institute für Theoretische Physik, Universität Leipzig,Brüderstr. 16, 04103 Leipzig (Germany); Pinamonti, Nicola [Dipartimento di Matematica, Università di Genova,Via Dodecaneso 35, 16146 Genova (Italy); INFN, Sezione di Genova,Via Dodecaneso 33, 16146 Genova (Italy); Rejzner, Katarzyna [Department of Mathematics, University of York,Heslington, York YO10 5DD (United Kingdom)
2016-08-04
It is shown how cosmological perturbation theory arises from a fully quantized perturbative theory of quantum gravity. Central for the derivation is a non-perturbative concept of gauge-invariant local observables by means of which perturbative invariant expressions of arbitrary order are generated. In particular, in the linearised theory, first order gauge-invariant observables familiar from cosmological perturbation theory are recovered. Explicit expressions of second order quantities are presented as well.
Perturbation theory for Alfven wave
International Nuclear Information System (INIS)
Yoshida, Z.; Mahajan, S.M.
1995-01-01
The Alfven wave is the dominant low frequency transverse mode of a magnetized plasma. The Alfven wave propagation along the magnetic field, and displays a continuous spectrum even in a bounded plasma. This is essentially due to the degeneracy of the wave characteristics, i.e. the frequency (ω) is primarily determined by the wave number in the direction parallel to the ambient magnetic field (k parallel ) and is independent of the perpendicular wavenumbers. The characteristics, that are the direction along which the wave energy propagates, are identical to the ambient magnetic field lines. Therefore, the spectral structure of the Alfven wave has a close relationship with the geometric structure of the magnetic field lines. In an inhomogeneous plasma, the Alfven resonance constitutes a singularity for the defining wave equation; this results in a singular eigenfunction corresponding to the continuous spectrum. The aim of this review is to present an overview of the perturbation theory for the Alfven wave. Emphasis is placed on those perturbations of the continuous spectrum which lead to the creation of point spectra. Such qualitative changes in the spectrum are relevant to many plasma phenomena
Perturbative treatment of potential walls or potential cores in quantum mechanics
International Nuclear Information System (INIS)
Mei, W.N.
1987-01-01
The general problem involving an infinite potential barrier is treated by first constructing a pseudopotential H' that is shown to reproduce the effect of the barrier. A new procedure is then developed to handle the perturbative effect of H' since the standard formulae become invalid. The case of a finite potential well with large height V/sub o/ can the be solved by reducing it to that of an equivalent infinite barrier. The perturbation parameter turns out to be proportional 1/V/sub o/-E)/sup 1/2/ where E is the energy of the unperturbed state, defying, therefore, the conventional perturbation series treatment that depends on a split-off Hamiltonian for its expansion parameter. These methods are first illustrated with simple examples and then compared to more complex cases. Recently, they have extended this method to the case of degenerate perturbation. The calculation of the hydrogen-like impurity states in quantum well is in progress. Their result should also furnish a check for any specific problem involving a barrier solved by other approximate means such as the variational method
Anisotropic perturbations and stability of a static universe in f(G,T) gravity
Sharif, M.; Ikram, Ayesha
2017-12-01
The aim of this paper is to analyze the stability of the Einstein universe against anisotropic homogeneous perturbations in f(G,T) gravity ( G and T represent the Gauss-Bonnet invariant and trace of the energy-momentum tensor, respectively). The corresponding field equations are constructed for static as well as perturbed configurations in the presence of a perfect fluid. We consider two specific forms of generic function f(G,T) associated with zero as well as non-zero covariant divergence of the energy-momentum tensor and explore the stability regions of the Einstein universe parameterized by the equation of state parameter. It is concluded that a stable Einstein universe exists for an appropriate choice of model parameters.
Perturbations i have Known and Loved
Field, Robert W.
2011-06-01
A spectroscopic perturbation is a disruption of a ^1Σ-^1Σ-like regular pattern that can embody level-shifts, extra lines, and intensity anomalies. Once upon a time, when a band was labeled ``perturbed,'' it was considered worthless because it could at best yield molecular constants unsuited for archival tables. Nevertheless, a few brave spectroscopists, notably Albin Lagerqvist and Richard Barrow, collected perturbations because they knew that the pattern of multiple perturbations formed an intricate puzzle that would eventually reveal the presence and electronic symmetry of otherwise unobservable electronic states. There are many kinds of patterns of broken patterns. In my PhD thesis I showed how to determine absolute vibrational assignments for the perturber from patterns among the observed values of perturbation matrix elements. When a ^3Π state is perturbed, its six (Ω, parity) components capture a pattern of level shifts and intensity anomalies that reveals more about the nature of the perturber than a simple perturbation of the single component of a ^1Σ state. In perturbation-facilitated OODR, a perturbed singlet level acts as a spectroscopic doorway through which the entire triplet manifold may be systematically explored. For polyatomic molecule vibrations, a vibrational polyad (a group of mutually perturbing vibrational levels, among which the perturbation matrix elements are expected to follow harmonic oscillator scaling rules) can contain more components than a ^3Π state and intrapolyad patterns can be exquisitely sensitive not merely to the nature of an interloper within the polyad but also to the eigenvector character of the vibronic state from which the polyad is viewed. Variation of scaled polyad interaction parameters from one polyad to the next, a pattern of patterns, can signal proximity to an isomerization barrier. Everything in Rydberg-land seems to scale as N⋆-3, yet a trespassing valence state causes all scaling and propensity rules go
Perturbation theory of a superconducting 0 - π impurity quantum phase transition.
Žonda, M; Pokorný, V; Janiš, V; Novotný, T
2015-03-06
A single-level quantum dot with Coulomb repulsion attached to two superconducting leads is studied via the perturbation expansion in the interaction strength. We use the Nambu formalism and the standard many-body diagrammatic representation of the impurity Green functions to formulate the Matsubara self-consistent perturbation expansion. We show that at zero temperature second order of the expansion in its spin-symmetric version yields a nearly perfect agreement with the numerically exact calculations for the position of the 0 - π phase boundary at which the Andreev bound states reach the Fermi energy as well as for the values of single-particle quantities in the 0-phase. We present results for phase diagrams, level occupation, induced local superconducting gap, Josephson current, and energy of the Andreev bound states with the precision surpassing any (semi)analytical approaches employed thus far.
On post-inflation validity of perturbation theory in Horndeski scalar-tensor models
Energy Technology Data Exchange (ETDEWEB)
Germani, Cristiano [Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona, Martí Franquès 1, E08028 Barcelona (Spain); Kudryashova, Nina [Arnold Sommerfeld Center, Ludwig-Maximilians-University, Theresienstr. 37, 80333 Muenchen (Germany); Watanabe, Yuki, E-mail: germani@icc.ub.edu, E-mail: nina.kudryashova@campus.lmu.de, E-mail: yuki.watanabe@nat.gunma-ct.ac.jp [Department of Physics, National Institute of Technology, Gunma College, Gunma 371-8530 (Japan)
2016-08-01
By using the newtonian gauge, we re-confirm that, as in the minimal case, the re-scaled Mukhanov-Sasaki variable is conserved leading to a constraint equation for the Newtonian potential. However, conversely to the minimal case, in Horndeski theories, the super-horizon Newtonian potential can potentially grow to very large values after inflation exit. If that happens, inflationary predictability is lost during the oscillating period. When this does not happen, the perturbations generated during inflation can be standardly related to the CMB, if the theory chosen is minimal at low energies. As a concrete example, we analytically and numerically discuss the new Higgs inflationary case. There, the Inflaton is the Higgs boson that is non-minimally kinetically coupled to gravity. During the high-energy part of the post-inflationary oscillations, the system is anisotropic and the Newtonian potential is largely amplified. Thanks to the smallness of today's amplitude of curvature perturbations, however, the system stays in the linear regime, so that inflationary predictions are not lost. At low energies, when the system relaxes to the minimal case, the anisotropies disappear and the Newtonian potential converges to a constant value. We show that the constant value to which the Newtonian potential converges is related to the frozen part of curvature perturbations during inflation, precisely like in the minimal case.
Hartree–Fock many-body perturbation theory for nuclear ground-states
Directory of Open Access Journals (Sweden)
Alexander Tichai
2016-05-01
Full Text Available We investigate the order-by-order convergence behavior of many-body perturbation theory (MBPT as a simple and efficient tool to approximate the ground-state energy of closed-shell nuclei. To address the convergence properties directly, we explore perturbative corrections up to 30th order and highlight the role of the partitioning for convergence. The use of a simple Hartree–Fock solution for the unperturbed basis leads to a convergent MBPT series for soft interactions, in contrast to the divergent MBPT series obtained with a harmonic oscillator basis. For larger model spaces and heavier nuclei, where a direct high-order MBPT calculation is not feasible, we perform third-order calculations and compare to advanced ab initio coupled-cluster results for the same interactions and model spaces. We demonstrate that third-order MBPT provides ground-state energies for nuclei up into the tin isotopic chain in excellent agreement with the best available coupled-cluster calculations at a fraction of the computational cost.
Hartree–Fock many-body perturbation theory for nuclear ground-states
Energy Technology Data Exchange (ETDEWEB)
Tichai, Alexander, E-mail: alexander.tichai@physik.tu-darmstadt.de [Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt (Germany); Langhammer, Joachim [Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt (Germany); Binder, Sven [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996 (United States); Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Roth, Robert, E-mail: robert.roth@physik.tu-darmstadt.de [Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt (Germany)
2016-05-10
We investigate the order-by-order convergence behavior of many-body perturbation theory (MBPT) as a simple and efficient tool to approximate the ground-state energy of closed-shell nuclei. To address the convergence properties directly, we explore perturbative corrections up to 30th order and highlight the role of the partitioning for convergence. The use of a simple Hartree–Fock solution for the unperturbed basis leads to a convergent MBPT series for soft interactions, in contrast to the divergent MBPT series obtained with a harmonic oscillator basis. For larger model spaces and heavier nuclei, where a direct high-order MBPT calculation is not feasible, we perform third-order calculations and compare to advanced ab initio coupled-cluster results for the same interactions and model spaces. We demonstrate that third-order MBPT provides ground-state energies for nuclei up into the tin isotopic chain in excellent agreement with the best available coupled-cluster calculations at a fraction of the computational cost.
The causal perturbation expansion revisited: Rescaling the interacting Dirac sea
International Nuclear Information System (INIS)
Finster, Felix; Grotz, Andreas
2010-01-01
The causal perturbation expansion defines the Dirac sea in the presence of a time-dependent external field. It yields an operator whose image generalizes the vacuum solutions of negative energy and thus gives a canonical splitting of the solution space into two subspaces. After giving a self-contained introduction to the ideas and techniques, we show that this operator is, in general, not idempotent. We modify the standard construction by a rescaling procedure giving a projector on the generalized negative-energy subspace. The resulting rescaled causal perturbation expansion uniquely defines the fermionic projector in terms of a series of distributional solutions of the Dirac equation. The technical core of the paper is to work out the combinatorics of the expansion in detail. It is also shown that the fermionic projector with interaction can be obtained from the free projector by a unitary transformation. We finally analyze the consequences of the rescaling procedure on the light-cone expansion.
The causal perturbation expansion revisited: Rescaling the interacting Dirac sea
Finster, Felix; Grotz, Andreas
2010-07-01
The causal perturbation expansion defines the Dirac sea in the presence of a time-dependent external field. It yields an operator whose image generalizes the vacuum solutions of negative energy and thus gives a canonical splitting of the solution space into two subspaces. After giving a self-contained introduction to the ideas and techniques, we show that this operator is, in general, not idempotent. We modify the standard construction by a rescaling procedure giving a projector on the generalized negative-energy subspace. The resulting rescaled causal perturbation expansion uniquely defines the fermionic projector in terms of a series of distributional solutions of the Dirac equation. The technical core of the paper is to work out the combinatorics of the expansion in detail. It is also shown that the fermionic projector with interaction can be obtained from the free projector by a unitary transformation. We finally analyze the consequences of the rescaling procedure on the light-cone expansion.
Perturbative description of inclusive energy spectra
Energy Technology Data Exchange (ETDEWEB)
Lupia, S. [Max-Planck-Institut fuer Physik, Muenchen (Germany). Werner-Heisenberg-Institut
1996-03-01
The recent LEP-1.5 data of charged particle inclusive energy spectra are analyzed within the analytical QCD approach based on modified leading log approximation plus local parton hadron duality. The shape, the position of the maximum and the cumulant moments of the inclusive energy spectrum are well described within this model. The sensitivity of the results to the running of the coupling is pointed out. A scaling law for the one-particle invariant density E dn/d{sup 3}p at small momenta is observed, consistently with the predictions of colour coherence in soft gluon bremsstrahlung. (orig.).
Perturbative description of inclusive energy spectra
International Nuclear Information System (INIS)
Lupia, S.
1996-01-01
The recent LEP-1.5 data of charged particle inclusive energy spectra are analyzed within the analytical QCD approach based on modified leading log approximation plus local parton hadron duality. The shape, the position of the maximum and the cumulant moments of the inclusive energy spectrum are well described within this model. The sensitivity of the results to the running of the coupling is pointed out. A scaling law for the one-particle invariant density E dn/d 3 p at small momenta is observed, consistently with the predictions of colour coherence in soft gluon bremsstrahlung. (orig.)
DEFF Research Database (Denmark)
Sadegh, Payman; Spall, J. C.
1998-01-01
simultaneous perturbation approximation to the gradient based on loss function measurements. SPSA is based on picking a simultaneous perturbation (random) vector in a Monte Carlo fashion as part of generating the approximation to the gradient. This paper derives the optimal distribution for the Monte Carlo...
A non-perturbative analysis in finite volume gauge theory
International Nuclear Information System (INIS)
Koller, J.; State Univ. of New York, Stony Brook; Van Baal, P.; State Univ. of New York, Stony Brook
1988-01-01
We discuss SU(2) gauge theory on a three-torus using a finite volume expansion. Our discovery of natural coordinates allows us to obtain continuum results in a region where Monte Carlo data are also available. The obtained results agree well with the perturbative and semiclassical analysis for small volumes, and there is fair agreement with the Monte Carlo results in intermediate volumes. The simple picture which emerges for the approximate low energy dynamics is that of three interacting particles enclosed in a sphere, with zero total 'angular momentum'. The validity of an adiabatic approximation is investigated. The fundamentally new understanding gained, is that non-perturbative dynamics can be incorporated by imposing boundary conditions which arise through the nontrivial topology of configuration space. (orig.)
Directory of Open Access Journals (Sweden)
Mustafa Kemal BAHAR
2010-06-01
Full Text Available In this study, the effects of applied electric field on the isolated square quantum well was investigated by analytic and perturbative method. The energy eigen values and wave functions in quantum well were found by perturbative method. Later, the electric field effects were investigated by analytic method, the results of perturbative and analytic method were compared. As well as both of results fit with each other, it was observed that externally applied electric field changed importantly electronic properties of the system.
Preheating curvaton perturbations
International Nuclear Information System (INIS)
Bastero-Gil, M.; Di Clemente, V.; King, S.F.
2005-01-01
We discuss the potentially important role played by preheating in certain variants of the curvaton mechanism in which isocurvature perturbations of a D-flat (and F-flat) direction become converted to curvature perturbations during reheating. We discover that parametric resonance of the isocurvature components amplifies the superhorizon fluctuations by a significant amount. As an example of these effects we develop a particle physics motivated model which involves hybrid inflation with the waterfall field N being responsible for generating the μ term, the right-handed neutrino mass scale, and the Peccei-Quinn symmetry breaking scale. The role of the curvaton field can be played either by usual Higgs field, or the lightest right-handed sneutrino. Our new results show that it is possible to achieve the correct curvature perturbations for initial values of the curvaton fields of order the weak scale. In this model we show that the prediction for the spectral index of the final curvature perturbation only depends on the mass of the curvaton during inflation, where consistency with current observational data requires the ratio of this mass to the Hubble constant to be 0.3
High energy asymptotics of perturbative multi-color QCD
International Nuclear Information System (INIS)
Lipatov, L.N.
1993-01-01
The structure functions of deep-inelastic scattering at small-x satisfy two different equations in the leading logarithmic approximation (LLA). The first one -- the GLAP equation, describes the Q 2 -evolution of partonic distributions h i (x). The second one -- the BFKL, equation determines the x-dependence of parton densities H i (x, k perpendicular ). Analogous equations for matrix elements of higher twist operators were constructed in Refs. 3 and 4. Here the author discusses the possibility of finding an exact solution for multi-gluon compound states in LLA for the color group SU(N), in the limit N → ∞. The contributions of diagrams with many reggeized gluons are important for the unitarization of the perturbative Pomeron in QCD. It is shown that the Bethe-Salpeter equations for compound states of many reggeized gluons are conformally invariant in the two-dimensional impact parameter space. Their solutions can be written in holomorphically factorized form and there is a differential operator commuting with the holomorphic part of the corresponding Hamiltonian
Inclusive central region in perturbative Reggeon calculus
International Nuclear Information System (INIS)
Pajares, C.; Pascual, R.
1976-01-01
The single-particle inclusive cross section and the correlation function are studied in the perturbative approach to Gribov's Reggeon calculus; the leading contributions to both functions are evaluated. The large energy rise of the inclusive cross section appears as a consequence of the Pomerons having an intercept larger than 1. The same set of parameters which describes correctly the cross-section data and the triple-Regge region also describes the inclusive data in the central region
Ferromagnetism in the Hubbard model: a modified perturbation theory
International Nuclear Information System (INIS)
Gangadhar Reddy, G.; Ramakanth, A.; Nolting, W.
2005-01-01
We study the possibility of ferromagnetism in the Hubbard model using the modified perturbation theory. In this approach an Ansatz is made for the self-energy of the electron which contains the second order contribution developed around the Hartree-Fock solution and two parameters. The parameters are fixed by using a moment method. This self energy satisfies several known exact limiting cases. Using this self energy, the Curie temperature T c as a function of band filling n is investigated. It is found that T c falls off abruptly as n approaches half filling. The results are in qualitative agreement with earlier calculations using other approximation schemes. (author)
Testing QCD in the non-perturbative regime
Energy Technology Data Exchange (ETDEWEB)
A.W. Thomas
2007-01-01
This is an exciting time for strong interaction physics. We have a candidate for a fundamental theory, namely QCD, which has passed all the tests thrown at it in the perturbative regime. In the non-perturbative regime it has also produced some promising results and recently a few triumphs but the next decade will see enormous progress in our ability to unambiguously calculate the consequences of non-perturbative QCD and to test those predictions experimentally. Amongst the new experimental facilities being constructed, the hadronic machines at JPARC and GSI-FAIR and the 12 GeV Upgrade at Jefferson Lab, the major new electromagnetic facility worldwide, present a beautifully complementary network aimed at producing precise new measurements which will advance our knowledge of nuclear systems and push our ability to calculate the consequences of QCD to the limit. We will first outline the plans at Jefferson Lab for doubling the energy of CEBAF. The new facility presents some wonderful opportunities for discovery in strong interaction physics, as well as beyond the standard model. Then we turn to the theoretical developments aimed at extracting precise results for physical hadron properties from lattice QCD simulations. This discussion will begin with classical examples, such as the mass of the nucleon and ?, before dealing with a very recent and spectacular success involving information extracted from modern parity violating electron scattering.
Diagrammatic many-body perturbation expansion for atoms and molecules. Pt. 6
International Nuclear Information System (INIS)
Moncrieff, D.; Baker, D.J.; Wilson, S.
1989-01-01
The efficient evaluation of the second-order expression in the many-body perturbation theory expansion for the correlation energy on vector processing and parallel processing computers is discussed. It is argued that the linked diagram theorem not only leads to the well known theoretical advantages of the many-body perturbation theory approach which allows the calculation of correlation energies for large (i.e. extended molecules or species containing heavy atoms) systems but also decouples the many-electron problem allowing efficient implementation on parallel processing machines. Furthermore, the computation associated with each of the resulting subproblems is very well suited to vector processing machines. Timing tests are reported for the CRAY 1 and CDC Cyber 205 vector processors, for a 1 processor implementation on the CRAY X-MP/48 and the ETA-10E, and for a 4 processor implementation on the Cray X-MP/48. (orig.)
An algebraic description of perturbation theory in quantum electrodynamics
International Nuclear Information System (INIS)
Wright, J.D.
1982-01-01
An algebraic formulation of the electromagnetic field, in which various quantization procedures can be described, is used to discuss perturbation calculations. The Feynman rules and the second order calculation of the self-energy of the electron can be developed on the basis of the Fermi method of quantization. The algebraic approach clarifies the problems in defining the vacuum and other states, which are associated with calculations in terms of field algebra operators. The vacuum state defined on the field algebra by Schwinger leads to incorrect results in the self-energy calculation
CERN. Geneva
2015-01-01
Following a short theoretical motivation based on non-perturbative B+L violating physics within the SM, the talk will be based on applying instead a purely perturbative technique for computing amplitudes and cross sections for processes involving very high multiplicities of Higgses and massive vector bosons. At tree-level, I’ll review known results for such amplitudes on multiparticle mass-thresholds and will generalise these computations to more general kinematics away from the threshold. I’ll explain that these processes exhibit a factorial growth with the number of massive particle in the final state and that this is in contradiction with perturbative unitarity. This signals the breakdown of our trusted weakly coupled perturbation theory at energies ~ 50 - 1000 TeV and can lead to new unexpected physics signatures and phenomena at these energy scales. I’ll comment on what is currently known about the loop effects and will discuss the general expected structure of the high-energy high-multiplicity c...
Atomistic modeling of an impurity element and a metal-impurity system: pure P and Fe-P system
International Nuclear Information System (INIS)
Ko, Won-Seok; Lee, Byeong-Joo; Kim, Nack J
2012-01-01
An interatomic potential for pure phosphorus, an element that has van der Waals, covalent and metallic bonding character, simultaneously, has been developed for the purpose of application to metal-phosphorus systems. As a simplification, the van der Waals interaction, which is less important in metal-phosphorus systems, was omitted in the parameterization process and potential formulation. On the basis of the second-nearest-neighbor modified embedded-atom method (2NN MEAM) interatomic potential formalism applicable to both covalent and metallic materials, a potential that can describe various fundamental physical properties of a wide range of allotropic or transformed crystalline structures of pure phosphorus could be developed. The potential was then extended to the Fe-P binary system describing various physical properties of intermetallic compounds, bcc and liquid alloys, and also the segregation tendency of phosphorus on grain boundaries of bcc iron, in good agreement with experimental information. The suitability of the present potential and the parameterization process for atomic scale investigations about the effects of various non-metallic impurity elements on metal properties is demonstrated. (paper)
Reggeon calculus at collider energies
International Nuclear Information System (INIS)
Pajares, C.; Varias, A.; Yepes, P.
1983-01-01
The phenomenology of the perturbative reggeon calculus at collider energies is studied. It is found that the graphs which were neglected at ISR energies are still negligeable at √s=540 GeV. The perturbative series for the total cross section still converges reasonably fast. The values of the different parameters which describe rightly the data up to ISR energies give rise to a total cross section of around 60 mb at √s=540 GeV. For these values, the corresponding low mass and high mass eikonal series converges much more slowly. The non perturbative reggeon calculus gives rise to a total cross section less than 60 mb. (orig.)
Non-perturbative renormalization of static-light four-fermion operators in quenched lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Palombi, F. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Papinutto, M.; Pena, C. [CERN, Geneva (Switzerland). Physics Dept., Theory Div.; Wittig, H. [Mainz Univ. (Germany). Inst. fuer Kernphysik
2007-06-15
We perform a non-perturbative study of the scale-dependent renormalization factors of a multiplicatively renormalizable basis of {delta}B=2 parity-odd four-fermion operators in quenched lattice QCD. Heavy quarks are treated in the static approximation with various lattice discretizations of the static action. Light quarks are described by nonperturbatively O(a) improved Wilson-type fermions. The renormalization group running is computed for a family of Schroedinger functional (SF) schemes through finite volume techniques in the continuum limit. We compute non-perturbatively the relation between the renormalization group invariant operators and their counterparts renormalized in the SF at a low energy scale. Furthermore, we provide non-perturbative estimates for the matching between the lattice regularized theory and all the SF schemes considered. (orig.)
Singular perturbation of simple eigenvalues
International Nuclear Information System (INIS)
Greenlee, W.M.
1976-01-01
Two operator theoretic theorems which generalize those of asymptotic regular perturbation theory and which apply to singular perturbation problems are proved. Application of these theorems to concrete problems is involved, but the perturbation expansions for eigenvalues and eigenvectors are developed in terms of solutions of linear operator equations. The method of correctors, as well as traditional boundary layer techniques, can be used to apply these theorems. The current formulation should be applicable to highly singular ''hard core'' potential perturbations of the radial equation of quantum mechanics. The theorems are applied to a comparatively simple model problem whose analysis is basic to that of the quantum mechanical problem
Separation of acoustic waves in isentropic flow perturbations
International Nuclear Information System (INIS)
Henke, Christian
2015-01-01
The present contribution investigates the mechanisms of sound generation and propagation in the case of highly-unsteady flows. Based on the linearisation of the isentropic Navier–Stokes equation around a new pathline-averaged base flow, it is demonstrated for the first time that flow perturbations of a non-uniform flow can be split into acoustic and vorticity modes, with the acoustic modes being independent of the vorticity modes. Therefore, we can propose this acoustic perturbation as a general definition of sound. As a consequence of the splitting result, we conclude that the present acoustic perturbation is propagated by the convective wave equation and fulfils Lighthill’s acoustic analogy. Moreover, we can define the deviations of the Navier–Stokes equation from the convective wave equation as “true” sound sources. In contrast to other authors, no assumptions on a slowly varying or irrotational flow are necessary. Using a symmetry argument for the conservation laws, an energy conservation result and a generalisation of the sound intensity are provided. - Highlights: • First splitting of non-uniform flows in acoustic and non-acoustic components. • These result leads to a generalisation of sound which is compatible with Lighthill’s acoustic analogy. • A closed equation for the generation and propagation of sound is given
International Nuclear Information System (INIS)
Suslov, I.M.
2005-01-01
Various perturbation series are factorially divergent. The behavior of their high-order terms can be determined by Lipatov's method, which involves the use of instanton configurations of appropriate functional integrals. When the Lipatov asymptotic form is known and several lowest order terms of the perturbation series are found by direct calculation of diagrams, one can gain insight into the behavior of the remaining terms of the series, which can be resummed to solve various strong-coupling problems in a certain approximation. This approach is demonstrated by determining the Gell-Mann-Low functions in φ 4 theory, QED, and QCD with arbitrary coupling constants. An overview of the mathematical theory of divergent series is presented, and interpretation of perturbation series is discussed. Explicit derivations of the Lipatov asymptotic form are presented for some basic problems in theoretical physics. A solution is proposed to the problem of renormalon contributions, which hampered progress in this field in the late 1970s. Practical perturbation-series summation schemes are described both for a coupling constant of order unity and in the strong-coupling limit. An interpretation of the Borel integral is given for 'non-Borel-summable' series. Higher order corrections to the Lipatov asymptotic form are discussed
Zhang, Xiaoqing; Sessler, Gerhard M.; Ma, Xingchen; Xue, Yuan; Wu, Liming
2018-06-01
Wavy fluorinated ethylene propylene (FEP) electret films with negative charges were prepared by a patterning method followed by a corona charging process. The thermal stability of these films was characterized by the surface potential decay with annealing time at elevated temperatures. The results show that thermally stable electret films can be made by corona charging followed by pre-aging treatment. Vibration energy harvesters having a very simple sandwich structure, consisting of a central wavy FEP electret film and two outside metal plates, were designed and their performance, including the resonance frequency, output power, half power bandwidth, and device stability, was investigated. These harvesters show a broad bandwidth as well as high output power. Their performance can be further improved by using a wavy-shaped counter electrode. For an energy harvester with an area of 4 cm2 and a seismic mass of 80 g, the output power referred to 1 g (g is the gravity of the earth), the resonance frequency, and the 3 dB bandwidth are 1.85 mW, 90 Hz, and 24 Hz, respectively. The output power is sufficient to power some electronic devices. Such devices may be embedded in shoe soles, carpets or seat cushions where the flexibility is required and large force is available.
Non-perturbative measurement of low-intensity charged particle beams
Fernandes, M.; Geithner, R.; Golm, J.; Neubert, R.; Schwickert, M.; Stöhlker, T.; Tan, J.; Welsch, C. P.
2017-01-01
Non-perturbative measurements of low-intensity charged particle beams are particularly challenging to beam diagnostics due to the low amplitude of the induced electromagnetic fields. In the low-energy antiproton decelerator (AD) and the future extra low energy antiproton rings at CERN, an absolute measurement of the beam intensity is essential to monitor the operation efficiency. Superconducting quantum interference device (SQUID) based cryogenic current comparators (CCC) have been used for measuring slow charged beams in the nA range, showing a very good current resolution. But these were unable to measure fast bunched beams, due to the slew-rate limitation of SQUID devices and presented a strong susceptibility to external perturbations. Here, we present a CCC system developed for the AD machine, which was optimised in terms of its current resolution, system stability, ability to cope with short bunched beams, and immunity to mechanical vibrations. This paper presents the monitor design and the first results from measurements with a low energy antiproton beam obtained in the AD in 2015. These are the first CCC beam current measurements ever performed in a synchrotron machine with both coasting and short bunched beams. It is shown that the system is able to stably measure the AD beam throughout the entire cycle, with a current resolution of 30 {nA}.
Effect of initial perturbation amplitude on Richtmyer-Meshkov flows induced by strong shocks
Energy Technology Data Exchange (ETDEWEB)
Dell, Z.; Abarzhi, S. I., E-mail: snezhana.abarzhi@gmail.com, E-mail: sabarji@andrew.cmu.edu [Mellon College of Science and Carnegie Mellon University – Qatar, Carnegie Mellon University, Pittsburgh, Pennsylvania 15231 (United States); Stellingwerf, R. F. [Stellingwerf Consulting, Huntsville, Alabama 35803 (United States)
2015-09-15
We systematically study the effect of the initial perturbation on Richtmyer-Meshkov (RM) flows induced by strong shocks in fluids with contrasting densities. Smooth Particle Hydrodynamics simulations are employed. A broad range of shock strengths and density ratios is considered. The amplitude of the initial single mode sinusoidal perturbation of the interface varies from 0% to 100% of its wavelength. The simulations results are compared, wherever possible, with four rigorous theories, and with other experiments and simulations, achieving good quantitative and qualitative agreement. Our study is focused on early time dynamics of the Richtmyer-Meshkov instability (RMI). We analyze the initial growth-rate of RMI immediately after the shock passage, when the perturbation amplitude increases linearly with time. For the first time, to the authors' knowledge, we find that the initial growth-rate of RMI is a non-monotone function of the initial perturbation amplitude, thus restraining the amount of energy that can be deposited by the shock at the interface. The maximum value of the initial growth-rate depends on the shock strength and the density ratio, whereas the corresponding value of the initial perturbation amplitude depends only slightly on the shock strength and density ratio.
Large-order perturbation theory
International Nuclear Information System (INIS)
Wu, T.T.
1982-01-01
The original motivation for studying the asymptotic behavior of the coefficients of perturbation series came from quantum field theory. An overview is given of some of the attempts to understand quantum field theory beyond finite-order perturbation series. At least is the case of the Thirring model and probably in general, the full content of a relativistic quantum field theory cannot be recovered from its perturbation series. This difficulty, however, does not occur in quantum mechanics, and the anharmonic oscillator is used to illustrate the methods used in large-order perturbation theory. Two completely different methods are discussed, the first one using the WKB approximation, and a second one involving the statistical analysis of Feynman diagrams. The first one is well developed and gives detailed information about the desired asymptotic behavior, while the second one is still in its infancy and gives instead information about the distribution of vertices of the Feynman diagrams
Perturbation theory in light-cone gauge
International Nuclear Information System (INIS)
Vianello, Eliana
2000-01-01
Perturbation calculations are presented for the light-cone gauge Schwinger model. Eigenstates can be calculated perturbatively but the perturbation theory is nonstandard. We hope to extend the work to QCD 2 to resolve some outstanding issues in those theories
Stochastic many-body perturbation theory for anharmonic molecular vibrations
Energy Technology Data Exchange (ETDEWEB)
Hermes, Matthew R. [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); Hirata, So, E-mail: sohirata@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)
2014-08-28
A new quantum Monte Carlo (QMC) method for anharmonic vibrational zero-point energies and transition frequencies is developed, which combines the diagrammatic vibrational many-body perturbation theory based on the Dyson equation with Monte Carlo integration. The infinite sums of the diagrammatic and thus size-consistent first- and second-order anharmonic corrections to the energy and self-energy are expressed as sums of a few m- or 2m-dimensional integrals of wave functions and a potential energy surface (PES) (m is the vibrational degrees of freedom). Each of these integrals is computed as the integrand (including the value of the PES) divided by the value of a judiciously chosen weight function evaluated on demand at geometries distributed randomly but according to the weight function via the Metropolis algorithm. In this way, the method completely avoids cumbersome evaluation and storage of high-order force constants necessary in the original formulation of the vibrational perturbation theory; it furthermore allows even higher-order force constants essentially up to an infinite order to be taken into account in a scalable, memory-efficient algorithm. The diagrammatic contributions to the frequency-dependent self-energies that are stochastically evaluated at discrete frequencies can be reliably interpolated, allowing the self-consistent solutions to the Dyson equation to be obtained. This method, therefore, can compute directly and stochastically the transition frequencies of fundamentals and overtones as well as their relative intensities as pole strengths, without fixed-node errors that plague some QMC. It is shown that, for an identical PES, the new method reproduces the correct deterministic values of the energies and frequencies within a few cm{sup −1} and pole strengths within a few thousandths. With the values of a PES evaluated on the fly at random geometries, the new method captures a noticeably greater proportion of anharmonic effects.
Degenerate R-S perturbation theory
Hirschfelder, J. O.; Certain, P. R.
1973-01-01
A concise, systematic procedure is given for determining the Rayleigh-Schrodinger energies and wave functions of degenerate states to arbitrarily high orders even when the degeneracies of the various states are resolved in arbitrary orders. The procedure is expressed in terms of an iterative cycle in which the energy through the (2n+1)st order is expressed in terms of the partially determined wave function through the n-th order. Both a direct and an operator derivation are given. The two approaches are equivalent and can be transcribed into each other. The direct approach deals with the wave functions (without the use of formal operators) and has the advantage that it resembles the usual treatment of nondegenerate perturbations and maintains close contact with the basic physics. In the operator approach, the wave functions are expressed in terms of infinite order operators which are determined by the successive resolution of the space of the zeroth order functions.
Smoothing expansion rate data to reconstruct cosmological matter perturbations
Energy Technology Data Exchange (ETDEWEB)
Gonzalez, J.E.; Alcaniz, J.S.; Carvalho, J.C., E-mail: javierernesto@on.br, E-mail: alcaniz@on.br, E-mail: jcarvalho@on.br [Departamento de Astronomia, Observatório Nacional, Rua Gal. José Cristino, 77, Rio de Janeiro, RJ 20921-400 (Brazil)
2017-08-01
The existing degeneracy between different dark energy and modified gravity cosmologies at the background level may be broken by analyzing quantities at the perturbative level. In this work, we apply a non-parametric smoothing (NPS) method to reconstruct the expansion history of the Universe ( H ( z )) from model-independent cosmic chronometers and high- z quasar data. Assuming a homogeneous and isotropic flat universe and general relativity (GR) as the gravity theory, we calculate the non-relativistic matter perturbations in the linear regime using the H ( z ) reconstruction and realistic values of Ω {sub m} {sub 0} and σ{sub 8} from Planck and WMAP-9 collaborations. We find a good agreement between the measurements of the growth rate and f σ{sub 8}( z ) from current large-scale structure observations and the estimates obtained from the reconstruction of the cosmic expansion history. Considering a recently proposed null test for GR using matter perturbations, we also apply the NPS method to reconstruct f σ{sub 8}( z ). For this case, we find a ∼ 3σ tension (good agreement) with the standard relativistic cosmology when the Planck (WMAP-9) priors are used.
Smoothing expansion rate data to reconstruct cosmological matter perturbations
International Nuclear Information System (INIS)
Gonzalez, J.E.; Alcaniz, J.S.; Carvalho, J.C.
2017-01-01
The existing degeneracy between different dark energy and modified gravity cosmologies at the background level may be broken by analyzing quantities at the perturbative level. In this work, we apply a non-parametric smoothing (NPS) method to reconstruct the expansion history of the Universe ( H ( z )) from model-independent cosmic chronometers and high- z quasar data. Assuming a homogeneous and isotropic flat universe and general relativity (GR) as the gravity theory, we calculate the non-relativistic matter perturbations in the linear regime using the H ( z ) reconstruction and realistic values of Ω m 0 and σ 8 from Planck and WMAP-9 collaborations. We find a good agreement between the measurements of the growth rate and f σ 8 ( z ) from current large-scale structure observations and the estimates obtained from the reconstruction of the cosmic expansion history. Considering a recently proposed null test for GR using matter perturbations, we also apply the NPS method to reconstruct f σ 8 ( z ). For this case, we find a ∼ 3σ tension (good agreement) with the standard relativistic cosmology when the Planck (WMAP-9) priors are used.
Perturbation Theory of Embedded Eigenvalues
DEFF Research Database (Denmark)
Engelmann, Matthias
project gives a general and systematic approach to analytic perturbation theory of embedded eigenvalues. The spectral deformation technique originally developed in the theory of dilation analytic potentials in the context of Schrödinger operators is systematized by the use of Mourre theory. The group...... of dilations is thereby replaced by the unitary group generated y the conjugate operator. This then allows to treat the perturbation problem with the usual Kato theory.......We study problems connected to perturbation theory of embedded eigenvalues in two different setups. The first part deals with second order perturbation theory of mass shells in massive translation invariant Nelson type models. To this end an expansion of the eigenvalues w.r.t. fiber parameter up...
Thermal gluons beyond pure perturbation theory
International Nuclear Information System (INIS)
Reinbach, J.
2000-01-01
The perturbative treatment of non-abelian gauge theory at high temperature leads to a threshold in calculation because of chromomagnetic effects. Infinitely many terms of the same order of magnitude arise. The numerical series to be summed is contained in the part of the theory reduced on 3D, which was recently treated non-perturbative as 2+1D Yang-Mills theory at T=0 by Karabali, Kim and Nair. In the thesis in question the exact 3D results are combined with the thermal 4D diagrammatic. In particular the splitting of the space-part of the transverse self-energy in the static limit is treated. As expected, the 3D subsystem can separate as regularized 3D Yang-Mills theory from the 4D structure. In 1-loop order the regulators are received explicit. For 2-loop order it can be shown amongst other things, that the generic contribution with hard inner momenta vanishes. It is examined, how the magnetic mass could follow. Under pressure it is possible to separate the 3D part in 1- and 2-loop order and to receive regulators [de
Energy constraints in pulsed phase control of chaos
International Nuclear Information System (INIS)
Meucci, R.; Euzzor, S.; Zambrano, S.; Pugliese, E.; Francini, F.; Arecchi, F.T.
2017-01-01
Phase control of chaos is a powerful technique but little is known about its physical constraints, relevant for real systems. As a fact, it has not been explored whether this technique can also be applied when the controlling perturbation is not harmonic. Here we apply phase control on a driven double well Duffing oscillator using periodic rectangular pulsed perturbations instead of the classical sinusoidal perturbations. Experimental measurements and numerical simulations show that this kind of perturbation is also able to stabilize the chaotic orbits for an adequate selection of the phase. Furthermore, as the duty cycle of the perturbation (that is, the fraction of the time that the periodically pulsed control is active) is increased, two separate regimes occur. In the first one, the perturbations leading to stabilization of periodic solutions are of constant energy (taken as the product of the duty cycle and the amplitude) and in the second one, a saturation phenomenon occurs, implying that increasing energy values of the perturbations are wasted. Our results unveil the versatility of the pulsed phase control scheme and the importance of energy constraints.
Energy constraints in pulsed phase control of chaos
Energy Technology Data Exchange (ETDEWEB)
Meucci, R., E-mail: riccardo.meucci@ino.it [Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Largo E. Fermi 6, 50125 Firenze (Italy); Euzzor, S. [Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Largo E. Fermi 6, 50125 Firenze (Italy); Zambrano, S. [Università Vita-Salute San Raffaele, Via Olgettina 58, 20132 Milano (Italy); Pugliese, E. [Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Largo E. Fermi 6, 50125 Firenze (Italy); Dipartimento di Scienze della Terra, Università di Firenze, Via G. La Pira 4, 50100 Firenze (Italy); Francini, F. [Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Largo E. Fermi 6, 50125 Firenze (Italy); Arecchi, F.T. [Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Largo E. Fermi 6, 50125 Firenze (Italy); Università di Firenze, Firenze (Italy)
2017-01-15
Phase control of chaos is a powerful technique but little is known about its physical constraints, relevant for real systems. As a fact, it has not been explored whether this technique can also be applied when the controlling perturbation is not harmonic. Here we apply phase control on a driven double well Duffing oscillator using periodic rectangular pulsed perturbations instead of the classical sinusoidal perturbations. Experimental measurements and numerical simulations show that this kind of perturbation is also able to stabilize the chaotic orbits for an adequate selection of the phase. Furthermore, as the duty cycle of the perturbation (that is, the fraction of the time that the periodically pulsed control is active) is increased, two separate regimes occur. In the first one, the perturbations leading to stabilization of periodic solutions are of constant energy (taken as the product of the duty cycle and the amplitude) and in the second one, a saturation phenomenon occurs, implying that increasing energy values of the perturbations are wasted. Our results unveil the versatility of the pulsed phase control scheme and the importance of energy constraints.
Perturbative odderon in the dipole model
International Nuclear Information System (INIS)
Kovchegov, Yuri V.; Szymanowski, Lech; Wallon, Samuel
2004-01-01
We show that, in the framework of Mueller's dipole model, the perturbative QCD odderon is described by the dipole model equivalent of the BFKL equation with a C-odd initial condition. The eigenfunctions and eigenvalues of the odderon solution are the same as for the dipole BFKL equation and are given by the functions E n,ν and χ(n,ν) correspondingly, where the C-odd initial condition allows only for odd values of n. The leading high-energy odderon intercept is given by α odd -1=((2α s N c )/(π))χ(n=1,ν=0)=0 in agreement with the solution found by Bartels, Lipatov and Vacca. We proceed by writing down an evolution equation for the odderon including the effects of parton saturation. We argue that saturation makes the odderon solution a decreasing function of energy
Dynamics of a single ion in a perturbed Penning trap: Octupolar perturbation
International Nuclear Information System (INIS)
Lara, Martin; Salas, J. Pablo
2004-01-01
Imperfections in the design or implementation of Penning traps may give rise to electrostatic perturbations that introduce nonlinearities in the dynamics. In this paper we investigate, from the point of view of classical mechanics, the dynamics of a single ion trapped in a Penning trap perturbed by an octupolar perturbation. Because of the axial symmetry of the problem, the system has two degrees of freedom. Hence, this model is ideal to be managed by numerical techniques like continuation of families of periodic orbits and Poincare surfaces of section. We find that, through the variation of the two parameters controlling the dynamics, several periodic orbits emanate from two fundamental periodic orbits. This process produces important changes (bifurcations) in the phase space structure leading to chaotic behavior
Quantum inflaton, primordial perturbations, and CMB fluctuations
International Nuclear Information System (INIS)
Cao, F.J.; Vega, H.J. de; Sanchez, N.G.
2004-01-01
We compute the primordial scalar, vector and tensor metric perturbations arising from quantum field inflation. Quantum field inflation takes into account the nonperturbative quantum dynamics of the inflaton consistently coupled to the dynamics of the (classical) cosmological metric. For chaotic inflation, the quantum treatment avoids the unnatural requirements of an initial state with all the energy in the zero mode. For new inflation it allows a consistent treatment of the explosive particle production due to spinodal instabilities. Quantum field inflation (under conditions that are the quantum analog of slow-roll) leads, upon evolution, to the formation of a condensate starting a regime of effective classical inflation. We compute the primordial perturbations taking the dominant quantum effects into account. The results for the scalar, vector and tensor primordial perturbations are expressed in terms of the classical inflation results. For a N-component field in a O(N) symmetric model, adiabatic fluctuations dominate while isocurvature or entropy fluctuations are negligible. The results agree with the current Wilkinson Microwave Anisotropy Probe observations and predict corrections to the power spectrum in classical inflation. Such corrections are estimated to be of the order of (m 2 /NH 2 ), where m is the inflaton mass and H the Hubble constant at the moment of horizon crossing. An upper estimate turns to be about 4% for the cosmologically relevant scales. This quantum field treatment of inflation provides the foundations to the classical inflation and permits to compute quantum corrections to it
International Nuclear Information System (INIS)
Collins, J.C.
1985-01-01
Progress in quantum chromodynamics in the past year is reviewed in these specific areas: proof of factorization for hadron-hadron collisions, fast calculation of higher order graphs, perturbative Monte Carlo calculations for hadron-hadron scattering, applicability of perturbative methods to heavy quark production, and understanding of the small-x problem. 22 refs
An intermolecular perturbation theory for the region of moderate overlap
International Nuclear Information System (INIS)
Hayes, I.C.; Stone, A.J.
1984-01-01
A perturbational method is described for calculating the interaction energy of two molecules in the region where the overlap between their wave-functions is significant. By working directly with a basis of determinants constructed from the SCF orbitals of the separated molecules, without orthogonalization, it is possible to avoid many of the disadvantages of other methods. (author)
FRW Cosmological Perturbations in Massive Bigravity
Comelli, D; Pilo, L
2014-01-01
Cosmological perturbations of FRW solutions in ghost free massive bigravity, including also a second matter sector, are studied in detail. At early time, we find that sub horizon exponential instabilities are unavoidable and they lead to a premature departure from the perturbative regime of cosmological perturbations.
Joint queue-perturbed and weakly-coupled power control for wireless backbone networks
CSIR Research Space (South Africa)
Olwal, TO
2012-09-01
Full Text Available perturbation and weakly-coupled based power control approach for the WBNs. The ultimate objectives are to increase energy-efficiency and the overal network capacity. In order to achieve these objectives, a Markov chain model is first presented to describe...
Chaotic inflation with metric and matter perturbations
International Nuclear Information System (INIS)
Feldman, H.A.; Brandenberger, R.H.
1989-01-01
A perturbative scheme to analyze the evolution of both metric and scalar field perturbations in an expanding universe is developed. The scheme is applied to study chaotic inflation with initial metric and scalar field perturbations present. It is shown that initial gravitational perturbations with wavelength smaller than the Hubble radius rapidly decay. The metric simultaneously picks up small perturbations determined by the matter inhomogeneities. Both are frozen in once the wavelength exceeds the Hubble radius. (orig.)
Runaway electrons in disruptions and perturbed magnetic topologies of tokamak plasmas
International Nuclear Information System (INIS)
Forster, Michael
2012-01-01
spectra are found. The radial decay of the runaways is studied and approximated by an exponential distribution. Deriving from the measurements, resistive tearing modes or kink modes are suggested to trigger the formation of the bursts. Measurements of the total runaway electron energy are carried out using the calorimeter probe during induced TEXTOR disruptions. The dependencies of the runaway energy on the runaway current, the radial probe position, the toroidal magnetic field and the predisruptive plasma current are studied. The conversion efficiency of the magnetic plasma energy into runaway energy is estimated. The losses of runaways due to resonant magnetic perturbation fields are measured applying a scintillator probe. The effects of well defined amplitudes of the perturbation on the temporal evolution of the runaway losses and the spectral properties of the runaways are analysed. The runaway transport towards the plasma edge is described by a model which takes magnetic turbulences and the magnetic perturbation field into account. Using an asymptotic theory, the orbits as well as radially and energy dependent transport coefficients for the runaways are calculated. A diffusion equation which utilises the coefficients is solved delivering the density and the flux of the runaways. The model reproduces the measured enhancement of the runaway losses. Qualitatively different runaway spectra are found inside the plasma and at the edge. The spectra are explained by estimations of the competition between the secondary generation rate of the runaways and their radial diffusion. The runaway transport is found to be determined by the magnetic turbulence, the magnetic topology at the edge as well as inside the plasma and by the runaway energy. The mitigation of the runaways due to the magnetic perturbations can be understood by the enhancement of the losses of the low energy runaways. Eventually, a self consistent understanding of the temporal and spectral properties of the
Bound-state perturbation theory and annihilation effects in positronium
International Nuclear Information System (INIS)
Abbasabadi, A.; Repko, W.W.
1987-01-01
Working in Coulomb gauge and using the lowest-order equation proposed by Barbieri and Remiddi it is calculated, in the one-loop order of perturbation theory, the decay rate and the energy shift of the ground states of parapositronium and orthopositronium, respectively. Our result for the decay rate agrees with that of Harris and Brown. For contribution of one-photon-annihilation channel to the energy shift, it is confirmed the result of Karplus and Klein. These results are derived completely within the bound-state formalism and avoid the necessity of performing on-mass-shell wave function and vertex renormalization subtractions
Physics beyond the standard model in the non-perturbative unification scheme
International Nuclear Information System (INIS)
Kapetanakis, D.; Zoupanos, G.
1990-01-01
The non-perturbative unification scenario predicts reasonably well the low energy gauge couplings of the standard model. Agreement with the measured low energy couplings is obtained by assuming certain kind of physics beyond the standard model. A number of possibilities for physics beyond the standard model is examined. The best candidates so far are the standard model with eight fermionic families and a similar number of Higgs doublets, and the supersymmetric standard model with five families. (author)
Cosmological perturbations in antigravity
Oltean, Marius; Brandenberger, Robert
2014-10-01
We compute the evolution of cosmological perturbations in a recently proposed Weyl-symmetric theory of two scalar fields with oppositely signed conformal couplings to Einstein gravity. It is motivated from the minimal conformal extension of the standard model, such that one of these scalar fields is the Higgs while the other is a new particle, the dilaton, introduced to make the Higgs mass conformally symmetric. At the background level, the theory admits novel geodesically complete cyclic cosmological solutions characterized by a brief period of repulsive gravity, or "antigravity," during each successive transition from a big crunch to a big bang. For simplicity, we consider scalar perturbations in the absence of anisotropies, with potential set to zero and without any radiation. We show that despite the necessarily wrong-signed kinetic term of the dilaton in the full action, these perturbations are neither ghostlike nor tachyonic in the limit of strongly repulsive gravity. On this basis, we argue—pending a future analysis of vector and tensor perturbations—that, with respect to perturbative stability, the cosmological solutions of this theory are viable.
Gauge-invariant cosmological density perturbations
International Nuclear Information System (INIS)
Sasaki, Misao.
1986-06-01
Gauge-invariant formulation of cosmological density perturbation theory is reviewed with special emphasis on its geometrical aspects. Then the gauge-invariant measure of the magnitude of a given perturbation is presented. (author)
Twisting perturbed parafermions
Directory of Open Access Journals (Sweden)
A.V. Belitsky
2017-07-01
Full Text Available The near-collinear expansion of scattering amplitudes in maximally supersymmetric Yang–Mills theory at strong coupling is governed by the dynamics of stings propagating on the five sphere. The pentagon transitions in the operator product expansion which systematize the series get reformulated in terms of matrix elements of branch-point twist operators in the two-dimensional O(6 nonlinear sigma model. The facts that the latter is an asymptotically free field theory and that there exists no local realization of twist fields prevents one from explicit calculation of their scaling dimensions and operator product expansion coefficients. This complication is bypassed making use of the equivalence of the sigma model to the infinite-level limit of WZNW models perturbed by current–current interactions, such that one can use conformal symmetry and conformal perturbation theory for systematic calculations. Presently, to set up the formalism, we consider the O(3 sigma model which is reformulated as perturbed parafermions.
Directory of Open Access Journals (Sweden)
Elham Azimzadeh
2013-01-01
Full Text Available Objectives: Falling is a main cause of mortality in elderly. Balance training exercises can help to prevent falls in older adults. According to the principle of specificity of training, the perturbation-based trainings are more similar to the real world. So these training programs can improve balance in elderly. Furthermore, exercising in an aquatic environment can reduce the limitations for balance training rather than a non-aquatic on. The aim of this study is comparing the effectiveness of perturbed and non-perturbed balance training programs in water on static and dynamic balance in aforementioned population group. Methods & Materials: 37 old women (age 80-65, were randomized to the following groups: perturbation-based training (n=12, non-perturbation-based training (n=12 and control (n=13 groups. Static and dynamic balance had been tested before and after the eight weeks of training by the postural stability test of the Biodex balance system using dynamic (level 4 and static platform. The data were analyzed by one sample paired t-test, Independent t-test and ANOVA. Results: There was a significant improvement for all indexes of static and dynamic balance in perturbation-based training (P<0.05. However, in non-perturbed group, all indexes were improved except ML (P<0.05. ANOVA showed that perturbed training was more effective than non-perturbed training on both static and dynamic balances. Conclusion: The findings confirmed the specificity principle of training. Although balance training can improve balance abilities, these kinds of trainings are not such specific for improving balance neuromuscular activities.The perturbation-based trainings can activate postural compensatory responses and reduce falling risk. According to results, we can conclude that hydrotherapy especially with perturbation-based programs will be useful for rehabilitation interventions in elderly .
Perturbative estimates of lepton mixing angles in unified models
International Nuclear Information System (INIS)
Antusch, Stefan; King, Stephen F.; Malinsky, Michal
2009-01-01
Many unified models predict two large neutrino mixing angles, with the charged lepton mixing angles being small and quark-like, and the neutrino masses being hierarchical. Assuming this, we present simple approximate analytic formulae giving the lepton mixing angles in terms of the underlying high energy neutrino mixing angles together with small perturbations due to both charged lepton corrections and renormalisation group (RG) effects, including also the effects of third family canonical normalization (CN). We apply the perturbative formulae to the ubiquitous case of tri-bimaximal neutrino mixing at the unification scale, in order to predict the theoretical corrections to mixing angle predictions and sum rule relations, and give a general discussion of all limiting cases. We also discuss the implications for the sum rule relations of the measurement of a non-zero reactor angle, as hinted at by recent experimental measurements.
Charmless decays of the B-meson in perturbative QCD
International Nuclear Information System (INIS)
Libo Guo; Dongsheng Du; Lianshou Liu
1999-01-01
Using the perturbative QCD method and Chau's six-quark-graph scheme, we report a theoretical calculation of exclusive nonleptonic decays of the B meson into two light pseudoscalar mesons in the context of the low-energy effective Hamiltonian. The contributions from both tree-level and one-loop diagrams are taken into account. Under the approximation of neglecting light quark and light meson masses, we find that (i) within perturbative QCD there is no singularity which exists in the computation of spacelike penguin diagrams when the BSW model is used; (ii) the contributions from spacelike-type (W-annihilation, W-exchange, spacelike penguin and penguin-annihilation) graphs are strongly suppressed relative to those from timelike-type (external W-emission, internal W-emission and timelike penguin) ones; (iii) our results are well below the experimental upper limits but lower than the BSW ones. (author)
Evolution of perturbations of squashed Kaluza-Klein black holes: Escape from instability
International Nuclear Information System (INIS)
Ishihara, Hideki; Kimura, Masashi; Konoplya, Roman A.; Murata, Keiju; Soda, Jiro; Zhidenko, Alexander
2008-01-01
The squashed Kaluza-Klien (KK) black holes differ from the Schwarzschild black holes with asymptotic flatness or the black strings even at energies for which the KK modes are not excited yet, so that squashed KK black holes open a window in higher dimensions. Another important feature is that the squashed KK black holes are apparently stable and, thereby, let us avoid the Gregory-Laflamme instability. In the present paper, the evolution of scalar and gravitational perturbations in time and frequency domains is considered for these squashed KK black holes. The scalar field perturbations are analyzed for general rotating squashed KK black holes. Gravitational perturbations for the so-called zero mode are shown to be decayed for nonrotating black holes, in concordance with the stability of the squashed KK black holes. The correlation of quasinormal frequencies with the size of extra dimension is discussed.
Multiplicative perturbations of local C-semigroups
Indian Academy of Sciences (India)
In this paper, we establish some left and right multiplicative perturbation theorems concerning local -semigroups when the generator of a perturbed local -semigroup S ( ⋅ ) may not be densely defined and the perturbation operator is a bounded linear operator from D ( A ) ¯ into () such that = on D ( A ) ¯ ...
Multiplicative perturbations of local C-semigroups
Indian Academy of Sciences (India)
2016-08-26
Aug 26, 2016 ... In this paper, we establish some left and right multiplicative perturbation theorems concerning local -semigroups when the generator of a perturbed local -semigroup S(⋅) may not be densely defined and the perturbation operator is a bounded linear operator from ¯D(A) into () such that = ...
The sine-Gordon model and the small κ+ region of light- cone perturbation theory
International Nuclear Information System (INIS)
Griffin, P.A.
1992-01-01
The non-perturbative ultraviolet divergence of the sine-Gordon model is used to study the k + = 0 region of light-cone perturbation theory. The light-cone vacuum is shown to be unstable at the non- perturbative β 2 = 8π critical point by a light-cone version of Coleman's variational method. Vacuum bubbles, which are k + = 0 diagram in light-cone field theory and are individually finite and non-vanishing for all β, conspire to generate ultraviolet divergences of the light-cone energy density. The k + = 0 region of momentum also contributed to connected Green's functions: the connected two point function will not diverge, as it should, at the critical point unless diagrams which contribute only at k + = 0 are properly included. This analysis shows in a simple way how the k + = 0 region cannot be ignored even for connected diagrams. This phenomenon is expected to occur in higher dimensional gauge theories starting at two loop order in light-cone perturbation theory
Dynamics of linear perturbations in f(R) gravity
International Nuclear Information System (INIS)
Bean, Rachel; Bernat, David; Pogosian, Levon; Silvestri, Alessandra; Trodden, Mark
2007-01-01
We consider predictions for structure formation from modifications to general relativity in which the Einstein-Hilbert action is replaced by a general function of the Ricci scalar. We work without fixing a gauge, as well as in explicit popular coordinate choices, appropriate for the modification of existing cosmological code. We present the framework in a comprehensive and practical form that can be directly compared to standard perturbation analyses. By considering the full evolution equations, we resolve perceived instabilities previously suggested, and instead find a suppression of perturbations. This result presents significant challenges for agreement with current cosmological structure formation observations. The findings apply to a broad range of forms of f(R) for which the modification becomes important at low curvatures, disfavoring them in comparison with the ΛCDM scenario. As such, these results provide a powerful method to rule out a wide class of modified gravity models aimed at providing an alternative explanation to the dark energy problem
International Nuclear Information System (INIS)
Jivani, A.R.; Trivedi, H.J.; Gajjar, P.N.; Jani, A.R.
2005-01-01
Recently proposed model potential for describing the electron-ion interaction is employed to calculate total energy, energy band gap at Jones-zone face at X, equation of state and bulk modulus of GaP, GaAs and GaSb compounds using higher-order perturbation theory. The covalent correction term corresponding to third- and fourth-order perturbation energy terms are used to take account of covalent bonding effect in such semiconductors. The significant value of the covalent bonding term shows the essentiality of higher-order correction for zincblende-type crystals. We have employed five different screening functions along with the latest screening function proposed by Sarkar et al. in the present work. The numerical results for the total energy, energy band gap at Jones-zone face and bulk modulus of these compounds are in good agreement with the experimental data and found better than other such theoretical findings. The pressure and bulk modulus at different volumes are obtained by using such higher-order perturbation theory with the application of our model potential. The pressure obtained by this method is compared with pressure obtained by equations proposed by Murnarghan and Vinet et al. The present study also shows that the incorporation of different screening functions generates distinct effects
Hyperon decay form factors in chiral perturbation theory
International Nuclear Information System (INIS)
Lacour, Andre; Kubis, Bastian; Meissner, Ulf-G.
2007-01-01
We present a complete calculation of the SU(3)-breaking corrections to the hyperon vector form factors up to O(p 4 ) in covariant baryon chiral perturbation theory. Partial higher-order contributions are obtained, and we discuss chiral extrapolations of the vector form factor at zero momentum transfer. In addition we derive low-energy theorems for the subleading moments in hyperon decays, the weak Dirac radii and the weak anomalous magnetic moments, up to O(p 4 )
Geometric Hamiltonian structures and perturbation theory
International Nuclear Information System (INIS)
Omohundro, S.
1984-08-01
We have been engaged in a program of investigating the Hamiltonian structure of the various perturbation theories used in practice. We describe the geometry of a Hamiltonian structure for non-singular perturbation theory applied to Hamiltonian systems on symplectic manifolds and the connection with singular perturbation techniques based on the method of averaging
Dynamics of cosmological perturbations and reheating in the anamorphic universe
Energy Technology Data Exchange (ETDEWEB)
Graef, L.L.; Ferreira, Elisa G.M.; Brandenberger, Robert [Physics Department, McGill University, Montreal, QC, H3A 2T8 (Canada); Hipólito-Ricaldi, W.S., E-mail: leilagraef@on.br, E-mail: wiliam.ricaldi@ufes.br, E-mail: elisa.ferreira@mail.mcgill.ca, E-mail: rhb@physics.mcgill.ca [Departamento de Ciências Naturais, Universidade Federal do Espírito Santo, Rodovia BR 101 Norte, km. 60, São Mateus, ES (Brazil)
2017-04-01
We discuss scalar-tensor realizations of the Anamorphic cosmological scenario recently proposed by Ijjas and Steinhardt [1]. Through an analysis of the dynamics of cosmological perturbations we obtain constraints on the parameters of the model. We also study gravitational Parker particle production in the contracting Anamorphic phase and we compute the fraction between the energy density of created particles at the end of the phase and the background energy density. We find that, as in the case of inflation, a new mechanism is required to reheat the universe.
International Nuclear Information System (INIS)
Hwang, Sun Gu; Chung, Doo Soo; Jang, Yun Hee; Ryu, Gean Ha
1999-01-01
Free energy perturbation and molecular dynamics simulations were carried out to investigate the relative binding affinities of [1 7 ]ketonand (1) toward alkali metal cations in methanol. The binding affinities of 1 toward the alkali metal cations were calculated to be in the order Li + >Na + >K + >Rb + >Cs + , whereas our recent theoretically predicted and experimentally observed binding affinities for [1 8 ]starand (2) were in the order K + >Rb + >Cs + >Na + >Li + . The extremely different affinities of 1 and 2 toward smaller cations, Li + and Na + , were explained in terms of the differences in their ability to change the conformation to accommodate cations of different sizes. The carbonyl groups constituting the central cavity of 1 can reorganize to form a cavity with the optimal M + -O distance, even for the smallest Li + , without imposing serious strain on 1. The highest affinity of 1 for Li + was predominantly due to the highest Coulombic attraction between the smallest Li + and the carbonyl oxygens of 1
Short-time perturbation theory and nonrelativistic duality
International Nuclear Information System (INIS)
Whitenton, J.B.; Durand, B.; Durand, L.
1983-01-01
We give a simple proof of the nonrelativistic duality relation 2 sigma/sub bound/>roughly-equal 2 sigma/sub free/> for appropriate energy averages of the cross sections for e + e - →(qq-bar bound states) and e + e - →(free qq-bar pair), and calculate the corrections to the relation by relating W 2 sigma to the Fourier transform of the Feynman propagation function and developing a short-time perturbation series for that function. We illustrate our results in detail for simple power-law potentials and potentials which involve combinations of powers
Non-perturbative effects in supersymmetry
International Nuclear Information System (INIS)
Veneziano, G.
1987-01-01
Some non perturbative aspects of globally supersymmetric (SUSY) gauge theories are discussed. These share with their non-supersymmetric analogues interesting non perturbative features, such as the spontaneous breaking of chiral symmetries via condensates. What is peculiar about supersymmetric theories, however, is that one is able to say a lot about non-perturbative effects even without resorting to elaborate numerical calculations: general arguments, supersymmetric and chiral Ward identities and analytic, dynamical calculations will turn out to effectively determine most of the supersymmetric vacuum properties. 28 references, 5 figures
The theory of singular perturbations
De Jager, E M
1996-01-01
The subject of this textbook is the mathematical theory of singular perturbations, which despite its respectable history is still in a state of vigorous development. Singular perturbations of cumulative and of boundary layer type are presented. Attention has been given to composite expansions of solutions of initial and boundary value problems for ordinary and partial differential equations, linear as well as quasilinear; also turning points are discussed. The main emphasis lies on several methods of approximation for solutions of singularly perturbed differential equations and on the mathemat
Dissipative motion perturbation theory and exact solutions
International Nuclear Information System (INIS)
Lodder, J.J.
1976-06-01
Dissipative motion of classical and quantum systems is described. In particular, attention is paid to systems coupled to the radiation field. A dissipative equation of motion for a particle in an arbitrary potential coupled to the radiation field is derived by means of perturbation theory. The usual divrgencies associated with the radiation field are eliminated by the application of a theory of generalized functions. This theory is developed as a subject in its own right and is presented independently. The introduction of classical zero-point energy makes the classical equa tion of motion for the phase density formally the same as its quantum counterpart. In particular, it is shown that the classical zero-point energy prevents the collapse of a classical H-atom and gives rise to a classical ground state. For systems with a quadratic Hamiltoian, the equation of motion can be solved exactly, even in the continuum limit for the radiation field, by means of the new generalized functions. Classically, the Fokker-Planck equation is found without any approximations, and quantum mechanically, the only approximation is the neglect of the change in the ground state caused by the interaction. The derivation is valid even for strong damping and arbitrarily short times. There is no transient time. For harmonic oscillators complete equivalence is shown to exist between quantum mechanics and classical mechanics with zero-point energy. A discussion of the derivation of the Pauli equation is given and perturbation theory is compared with the exact derivation. The exactly solvable models are used to calculate the Langevin force of the radiation field. The result is that the classical Langevin force is exactly delta-correlated, while the quantum Langevin force is not delta-correlated at all. The fluctuation-dissipation theorem is shown to be an exact consequence of the solution to the equations of motion
Helmich-Paris, B.; Knecht, Stefan
2017-01-01
In the present article, we show how to formulate the partially contracted n-electron valence second-order perturbation theory (NEVPT2) energies in the atomic and active molecular orbital basis by employing the Laplace transformation of orbital-energy denominators (OEDs). As atomic-orbital (AO) basis
Perturbative odderon in the dipole model
Energy Technology Data Exchange (ETDEWEB)
Kovchegov, Yuri V.; Szymanowski, Lech; Wallon, Samuel
2004-04-29
We show that, in the framework of Mueller's dipole model, the perturbative QCD odderon is described by the dipole model equivalent of the BFKL equation with a C-odd initial condition. The eigenfunctions and eigenvalues of the odderon solution are the same as for the dipole BFKL equation and are given by the functions E{sup n,{nu}} and {chi}(n,{nu}) correspondingly, where the C-odd initial condition allows only for odd values of n. The leading high-energy odderon intercept is given by {alpha}{sub odd}-1=((2{alpha}{sub s}N{sub c})/({pi})){chi}(n=1,{nu}=0)=0 in agreement with the solution found by Bartels, Lipatov and Vacca. We proceed by writing down an evolution equation for the odderon including the effects of parton saturation. We argue that saturation makes the odderon solution a decreasing function of energy.
International Nuclear Information System (INIS)
Crebbin, K.C.
1985-05-01
Uniform magnetic field perturbations cause a closed orbit distortion in a circular accelerator. If the magnetic guide field is non-linear these perturbations can also cause a Nu shift in the betatron oscillations. Such a shift in radial Nu values has been observed in the Bevalac while studying the low energy resonant extraction system. In the Bevalac, the radial perturbation comes from the quadrants being magnetically about 0.8% longer than 90 0 . The normal effect of this type of perturbation is a radial closed orbit shift and orbit distortion. The Nu shift, associated with this type of perturbation in the presence of a non-linear guide field, is discussed in this paper. A method of handling the non-linear n values is discussed as well as the mechanism for the associated Nu shift. Computer calculations are compared to measurements. 2 refs., 4 figs
Total energy calculations from self-energy models
International Nuclear Information System (INIS)
Sanchez-Friera, P.
2001-06-01
Density-functional theory is a powerful method to calculate total energies of large systems of interacting electrons. The usefulness of this method, however, is limited by the fact that an approximation is required for the exchange-correlation energy. Currently used approximations (LDA and GGA) are not sufficiently accurate in many physical problems, as for instance the study of chemical reactions. It has been shown that exchange-correlation effects can be accurately described via the self-energy operator in the context of many-body perturbation theory. This is, however, a computationally very demanding approach. In this thesis a new scheme for calculating total energies is proposed, which combines elements from many-body perturbation theory and density-functional theory. The exchange-correlation energy functional is built from a simplified model of the self-energy, that nevertheless retains the main features of the exact operator. The model is built in such way that the computational effort is not significantly increased with respect to that required in a typical density-functional theory calculation. (author)
Pion parameters in nuclear medium from chiral perturbation theory and virial expansion
International Nuclear Information System (INIS)
Mallik, S.; Sarkar, Sourav
2004-01-01
We consider two methods to find the effective parameters of the pion traversing a nuclear medium. One is the first order chiral perturbation theoretic evaluation of the pion pole contribution to the two-point function of the axial-vector current. The other is the exact, first order virial expansion of the pion self-energy. We find that, although the results of chiral perturbation theory are not valid at normal nuclear density, those from the virial expansion may be reliable at such density. The latter predicts both the mass shift and the in-medium decay width of the pion to be small, of about a few MeV
Local perturbations perturb—exponentially–locally
International Nuclear Information System (INIS)
De Roeck, W.; Schütz, M.
2015-01-01
We elaborate on the principle that for gapped quantum spin systems with local interaction, “local perturbations [in the Hamiltonian] perturb locally [the groundstate].” This principle was established by Bachmann et al. [Commun. Math. Phys. 309, 835–871 (2012)], relying on the “spectral flow technique” or “quasi-adiabatic continuation” [M. B. Hastings, Phys. Rev. B 69, 104431 (2004)] to obtain locality estimates with sub-exponential decay in the distance to the spatial support of the perturbation. We use ideas of Hamza et al. [J. Math. Phys. 50, 095213 (2009)] to obtain similarly a transformation between gapped eigenvectors and their perturbations that is local with exponential decay. This allows to improve locality bounds on the effect of perturbations on the low lying states in certain gapped models with a unique “bulk ground state” or “topological quantum order.” We also give some estimate on the exponential decay of correlations in models with impurities where some relevant correlations decay faster than one would naively infer from the global gap of the system, as one also expects in disordered systems with a localized groundstate
Aspects of meson-baryon scattering in three- and two-flavor chiral perturbation theory
International Nuclear Information System (INIS)
Mai, Maxim; Bruns, Peter C.; Kubis, Bastian; Meissner, Ulf-G.
2009-01-01
We analyze meson-baryon scattering lengths in the framework of covariant baryon chiral perturbation theory at leading one-loop order. We compute the complete set of matching relations between the dimension-two low-energy constants in the two- and three-flavor formulations of the theory. We derive new two-flavor low-energy theorems for pion-hyperon scattering that can be tested in lattice simulations.
Energy Technology Data Exchange (ETDEWEB)
Malinowski, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires
1960-07-01
After classifying the various types of perturbations, the author attempts to explain their causes. He then gives examples of possibilities of suppressing them. (author) [French] Ayant classe les divers types de perturbations en categories, l'auteur essaie d'expliquer les causes de ces perturbations. Il donne ensuite des exemples de possibilites de les supprimer. (auteur)
International Nuclear Information System (INIS)
Kang, Kai; Qin, Shaojing; Wang, Chuilin
2011-01-01
We calculated numerically the localization length of one-dimensional Anderson model with diagonal disorder. For weak disorder, we showed that the localization length changes continuously as the energy changes from the band center to the boundary of the anomalous region near the band edge. We found that all the localization lengths for different disorder strengths and different energies collapse onto a single curve, which can be fitted by a simple equation. Thus the description of the perturbation theory and the band center anomaly were unified into this equation. -- Highlights: → We study the band center anomaly of one-dimensional Anderson localization. → We study numerically the Lyapunov exponent through a parametrization method of the transfer matrix. → We give a unified equation to describe the band center anomaly and perturbation theory.
Perturbation theory of effective Hamiltonians
International Nuclear Information System (INIS)
Brandow, B.H.
1975-01-01
This paper constitutes a review of the many papers which have used perturbation theory to derive ''effective'' or ''model'' Hamiltonians. It begins with a brief review of nondegenerate and non-many-body perturbation theory, and then considers the degenerate but non-many-body problem in some detail. It turns out that the degenerate perturbation problem is not uniquely defined, but there are some practical criteria for choosing among the various possibilities. Finally, the literature dealing with the linked-cluster aspects of open-shell many-body systems is reviewed. (U.S.)
Martin, Alexandre; Torrent, Marc; Caracas, Razvan
2015-03-01
A formulation of the response of a system to strain and electric field perturbations in the pseudopotential-based density functional perturbation theory (DFPT) has been proposed by D.R Hamman and co-workers. It uses an elegant formalism based on the expression of DFT total energy in reduced coordinates, the key quantity being the metric tensor and its first and second derivatives. We propose to extend this formulation to the Projector Augmented-Wave approach (PAW). In this context, we express the full elastic tensor including the clamped-atom tensor, the atomic-relaxation contributions (internal stresses) and the response to electric field change (piezoelectric tensor and effective charges). With this we are able to compute the elastic tensor for all materials (metals and insulators) within a fully analytical formulation. The comparison with finite differences calculations on simple systems shows an excellent agreement. This formalism has been implemented in the plane-wave based DFT ABINIT code. We apply it to the computation of elastic properties and seismic-wave velocities of iron with impurity elements. By analogy with the materials contained in meteorites, tested impurities are light elements (H, O, C, S, Si).
On the non-perturbative effects
International Nuclear Information System (INIS)
Manjavidze, J.; Voronyuk, V.
2004-01-01
The quantum correspondence principle based on the time reversibility is adopted to take into account the non-Abelian symmetry constrains. The main properties of the new strong-coupling perturbation theory which take into account non-perturbative effects are described. (author)
Evolution of the curvature perturbations during warm inflation
International Nuclear Information System (INIS)
Matsuda, Tomohiro
2009-01-01
This paper considers warm inflation as an interesting application of multi-field inflation. Delta-N formalism is used for the calculation of the evolution of the curvature perturbations during warm inflation. Although the perturbations considered in this paper are decaying after the horizon exit, the corrections to the curvature perturbations sourced by these perturbations can remain and dominate the curvature perturbations at large scales. In addition to the typical evolution of the curvature perturbations, inhomogeneous diffusion rate is considered for warm inflation, which may lead to significant non-Gaussianity of the spectrum
The free energy principle, negative energy modes, and stability
International Nuclear Information System (INIS)
Morrison, P.J.; Kotschenreuther, M.
1990-01-01
This paper is concerned with instability of equilibria of Hamiltonian, fluid and plasma dynamical systems. Usually the dynamical equilibrium of interest is not the state of thermodynamic equilibrium, and does not correspond to a free energy minimum. The relaxation of this type of equilibrium is conventionally considered to be initiated by linear instability. However, there are many cases where linear instability is not present, but the equilibrium is nonlinearly unstable to arbitrarily small perturbations. This paper is about general free energy expressions for determining the presence of linear or nonlinear instabilities. These expressions are simple and practical, and can be obtained for all equilibria of all ideal fluid and plasma models. By free energy, we mean the energy change upon perturbations of the equilibrium that respect dynamical phase space constraints. This quantity is measured by a self-adjoint quadratic form, called δ 2 F. The free energy can result in instability when δ 2 F is indefinite; i.e. there exist accessible perturbations that lower the free energy of the system. A primary purpose of this paper is to tie together three manifestations of what we will refer to as negative energy modes. The first is the conventional plasma physics notion of negative energy mode that is based on the definition of the energy in a homogeneous dielectric medium. A negative energy mode is a normal mode of the medium (plasma) that possesses negative dielectric energy. The second manifestation occurs in finite degree-of-freedom Hamiltonian normal form theory. The quadratic part of a Hamiltonian in the vicinity of an equilibrium point, which possesses only distinct oscillatory eigenvalues, has an invariant signature. Thus in cases where the quadratic form is indefinite, it is natural to refer to the modes corresponding to the negative signature as negative energy modes
The volume conjecture, perturbative knot invariants, and recursion relations for topological strings
Dijkgraaf, R.; Fuji, H.; Manabe, M.
2011-01-01
We study the relation between perturbative knot invariants and the free energies defined by topological string theory on the character variety of the knot. Such a correspondence between SL(2;C) Chern-Simons gauge theory and the topological open string theory was proposed earlier on the basis of the
Perturbative spacetimes from Yang-Mills theory
Energy Technology Data Exchange (ETDEWEB)
Luna, Andrés [School of Physics and Astronomy, University of Glasgow,Glasgow G12 8QQ, Scotland (United Kingdom); Monteiro, Ricardo [Theoretical Physics Department, CERN,Geneva (Switzerland); Nicholson, Isobel; Ochirov, Alexander; O’Connell, Donal [Higgs Centre for Theoretical Physics,School of Physics and Astronomy, The University of Edinburgh,Edinburgh EH9 3JZ, Scotland (United Kingdom); Westerberg, Niclas [Institute of Photonics and Quantum Sciences,School of Engineering and Physical Sciences, Heriot-Watt University,Edinburgh (United Kingdom); Higgs Centre for Theoretical Physics,School of Physics and Astronomy, The University of Edinburgh,Edinburgh EH9 3JZ, Scotland (United Kingdom); White, Chris D. [Centre for Research in String Theory,School of Physics and Astronomy, Queen Mary University of London,327 Mile End Road, London E1 4NS (United Kingdom)
2017-04-12
The double copy relates scattering amplitudes in gauge and gravity theories. In this paper, we expand the scope of the double copy to construct spacetime metrics through a systematic perturbative expansion. The perturbative procedure is based on direct calculation in Yang-Mills theory, followed by squaring the numerator of certain perturbative diagrams as specified by the double-copy algorithm. The simplest spherically symmetric, stationary spacetime from the point of view of this procedure is a particular member of the Janis-Newman-Winicour family of naked singularities. Our work paves the way for applications of the double copy to physically interesting problems such as perturbative black-hole scattering.
International Nuclear Information System (INIS)
Takahashi, M.; Bracken, P.; Cizek, J.; Paldus, J.
1995-01-01
The perturbation expansion coefficients for the ground-state energy of the half-filled one-dimensional Hubbard model with N = 4 ν + 2, (ν = 1,2,...) sites and satisfying cyclic boundary conditions were calculated in the Hueckel limit (U/β → 0), where β designates the one-electron hopping or resonance integral, and U, the two-electron on-site Coulomb integral. This was achieved by solving-order by order-the Lieb-Wu equations, a system of transcendental equations that determines the set of quasi-momenta (k i ) and spin variable τ α for this model. The exact values for these quantities were found for the N = 6 member ring up to the 20th order in terms of the coupling constant B = U/2β, as well as numerically for 10 ≤ N ≤ 50, and the N = 6 Lieb-Wu system was reduced to a system of sextic algebraic equations. These results are compared with those of the infinite system derived analytically by Misurkin and Ovchinnikov. It is further shown how the results of this article can be used for the interpolation by the root of a polynomial. It is demonstrated that a polynomial of relatively small degree provides a very good approximation for the energy in the intermediate coupling region. 20 refs., 3 tabs
Non-perturbative computation of the strong coupling constant on the lattice
International Nuclear Information System (INIS)
Sommer, Rainer; Humboldt-Universitaet, Berlin; Wolff, Ulli
2015-01-01
We review the long term project of the ALPHA collaboration to compute in QCD the running coupling constant and quark masses at high energy scales in terms of low energy hadronic quantities. The adapted techniques required to numerically carry out the required multiscale non-perturbative calculation with our special emphasis on the control of systematic errors are summarized. The complete results in the two dynamical flavor approximation are reviewed and an outlook is given on the ongoing three flavor extension of the programme with improved target precision.
International Nuclear Information System (INIS)
Bernard, V.; Kubis, B.; Meissner, U.G.
2005-01-01
We analyze the Fubini-Furlan-Rosetti sum rule in the framework of covariant baryon chiral perturbation theory to leading one-loop accuracy and including next-to-leading-order polynomial contributions. We discuss the relation between the subtraction constants in the invariant amplitudes and certain low-energy constants employed in earlier chiral perturbation theory studies of threshold neutral pion photoproduction off nucleons. In particular, we consider the corrections to the sum rule due to the finite pion mass and show that below the threshold they agree well with determinations based on fixed-t dispersion relations. We also discuss the energy dependence of the electric dipole amplitude E 0+ . (orig.)
Energy Technology Data Exchange (ETDEWEB)
Bernard, V. [Universite Louis Pasteur, Laboratoire de Physique Theorique, Strasbourg Cedex 2 (France); Kubis, B. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Bonn (Germany); Meissner, U.G. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Bonn (Germany); Forschungszentrum Juelich, Institut fuer Kernphysik (Theorie), Juelich (Germany)
2005-09-01
We analyze the Fubini-Furlan-Rosetti sum rule in the framework of covariant baryon chiral perturbation theory to leading one-loop accuracy and including next-to-leading-order polynomial contributions. We discuss the relation between the subtraction constants in the invariant amplitudes and certain low-energy constants employed in earlier chiral perturbation theory studies of threshold neutral pion photoproduction off nucleons. In particular, we consider the corrections to the sum rule due to the finite pion mass and show that below the threshold they agree well with determinations based on fixed-t dispersion relations. We also discuss the energy dependence of the electric dipole amplitude E{sub 0+}. (orig.)
Intermolecular symmetry-adapted perturbation theory study of large organic complexes
International Nuclear Information System (INIS)
Heßelmann, Andreas; Korona, Tatiana
2014-01-01
Binding energies for the complexes of the S12L database by Grimme [Chem. Eur. J. 18, 9955 (2012)] were calculated using intermolecular symmetry-adapted perturbation theory combined with a density-functional theory description of the interacting molecules. The individual interaction energy decompositions revealed no particular change in the stabilisation pattern as compared to smaller dimer systems at equilibrium structures. This demonstrates that, to some extent, the qualitative description of the interaction of small dimer systems may be extrapolated to larger systems, a method that is widely used in force-fields in which the total interaction energy is decomposed into atom-atom contributions. A comparison of the binding energies with accurate experimental reference values from Grimme, the latter including thermodynamic corrections from semiempirical calculations, has shown a fairly good agreement to within the error range of the reference binding energies
International Nuclear Information System (INIS)
Dvoeglazov, V.V.; Skachkov, N.B.
1991-01-01
Self-energy and vertex blocks that enter into the amplitude of Higgs-Higgs-interaction are calculated up to the fourth order of perturbation theory in the framework of the model of electroweak interaction with two Higgs doublets and an arbitrary number of fermions. The renormalization is performed on the mass shell of the physical fields after a spontaneous symmetry breaking. The values of the coupling constants are, as a rule, not concretized in the paper. In the cases where it is needed to use them, their values obtained in the model with the minimal supersymmetric extension of the standard model (MSSM) are taken. 29 refs.; 1 tab
The power of perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Serone, Marco [SISSA International School for Advanced Studies and INFN Trieste, Via Bonomea 265, 34136, Trieste (Italy); Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151, Trieste (Italy); Spada, Gabriele [SISSA International School for Advanced Studies and INFN Trieste, Via Bonomea 265, 34136, Trieste (Italy); Villadoro, Giovanni [Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151, Trieste (Italy)
2017-05-10
We study quantum mechanical systems with a discrete spectrum. We show that the asymptotic series associated to certain paths of steepest-descent (Lefschetz thimbles) are Borel resummable to the full result. Using a geometrical approach based on the Picard-Lefschetz theory we characterize the conditions under which perturbative expansions lead to exact results. Even when such conditions are not met, we explain how to define a different perturbative expansion that reproduces the full answer without the need of transseries, i.e. non-perturbative effects, such as real (or complex) instantons. Applications to several quantum mechanical systems are presented.
Wu, Zedong
2017-07-04
Reflection-waveform inversion (RWI) can help us reduce the nonlinearity of the standard full-waveform inversion (FWI) by inverting for the background velocity model using the wave-path of a single scattered wavefield to an image. However, current RWI implementations usually neglect the multi-scattered energy, which will cause some artifacts in the image and the update of the background. To improve existing RWI implementations in taking multi-scattered energy into consideration, we split the velocity model into background and perturbation components, integrate them directly in the wave equation, and formulate a new optimization problem for both components. In this case, the perturbed model is no longer a single-scattering model, but includes all scattering. Through introducing a new cheap implementation of scattering angle enrichment, the separation of the background and perturbation components can be implemented efficiently. We optimize both components simultaneously to produce updates to the velocity model that is nonlinear with respect to both the background and the perturbation. The newly introduced perturbation model can absorb the non-smooth update of the background in a more consistent way. We apply the proposed approach on the Marmousi model with data that contain frequencies starting from 5 Hz to show that this method can converge to an accurate velocity starting from a linearly increasing initial velocity. Also, our proposed method works well when applied to a field data set.
Closed form bound-state perturbation theory
Directory of Open Access Journals (Sweden)
Ollie J. Rose
1980-01-01
Full Text Available The perturbed Schrödinger eigenvalue problem for bound states is cast into integral form using Green's Functions. A systematic algorithm is developed and applied to the resulting equation giving rise to approximate solutions expressed as functions of the given perturbation parameter. As a by-product, convergence radii for the traditional Rayleigh-Schrödinger and Brillouin-Wigner perturbation theories emerge in a natural way.
DR Argillite Disposal R&D at LBNL
International Nuclear Information System (INIS)
Zheng, Liange; Kim, Kunhwi; Xu, Hao; Rutqvist, Jonny
2016-01-01
Within the Natural Barrier System (NBS) group of the Used Fuel Disposition (UFD) Campaign at the Department of Energy's (DOE) Office of Nuclear Energy, LBNL's research activities have focused on understanding and modeling EDZ evolution and the associated coupled processes and impacts of high temperature on parameters and processes relevant to performance of a clay repository to establish the technical base for the maximum allowable temperature. This report documents results from some of these activities. These activities address key Features, Events, and Processes (FEPs), which have been ranked in importance from medium to high, as listed in Table 7 of the Used Fuel Disposition Campaign Disposal Research and Development Roadmap (FCR&D-USED-2011-000065 REV0) (Nutt, 2011). Specifically, they address FEP 2.2.01, Excavation Disturbed Zone, for clay/shale, by investigating how coupled processes affect EDZ evolution; FEP 2.2.05, Flow and Transport Pathways; and FEP 2.2.08, Hydrologic Processes, and FEP 2.2.07, Mechanical Processes, and FEP 2.2.09, Chemical Process-Transport, by studying near-field coupled THMC processes in clay/shale repositories. The activities documented in this report also address a number of research topics identified in Research & Development (R&D) Plan for Used Fuel Disposition Campaign (UFDC) Natural System Evaluation and Tool Development (Wang 2011), including Topics S3, Disposal system modeling - Natural System; P1, Development of discrete fracture network (DFN) model; P14, Technical basis for thermal loading limits; and P15 Modeling of disturbed rock zone (DRZ) evolution (clay repository).
On summation of perturbation expansions
International Nuclear Information System (INIS)
Horzela, A.
1985-04-01
The problem of the restoration of physical quantities defined by divergent perturbation expansions is analysed. The Pad'e and Borel summability is proved for alternating perturbation expansions with factorially growing coefficients. The proof is based on the methods of the classical moments theory. 17 refs. (author)
Energy of linear quasi-neutral electrostatic drift waves
International Nuclear Information System (INIS)
Pfirsch, D.; Correa-Restrepo, D.
1992-01-01
An exact energy expression for linear quasi-neutral electrostatic perturbations is derived within the framework of dissipationless multi-fluid theory, valid for any geometry. Taking the mass as a tensor with, in general, different masses parallel and perpendicular to an ambient magnetic field allows one to treat the full dynamics and also to restrict consideration to parallel dynamics or to the completely adiabatic case. Application to slab configurations yields the result that in plane geometry the adiabatic approximation does not allow negative-energy perturbations, whereas inclusion of the parallel dynamics does. This is in agreement with a numerical study of drift-wave turbulence within the framework of collisional two-fluid theory by B. Scott. Unlike Scott, we consider a dissipationless theory. Whereas the nonlinear energy is just kinetic plus potential plus thermal energy, the energy of perturbations depends on constraints. In a multi-fluid quasi-neutral electrostatic theory, from which we start, such constraints are mass conservation and entropy conservation. The latter is violated if heat conduction, heat sources (e.g. Joule heating) and heat sinks play a role. Hence, the energy expressions obtained are, valid only when situations where this is not the case or where these phenomena do not influence the entropy constraint. The latter is the case if the heat conduction is infinitely large such that the equilibrium temperature profiles T ν (x) of the various particle species ν are independent of x and δT ν =0. A vanishing temperature perturbation results in an entropy-conserving theory if one takes the adiabatic coefficients γ ν =1. This is possible, however, only for the perturbations; the equilibrium energy would diverge. When we consider this case, we do it in the way that the γs are put equal to 1 only after having obtained the perturbed energy for general γs. (author) 7 refs
Perturbation theory and collision probability formalism. Vol. 2
Energy Technology Data Exchange (ETDEWEB)
Nasr, M [National Center for Nuclear Safety and Radiation Control, Atomic Energy Authority, Cairo (Egypt)
1996-03-01
Perturbation theory is commonly used in evaluating the activity effects, particularly those resulting from small and localized perturbation in multiplying media., e.g. in small sample reactivity measurements. The Boltzmann integral transport equation is generally used for evaluating the direct and adjoint fluxes in the heterogenous lattice cells to be used in the perturbation equations. When applying perturbation theory in this formalism, a term involving the perturbation effects on the special transfer kernel arises. This term is difficult to evaluate correctly, since it involves an integration all over the entire system. The main advantage of the perturbation theory which is the limitation of the integration procedure on the perturbation region is found to be of no practical use in such cases. In the present work, the perturbation equation in the collision probability formalism is analyzed. A mathematical treatment of the term in question is performed. A new mathematical expression for this term is derived. The new expression which can be estimated easily is derived.
A quantitative comparison of lightning-induced electron precipitation and VLF signal perturbations
Peter, W. B.; Inan, U. S.
2007-12-01
VLF signal perturbations recorded on the Holographic Array for Ionospheric/Lightning Research (HAIL) are quantitatively related to a comprehensive model of lightning-induced electron precipitation (LEP) events. The model consists of three major components: a test-particle model of gyroresonant whistler-induced electron precipitation, a Monte Carlo simulation of energy deposition into the ionosphere, and a model of VLF subionospheric signal propagation. For the two representative LEP events studied, the model calculates peak VLF amplitude perturbations within a factor of three of those observed, well within the expected variability of radiation belt flux levels. The phase response of the observed VLF signal to precipitation varied dramatically over the course of the two nights and this variability in phase response is not properly reproduced by the model. The model calculates a peak in the precipitation that is poleward displaced ~6° from the causative lightning flash, consistent with observations. The modeled precipitated energy flux (E > 45 keV) peaks at ~1 × 10-2 (ergs s-1 cm-2), resulting in a peak loss of ~0.001% from a single flux tube at L ~ 2.2, consistent with previous satellite measurements of LEP events. The precipitation calculated by the model is highly dependent on the near-loss-cone trapped radiation belt flux levels assumed, and hence our main objective is not to compare the model calculations and the VLF signal observations on an absolute basis but is rather to develop metrics with which we can characterize the VLF signal perturbations recorded on HAIL in terms of the associated precipitation flux. Metrics quantifying the ionospheric density enhancement (N ILDE) and the electron precipitation (Γ) along a VLF signal path are strongly correlated with the VLF signal perturbations calculated by the model. A conversion ratio Ψ, relating VLF signal amplitude perturbations (ΔA) to the time-integrated precipitation (100-300 keV) along the VLF path (
Milosevic, Matija; Shinya, Masahiro; Masani, Kei; Patel, Kramay; McConville, Kristiina M V; Nakazawa, Kimitaka; Popovic, Milos R
2016-02-01
Trunk muscles are responsible for maintaining trunk stability during sitting. However, the effects of anticipation of perturbation on trunk muscle responses are not well understood. The objectives of this study were to identify the responses of trunk muscles to sudden support surface translations and quantify the effects of anticipation of direction and time of perturbation on the trunk neuromuscular responses. Twelve able-bodied individuals participated in the study. Participants were seated on a kneeling chair and support surface translations were applied in the forward and backward directions with and without direction and time of perturbation cues. The trunk started moving on average approximately 40ms after the perturbation. During unanticipated perturbations, average latencies of the trunk muscle contractions were in the range between 103.4 and 117.4ms. When participants anticipated the perturbations, trunk muscle latencies were reduced by 16.8±10.0ms and the time it took the trunk to reach maximum velocity was also reduced, suggesting a biomechanical advantage caused by faster muscle responses. These results suggested that trunk muscles have medium latency responses and use reflexive mechanisms. Moreover, anticipation of perturbation decreased trunk muscles latencies, suggesting that the central nervous system modulated readiness of the trunk based on anticipatory information. Copyright © 2015 Elsevier Ltd. All rights reserved.
An Introduction to Perturbative Methods in Gauge Theories
International Nuclear Information System (INIS)
T Muta
1998-01-01
This volume develops the techniques of perturbative QCD in great pedagogical detail starting with field theory. Aside from extensive treatments of the renormalization group technique, the operator product expansion formalism and their applications to short-distance reactions, this book provides a comprehensive introduction to gauge theories. Examples and exercises are provided to amplify the discussions on important topics. This is an ideal textbook on the subject of quantum chromodynamics and is essential for researchers and graduate students in high energy physics, nuclear physics and mathematical physics
Quantum inflaton, primordial metric perturbations and CMB fluctuations
International Nuclear Information System (INIS)
Cao, F J
2007-01-01
We compute the primordial scalar, vector and tensor metric perturbations arising from quantum field inflation. Quantum field inflation takes into account the nonperturbative quantum dynamics of the inflaton consistently coupled to the dynamics of the (classical) cosmological metric. For chaotic inflation, the quantum treatment avoids the unnatural requirements of an initial state with all the energy in the zero mode. For new inflation it allows a consistent treatment of the explosive particle production due to spinodal instabilities. Quantum field inflation (under conditions that are the quantum analog of slow roll) leads, upon evolution, to the formation of a condensate starting a regime of effective classical inflation. We compute the primordial perturbations taking the dominant quantum effects into account. The results for the scalar, vector and tensor primordial perturbations are expressed in terms of the classical inflation results. For a N-component field in a O(N) symmetric model, adiabatic fluctuations dominate while isocurvature or entropy fluctuations are negligible. The results agree with the current WMAP observations and predict corrections to the power spectrum in classical inflation. Such corrections are estimated to be of the order of m 2 /[NH 2 ] where m is the inflaton mass and H the Hubble constant at horizon crossing. This turns to be about 4% for the cosmologically relevant scales. This quantum field treatment of inflation provides the foundations to the classical inflation and permits to compute quantum corrections to it
International Nuclear Information System (INIS)
Passos, E.M.J. de
1976-01-01
The relationship between the Johnson-Baranger time-dependent folded diagram (JBFD) expansion, and the time independent methods of perturbation theory, are investigated. In the nondegenerate case, the JBFD expansion and the Rayleigh-Schroedinger perturbation expansion, for the ground state energy, are identical. On the other hand, in the degenerate case, for the nonhermitian effective interaction considered, the JBFD expansion, of the effective interaction, is equal to the perturbative expansion of the effective interaction of the nonhermitian eigenvalue problem of Bloch and Brandow-Des Cloizeaux. For the two hermitian effective interactions, the JBFD expansion of the effective interaction differs from the perturbation expansion of the effective interaction of the hermitian eigenvalue problem of Des Cloizeaux [pt
Approximate Solution of Schrödinger Equation with Pseudo-Gaussian Potential Viewed as a Perturbation
Directory of Open Access Journals (Sweden)
Iacob Theodor-Felix
2015-12-01
Full Text Available We consider the Schrödinger equation with pseudo-Gaussian potential and point out that it is basically made up by a term representing the harmonic oscillator potential and an additional term, which is actually a power series that converges rapidly. Based on this observation the system can be considered as a perturbation of harmonic oscillator. The perturbation method is used to approximate the energy levels of pseudo- Gaussian oscillator. The results are compared with those obtained in the analytic and numeric case.
Perturbation theory with respect to intercenter electron exchange and superexchange with degeneracy
International Nuclear Information System (INIS)
Orlenko, E.V.; Rumyantsev, A.A.
1990-01-01
The corrections to the energy and wave functions of a multielectron system of interacting atoms are calculated in a general analytic form by taking into account degeneracy of the states in accordance with the Young schemes. The rule for writing down the perturbation operator in such systems is formulated in the case when the ground and excited state vectors are antisymmetrized with respect to interchange of electrons between the centers. A secular equation of the theory is derived by applying perturbation theory, one of the parameters of which is the degree of overlap of the wave functions. Some concrete examples of interatomic interactions of an unpaired nature which are due to exchange and superexchange effects are considered
Reddy, M Rami; Erion, Mark D
2009-12-01
Molecular dynamics (MD) simulations in conjunction with thermodynamic perturbation approach was used to calculate relative solvation free energies of five pairs of small molecules, namely; (1) methanol to ethane, (2) acetone to acetamide, (3) phenol to benzene, (4) 1,1,1 trichloroethane to ethane, and (5) phenylalanine to isoleucine. Two studies were performed to evaluate the dependence of the convergence of these calculations on MD simulation length and starting configuration. In the first study, each transformation started from the same well-equilibrated configuration and the simulation length was varied from 230 to 2,540 ps. The results indicated that for transformations involving small structural changes, a simulation length of 860 ps is sufficient to obtain satisfactory convergence. In contrast, transformations involving relatively large structural changes, such as phenylalanine to isoleucine, require a significantly longer simulation length (>2,540 ps) to obtain satisfactory convergence. In the second study, the transformation was completed starting from three different configurations and using in each case 860 ps of MD simulation. The results from this study suggest that performing one long simulation may be better than averaging results from three different simulations using a shorter simulation length and three different starting configurations.
Stepping stability: effects of sensory perturbation
Directory of Open Access Journals (Sweden)
Krebs David E
2005-05-01
Full Text Available Abstract Background Few tools exist for quantifying locomotor stability in balance impaired populations. The objective of this study was to develop and evaluate a technique for quantifying stability of stepping in healthy people and people with peripheral (vestibular hypofunction, VH and central (cerebellar pathology, CB balance dysfunction by means a sensory (auditory perturbation test. Methods Balance impaired and healthy subjects performed a repeated bench stepping task. The perturbation was applied by suddenly changing the cadence of the metronome (100 beat/min to 80 beat/min at a predetermined time (but unpredictable by the subject during the trial. Perturbation response was quantified by computing the Euclidian distance, expressed as a fractional error, between the anterior-posterior center of gravity attractor trajectory before and after the perturbation was applied. The error immediately after the perturbation (Emax, error after recovery (Emin and the recovery response (Edif were documented for each participant, and groups were compared with ANOVA. Results Both balance impaired groups exhibited significantly higher Emax (p = .019 and Emin (p = .028 fractional errors compared to the healthy (HE subjects, but there were no significant differences between CB and VH groups. Although response recovery was slower for CB and VH groups compared to the HE group, the difference was not significant (p = .051. Conclusion The findings suggest that individuals with balance impairment have reduced ability to stabilize locomotor patterns following perturbation, revealing the fragility of their impairment adaptations and compensations. These data suggest that auditory perturbations applied during a challenging stepping task may be useful for measuring rehabilitation outcomes.
Cosmological perturbations beyond linear order
CERN. Geneva
2013-01-01
Cosmological perturbation theory is the standard tool to understand the formation of the large scale structure in the Universe. However, its degree of applicability is limited by the growth of the amplitude of the matter perturbations with time. This problem can be tackled with by using N-body simulations or analytical techniques that go beyond the linear calculation. In my talk, I'll summarise some recent efforts in the latter that ameliorate the bad convergence of the standard perturbative expansion. The new techniques allow better analytical control on observables (as the matter power spectrum) over scales very relevant to understand the expansion history and formation of structure in the Universe.
Instabilities in mimetic matter perturbations
Energy Technology Data Exchange (ETDEWEB)
Firouzjahi, Hassan; Gorji, Mohammad Ali [School of Astronomy, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Mansoori, Seyed Ali Hosseini, E-mail: firouz@ipm.ir, E-mail: gorji@ipm.ir, E-mail: shosseini@shahroodut.ac.ir, E-mail: shossein@ipm.ir [Physics Department, Shahrood University of Technology, P.O. Box 3619995161 Shahrood (Iran, Islamic Republic of)
2017-07-01
We study cosmological perturbations in mimetic matter scenario with a general higher derivative function. We calculate the quadratic action and show that both the kinetic term and the gradient term have the wrong sings. We perform the analysis in both comoving and Newtonian gauges and confirm that the Hamiltonians and the associated instabilities are consistent with each other in both gauges. The existence of instabilities is independent of the specific form of higher derivative function which generates gradients for mimetic field perturbations. It is verified that the ghost instability in mimetic perturbations is not associated with the higher derivative instabilities such as the Ostrogradsky ghost.
Gauge-invariant perturbations in a spatially flat anisotropic universe
International Nuclear Information System (INIS)
Den, Mitsue.
1986-12-01
The gauge-invariant perturbations in a spatially flat anisotropic universe with an arbitrary dimension (= N) are studied. In a previous paper the equations for the perturbations with a wave vector k a in one of the axial directions were derived and their solutions were shown. In this paper the perturbations with k a in arbitrary directions are treated. The remarkable properties are that all three types (scalar, vector, and tensor) of perturbations are generally coupled, so that a density perturbation can be produced also by vector or tensor perturbations. The formulation is quite general, but the behavior of the perturbations is discussed in a simple case such that N = 4 and k a is orthogonal to one of the axial directions. In this case, the perturbations are divided into two groups which are dynamically decoupled from each other. The asymptotic behavior of the perturbations in the group containing the density perturbation is discussed. (author)
Perturbative analysis of transport and fluctuation studies on RFX
International Nuclear Information System (INIS)
Martini, S.
2002-01-01
On the RFX reversed field pinch different transport mechanisms govern the centre and the edge of the plasma. Core transport is driven by parallel transport in a stochastic magnetic field, giving rise to an outward directed particle convection velocity. At the edge, roughly corresponding to the region outside the toroidal field reversal surface (where q=0), electrostatic fluctuations are an important loss channel, but more than 50% of the power losses have been associated to localized plasma-wall interaction due to the non-axisymmetric magnetic perturbations caused by locked modes. In the paper we present the most recent progress made in the modeling and understanding of the above mechanisms underlying particle and energy transport. The paper also discusses the correlations between core and edge transport phenomena. The main tools are perturbative transport studies by pellet injection and the analysis of the contribution of intermittency processes to particle transport in the edge. (author)
Lattice regularized chiral perturbation theory
International Nuclear Information System (INIS)
Borasoy, Bugra; Lewis, Randy; Ouimet, Pierre-Philippe A.
2004-01-01
Chiral perturbation theory can be defined and regularized on a spacetime lattice. A few motivations are discussed here, and an explicit lattice Lagrangian is reviewed. A particular aspect of the connection between lattice chiral perturbation theory and lattice QCD is explored through a study of the Wess-Zumino-Witten term
Output synchronization of chaotic systems under nonvanishing perturbations
Energy Technology Data Exchange (ETDEWEB)
Lopez-Mancilla, Didier [Departamento de Ciencias Exactas y Tecnologicas, Centro Universitario de los Lagos, Universidad de Guadalajara (CULagos-UdeG), Enrique Diaz de Leon s/n, 47460 Lagos de Moreno, Jal. (Mexico)], E-mail: didier@uabc.mx; Cruz-Hernandez, Cesar [Electronics and Telecommunications Department, Scientific Research and Advanced Studies of Ensenada (CICESE), Km. 107, Carretera Tijuana-Ensenada, 22860 Ensenada, B.C. (Mexico)], E-mail: ccruz@cicese.mx
2008-08-15
In this paper, an analysis for chaos synchronization under nonvanishing perturbations is presented. In particular, we use model-matching approach from nonlinear control theory for output synchronization of identical and nonidentical chaotic systems under nonvanishing perturbations in a master-slave configuration. We show that the proposed approach is indeed suitable to synchronize a class of perturbed slaves with a chaotic master system; that is the synchronization error trajectories remain bounded if the perturbations satisfy some conditions. In order to illustrate this robustness synchronization property, we present two cases of study: (i) for identical systems, a pair of coupled Roessler systems, the first like a master and the other like a perturbed slave, and (ii) for nonidentical systems, a Chua's circuit driving a Roessler/slave system with a perturbed control law, in both cases a quantitative analysis on the perturbation is included.
Output synchronization of chaotic systems under nonvanishing perturbations
International Nuclear Information System (INIS)
Lopez-Mancilla, Didier; Cruz-Hernandez, Cesar
2008-01-01
In this paper, an analysis for chaos synchronization under nonvanishing perturbations is presented. In particular, we use model-matching approach from nonlinear control theory for output synchronization of identical and nonidentical chaotic systems under nonvanishing perturbations in a master-slave configuration. We show that the proposed approach is indeed suitable to synchronize a class of perturbed slaves with a chaotic master system; that is the synchronization error trajectories remain bounded if the perturbations satisfy some conditions. In order to illustrate this robustness synchronization property, we present two cases of study: (i) for identical systems, a pair of coupled Roessler systems, the first like a master and the other like a perturbed slave, and (ii) for nonidentical systems, a Chua's circuit driving a Roessler/slave system with a perturbed control law, in both cases a quantitative analysis on the perturbation is included
Radiation perturbation theory in gravity and quantum universe as a hydrogen atom
International Nuclear Information System (INIS)
Pervushin, V.N.
1992-01-01
In quantum theory of gravity of the (n+1)-dimensional space-time the Faddeev-Popov functional integral is constructed for radiation perturbation theory. In this version the Universe expansion looks as the collective superfluid motion of quantum space, and the vacuum energy density plays the role of the hidden mass. 6 refs
New hybrid non-linear transformations of divergent perturbation series for quadratic Zeeman effects
International Nuclear Information System (INIS)
Belkic, D.
1989-01-01
The problem of hydrogen atoms in an external uniform magnetic field (quadratic Zeeman effect) is studied by means of perturbation theory. The power series for the ground-state energy in terms of magnetic-field strength B is divergent. Nevertheless, it is possible to induce convergence of this divergent series by applying various non-linear transformations. These transformations of originally divergent perturbation series yield new sequences, which then converge. The induced convergence is, however, quite slow. A new hybrid Shanks-Levin non-linear transform is devised here for accelerating these slowly converging series and sequences. Significant improvement in the convergence rate is obtained. Agreement with the exact results is excellent. (author)
Energy Technology Data Exchange (ETDEWEB)
Skagius, K; Wiborgh, M [Kemakta, Stockholm (Sweden); Stroem, A [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)
1995-11-01
The basic device in the Rock Engineering Systems approach, the interaction matrix, has been used to identify, structure and rank Features, Events, and Processes (FEPs) describing barrier performance and radionuclide behaviour in the far-field of a deep geologic repository for spent fuel. The result is a first version of the Process System (PS), for the far-field of a deep repository, structured in an interaction matrix with supporting documentation. The documentation is compiled in databases, one containing matrix specific information and one containing general FEP descriptions. The study has shown that an interaction matrix is feasible to use both for the structuring of the PS and for visualisation of the PS. The developed documentation system increases the transparency of the system description and makes it possible to trace back the judgements made during the construction of the matrix. This will facilitate review work and future revisions as well as consistent treatment of different issues in the system. This study is a first step in the application of a systematic method to establish a structured description of the PS for a deep repository for spent fuel. The work could be seen as a part of the preparation for the forthcoming performance and safety analysis. The next step would be to develop the PS for the remaining parts of the repository system to the same level as has been done for the far-field system. Before the PS is evaluated for different selected system premises, a scientific review of the contents of the PS for the whole repository system would be beneficial. 5 refs.
International Nuclear Information System (INIS)
Skagius, K.; Wiborgh, M.; Stroem, A.
1995-11-01
The basic device in the Rock Engineering Systems approach, the interaction matrix, has been used to identify, structure and rank Features, Events, and Processes (FEPs) describing barrier performance and radionuclide behaviour in the far-field of a deep geologic repository for spent fuel. The result is a first version of the Process System (PS), for the far-field of a deep repository, structured in an interaction matrix with supporting documentation. The documentation is compiled in databases, one containing matrix specific information and one containing general FEP descriptions. The study has shown that an interaction matrix is feasible to use both for the structuring of the PS and for visualisation of the PS. The developed documentation system increases the transparency of the system description and makes it possible to trace back the judgements made during the construction of the matrix. This will facilitate review work and future revisions as well as consistent treatment of different issues in the system. This study is a first step in the application of a systematic method to establish a structured description of the PS for a deep repository for spent fuel. The work could be seen as a part of the preparation for the forthcoming performance and safety analysis. The next step would be to develop the PS for the remaining parts of the repository system to the same level as has been done for the far-field system. Before the PS is evaluated for different selected system premises, a scientific review of the contents of the PS for the whole repository system would be beneficial. 5 refs
International Nuclear Information System (INIS)
Hurricane, O.A.
1994-09-01
In this dissertation, a new linear Vlasov kinetic theory is developed for calculating the plasma response to perturbing electromagnetic fields in cases where the particle dynamics are stochastic; for modes with frequencies less than the typical particle bounce frequency. A variational form is arrived at which allows one to properly perform a stability analysis for a stochastic plasma. In the case of stochastic dynamics, the authors demonstrate that the plasma responds to the flux tube volume average of the perturbing potentials as opposed to the usual case of adiabatic dynamics where plasma responds to the bounce average of the perturbed potentials. They show that for the stochastic plasma, the kinetic variational form maps into the Bernstein energy principle if the perturbation frequency is large compared to all drift frequencies, the perpendicular wavelength is large compared to the Larmor radius, and vanishing of the potentials associated with the parallel electric field are all assumed. By explicit minimization of the energy principle, it is established that the stochastic plasma is always less stable than an adiabatic plasma. Lastly, the effect of strictly enforcing the quasi-neutrality (QN) condition upon a gyro-kinetic type stability analysis is explored. From simple mathematical considerations, it is shown that when the QN condition is imposed convective type modes that are equipotentials along magnetic field lines are created that alter the stability properties of the plasma. The pertinent modifications to the Bernstein energy principle are given
Isocurvature perturbations in the Ekpyrotic Universe
International Nuclear Information System (INIS)
Notari, A.; Riotto, A.
2002-01-01
The Ekpyrotic scenario assumes that our visible Universe is a boundary brane in a five-dimensional bulk and that the hot Big Bang occurs when a nearly supersymmetric five-brane travelling along the fifth dimension collides with our visible brane. We show that the generation of isocurvature perturbations is a generic prediction of the Ekpyrotic Universe. This is due to the interactions in the kinetic terms between the brane modulus parameterizing the position of the five-brane in the bulk and the dilaton and volume moduli. We show how to separate explicitly the adiabatic and isocurvature modes by performing a rotation in field space. Our results indicate that adiabatic and isocurvature perturbations might be cross-correlated and that curvature perturbations might be entirely seeded by isocurvature perturbations
Driven similarity renormalization group: Third-order multireference perturbation theory.
Li, Chenyang; Evangelista, Francesco A
2017-03-28
A third-order multireference perturbation theory based on the driven similarity renormalization group (DSRG-MRPT3) approach is presented. The DSRG-MRPT3 method has several appealing features: (a) it is intruder free, (b) it is size consistent, (c) it leads to a non-iterative algorithm with O(N 6 ) scaling, and (d) it includes reference relaxation effects. The DSRG-MRPT3 scheme is benchmarked on the potential energy curves of F 2 , H 2 O 2 , C 2 H 6 , and N 2 along the F-F, O-O, C-C, and N-N bond dissociation coordinates, respectively. The nonparallelism errors of DSRG-MRPT3 are consistent with those of complete active space third-order perturbation theory and multireference configuration interaction with singles and doubles and show significant improvements over those obtained from DSRG second-order multireference perturbation theory. Our efficient implementation of the DSRG-MRPT3 based on factorized electron repulsion integrals enables studies of medium-sized open-shell organic compounds. This point is demonstrated with computations of the singlet-triplet splitting (Δ ST =E T -E S ) of 9,10-anthracyne. At the DSRG-MRPT3 level of theory, our best estimate of the adiabatic Δ ST is 3.9 kcal mol -1 , a value that is within 0.1 kcal mol -1 from multireference coupled cluster results.
Fluid dynamic propagation of initial baryon number perturbations on a Bjorken flow background
Floerchinger, Stefan
2015-01-01
Baryon number density perturbations offer a possible route to experimentally measure baryon number susceptibilities and heat conductivity of the quark gluon plasma. We study the fluid dynamical evolution of local and event-by-event fluctuations of baryon number density, flow velocity and energy density on top of a (generalized) Bjorken expansion. To that end we use a background-fluctuation splitting and a Bessel-Fourier decomposition for the fluctuating part of the fluid dynamical fields with respect to the azimuthal angle, the radius in the transverse plane and rapidity. We examine how the time evolution of linear perturbations depends on the equation of state as well as on shear viscosity, bulk viscosity and heat conductivity for modes with different azimuthal, radial and rapidity wave numbers. Finally we discuss how this information is accessible to experiments in terms of the transverse and rapidity dependence of correlation functions for baryonic particles in high energy nuclear collisions.
Continual integral in perturbation theory
International Nuclear Information System (INIS)
Slavnov, A.A.
1975-01-01
It is shown that all results obtained by means of continual integration within the framework of perturbation theory are completely equivalent to those obtained by the usual diagram technique and are therfore just as rigorous. A rigorous justification is given for the rules for operating with continual integrals in perturbation theory. (author)
International Nuclear Information System (INIS)
Li Lei; Robertson-Honecker, Jennifer; Vaghela, Vishal; King, Fred L.
2006-01-01
This study employed a power perturbation method to examine the energy transfer processes at different locations within the afterpeak regime of a millisecond pulsed glow discharge plasma. Brief power perturbation pulses were applied during the afterpeak regime altering the environment of the collapsing plasma. Responses of several transitions to the power perturbations were measured via atomic emission and absorption spectroscopic methods at various distances from the surface of the cathode. The experimental data provide further insight into the energy transfer processes that occur at different spatial locations and in different temporal regimes of these pulsed glow discharge plasmas. Although the enhancement of the large population of metastable argon atoms is again confirmed, the mechanism responsible for this enhancement remains unclear. The most likely possibility involves some form of ion-electron recombination followed by radiative relaxation of the resulting species. The metastable argon atoms subsequently Penning ionize sputtered copper atoms which then appear to undergo a similar ion-electron recombination process yielding variable degrees of observable afterpeak emission for copper atom transitions. The kinetic information of these processes was approximated from the corresponding relaxation time. The electron thermalization time allowing for recombination with ions was found to be ∼25 μs after the discharge power termination
Kato expansion in quantum canonical perturbation theory
International Nuclear Information System (INIS)
Nikolaev, Andrey
2016-01-01
This work establishes a connection between canonical perturbation series in quantum mechanics and a Kato expansion for the resolvent of the Liouville superoperator. Our approach leads to an explicit expression for a generator of a block-diagonalizing Dyson’s ordered exponential in arbitrary perturbation order. Unitary intertwining of perturbed and unperturbed averaging superprojectors allows for a description of ambiguities in the generator and block-diagonalized Hamiltonian. We compare the efficiency of the corresponding computational algorithm with the efficiencies of the Van Vleck and Magnus methods for high perturbative orders.
Kato expansion in quantum canonical perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Nikolaev, Andrey, E-mail: Andrey.Nikolaev@rdtex.ru [Institute of Computing for Physics and Technology, Protvino, Moscow Region, Russia and RDTeX LTD, Moscow (Russian Federation)
2016-06-15
This work establishes a connection between canonical perturbation series in quantum mechanics and a Kato expansion for the resolvent of the Liouville superoperator. Our approach leads to an explicit expression for a generator of a block-diagonalizing Dyson’s ordered exponential in arbitrary perturbation order. Unitary intertwining of perturbed and unperturbed averaging superprojectors allows for a description of ambiguities in the generator and block-diagonalized Hamiltonian. We compare the efficiency of the corresponding computational algorithm with the efficiencies of the Van Vleck and Magnus methods for high perturbative orders.
Invariant exchange perturbation theory for multicenter systems: Time-dependent perturbations
International Nuclear Information System (INIS)
Orlenko, E. V.; Evstafev, A. V.; Orlenko, F. E.
2015-01-01
A formalism of exchange perturbation theory (EPT) is developed for the case of interactions that explicitly depend on time. Corrections to the wave function obtained in any order of perturbation theory and represented in an invariant form include exchange contributions due to intercenter electron permutations in complex multicenter systems. For collisions of atomic systems with an arbitrary type of interaction, general expressions are obtained for the transfer (T) and scattering (S) matrices in which intercenter electron permutations between overlapping nonorthogonal states belonging to different centers (atoms) are consistently taken into account. The problem of collision of alpha particles with lithium atoms accompanied by the redistribution of electrons between centers is considered. The differential and total charge-exchange cross sections of lithium are calculated
Strings as perturbations of evolving spin networks
International Nuclear Information System (INIS)
Smolin, Lee
2000-01-01
One step in the construction of a background independent formulation of string theory is detailed, in which it is shown how perturbative strings may arise as small fluctuations around histories in a formulation of non-perturbative dynamics of spin networks due to Markopoulou. In this formulation the dynamics of spin network states and their generalizations is described in terms of histories which have discrete analogues of the causal structure and many fingered time of Lorentzian spacetimes. Perturbations of these histories turn out to be described in terms of spin systems defined on 2-dimensional timelike surfaces embedded in the discrete spacetime. When the history has a classical limit which is Minkowski spacetime, the action of the perturbation theory is given to leading order by the spacetime area of the surface, as in bosonic string theory. This map between a non-perturbative formulation of quantum gravity and a 1+1 dimensional theory generalizes to a large class of theories in which the group SU(2) i s extended to any quantum group or supergroup. It is argued that a necessary condition for the non-perturbative theory to have a good classical limit is that the resulting 1+1 dimensional theory defines a consistent and stable perturbative string theory
Acoustic anisotropic wavefields through perturbation theory
Alkhalifah, Tariq Ali
2013-09-01
Solving the anisotropic acoustic wave equation numerically using finite-difference methods introduces many problems and media restriction requirements, and it rarely contributes to the ability to resolve the anisotropy parameters. Among these restrictions are the inability to handle media with η<0 and the presence of shear-wave artifacts in the solution. Both limitations do not exist in the solution of the elliptical anisotropic acoustic wave equation. Using perturbation theory in developing the solution of the anisotropic acoustic wave equation allows direct access to the desired limitation-free solutions, that is, solutions perturbed from the elliptical anisotropic background medium. It also provides a platform for parameter estimation because of the ability to isolate the wavefield dependency on the perturbed anisotropy parameters. As a result, I derive partial differential equations that relate changes in the wavefield to perturbations in the anisotropy parameters. The solutions of the perturbation equations represented the coefficients of a Taylor-series-type expansion of the wavefield as a function of the perturbed parameter, which is in this case η or the tilt of the symmetry axis. The expansion with respect to the symmetry axis allows use of an acoustic transversely isotropic media with a vertical symmetry axis (VTI) kernel to estimate the background wavefield and the corresponding perturbation coefficients. The VTI extrapolation kernel is about one-fourth the cost of the transversely isotropic model with a tilt in the symmetry axis kernel. Thus, for a small symmetry axis tilt, the cost of migration using a first-order expansion can be reduced. The effectiveness of the approach was demonstrated on the Marmousi model.
Data-free and data-driven spectral perturbations for RANS UQ
Edeling, Wouter; Mishra, Aashwin; Iaccarino, Gianluca
2017-11-01
Despite recent developments in high-fidelity turbulent flow simulations, RANS modeling is still vastly used by industry, due to its inherent low cost. Since accuracy is a concern in RANS modeling, model-form UQ is an essential tool for assessing the impacts of this uncertainty on quantities of interest. Applying the spectral decomposition to the modeled Reynolds-Stress Tensor (RST) allows for the introduction of decoupled perturbations into the baseline intensity (kinetic energy), shape (eigenvalues), and orientation (eigenvectors). This constitutes a natural methodology to evaluate the model form uncertainty associated to different aspects of RST modeling. In a predictive setting, one frequently encounters an absence of any relevant reference data. To make data-free predictions with quantified uncertainty we employ physical bounds to a-priori define maximum spectral perturbations. When propagated, these perturbations yield intervals of engineering utility. High-fidelity data opens up the possibility of inferring a distribution of uncertainty, by means of various data-driven machine-learning techniques. We will demonstrate our framework on a number of flow problems where RANS models are prone to failure. This research was partially supported by the Defense Advanced Research Projects Agency under the Enabling Quantification of Uncertainty in Physical Systems (EQUiPS) project (technical monitor: Dr Fariba Fahroo), and the DOE PSAAP-II program.
Perturbations of higher-dimensional spacetimes
Energy Technology Data Exchange (ETDEWEB)
Durkee, Mark; Reall, Harvey S, E-mail: M.N.Durkee@damtp.cam.ac.uk, E-mail: H.S.Reall@damtp.cam.ac.uk [DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom)
2011-02-07
We discuss linearized gravitational perturbations of higher-dimensional spacetimes. For algebraically special spacetimes (e.g. Myers-Perry black holes), we show that there exist local gauge invariant quantities linear in the metric perturbation. These are the higher-dimensional generalizations of the 4D Newman-Penrose scalars that (in an algebraically special vacuum spacetime) satisfy decoupled equations of motion. We show that decoupling occurs in more than four dimensions if, and only if, the spacetime admits a null geodesic congruence with vanishing expansion, rotation and shear. Decoupling of electromagnetic perturbations occurs under the same conditions. Although these conditions are not satisfied in black hole spacetimes, they are satisfied in the near-horizon geometry of an extreme black hole.
't Hooft loops and perturbation theory
De Forcrand, Philippe; Noth, D; Forcrand, Philippe de; Lucini, Biagio; Noth, David
2005-01-01
We show that high-temperature perturbation theory describes extremely well the area law of SU(N) spatial 't Hooft loops, or equivalently the tension of the interface between different Z_N vacua in the deconfined phase. For SU(2), the disagreement between Monte Carlo data and lattice perturbation theory for sigma(T)/T^2 is less than 2%, down to temperatures O(10) T_c. For SU(N), N>3, the ratios of interface tensions, (sigma_k/sigma_1)(T), agree with perturbation theory, which predicts tiny deviations from the ratio of Casimirs, down to nearly T_c. In contrast, individual tensions differ markedly from the perturbative expression. In all cases, the required precision Monte Carlo measurements are made possible by a simple but powerful modification of the 'snake' algorithm.
Propagation of Ion Acoustic Perturbations
DEFF Research Database (Denmark)
Pécseli, Hans
1975-01-01
Equations describing the propagation of ion acoustic perturbations are considered, using the assumption that the electrons are Boltzman distributed and isothermal at all times. Quasi-neutrality is also considered.......Equations describing the propagation of ion acoustic perturbations are considered, using the assumption that the electrons are Boltzman distributed and isothermal at all times. Quasi-neutrality is also considered....
Dynamical evolution of quintessence dark energy in collapsing dark matter halos
International Nuclear Information System (INIS)
Wang Qiao; Fan Zuhui
2009-01-01
In this paper, we analyze the dynamical evolution of quintessence dark energy induced by the collapse of dark matter halos. Different from other previous studies, we develop a numerical strategy which allows us to calculate the dark energy evolution for the entire history of the spherical collapse of dark matter halos, without the need of separate treatments for linear, quasilinear, and nonlinear stages of the halo formation. It is found that the dark energy perturbations evolve with redshifts, and their specific behaviors depend on the quintessence potential as well as the collapsing process. The overall energy density perturbation is at the level of 10 -6 for cluster-sized halos. The perturbation amplitude decreases with the decrease of the halo mass. At a given redshift, the dark energy perturbation changes with the radius to the halo center, and can be either positive or negative depending on the contrast of ∂ t φ, ∂ r φ, and φ with respect to the background, where φ is the quintessence field. For shells where the contrast of ∂ r φ is dominant, the dark energy perturbation is positive and can be as high as about 10 -5 .
Sasaki, Misao; Wands, David
2010-06-01
In recent years there has been a resurgence of interest in the study of non-linear perturbations of cosmological models. This has been the result of both theoretical developments and observational advances. New theoretical challenges arise at second and higher order due to mode coupling and the need to develop new gauge-invariant variables beyond first order. In particular, non-linear interactions lead to deviations from a Gaussian distribution of primordial perturbations even if initial vacuum fluctuations are exactly Gaussian. These non-Gaussianities provide an important probe of models for the origin of structure in the very early universe. We now have a detailed picture of the primordial distribution of matter from surveys of the cosmic microwave background, notably NASA's WMAP satellite. The situation will continue to improve with future data from the ESA Planck satellite launched in 2009. To fully exploit these data cosmologists need to extend non-linear cosmological perturbation theory beyond the linear theory that has previously been sufficient on cosmological scales. Another recent development has been the realization that large-scale structure, revealed in high-redshift galaxy surveys, could also be sensitive to non-linearities in the primordial curvature perturbation. This focus section brings together a collection of invited papers which explore several topical issues in this subject. We hope it will be of interest to theoretical physicists and astrophysicists alike interested in understanding and interpreting recent developments in cosmological perturbation theory and models of the early universe. Of course it is only an incomplete snapshot of a rapidly developing field and we hope the reader will be inspired to read further work on the subject and, perhaps, fill in some of the missing pieces. This focus section is dedicated to the memory of Lev Kofman (1957-2009), an enthusiastic pioneer of inflationary cosmology and non-Gaussian perturbations.
Multidimensional periodic Schrödinger operator perturbation theory and applications
Veliev, Oktay
2015-01-01
The book describes the direct problems and the inverse problem of the multidimensional Schrödinger operator with a periodic potential. This concerns perturbation theory and constructive determination of the spectral invariants and finding the periodic potential from the given Bloch eigenvalues. The unique method of this book derives the asymptotic formulas for Bloch eigenvalues and Bloch functions for arbitrary dimension. Moreover, the measure of the iso-energetic surfaces in the high energy region is construct and estimated. It implies the validity of the Bethe-Sommerfeld conjecture for arbitrary dimensions and arbitrary lattices. Using the perturbation theory constructed in this book, the spectral invariants of the multidimensional operator from the given Bloch eigenvalues are determined. Some of these invariants are explicitly expressed by the Fourier coefficients of the potential. This way the possibility to determine the potential constructively by using Bloch eigenvalues as input data is given. In the ...
Theory of deep inelastic neutron scattering: Hard-core perturbation theory
International Nuclear Information System (INIS)
Silver, R.N.
1988-01-01
Details are presented of a new many-body theory for deep inelastic neutron scattering (DINS) experiments to measure momentum distributions in quantum fluids and solids. The high-momentum and energy-transfer scattering law in helium is shown to be a convolution of the impulse approximation with a final-state broadening function which depends on the scattering phase shifts and the radial distribution function. The predicted broadening satisfies approximate Y scaling, is neither Lorentzian nor Gaussian, and obeys the f, ω 2 , and ω 3 sum rules. The derivation uses a combination of Liouville perturbation theory, projection superoperators, and semiclassical methods which I term ''hard-core perturbation theory.'' A review is presented of the predictions of prior theories for DINS experiments in relation to the present work. A subsequent paper will present massive numerical predictions and a discussion of DINS experiments on superfluid 4 He