Baryon form factors in chiral perturbation theory
Kubis, B; Kubis, Bastian; Meissner, Ulf-G.
2001-01-01
We analyze the electromagnetic form factors of the ground state baryon octet to fourth order in relativistic baryon chiral perturbation theory. Predictions for the \\Sigma^- charge radius and the \\Lambda-\\Sigma^0 transition moment are found to be in excellent agreement with the available experimental information. Furthermore, the convergence behavior of the hyperon charge radii is shown to be more than satisfactory.
Some New Perturbation Bounds for Subunitary Polar Factors
Institute of Scientific and Technical Information of China (English)
Wen LI
2005-01-01
In this paper, we present some new perturbation bounds for subunitary polar factors in a special unitarily invariant norm called a Q-norm. Some recent results in the Frobenius norm and the spectral norm are extended to the Q-norm on one hand. On the other hand we also present some relative perturbation bounds for subunitary polar factors.
Determining the penetrability factor using a small perturbations method
Energy Technology Data Exchange (ETDEWEB)
Khayrullin, M.Kh.
1983-01-01
An iterational process is built for finding the penetrability factor which is based on small perturbation formulas with the assumption that the penetrability factor belongs to a class of piecewise constant functions. The iteration process is built in the following manner: finite differential analogies of direct and adjacent problems are solved in each step, then these solutions are used for obtaining a system of linear algebraic equations relative to perturbations in the penetrability factor. The refined values of the penetrability factor serve as the initial data for the next step of the iteration process. When the penetrability factor belongs to another class of functions, then it is possible to build its evaluation in the class of piecewise constant functions using the known values of the bottom hole pressures and flow rates using this iteration process. Examples of calculations of such evaluations are given and they are compared with evaluations obtained through a least squares method in the class of piecewise constant functions.
Hyperon decay form factors in chiral perturbation theory
Lacour, Andre; 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).
Perturbation analysis for best approximation and the polar factor by subunitary matrices
Institute of Scientific and Technical Information of China (English)
Xinguo LIU; Weiguo WANG; Yimin WEI
2008-01-01
This paper is a continuation and improvement over the results of Laszkiewicz and Zietak [BIT, 2006, 46: 345-366], studying perturbation analysis for polar decomposition. Some basic properties of best approximation subunitary matrices are investigated in detail. The perturbation bounds of the polar factor are also derived.
Factorization and infrared properties of non-perturbative contributions to DIS structure functions
Energy Technology Data Exchange (ETDEWEB)
Ermolaev, B.I. [Ioffe Physico-Technical Institute, St. Petersburg (Russian Federation); Greco, M. [University Roma Tre, Department of Physics (Italy); INFN, Rome (Italy); Troyan, S.I. [St. Petersburg Institute of Nuclear Physics, Gatchina (Russian Federation)
2011-09-15
In this paper we present a new derivation of QCD factorization. We deduce the k{sub T} and collinear factorizations for the DIS structure functions by consecutive reductions of a more general theoretical construction. We begin by studying the amplitude of forward Compton scattering off a hadron target, representing this amplitude as a set of convolutions of two blobs connected by the simplest, two-parton intermediate states. Each blob in the convolutions can contain both the perturbative and non-perturbative contributions. We formulate conditions for separating the perturbative and non-perturbative contributions and attributing them to the different blobs. After that the convolutions correspond to QCD factorization. Then we reduce this totally unintegrated (basic) factorization first to k{sub T} -factorization and finally to collinear factorization. In order to yield a finite expression for the Compton amplitude, the integration over the loop momentum in the basic factorization must be free of both ultraviolet and infrared singularities. This obvious mathematical requirement leads to theoretical restrictions on the non-perturbative contributions (parton distributions) to the Compton amplitude and the DIS structure functions related to the Compton amplitude through the Optical Theorem. In particular, our analysis excludes the use of the singular factors x{sup -a} (with a >0) in the fits for the quark and gluon distributions because such factors contradict the integrability of the basic convolutions for the Compton amplitude. This restriction is valid for all DIS structure functions in the framework of both k{sub T} -factorization and collinear factorization if we attribute the perturbative contributions only to the upper blob. The restrictions on the non-perturbative contributions obtained in the present paper can easily be extended to other QCD processes where the factorization is exploited. (orig.)
Non-perturbative gluon-hadron inputs for all available forms of QCD factorization
Ermolaev, B I
2016-01-01
Description of hadronic reactions at high energies is conventionally done on basis of QCD factoriza- tion so that factorization convolutions involve non-perturbative inputs mimicking non-perturbative contributions and perturbative evolution of those inputs. We construct the 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 both polarized and unpolarized hadrons. Firstly, we derive general mathematical criteria which any model for the inputs should obey and then suggest a Resonance Model satisfying those criteria. This model is inspired by a simple observation: after emitting an active parton off the hadron, the remaining ensemble of spectators becomes unstable and therefore it can be described through factors of the resonance type. Exploiting Resonance Model, we obtain non-perturbative inputs for gluon distributions in unpolarized and polarized hadrons for all available forms of QCD factorization...
Axial form factor of the nucleon in the perturbative chiral quark model
Khosonthongkee, K; Faessler, Amand; Gutsche, T; Lyubovitskij, V E; Pumsa-ard, K; Yan, Y
2004-01-01
We apply the perturbative chiral quark model (PCQM) at one loop to analyze the axial form factor of the nucleon. This chiral quark model is based on an effective Lagrangian, where baryons are described by relativistic valence quarks and a perturbative cloud of Goldstone bosons as dictated by chiral symmetry. We apply the formalism to obtain analytical expressions for the axial form factor of the nucleon, which is given in terms of fundamental parameters of low-energy pion-nucleon physics (weak pion decay constant, strong pion-nucleon form factor) and of only one model parameter (radius of the nucleonic three-quark core).
The asymptotic convergence factor for a polygon under a perturbation
Energy Technology Data Exchange (ETDEWEB)
Li, X. [Georgia Southern Univ., Statesboro, GA (United States)
1994-12-31
Let Ax = b be a large system of linear equations, where A {element_of} C{sup NxN}, nonsingular and b {element_of} C{sup N}. A few iterative methods for solving have recently been presented in the case where A is nonsymmetric. Many of their algorithms consist of two phases: Phase I: estimate the extreme eigenvalues of A; Phase II: construct and apply an iterative method based on the estimates. For convenience, it is rewritten as an equivalent fixed-point form, x = Tx + c. Let {Omega} be a compact set excluding 1 in the complex plane, and let its complement in the extended complex plane be simply connected. The asymptotic convergence factor (ACF) for {Omega}, denoted by {kappa}({Omega}), measures the rate of convergence for the asymptotically optimal semiiterative methods for solving, where {sigma}(T) {contained_in} {Omega}.
Analysis of dose perturbation factors of a NACP-02 ionization chamber in clinical electron beams.
Chin, E; Palmans, H; Shipley, D; Bailey, M; Verhaegen, F
2009-01-21
For well-guarded plane-parallel ionization chambers, international dosimetry protocols recommend a value of unity for electron perturbation factors in water. However, recent data published by various groups have challenged this. Specifically for the NACP-02 chamber, non-unity electron perturbation factors have already been published by Verhaegen et al (2006 Phys. Med. Biol. 51 1221-35) and Buckley and Rogers (2006 Med. Phys. 33 1788-96). Recently it was found that the mass thickness of the front chamber window can be 35% greater than is listed in the IAEA's TRS-398 absorbed dose protocol (Chin et al 2008 Phys. Med. Biol. 53 N119-26). This study therefore recalculated NACP-02 electron perturbation correction factors for energies 4-18 MeV at depths z(ref) and R(50) to determine the effect of the chamber model change. Results showed that perturbation factors at z(ref) are fairly stable for similar chamber models but become highly sensitive to small changes at deeper depths. The results also showed some dependence on using 1 keV versus 10 keV for the transport cut-off. Additional investigations revealed that the wall perturbation factor, p(wall), is strongly influenced by the chamber back wall at z(ref) and at larger depths small changes in the positioning of the effective point of measurement cause large fluctuations in the final value. Finally, the cavity perturbation factor, p(cav), was found to be primarily influenced by electron backscatter.
Electromagnetic form factors of the baryon octet in the perturbative chiral quark model
Cheedket, S; Gutsche, T; Faessler, A; Pumsa-ard, K; Yan, Y; Gutsche, Th.; Faessler, Amand
2002-01-01
We apply the perturbative chiral quark model at one loop to analyze the electromagnetic form factors of the baryon octet. The analytic expressions for baryon form factors, which are given in terms of fundamental parameters of low-energy pion-nucleon physics(weak pion decay constant, axial nucleon coupling, strong pion-nucleon form factor), and the numerical results for baryon magnetic moments, charge and magnetic radii are presented. Our results are in good agreement with experimental data.
Factorization and infrared properties of non-perturbative contributions to DIS structure functions
Ermolaev, B I; Troyan, S I
2010-01-01
Analytical expressions for the non-perturbative components of the hadronic scattering amplitudes and the DIS structure functions are not usually obtained from theoretical considerations, but are introduced phenomenologically by fitting the data. We derive some restrictions for such contributions from the general concepts of factorization and integrability. These restrictions are obtained in the context of both k_T and collinear factorizations. We also show that the use of the collinear factorization basically makes the DIS structure functions be dependent on the factorization scale. Our analysis shows that singular factors of the type x^{-a} in the initial parton densities can be used for the singlet component of the structure function F_1, provided a <1, but excludes the use of them for the other structure functions. The restrictions for the non-perturbative contributions we obtain can also be applied to other QCD reactions at high energies.
The electric dipole form factor of the nucleon in chiral perturbation theory to subleading order
Mereghetti, E; de Vries, Jordy; Hockings, W.H.; Maekawa, C.M.; van Kolck, U
2011-01-01
The electric dipole form factor (EDFF) of the nucleon stemming from the QCD ¯ term and from the quark color-electric dipole moments is calculated in chiral perturbation theory to sub-leading order. This is the lowest order in which the isoscalar EDFF receives a calculable, non-analytic contribution
Curtain, RF
2004-01-01
We solve the problem of robust stabilization with respect to left coprime factor perturbations for a class of irrational transfer functions with a state space realization. We obtain a parameterization of the robustly stabilizing controllers in terms of the generating operators and an arbitrary
Perturbative calculation of the Sternheimer anti-shielding factor with Hartree-Fock atomic orbitals
2012-01-01
We report a calculation of the Sternheimer anti-shielding factor, \\gamma, by means of first order perturbation theory. In quality of basis functions, we use Hartree-Fock electronic orbitals, expanded on hydrogenic atomic states. The computed \\gamma(r) for Fe^{3+} and Cu^{1+} inner electronic cores are reported and compared with literature values, obtained from alternative methodologies.
Do fragmentation functions in factorization theorems correctly treat non-perturbative effects?
Collins, John
2016-01-01
Current all-orders proofs of factorization of hard processes are made by extracting the leading power behavior of Feynman graphs, i.e., by extracting asymptotics strictly order-by-order in perturbation theory. The resulting parton densities and fragmentation functions include non-perturbative effects. I show how there are missing elements in the proofs; these are related to and exemplified by string and cluster models of hadronization. The proofs rely on large rapidity differences between different parts of graphs for the process; but in reality large rapidity gaps are filled in
A perturbation-based framework for link prediction via non-negative matrix factorization
Wang, Wenjun; Cai, Fei; Jiao, Pengfei; Pan, Lin
2016-12-01
Many link prediction methods have been developed to infer unobserved links or predict latent links based on the observed network structure. However, due to network noises and irregular links in real network, the performances of existed methods are usually limited. Considering random noises and irregular links, we propose a perturbation-based framework based on Non-negative Matrix Factorization to predict missing links. We first automatically determine the suitable number of latent features, which is inner rank in NMF, by Colibri method. Then, we perturb training set of a network by perturbation sets many times and get a series of perturbed networks. Finally, the common basis matrix and coefficients matrix of these perturbed networks are obtained via NMF and form similarity matrix of the network for link prediction. Experimental results on fifteen real networks show that the proposed framework has competitive performances compared with state-of-the-art link prediction methods. Correlations between the performances of different methods and the statistics of networks show that those methods with good precisions have similar consistence.
Nucleon-to-Delta axial transition form factors in relativistic baryon chiral perturbation theory
Geng, L S; Alvarez-Ruso, L; Vacas, M J Vicente
2008-01-01
We report a theoretical study of the axial Nucleon to Delta(1232) ($N\\to\\Delta$) transition form factors up to one-loop order in relativistic baryon chiral perturbation theory. We adopt a formalism in which the $\\Delta$ couplings obey the spin-3/2 gauge symmetry and, therefore, decouple the unphysical spin-1/2 fields. We compare the results with phenomenological form factors obtained from neutrino bubble chamber data and in quark models.
Li, Hao-Song; Chen, Xiao-Lin; Deng, Wei-Zhen; Zhu, Shi-Lin
2016-01-01
We have systematically investigated the magnetic moments and magnetic form factors of the decuplet baryons to the next-to-next-leading order in the framework of the heavy baryon chiral perturbation theory. Our calculation includes the contributions from both the intermediate decuplet and octet baryon states in the loops. We also calculate the charge and magnetic dipole form factors of the decuplet baryons. Our results may be useful to the chiral extrapolation of the lattice simulations of the decuplet electromagnetic properties.
Soft and Collinear Radiation and Factorization in Perturbation Theory and Beyond
Gardi, Einan
2002-01-01
Power corrections to differential cross sections near a kinematic threshold are analysed by Dressed Gluon Exponentiation. Exploiting the factorization property of soft and collinear radiation, the dominant radiative corrections in the threshold region are resummed, yielding a renormalization-scale-invariant expression for the Sudakov exponent. The interplay between Sudakov logs and renormalons is clarified, and the necessity to resum the latter whenever power corrections are non-negligible is emphasized. The presence of power-suppressed ambiguities in the exponentiation kernel suggests that power corrections exponentiate as well. This leads to a non-perturbative factorization formula with non-trivial predictions on the structure of power corrections, which can be contrasted with the OPE. Two examples are discussed. The first is event-shape distributions in the two-jet region, where a wealth of precise data provides a strong motivation for the improved perturbative technique and an ideal situation to study had...
Experimental determination of pCo perturbation factors for plane-parallel chambers.
Kapsch, R P; Bruggmoser, G; Christ, G; Dohm, O S; Hartmann, G H; Schüle, E
2007-12-07
For plane-parallel chambers used in electron dosimetry, modern dosimetry protocols recommend a cross-calibration against a calibrated cylindrical chamber. The rationale for this is the unacceptably large (up to 3-4%) chamber-to-chamber variations of the perturbation factors (pwall)Co, which have been reported for plane-parallel chambers of a given type. In some recent publications, it was shown that this is no longer the case for modern plane-parallel chambers. The aims of the present study are to obtain reliable information about the variation of the perturbation factors for modern types of plane-parallel chambers, and-if this variation is found to be acceptably small-to determine type-specific mean values for these perturbation factors which can be used for absorbed dose measurements in electron beams using plane-parallel chambers. In an extensive multi-center study, the individual perturbation factors pCo (which are usually assumed to be equal to (pwall)Co) for a total of 35 plane-parallel chambers of the Roos type, 15 chambers of the Markus type and 12 chambers of the Advanced Markus type were determined. From a total of 188 cross-calibration measurements, variations of the pCo values for different chambers of the same type of at most 1.0%, 0.9% and 0.6% were found for the chambers of the Roos, Markus and Advanced Markus types, respectively. The mean pCo values obtained from all measurements are [Formula: see text] and [Formula: see text]; the relative experimental standard deviation of the individual pCo values is less than 0.24% for all chamber types; the relative standard uncertainty of the mean pCo values is 1.1%.
Morena, Deborah; Maestro, Nicola; Bersani, Francesca; Forni, Paolo Emanuele; Lingua, Marcello Francesco; Foglizzo, Valentina; Šćepanović, Petar; Miretti, Silvia; Morotti, Alessandro; Shern, Jack F; Khan, Javed; Ala, Ugo; Provero, Paolo; Sala, Valentina; Crepaldi, Tiziana; Gasparini, Patrizia; Casanova, Michela; Ferrari, Andrea; Sozzi, Gabriella; Chiarle, Roberto; Ponzetto, Carola; Taulli, Riccardo
2016-03-17
Embryonal Rhabdomyosarcoma (ERMS) and Undifferentiated Pleomorphic Sarcoma (UPS) are distinct sarcoma subtypes. Here we investigate the relevance of the satellite cell (SC) niche in sarcoma development by using Hepatocyte Growth Factor (HGF) to perturb the niche microenvironment. In a Pax7 wild type background, HGF stimulation mainly causes ERMS that originate from satellite cells following a process of multistep progression. Conversely, in a Pax7 null genotype ERMS incidence drops, while UPS becomes the most frequent subtype. Murine EfRMS display genetic heterogeneity similar to their human counterpart. Altogether, our data demonstrate that selective perturbation of the SC niche results in distinct sarcoma subtypes in a Pax7 lineage-dependent manner, and define a critical role for the Met axis in sarcoma initiation. Finally, our results provide a rationale for the use of combination therapy, tailored on specific amplifications and activated signaling pathways, to minimize resistance emerging from sarcomas heterogeneity.
$K_{l3}$ form factors at order $p^{6}$ of chiral perturbation theory
Post, P; 10.1007/s10052-002-0967-1
2002-01-01
This paper describes the calculation of the semileptonic K/sub l3/ decay form factors at order p/sup 6/ of chiral perturbation theory, which is the next-to-leading order correction to the well-known p/sup 4/ result achieved by Gasser and Leutwyler. At order p/sup 6/ the chiral expansion contains one- and two-loop diagrams which are discussed in detail. The irreducible two-loop graphs of the sunset topology are calculated numerically. In addition, the chiral Lagrangian L/sup (6)/ produces direct couplings with the W bosons. Due to these unknown couplings, one can always add linear terms in q /sup 2/ to the predictions of the form factor f/sub -/(q/sup 2/). For the form factor f/sub +/(q/sup 2/), this ambiguity involves even quadratic terms. Making use of the fact that the pion electromagnetic form factor involves the same q/sup 4/ counterterm, the q/sup 4/ ambiguity can be resolved. Apart from the possibility of adding an arbitrary linear term in q/sup 2/ our calculation shows that chiral perturbation theory c...
The neutron electric dipole form factor in the perturbative chiral quark model
Dib, C; Gutsche, T; Kovalenko, S; Kuckei, J; Lyubovitskij, V E; Pumsa-ard, K; Dib, Claudio; Faessler, Amand; Gutsche, Thomas; Kovalenko, Sergey; Kuckei, Jan; Lyubovitskij, Valery E.; Pumsa-ard, Kem
2006-01-01
We calculate the electric dipole form factor of the neutron in a perturbative chiral quark model, parameterizing CP-violation of generic origin by means of effective electric dipole moments of the constituent quarks and their CP-violating couplings to the chiral fields. We discuss the relation of these effective parameters to more fundamental ones such as the intrinsic electric and chromoelectric dipole moments of quarks and the Weinberg parameter. From the existing experimental upper limits on the neutron EDM we derive constraints on these CP-violating parameters.
A Perturbative QCD Analysis of the Nucleon's Pauli Form Factor F_2(Q^2)
Belitsky, A V; Yuan, F; Belitsky, Andrei V.; Ji, Xiangdong; Yuan, Feng
2003-01-01
We perform a perturbative QCD analysis of the nucleon's Pauli form factor $F_2(Q^2)$ in the asymptotically large $Q^2$ limit. We find that the leading contribution to $F_2(Q^2)$ goes like $1/Q^6$, consistent with the well-known folklore. Its coefficient is expressed in terms of an overlap integral involving the leading and subleading light-cone wave functions of the nucleon, the latter describing the quark state with one unit of orbital angular momentum. We estimate the numerical size of the coefficient and comment on the contribution from the end-point region.
Directory of Open Access Journals (Sweden)
Gaurang Mahajan
Full Text Available High-throughput experiments such as microarrays and deep sequencing provide large scale information on the pattern of gene expression, which undergoes extensive remodeling as the cell dynamically responds to varying environmental cues or has its function disrupted under pathological conditions. An important initial step in the systematic analysis and interpretation of genome-scale expression alteration involves identification of a set of perturbed transcriptional regulators whose differential activity can provide a proximate hypothesis to account for these transcriptomic changes. In the present work, we propose an unbiased and logically natural approach to transcription factor enrichment. It involves overlaying a list of experimentally determined differentially expressed genes on a background regulatory network coming from e.g. literature curation or computational motif scanning, and identifying that subset of regulators whose aggregated target set best discriminates between the altered and the unaffected genes. In other words, our methodology entails testing of all possible regulatory subnetworks, rather than just the target sets of individual regulators as is followed in most standard approaches. We have proposed an iterative search method to efficiently find such a combination, and benchmarked it on E. coli microarray and regulatory network data available in the public domain. Comparative analysis carried out on artificially generated differential expression profiles, as well as empirical factor overexpression data for M. tuberculosis, shows that our methodology provides marked improvement in accuracy of regulatory inference relative to the standard method that involves evaluating factor enrichment in an individual manner.
Mahajan, Gaurang; Mande, Shekhar C
2015-01-01
High-throughput experiments such as microarrays and deep sequencing provide large scale information on the pattern of gene expression, which undergoes extensive remodeling as the cell dynamically responds to varying environmental cues or has its function disrupted under pathological conditions. An important initial step in the systematic analysis and interpretation of genome-scale expression alteration involves identification of a set of perturbed transcriptional regulators whose differential activity can provide a proximate hypothesis to account for these transcriptomic changes. In the present work, we propose an unbiased and logically natural approach to transcription factor enrichment. It involves overlaying a list of experimentally determined differentially expressed genes on a background regulatory network coming from e.g. literature curation or computational motif scanning, and identifying that subset of regulators whose aggregated target set best discriminates between the altered and the unaffected genes. In other words, our methodology entails testing of all possible regulatory subnetworks, rather than just the target sets of individual regulators as is followed in most standard approaches. We have proposed an iterative search method to efficiently find such a combination, and benchmarked it on E. coli microarray and regulatory network data available in the public domain. Comparative analysis carried out on artificially generated differential expression profiles, as well as empirical factor overexpression data for M. tuberculosis, shows that our methodology provides marked improvement in accuracy of regulatory inference relative to the standard method that involves evaluating factor enrichment in an individual manner.
Form factors of descendant operators: Reduction to perturbed $M(2,2s+1)$ models
Lashkevich, Michael
2014-01-01
In the framework of the algebraic approach to form factors in two-dimensional integrable models of quantum field theory we consider the reduction of the sine-Gordon model to the $\\Phi_{13}$\\=/perturbation of minimal conformal models of the $M(2,2s+1)$ series. We find in an algebraic form the condition of compatibility of local operators with the reduction. We propose a construction that make it possible to obtain reduction compatible local operators in terms of screening currents. As an application we obtain exact multiparticle form factors for the compatible with the reduction conserved currents $T_{\\pm2k}$, $\\Theta_{\\pm(2k-2)}$, which correspond to the spin $\\pm(2k-1)$ integrals of motion, for any positive integer~$k$. Furthermore, we obtain all form factors of the operators $T_{2k}T_{-2l}$, which generalize the famous $T\\bar T$ operator. The construction is analytic in the $s$ parameter and, therefore, makes sense in the sine-Gordon theory.
Form factors of descendant operators: reduction to perturbed M(2,2s+1) models
Energy Technology Data Exchange (ETDEWEB)
Lashkevich, Michael [Landau Institute for Theoretical Physics,1a prospekt Akademika Semenova, 142432 Chernogolovka (Russian Federation); Moscow Institute of Physics and Technology,9 Institutsky per., 141707 Dolgoprudny (Russian Federation); Kharkevich Institute for Information Transmission Problems,19 Bolshoy Karetny per., 127994 Moscow (Russian Federation); Pugai, Yaroslav [Landau Institute for Theoretical Physics,1a prospekt Akademika Semenova, 142432 Chernogolovka (Russian Federation); Moscow Institute of Physics and Technology,9 Institutsky per., 141707 Dolgoprudny (Russian Federation)
2015-04-23
In the framework of the algebraic approach to form factors in two-dimensional integrable models of quantum field theory we consider the reduction of the sine-Gordon model to the Φ{sub 13}-perturbation of minimal conformal models of the M(2,2s+1) series. We find in an algebraic form the condition of compatibility of local operators with the reduction. We propose a construction that make it possible to obtain reduction compatible local operators in terms of screening currents. As an application we obtain exact multiparticle form factors for the compatible with the reduction conserved currents T{sub ±2k}, Θ{sub ±(2k−2)}, which correspond to the spin ±(2k−1) integrals of motion, for any positive integer k. Furthermore, we obtain all form factors of the operators T{sub 2k}T{sub −2l}, which generalize the famous TT̄ operator. The construction is analytic in the s parameter and, therefore, makes sense in the sine-Gordon theory.
Using Perturbed QR Factorizations To Solve Linear Least-Squares Problems
Energy Technology Data Exchange (ETDEWEB)
Avron, Haim; Ng, Esmond G.; Toledo, Sivan
2008-03-21
We propose and analyze a new tool to help solve sparse linear least-squares problems min{sub x} {parallel}Ax-b{parallel}{sub 2}. Our method is based on a sparse QR factorization of a low-rank perturbation {cflx A} of A. More precisely, we show that the R factor of {cflx A} is an effective preconditioner for the least-squares problem min{sub x} {parallel}Ax-b{parallel}{sub 2}, when solved using LSQR. We propose applications for the new technique. When A is rank deficient we can add rows to ensure that the preconditioner is well-conditioned without column pivoting. When A is sparse except for a few dense rows we can drop these dense rows from A to obtain {cflx A}. Another application is solving an updated or downdated problem. If R is a good preconditioner for the original problem A, it is a good preconditioner for the updated/downdated problem {cflx A}. We can also solve what-if scenarios, where we want to find the solution if a column of the original matrix is changed/removed. We present a spectral theory that analyzes the generalized spectrum of the pencil (A*A,R*R) and analyze the applications.
The electric dipole form factor of the nucleon in chiral perturbation theory to sub-leading order
Mereghetti, E.; de Vries, J.; Hockings, W. H.; Maekawa, C. M.; van Kolck, U.
2011-01-01
The electric dipole form factor (EDFF) of the nucleon stemming from the QCD (theta) over bar term and from the quark color-electric dipole moments is calculated in chiral perturbation theory to sub-leading order. This is the lowest order in which the isoscalar EDFF receives a calculable, non-analyti
Barnes, Daniel; Braxton-Gravin, Asiha; Jenkins, Jade; Ali, Halima; Punjabi, Alkesh
2013-10-01
The double-null map is the simplest symplectic map that has the generic magnetic topology of double-null divertor tokamaks. The generating function of the double-null map is given by S (x , y) = x2 /2 +y2 /2-y4/4. The equilibrium magnetic surfaces of the double-null map are calculated from the generating function. 0 1/4 gives open surfaces. The scaling of safety factor on the magnetic axis, q0, with map parameter k is calculated. The scaling of root mean square deviation of energy on the q95 surface with map parameter k is calculated and taken as the estimate of magnetic asymmetry to represent the magnetic perturbation. The results of this work will be reported. These results are used to calculate heteroclinic tangles of the separatrix of double-null map. This work is supported by grants DE-FG02-01ER54624, DE-FG02-04ER54793, and DE-FG02-07ER54937.
Loss of the Homeodomain Transcription Factor Prep1 Perturbs Adult Hematopoiesis in the Bone Marrow.
Directory of Open Access Journals (Sweden)
Kentaro Yoshioka
Full Text Available Prep1, a TALE-family homeodomain transcription factor, has been demonstrated to play a critical role in embryonic hematopoiesis, as its insufficiency caused late embryonic lethality associated with defective hematopoiesis and angiogenesis. In the present study, we generated hematopoietic- and endothelial cell-specific Prep1-deficient mice and demonstrated that expression of Prep1 in the hematopoietic cell compartment is not essential for either embryonic or adult hematopoiesis, although its absence causes significant hematopoietic abnormalities in the adult bone marrow. Loss of Prep1 promotes cell cycling of hematopoietic stem/progenitor cells (HSPC, leading to the expansion of the HSPC pool. Prep1 deficiency also results in the accumulation of lineage-committed progenitors, increased monocyte/macrophage differentiation and arrested erythroid maturation. Maturation of T cells and B cells is also perturbed in Prep-deficient mice. These findings provide novel insight into the pleiotropic roles of Prep1 in adult hematopoiesis that were unrecognized in previous studies using germline Prep1 hypomorphic mice.
Transition Form Factors: A Unique Opportunity to Connect Non-Perturbative Strong Interactions to QCD
Energy Technology Data Exchange (ETDEWEB)
Gothe, Ralf W. [University of South Carolina, Columbia, SC (United States)
2014-01-01
Meson-photoproduction measurements and their reaction-amplitude analyses can establish more sensitively, and in some cases in an almost model-independent way, nucleon excitations and non-resonant reaction amplitudes. However, to investigate the strong interaction from explored — where meson-cloud degrees of freedom contribute substantially to the baryon structure — to still unexplored distance scales — where quark degrees of freedom dominate and the transition from dressed to current quarks occurs — we depend on experiments that allow us to measure observables that are probing this evolving non-perturbative QCD regime over its full range. Elastic and transition form factors are uniquely suited to trace this evolution by measuring elastic electron scattering and exclusive single-meson and double-pion electroproduction cross sections off the nucleon. These exclusive measurements will be extended to higher momentum transfers with the energy-upgraded CEBAF beam at JLab to study the quark degrees of freedom, where their strong interaction is responsible for the ground and excited nucleon state formations. After establishing unprecedented high-precision data, the imminent next challenge is a high-quality analysis to extract these relevant electrocoupling parameters for various resonances that then can be compared to state-of-the-art models and QCD-based calculations. Recent results will demonstrate the status of the analysis and of their theoretical descriptions, and an experimental and theoretical outlook will highlight what shall and may be achieved in the new era of the 12-GeV upgraded transition form factor program.
Hannon, Kevin P; Li, Chenyang; Evangelista, Francesco A
2016-05-28
We report an efficient implementation of a second-order multireference perturbation theory based on the driven similarity renormalization group (DSRG-MRPT2) [C. Li and F. A. Evangelista, J. Chem. Theory Comput. 11, 2097 (2015)]. Our implementation employs factorized two-electron integrals to avoid storage of large four-index intermediates. It also exploits the block structure of the reference density matrices to reduce the computational cost to that of second-order Møller-Plesset perturbation theory. Our new DSRG-MRPT2 implementation is benchmarked on ten naphthyne isomers using basis sets up to quintuple-ζ quality. We find that the singlet-triplet splittings (ΔST) of the naphthyne isomers strongly depend on the equilibrium structures. For a consistent set of geometries, the ΔST values predicted by the DSRG-MRPT2 are in good agreements with those computed by the reduced multireference coupled cluster theory with singles, doubles, and perturbative triples.
Energy Technology Data Exchange (ETDEWEB)
Zink, K; Wulff, J [Institut fuer Medizinische Physik und Strahlenschutz-IMPS, University of Applied Sciences Giessen-Friedberg, Wiesenstr. 14, D-35390 Giessen (Germany)], E-mail: klemens.zink@tg.fh-giessen.de
2009-04-21
Current dosimetry protocols recommend the use of plane-parallel ionization chambers for the dosimetry of clinical electron beams. The necessary perturbation corrections p{sub wall} and p{sub cav} are assumed to be unity, independent of the depth of measurement and the energy of the primary electrons. To verify these assumptions detailed Monte Carlo studies of a Roos chamber in clinical electron beams with energies in the range of 6-21 MeV are performed at different depths in water and analyzed in terms of Spencer-Attix cavity theory. Separate simulations for the perturbation corrections p{sub wall} and p{sub cav} indicate quite different properties of both correction factors with depth. Dose as well as fluence calculations show a nearly depth-independent wall correction factor for a shift of the Roos chamber {delta}z = -0.017 cm toward the focus. This value is in good agreement with the positioning recommendation given in all dosimetry protocols. Regarding the fluence perturbation p{sub cav} the simulation of the electron fluence inside the air cavity in comparison to water unambiguously reveals an in-scattering of low energy electrons, despite the fact, that the cavity is 'well guarded'. For depths beyond the reference depth z{sub ref} this effect is superimposed by an increased loss of primary electrons from the beam resulting in p{sub cav} > 1. This effect is largest for low electron energies but present for all electron energies involved in this study. Based on the different depth dependences of p{sub wall} and p{sub cav} it is possible to choose a chamber shift {delta}z in a way to minimize the depth dependence of the overall perturbation factor p. For the Roos chamber this shift is {delta}z = -0.04 cm independent of electron energy.
Zink, K; Wulff, J
2009-04-21
Current dosimetry protocols recommend the use of plane-parallel ionization chambers for the dosimetry of clinical electron beams. The necessary perturbation corrections p(wall) and p(cav) are assumed to be unity, independent of the depth of measurement and the energy of the primary electrons. To verify these assumptions detailed Monte Carlo studies of a Roos chamber in clinical electron beams with energies in the range of 6-21 MeV are performed at different depths in water and analyzed in terms of Spencer-Attix cavity theory. Separate simulations for the perturbation corrections p(wall) and p(cav) indicate quite different properties of both correction factors with depth. Dose as well as fluence calculations show a nearly depth-independent wall correction factor for a shift of the Roos chamber Deltaz = -0.017 cm toward the focus. This value is in good agreement with the positioning recommendation given in all dosimetry protocols. Regarding the fluence perturbation p(cav) the simulation of the electron fluence inside the air cavity in comparison to water unambiguously reveals an in-scattering of low energy electrons, despite the fact, that the cavity is 'well guarded'. For depths beyond the reference depth z(ref) this effect is superimposed by an increased loss of primary electrons from the beam resulting in p(cav) > 1. This effect is largest for low electron energies but present for all electron energies involved in this study. Based on the different depth dependences of p(wall) and p(cav) it is possible to choose a chamber shift Deltaz in a way to minimize the depth dependence of the overall perturbation factor p. For the Roos chamber this shift is Deltaz = -0.04 cm independent of electron energy.
Ray, Sumanta; Maulik, Ujjwal
2016-12-20
Detecting perturbation in modular structure during HIV-1 disease progression is an important step to understand stage specific infection pattern of HIV-1 virus in human cell. In this article, we proposed a novel methodology on integration of multiple biological information to identify such disruption in human gene module during different stages of HIV-1 infection. We integrate three different biological information: gene expression information, protein-protein interaction information and gene ontology information in single gene meta-module, through non negative matrix factorization (NMF). As the identified metamodules inherit those information so, detecting perturbation of these, reflects the changes in expression pattern, in PPI structure and in functional similarity of genes during the infection progression. To integrate modules of different data sources into strong meta-modules, NMF based clustering is utilized here. Perturbation in meta-modular structure is identified by investigating the topological and intramodular properties and putting rank to those meta-modules using a rank aggregation algorithm. We have also analyzed the preservation structure of significant GO terms in which the human proteins of the meta-modules participate. Moreover, we have performed an analysis to show the change of coregulation pattern of identified transcription factors (TFs) over the HIV progression stages.
Energy Technology Data Exchange (ETDEWEB)
Broemmel, D. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Regensburg Univ. (Germany). Inst. fuer Physik 1 - Theoretische Physik; Horsley, R.; Zanotti, J. [Edinburgh Univ. (United Kingdom). School of Physics; Morozov, S.M. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Nakamura, Y.; Pleiter, D. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Schierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Stueben, H. [Konrad-Zuse-Zentrum fuer Informationstechnik Berlin (ZIB) (Germany)
2007-10-15
We present first results from the QCDSF collaboration for the kaon semileptonic decay form factors at zero momentum transfer, using two flavours of non-perturbatively O(a)-improved Wilson quarks. A lattice determination of these form factors is of particular interest to improve the accuracy on the CKM matrix element vertical stroke V{sub us} vertical stroke. Calculations are performed on lattices with lattice spacing of about 0.08 fm with different values of light and strange quark masses, which allows us to extrapolate to chiral limit. Employing double ratio techniques, we are able to get small statistical errors. (orig.)
Hannon, Kevin P; Evangelista, Francesco A
2016-01-01
We report an efficient implementation of a second-order multireference perturbation theory based on the driven similarity renormalization group (DSRG-MRPT2) [C. Li and F. A. Evangelista, J. Chem. Theory Comput. 11, 2097 (2015)]. Our implementation employs factorized two-electron integrals to avoid storage of large four-index intermediates. It also exploits the block structure of the reference density matrices to reduce the computational cost to that of second-order M{\\o}ller$-$Plesset perturbation theory. Our new DSRG-MRPT2 implementation is benchmarked on ten naphthyne isomers using basis sets up to quintuple-$\\zeta$ quality. We find that the singlet-triplet splittings ($\\Delta_\\text{ST}$) of the naphthyne isomers strongly depend on the equilibrium structures. For a consistent set of geometries, the $\\Delta_\\text{ST}$ values predicted by the DSRG-MRPT2 are in good agreements with those computed by the reduced multireference coupled cluster theory with singles, doubles, and perturbative triples.
Flisgen, Thomas; van Rienen, Ursula
2016-01-01
External quality factors are significant quantities to describe losses via waveguide ports in radio frequency resonators. The current contribution presents a novel approach to determine external quality factors by means of a two-step procedure: First, a state-space model for the lossless radio frequency structure is generated and its model order is reduced. Subsequently, a perturbation method is applied on the reduced model so that external losses are accounted for. The advantage of this approach results from the fact that the challenges in dealing with lossy systems are shifted to the reduced order model. This significantly saves computational costs. The present paper provides a short overview on existing methods to compute external quality factors. Then, the novel approach is introduced and validated in terms of accuracy and computational time by means of commercial software.
Indian Academy of Sciences (India)
Bhaskar Jyoti Hazarika; D K choudhury
2015-01-01
We use variationally improved perturbation theory (VIPT) for calculating the elastic form factors and charge radii of , $D_{s}$, $B$, $B_{s}$ and $B_{c}$ mesons in a quantum chromodynamics (QCD)-inspired potential model. For that, we use linear-cum-Coulombic potential and opt the Coulombic part first as parent and then the linear part as parent. The results show that charge radii and form factors are quite small for the Coulombic parent compared to the linear parent. Also, the analysis leads to a lower as well as upper bounds on the four-momentum transfer 2, hinting at a workable range of 2 within this approach, which may be useful in future experimental analyses. Comparison of both the options shows that the linear parent is the better option.
Perturbative Corrections to $\\Lambda_b \\to \\Lambda$ Form Factors from QCD Light-Cone Sum Rules
Wang, Yu-Ming
2015-01-01
We compute radiative corrections to $\\Lambda_b \\to \\Lambda$ from factors, at next-to-leading logarithmic accuracy, from QCD light-cone sum rules with $\\Lambda_b$-baryon distribution amplitudes. Employing the diagrammatic approach factorization of the vacuum-to-$\\Lambda_b$-baryon correlation function is justified at leading power in $\\Lambda/m_b$, with the aid of the method of regions. Hard functions entering the factorization formulae are identical to the corresponding matching coefficients of heavy-to-light currents from QCD onto soft-collinear effective theory. The universal jet function from integrating out the hard-collinear fluctuations exhibits richer structures compared with the one involved in the factorization expressions of the vacuum-to-$B$-meson correlation function. Based upon the QCD resummation improved sum rules we observe that the perturbative corrections at ${\\cal O}(\\alpha_s)$ shift the $\\Lambda_b \\to \\Lambda$ from factors at large recoil significantly and the dominant contribution originat...
Energy Technology Data Exchange (ETDEWEB)
Yoon, Hyunjin; Ansong, Charles; McDermott, Jason E.; Gritsenko, Marina A.; Smith, Richard D.; Heffron, Fred; Adkins, Joshua N.
2011-06-28
Background: Systemic bacterial infections are highly regulated and complex processes that are orchestrated by numerous virulence factors. Genes that are coordinately controlled by the set of regulators required for systemic infection are potentially required for pathogenicity. Results: In this study we present a systems biology approach in which sample-matched multi-omic measurements of fourteen virulence-essential regulator mutants were coupled with computational network analysis to efficiently identify Salmonella virulence factors. Immunoblot experiments verified network-predicted virulence factors and a subset was determined to be secreted into the host cytoplasm, suggesting that they are virulence factors directly interacting with host cellular components. Two of these, SrfN and PagK2, were required for full mouse virulence and were shown to be translocated independent of either of the type III secretion systems in Salmonella or the type III injectisome-related flagellar mechanism. Conclusions: Integrating multi-omic datasets from Salmonella mutants lacking virulence regulators not only identified novel virulence factors but also defined a new class of translocated effectors involved in pathogenesis. The success of this strategy at discovery of known and novel virulence factors suggests that the approach may have applicability for other bacterial pathogens.
Directory of Open Access Journals (Sweden)
Heffron Fred
2011-06-01
Full Text Available Abstract Background Systemic bacterial infections are highly regulated and complex processes that are orchestrated by numerous virulence factors. Genes that are coordinately controlled by the set of regulators required for systemic infection are potentially required for pathogenicity. Results In this study we present a systems biology approach in which sample-matched multi-omic measurements of fourteen virulence-essential regulator mutants were coupled with computational network analysis to efficiently identify Salmonella virulence factors. Immunoblot experiments verified network-predicted virulence factors and a subset was determined to be secreted into the host cytoplasm, suggesting that they are virulence factors directly interacting with host cellular components. Two of these, SrfN and PagK2, were required for full mouse virulence and were shown to be translocated independent of either of the type III secretion systems in Salmonella or the type III injectisome-related flagellar mechanism. Conclusions Integrating multi-omic datasets from Salmonella mutants lacking virulence regulators not only identified novel virulence factors but also defined a new class of translocated effectors involved in pathogenesis. The success of this strategy at discovery of known and novel virulence factors suggests that the approach may have applicability for other bacterial pathogens.
Perturbations can enhance qauntum search
Bae, J; Bae, Joonwoo; Kwon, Younghun
2003-01-01
In general, a quantum algorithm wants to avoid decoherence or perturbation, since such factors may cause errors in the algorithm. In this letter, we will supply the answer to the interesting question: can the factors seemingly harmful to a quantum algorithm(for example, perturbations) enhance the algorithm? We show that some perturbations to the generalized quantum search Hamiltonian can reduce the running time and enhance the success probability. We also provide the narrow bound to the perturbation which can be beneficial to quantum search. In addition, we show that the error induced by a perturbation on the Farhi and Gutmann Hamiltonian can be corrected by another perturbation.
Kozma, Gady
2012-01-01
We proved earlier that every measurable function on the circle, after a uniformly small perturbation, can be written as a power series (i.e. a series of exponentials with positive frequencies), which converges almost everywhere. Here we show that this result is basically sharp: the perturbation cannot be made smooth or even H\\"older. We discuss also a similar problem for perturbations with lacunary spectrum.
Perturbations of fibroblast growth factors 19 and 21 in type 2 diabetes.
Roesch, Stephen L; Styer, Amanda M; Wood, G Craig; Kosak, Zachary; Seiler, Jamie; Benotti, Peter; Petrick, Anthony T; Gabrielsen, Jon; Strodel, William E; Gerhard, Glenn S; Still, Christopher D; Argyropoulos, George
2015-01-01
Fibroblast growth factors 19 and 21 (FGF19 and FGF21) have been implicated, independently, in type 2 diabetes (T2D) but it is not known if their circulating levels correlate with each other or whether the associated hepatic signaling mechanisms that play a role in glucose metabolism are dysregulated in diabetes. We used a cross-sectional, case/control, experimental design involving Class III obese patients undergoing Roux-en-Y bariatric surgery (RYGB), and measured FGF19 and FGF21 serum levels and hepatic gene expression (mRNA) in perioperative liver wedge biopsies. We found that T2D patients had lower FGF19 and higher FGF21 serum levels. The latter was corroborated transcriptionally, whereby, FGF21, as well as CYP7A1, β-Klotho, FGFR4, HNF4α, and glycogen synthase, but not of SHP or FXR mRNA levels in liver biopsies were higher in T2D patients that did not remit diabetes after RYGB surgery, compared to T2D patients that remitted diabetes after RYGB surgery or did not have diabetes. In a Phenome-wide association analysis using 205 clinical variables, higher FGF21 serum levels were associated with higher glucose levels and various cardiometabolic disease phenotypes. When serum levels of FGF19 were 500 mg/mL, 91% of patients had diabetes. These data suggest that FGF19/FGF21 circulating levels and hepatic gene expression of the associated signaling pathway are significantly dysregulated in type 2 diabetes.
Perturbations of fibroblast growth factors 19 and 21 in type 2 diabetes.
Directory of Open Access Journals (Sweden)
Stephen L Roesch
Full Text Available Fibroblast growth factors 19 and 21 (FGF19 and FGF21 have been implicated, independently, in type 2 diabetes (T2D but it is not known if their circulating levels correlate with each other or whether the associated hepatic signaling mechanisms that play a role in glucose metabolism are dysregulated in diabetes. We used a cross-sectional, case/control, experimental design involving Class III obese patients undergoing Roux-en-Y bariatric surgery (RYGB, and measured FGF19 and FGF21 serum levels and hepatic gene expression (mRNA in perioperative liver wedge biopsies. We found that T2D patients had lower FGF19 and higher FGF21 serum levels. The latter was corroborated transcriptionally, whereby, FGF21, as well as CYP7A1, β-Klotho, FGFR4, HNF4α, and glycogen synthase, but not of SHP or FXR mRNA levels in liver biopsies were higher in T2D patients that did not remit diabetes after RYGB surgery, compared to T2D patients that remitted diabetes after RYGB surgery or did not have diabetes. In a Phenome-wide association analysis using 205 clinical variables, higher FGF21 serum levels were associated with higher glucose levels and various cardiometabolic disease phenotypes. When serum levels of FGF19 were 500 mg/mL, 91% of patients had diabetes. These data suggest that FGF19/FGF21 circulating levels and hepatic gene expression of the associated signaling pathway are significantly dysregulated in type 2 diabetes.
Directory of Open Access Journals (Sweden)
Emmanuelle Deniaud
Full Text Available BACKGROUND: The ubiquitous transcription factor Sp1 regulates the expression of a vast number of genes involved in many cellular functions ranging from differentiation to proliferation and apoptosis. Sp1 expression levels show a dramatic increase during transformation and this could play a critical role for tumour development or maintenance. Although Sp1 deregulation might be beneficial for tumour cells, its overexpression induces apoptosis of untransformed cells. Here we further characterised the functional and transcriptional responses of untransformed cells following Sp1 overexpression. METHODOLOGY AND PRINCIPAL FINDINGS: We made use of wild-type and DNA-binding-deficient Sp1 to demonstrate that the induction of apoptosis by Sp1 is dependent on its capacity to bind DNA. Genome-wide expression profiling identified genes involved in cancer, cell death and cell cycle as being enriched among differentially expressed genes following Sp1 overexpression. In silico search to determine the presence of Sp1 binding sites in the promoter region of modulated genes was conducted. Genes that contained Sp1 binding sites in their promoters were enriched among down-regulated genes. The endogenous sp1 gene is one of the most down-regulated suggesting a negative feedback loop induced by overexpressed Sp1. In contrast, genes containing Sp1 binding sites in their promoters were not enriched among up-regulated genes. These results suggest that the transcriptional response involves both direct Sp1-driven transcription and indirect mechanisms. Finally, we show that Sp1 overexpression led to a modified expression of G1/S transition regulatory genes such as the down-regulation of cyclin D2 and the up-regulation of cyclin G2 and cdkn2c/p18 expression. The biological significance of these modifications was confirmed by showing that the cells accumulated in the G1 phase of the cell cycle before the onset of apoptosis. CONCLUSION: This study shows that the binding to DNA
Directory of Open Access Journals (Sweden)
Stephen Pankavich
2015-02-01
Full Text Available Many mesoscopic N-atom systems derive their structural and dynamical properties from processes coupled across multiple scales in space and time. That is, they simultaneously deform or display collective behaviors, while experiencing atomic scale vibrations and collisions. Due to the large number of atoms involved and the need to simulate over long time periods of biological interest, traditional computational tools, like molecular dynamics, are often infeasible for such systems. Hence, in the current review article, we present and discuss two recent multiscale methods, stemming from the N-atom formulation and an underlying scale separation, that can be used to study such systems in a friction-dominated regime: multiscale perturbation theory and multiscale factorization. These novel analytic foundations provide a self-consistent approach to yield accurate and feasible long-time simulations with atomic detail for a variety of multiscale phenomena, such as viral structural transitions and macromolecular self-assembly. As such, the accuracy and efficiency of the associated algorithms are demonstrated for a few representative biological systems, including satellite tobacco mosaic virus (STMV and lactoferrin.
Perturbations of planar algebras
Das, Paramita; Gupta, Ved Prakash
2010-01-01
We introduce the concept of {\\em weight} of a planar algebra $P$ and construct a new planar algebra referred as the {\\em perturbation of $P$} by the weight. We establish a one-to-one correspondence between pivotal structures on 2-categories and perturbations of planar algebras by weights. To each bifinite bimodule over $II_1$-factors, we associate a {\\em bimodule planar algebra} bimodule corresponds naturally with sphericality of the bimodule planar algebra. As a consequence of this, we reproduce an extension of Jones' theorem (of associating 'subfactor planar algebras' to extremal subfactors). Conversely, given a bimodule planar algebra, we construct a bifinite bimodule whose associated bimodule planar algebra is the one which we start with using perturbations and Jones-Walker-Shlyakhtenko-Kodiyalam-Sunder method of reconstructing an extremal subfactor from a subfactor planar algebra. We show that the perturbation class of a bimodule planar algebra contains a unique spherical unimodular bimodule planar algeb...
Clustering under Perturbation Resilience
Balcan, Maria Florina
2011-01-01
Recently, Bilu and Linial \\cite{BL} formalized an implicit assumption often made when choosing a clustering objective: that the optimum clustering to the objective should be preserved under small multiplicative perturbations to distances between points. They showed that for max-cut clustering it is possible to circumvent NP-hardness and obtain polynomial-time algorithms for instances resilient to large (factor $O(\\sqrt{n})$) perturbations, and subsequently Awasthi et al. \\cite{ABS10} considered center-based objectives, giving algorithms for instances resilient to O(1) factor perturbations. In this paper, we greatly advance this line of work. For the $k$-median objective, we present an algorithm that can optimally cluster instances resilient to $(1 + \\sqrt{2})$-factor perturbations, solving an open problem of Awasthi et al.\\cite{ABS10}. We additionally give algorithms for a more relaxed assumption in which we allow the optimal solution to change in a small $\\epsilon$ fraction of the points after perturbation. ...
Kubis, B
2001-01-01
We analyze the electromagnetic form factors of the nucleon to fourth order in relativistic baryon chiral perturbation theory. We employ the recently proposed infrared regularization scheme and show that the convergence of the chiral expansion is improved as compared to the heavy-fermion approach. We also discuss the inclusion of vector mesons and obtain an accurate description of all four-nucleon form factors for momentum transfer squared up to Q sup 2 approx =0.4 GeV sup 2.
Constantinou, Martha; Frezzotti, Roberto; Lubicz, Vittorio; Panagopoulos, Haralambos; Skouroupathis, Apostolos; Stylianou, Fotos
2010-01-01
In this work we calculate the corrections to the amputated Green's functions of 4-fermion operators, in 1-loop Lattice Perturbation theory. One of the novel aspects of our calculations is that they are carried out to O(a^2) (a: lattice spacing). We employ the Wilson/clover action for massless fermions (also applicable for the twisted mass action in the chiral limit) and a family of Symanzik improved actions for gluons. Our calculations have been carried out in a general covariant gauge. Results have been obtained for several popular choices of values for the Symanzik coefficients. While our Green's function calculations regard any pointlike 4-fermion operators which do not mix with lower dimension ones, we pay particular attention to DF=2 operators, both Parity Conserving and Parity Violating (F: flavour). We compute the perturbative renormalization constants for a complete basis of 4-fermion operators and we study their mixing pattern. For some of the actions considered here, even O(a^0) results did not exis...
Wang, Chen-Wen; Yang, Ling; Zhu, Chaoyuan; Yu, Jian-Guo; Lin, Sheng-Hsien
2014-08-01
Damped harmonic oscillators are utilized to calculate Franck-Condon factors within displaced harmonic oscillator approximation. This is practically done by scaling unperturbed Hessian matrix that represents local modes of force constants for molecule in gaseous phase, and then by diagonalizing perturbed Hessian matrix it results in direct modification of Huang-Rhys factors which represent normal modes of solute molecule perturbed by solvent environment. Scaling parameters are empirically introduced for simulating absorption and fluorescence spectra of an isolated solute molecule in solution. The present method is especially useful for simulating vibronic spectra of polycyclic aromatic hydrocarbon molecules in which hydrogen atom vibrations in solution can be scaled equally, namely the same scaling factor being applied to all hydrogen atoms in polycyclic aromatic hydrocarbons. The present method is demonstrated in simulating solvent enhanced X 1Ag ↔ A1B1u absorption and fluorescence spectra of perylene (medium-sized polycyclic aromatic hydrocarbon) in benzene solution. It is found that one of six active normal modes v10 is actually responsible to the solvent enhancement of spectra observed in experiment. Simulations from all functionals (TD) B3LYP, (TD) B3LYP35, (TD) B3LYP50, and (TD) B3LYP100 draw the same conclusion. Hence, the present method is able to adequately reproduce experimental absorption and fluorescence spectra in both gas and solution phases.
Scherrer, Arne; Sebastiani, Daniel; Gross, E K U; Vuilleumier, Rodolphe
2015-01-01
The nuclear velocity perturbation current-density theory (NVPT) for vibrational circular dichroism (VCD) is derived from the exact factorization of the electron-nuclear wave function. This new formalism offers an exact starting point to include correction terms to the Born-Oppenheimer (BO) form of the molecular wave function, similarly to the complete-adiabatic approximation. The corrections depend on a small parameter that, in a classical treatment of the nuclei, is identified as the nuclear velocity. Apart from proposing a rigorous basis for the NVPT, we show that the rotational strength, related to the intensity of the VCD signal, contain a new contribution beyond-BO that can be evaluated with the NVPT and that only arises when the exact factorization approach is employed. Numerical results are presented for chiral and non-chiral systems to test the validity of the approach.
Cosmological density perturbations from perturbed couplings
Tsujikawa, S
2003-01-01
The density perturbations generated when the inflaton decay rate is perturbed by a light scalar field $\\chi$ are studied. By explicitly solving the perturbation equations for the system of two scalar fields and radiation, we show that even in low energy-scale inflation nearly scale-invariant spectra of scalar perturbations with an amplitude set by observations are obtained through the conversion of $\\chi$ fluctuations into adiabatic density perturbations. We demonstrate that the spectra depend on the average decay rate of the inflaton & on the inflaton fluctuations. We then apply this new mechanism to string cosmologies & generalized Einstein theories and discuss the conditions under which scale-invariant spectra are possible.
Irvine, Peter J.; Boucher, Olivier; Kravitz, Ben; Alterskjær, Kari; Cole, Jason N. S.; Ji, Duoying; Jones, Andy; Lunt, Daniel J.; Moore, John C.; Muri, Helene; Niemeier, Ulrike; Robock, Alan; Singh, Balwinder; Tilmes, Simone; Watanabe, Shingo; Yang, Shuting; Yoon, Jin-Ho
2014-07-01
Climate model studies of the consequences of solar geoengineering are central to evaluating whether such approaches may help to reduce the harmful impacts of global warming. In this study we compare the sunshade solar geoengineering response of a perturbed parameter ensemble (PPE) of the Hadley Centre Coupled Model version 3 (HadCM3) with a multimodel ensemble (MME) by analyzing the G1 experiment from the Geoengineering Model Intercomparison Project (GeoMIP). The PPE only perturbed a small number of parameters and shares a common structure with the unperturbed HadCM3 model, and so the additional weight the PPE adds to the robustness of the common climate response features in the MME is minor. However, analysis of the PPE indicates some of the factors that drive the spread within the MME. We isolate the role of global mean temperature biases for both ensembles and find that these biases have little effect on the ensemble spread in the hydrological response but do reduce the spread in surface air temperature response, particularly at high latitudes. We investigate the role of the preindustrial climatology and find that biases here are likely a key source of ensemble spread at the zonal and grid cell level. The role of vegetation, and its response to elevated CO2 concentrations through the CO2 physiological effect and changes in plant productivity, is also investigated and proves to have a substantial effect on the terrestrial hydrological response to solar geoengineering and to be a major source of variation within the GeoMIP ensemble.
Herbert, Andrew P; Deakin, Jon A; Schmidt, Christoph Q; Blaum, Bärbel S; Egan, Claire; Ferreira, Viviana P; Pangburn, Michael K; Lyon, Malcolm; Uhrín, Dusan; Barlow, Paul N
2007-06-29
A common single nucleotide polymorphism in the factor H gene predisposes to age-related macular degeneration. Factor H blocks the alternative pathway of complement on self-surfaces bearing specific polyanions, including the glycosaminoglycan chains of proteoglycans. Factor H also binds C-reactive protein, potentially contributing to noninflammatory apoptotic processes. The at risk sequence contains His (rather than Tyr) at position 402 (384 in the mature protein), in the seventh of the 20 complement control protein (CCP) modules (CCP7) of factor H. We expressed both His(402) and Tyr(402) variants of CCP7, CCP7,8, and CCP6-8. We determined structures of His(402) and Tyr(402) CCP7 and showed them to be nearly identical. The side chains of His/Tyr(402) have similar, solvent-exposed orientations far from interfaces with CCP6 and -8. Tyr(402) CCP7 bound significantly more tightly than His(402) CCP7 to a heparin affinity column as well as to defined-length sulfated heparin oligosaccharides employed in gel mobility shift assays. This observation is consistent with the position of the 402 side chain on the edge of one of two glycosaminoglycan-binding surface patches on CCP7 that we inferred on the basis of chemical shift perturbation studies with a sulfated heparin tetrasaccharide. According to surface plasmon resonance measurements, Tyr(402) CCP6-8 binds significantly more tightly than His(402) CCP6-8 to immobilized C-reactive protein. The data support a causal link between H402Y and age-related macular degeneration in which variation at position 402 modulates the response of factor H to age-related changes in the glycosaminoglycan composition and apoptotic activity of the macula.
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
Su, Fang; Yang, Yi-Bo; Zhuang, Ci
2008-01-01
The charmless bottom meson decays are systematically investigated based on an approximate six quark operator effective Hamiltonian from perturbative QCD. It is shown that within this framework the naive QCD factorization method provides a simple way to evaluate the hadronic matrix elements of two body mesonic decays. The singularities caused by on mass-shell quark propagator and gluon exchanging interaction are appropriately treated. Such a simple framework allows us to make theoretical predictions for the decay amplitudes with reasonable input parameters. The resulting theoretical predictions for all the branching ratios and CP asymmetries in the charmless $B^0, B^+, B_s\\to \\pi\\pi, \\pi K, KK$ decays are found to be consistent with the current experimental data except for a few decay modes. The observed large branching ratio in $B\\to \\pi^0\\pi^0$ decay remains a puzzle though the predicted branching ratio may be significantly improved by considering the large vertex corrections in the effective Wilson coeffici...
The ambiguity in ray perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Snieder, R.; Sambridge, M. [Utrecht Univ., Utrecht (Netherlands)]|[Cambridge Univ., Cambridge (United Kingdom)
1993-12-01
Ray perturbation theory is concerned with the change in ray paths and travel times due to changes in the slowness model or the end-point conditions of rays. Several different formulations of ray perturbation theory have been developed. Even for the same physical problem different perturbation equations have been derived. The reason for this is that ray perturbation theory contains a fundamental ambiguity. One can move a point along a curve without changing the shape of the curve. This means that the mapping from a reference curve to a perturbed curve is not uniquely defined, because on may associated a point on the reference curve with different points on the perturbed curve. The mapping that is used is usually defined implicitly by the choice of the coordinate system or the independent parameter. In this paper, a fomalism is developed where one can specify explicitly the mapping from the reference curve to the perturbed curve by choosing a stretch factor that relates increments in arc length along the reference curve and the perturbed curve. This is incorporated in a theory that is accurate to first order in the ray position and to second order in the travel time. The second order travel time perturbation describes the effect of changes in the position of the ray on the travel time. In the formulation of this paper, paraxial ray perturbations, slowness perturbations, and pure ray bending are treated in a uniform fashion. This may be very useful in nonlinear tomographic inversions which include earthquake relocation.
Brane World Cosmological Perturbations
Casali, A G; Wang, B; Casali, Adenauer G.; Abdalla, Elcio; Wang, Bin
2004-01-01
We consider a brane world and its gravitational linear perturbations. We present a general solution of the perturbations in the bulk and find the complete perturbed junction conditions for generic brane dynamics. We also prove that (spin 2) gravitational waves in the great majority of cases can only arise in connection with a non-vanishing anisotropic stress. This has far reaching consequences for inflation in the brane world. Moreover, contrary to the case of the radion, perturbations are stable.
Polar Factorization and Perturbation Bound for Row (Column)Skew Symmetric Matrix%行（列）反对称矩阵的极分解及其扰动界
Institute of Scientific and Technical Information of China (English)
袁晖坪
2014-01-01
The author studied the polar factorization and generalized inverse and perturbation bound of row (column ) skew symmetric matrix. In addition, the formula of the polar factorization and generalized inverse of row (column)skew symmetric matrix were given,which makes calculation easier.And some perturbation bounds of the polar factorization of row (column)skew symmetric matrix were also presented.%考虑行(列)反对称矩阵的极分解、广义逆和扰动界，给出了行(列)反对称矩阵的极分解和广义逆的计算公式，并给出了行(列)反对称矩阵极分解的系列扰动界。结果表明，所给方法既减少了计算量与存储量，又不会降低数值精度。
Automated Lattice Perturbation Theory
Energy Technology Data Exchange (ETDEWEB)
Monahan, Christopher
2014-11-01
I review recent developments in automated lattice perturbation theory. Starting with an overview of lattice perturbation theory, I focus on the three automation packages currently "on the market": HiPPy/HPsrc, Pastor and PhySyCAl. I highlight some recent applications of these methods, particularly in B physics. In the final section I briefly discuss the related, but distinct, approach of numerical stochastic perturbation theory.
Perturbative tests of non-perturbative counting
Dabholkar, Atish; Gomes, João
2010-03-01
We observe that a class of quarter-BPS dyons in mathcal{N} = 4 theories with charge vector ( Q, P) and with nontrivial values of the arithmetic duality invariant I := gcd( Q∧ P) are nonperturbative in one frame but perturbative in another frame. This observation suggests a test of the recently computed nonperturbative partition functions for dyons with nontrivial values of the arithmetic invariant. For all values of I, we show that the nonperturbative counting yields vanishing indexed degeneracy for this class of states everywhere in the moduli space in precise agreement with the perturbative result.
Generalized Supersymmetric Perturbation Theory
Institute of Scientific and Technical Information of China (English)
B. G(o)n(ǖ)l
2004-01-01
@@ Using the basic ingredient of supersymmetry, a simple alternative approach is developed to perturbation theory in one-dimensional non-relativistic quantum mechanics. The formulae for the energy shifts and wavefunctions do not involve tedious calculations which appear in the available perturbation theories. The model applicable in the same form to both the ground state and excited bound states, unlike the recently introduced supersymmetric perturbation technique which, together with other approaches based on logarithmic perturbation theory, are involved within the more general framework of the present formalism.
Density matrix perturbation theory.
Niklasson, Anders M N; Challacombe, Matt
2004-05-14
An orbital-free quantum perturbation theory is proposed. It gives the response of the density matrix upon variation of the Hamiltonian by quadratically convergent recursions based on perturbed projections. The technique allows treatment of embedded quantum subsystems with a computational cost scaling linearly with the size of the perturbed region, O(N(pert.)), and as O(1) with the total system size. The method allows efficient high order perturbation expansions, as demonstrated with an example involving a 10th order expansion. Density matrix analogs of Wigner's 2n+1 rule are also presented.
Institute of Scientific and Technical Information of China (English)
王建国; 曹广益; 朱新坚
2008-01-01
We investigate the best performance for linear feedback control systems in the case that plant uncertainty is to beconsidered. First, we define an average integral square criterion of tracking error over a class of stochastic model errors. Byutilizing spectral factorization to minimize the performance index, we derive an optimal controller design method and furtherstudy best performance in the presence of stochastic perturbation. The results can be used to evaluate optimal performancein practical control system designs.
Perturbative Topological Field Theory
Dijkgraaf, Robbert
We give a review of the application of perturbative techniques to topological quantum field theories, in particular three-dimensional Chern-Simons-Witten theory and its various generalizations. To this end we give an introduction to graph homology and homotopy algebras and the work of Vassiliev and Kontsevich on perturbative knot invariants.
Perturbing supersymmetric black hole
Onozawa, H; Mishima, T; Ishihara, H; Onozawa, Hisashi; Okamura, Takashi; Mishima, Takashi; Ishihara, Hideki
1996-01-01
An investigation of the perturbations of the Reissner-Nordstr\\"{o}m black hole in the N=2 supergravity is presented. In the extreme case, the black hole responds to the perturbation of each field in the same manner. This is possibly because we can match the modes of the graviton, gravitino, and photon using supersymmetry transformations.
Frame independent cosmological perturbations
Energy Technology Data Exchange (ETDEWEB)
Prokopec, Tomislav; Weenink, Jan, E-mail: t.prokopec@uu.nl, E-mail: j.g.weenink@uu.nl [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Leuvenlaan 4, 3585 CE Utrecht (Netherlands)
2013-09-01
We compute the third order gauge invariant action for scalar-graviton interactions in the Jordan frame. We demonstrate that the gauge invariant action for scalar and tensor perturbations on one physical hypersurface only differs from that on another physical hypersurface via terms proportional to the equation of motion and boundary terms, such that the evolution of non-Gaussianity may be called unique. Moreover, we demonstrate that the gauge invariant curvature perturbation and graviton on uniform field hypersurfaces in the Jordan frame are equal to their counterparts in the Einstein frame. These frame independent perturbations are therefore particularly useful in relating results in different frames at the perturbative level. On the other hand, the field perturbation and graviton on uniform curvature hypersurfaces in the Jordan and Einstein frame are non-linearly related, as are their corresponding actions and n-point functions.
Cosmological perturbations through a simple bounce
Allen, L E
2004-01-01
We present a detailed study of a simple scalar field model that yields non-singular cosmological solutions. We study both the qualitative dynamics of the homogeneous and isotropic background and the evolution of inhomogeneous linear perturbations. We calculate the spectrum of perturbations generated on super-Hubble scales during the collapse phase from initial vacuum fluctuations on small scales and then evolve these numerically through the bounce. We show there is a gauge that remains well-defined throughout the bounce, even though other commonly used gauges break down. We show that the comoving curvature perturbation calculated during the collapse phase provides a good estimate of the resulting large scale adiabatic perturbation in the expanding phase while the Bardeen metric potential is dominated by what becomes a decaying mode after the bounce. We show that a power-law collapse phase with scale factor proportional $(-t)^{2/3}$ can yield a scale-invariant spectrum of adiabatic scalar perturbations in the ...
Rong, Shu-Jun; Liu, Qiu-Yu
2012-04-01
The puma model on the basis of the Lorentz and CPT violation may bring an economical interpretation to the conventional neutrinos oscillation and part of the anomalous oscillations. We study the effect of the perturbation to the puma model. In the case of the first-order perturbation which keeps the (23) interchange symmetry, the mixing matrix element Ue3 is always zero. The nonzero mixing matrix element Ue3 is obtained in the second-order perturbation that breaks the (23) interchange symmetry.
Introduction to perturbation techniques
Nayfeh, Ali H
2011-01-01
Similarities, differences, advantages and limitations of perturbation techniques are pointed out concisely. The techniques are described by means of examples that consist mainly of algebraic and ordinary differential equations. Each chapter contains a number of exercises.
Perturbations around black holes
Wang, B
2005-01-01
Perturbations around black holes have been an intriguing topic in the last few decades. They are particularly important today, since they relate to the gravitational wave observations which may provide the unique fingerprint of black holes' existence. Besides the astrophysical interest, theoretically perturbations around black holes can be used as testing grounds to examine the proposed AdS/CFT and dS/CFT correspondence.
Perturbations and quantum relaxation
Kandhadai, Adithya
2016-01-01
We investigate whether small perturbations can cause relaxation to quantum equilibrium over very long timescales. We consider in particular a two-dimensional harmonic oscillator, which can serve as a model of a field mode on expanding space. We assume an initial wave function with small perturbations to the ground state. We present evidence that the trajectories are highly confined so as to preclude relaxation to equilibrium even over very long timescales. Cosmological implications are briefly discussed.
Institute of Scientific and Technical Information of China (English)
RONG Shu-Jun; LIU Qiu-Yu
2012-01-01
The puma model on the basis of the Lorentz and CPT violation may bring an economical interpretation to the conventional neutrinos oscillation and part of the anomalous oscillations.We study the effect of the perturbation to the puma model.In the case of the first-order perturbation which keeps the (23) interchange symmetry,the mixing matrix element Ue3 is always zero.The nonzero mixing matrix element Ue3 is obtained in the second-order perturbation that breaks the (23) interchange symmetry.%The puma model on the basis of the Lorentz and CPT violation may bring an economical interpretation to the conventional neutrinos oscillation and part of the anomalous oscillations. We study the effect of the perturbation to the puma model. In the case of the first-order perturbation which keeps the (23) interchange symmetry, the mixing matrix element Ue3 is always zero. The nonzero mixing matrix element Ue3 is obtained in the second-order perturbation that breaks the (23) interchange symmetry.
Perturbative loop corrections and nonlocal gravity
Maggiore, Michele
2016-01-01
Nonlocal gravity has been shown to provide a phenomenologically viable infrared modification of GR. A natural question is whether the required nonlocality can emerge from perturbative quantum loop corrections due to light particles. We show that this is not the case. For the value of the mass scale of the non-local models required by cosmology, the perturbative form factors obtained from the loop corrections, in the present cosmological epoch, are in the regime where they are local. The mechanism behind the generation of the required nonlocality must be more complex, possibly related to strong infrared effects and non-perturbative mass generation for the conformal mode.
Tuning Leaky Nanocavity Resonances - Perturbation Treatment
Shlafman, Michael; Salzman, Joseph
2010-01-01
Adiabatic frequency tuning of finite-lifetime-nanocavity electromagnetic modes affects also their quality-factor (Q). Perturbative Q change resulting from (real) frequency tuning, is a controllable parameter. Here, the influence of dielectric constant modulation (DCM) on cavity resonances is presented, by first order perturbation analysis for a 3D cavity with radiation losses. Semi-analytical expressions for DCM induced cavity mode frequency and Q changes are derived. The obtained results are in good agreement with numerical calculations.
Renormalized Cosmological Perturbation Theory
Crocce, M
2006-01-01
We develop a new formalism to study nonlinear evolution in the growth of large-scale structure, by following the dynamics of gravitational clustering as it builds up in time. This approach is conveniently represented by Feynman diagrams constructed in terms of three objects: the initial conditions (e.g. perturbation spectrum), the vertex (describing non-linearities) and the propagator (describing linear evolution). We show that loop corrections to the linear power spectrum organize themselves into two classes of diagrams: one corresponding to mode-coupling effects, the other to a renormalization of the propagator. Resummation of the latter gives rise to a quantity that measures the memory of perturbations to initial conditions as a function of scale. As a result of this, we show that a well-defined (renormalized) perturbation theory follows, in the sense that each term in the remaining mode-coupling series dominates at some characteristic scale and is subdominant otherwise. This is unlike standard perturbatio...
Institute of Scientific and Technical Information of China (English)
杨亚非; 袁幸伟
2011-01-01
主要围绕火星探测器在地球上空200 km处飞离地球开始一直到火星入轨点的转移轨道段轨道设计所做的轨道任务分析、摄动因素分析及近地轨道火星探测器姿态所受干扰力矩进行理论与仿真研究.一般情况下,火星探测器受到的摄动力与中心天体引力相比是很小的,但摄动力的长期累积作用不可忽视.轨道摄动研究已经成为轨道确定、观测预报、轨道改进和轨道设计等工作的基础,有利于寻找最佳的轨道修正位置,可显著减少轨道修正次数,从而降低火星探测器的燃料消耗.%Orbit tasks and perturbing factors about an orbit design of a Mars prober flying from an orbit at 200km above the Earth to an injection point of a target planet (Mars) are analyzed and simulated. Perturbing moments influenced on attitude of the Mars prober running on the Near-Earth orbit are studied and simulated.Usually, the perturbing force acting on the Mars prober is too small compared with a gravitation of a primary celestial body, but long-term cumulative effect of the perturbing force is great significant, so that it isn't neglected. The study on orbit perturbation already became a research fundament of orbit determination, orbit observation, orbit prediction, orbit improvement and orbit design; it is convenient to find the optimal position of orbit correction in order to decrease orbit adjustment frequency to reduce fuel consumption of Mars prober.
DEFF Research Database (Denmark)
jora, Renata; Schechter, Joseph; Naeem Shahid, M.
2009-01-01
We study the effects of the perturbation which violates the permutation symmetry of three Majorana neutrinos but preserves the well known (23) interchange symmetry. This is done in the presenceof an arbitrary Majorana phase which serves to insure the degeneracy of the three neutrinos at the unper...
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.
Instantaneous stochastic perturbation theory
Lüscher, Martin
2015-01-01
A form of stochastic perturbation theory is described, where the representative stochastic fields are generated instantaneously rather than through a Markov process. The correctness of the procedure is established to all orders of the expansion and for a wide class of field theories that includes all common formulations of lattice QCD.
High order multiplication perturbation method for singular perturbation problems
Institute of Scientific and Technical Information of China (English)
张文志; 黄培彦
2013-01-01
This paper presents a high order multiplication perturbation method for sin-gularly perturbed two-point boundary value problems with the boundary layer at one end. By the theory of singular perturbations, the singularly perturbed two-point boundary value problems are first transformed into the singularly perturbed initial value problems. With the variable coeﬃcient dimensional expanding, the non-homogeneous ordinary dif-ferential equations (ODEs) are transformed into the homogeneous ODEs, which are then solved by the high order multiplication perturbation method. Some linear and nonlinear numerical examples show that the proposed method has high precision.
Scalar perturbations of nonsingular nonrotating black holes in conformal gravity
Toshmatov, Bobir; Bambi, Cosimo; Ahmedov, Bobomurat; Stuchlík, Zdeněk; Schee, Jan
2017-09-01
We study scalar and electromagnetic perturbations of a family of nonsingular nonrotating black hole spacetimes that are solutions in a large class of conformally invariant theories of gravity. The effective potential for scalar perturbations depends on the exact form of the scaling factor. Electromagnetic perturbations do not feel the scaling factor, and the corresponding quasinormal mode spectrum is the same as in the Schwarzschild metric. We find that these black hole metrics are stable under scalar and electromagnetic perturbations. Assuming that the quasinormal mode spectrum for scalar perturbations is not too different from that for gravitational perturbations, we can expect that the calculation of the quasinormal mode spectrum and the observation with gravitational wave detectors of quasinormal modes from astrophysical black holes can constrain the scaling factor and test these solutions.
Aspects of perturbative unitarity
Anselmi, Damiano
2016-07-01
We reconsider perturbative unitarity in quantum field theory and upgrade several arguments and results. The minimum assumptions that lead to the largest time equation, the cutting equations and the unitarity equation are identified. Using this knowledge and a special gauge, we give a new, simpler proof of perturbative unitarity in gauge theories and generalize it to quantum gravity, in four and higher dimensions. The special gauge interpolates between the Feynman gauge and the Coulomb gauge without double poles. When the Coulomb limit is approached, the unphysical particles drop out of the cuts and the cutting equations are consistently projected onto the physical subspace. The proof does not extend to nonlocal quantum field theories of gauge fields and gravity, whose unitarity remains uncertain.
Aspects of perturbative unitarity
Anselmi, Damiano
2016-01-01
We reconsider perturbative unitarity in quantum field theory and upgrade several arguments and results. The minimum assumptions that lead to the largest time equation, the cutting equations and the unitarity equation are identified. Using this knowledge and a special gauge, we give a new, simpler proof of perturbative unitarity in gauge theories and generalize it to quantum gravity, in four and higher dimensions. The special gauge interpolates between the Feynman gauge and the Coulomb gauge without double poles. When the Coulomb limit is approached, the unphysical particles drop out of the cuts and the cutting equations are consistently projected onto the physical subspace. The proof does not extend to nonlocal quantum field theories of gauge fields and gravity, whose unitarity remains uncertain.
Degenerate Density Perturbation Theory
Palenik, Mark C
2016-01-01
Fractional occupation numbers can be used in density functional theory to create a symmetric Kohn-Sham potential, resulting in orbitals with degenerate eigenvalues. We develop the corresponding perturbation theory and apply it to a system of $N_d$ degenerate electrons in a harmonic oscillator potential. The order-by-order expansions of both the fractional occupation numbers and unitary transformations within the degenerate subspace are determined by the requirement that a differentiable map exists connecting the initial and perturbed states. Using the X$\\alpha$ exchange-correlation (XC) functional, we find an analytic solution for the first-order density and first through third-order energies as a function of $\\alpha$, with and without a self-interaction correction. The fact that the XC Hessian is not positive definite plays an important role in the behavior of the occupation numbers.
Large Spin Perturbation Theory
Alday, Luis F
2016-01-01
We consider conformal field theories around points of large twist degeneracy. Examples of this are theories with weakly broken higher spin symmetry and perturbations around generalised free fields. At the degenerate point we introduce twist conformal blocks. These are eigenfunctions of certain quartic operators and encode the contribution, to a given four-point correlator, of the whole tower of intermediate operators with a given twist. As we perturb around the degenerate point, the twist degeneracy is lifted. In many situations this breaking is controlled by inverse powers of the spin. In such cases the twist conformal blocks can be decomposed into a sequence of functions which we systematically construct. Decomposing the four-point correlator in this basis turns crossing symmetry into an algebraic problem. Our method can be applied to a wide spectrum of conformal field theories in any number of dimensions and at any order in the breaking parameter. As an example, we compute the spectrum of various theories ...
Cosmological Perturbations in Antigravity
Oltean, Marius
2014-01-01
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. We show that despite the necessarily wrong-signed kinetic term of the dilaton in the full action, its cosmological solutions are stable at the perturbative level.
Perturbatively charged holographic disorder
O'Keeffe, Daniel K
2015-01-01
Within the framework of holography applied to condensed matter physics, we study a model of perturbatively charged disorder in D=4 dimensions. Starting from initially uncharged AdS_4, a randomly fluctuating boundary chemical potential is introduced by turning on a bulk gauge field parameterized by a disorder strength and a characteristic scale k_0. Accounting for gravitational backreaction, we construct an asymptotically AdS solution perturbatively in the disorder strength. The disorder averaged geometry displays unphysical divergences in the deep interior. We explain how to remove these divergences and arrive at a well behaved solution. The disorder averaged DC conductivity is calculated and is found to contain a correction to the AdS result. The correction appears at second order in the disorder strength and scales inversely with k_0. We discuss the extension to a system with a finite initial charge density. The disorder averaged DC conductivity may be calculated by adopting a technique developed for hologr...
Degenerate density perturbation theory
Palenik, Mark C.; Dunlap, Brett I.
2016-09-01
Fractional occupation numbers can be used in density functional theory to create a symmetric Kohn-Sham potential, resulting in orbitals with degenerate eigenvalues. We develop the corresponding perturbation theory and apply it to a system of Nd degenerate electrons in a harmonic oscillator potential. The order-by-order expansions of both the fractional occupation numbers and unitary transformations within the degenerate subspace are determined by the requirement that a differentiable map exists connecting the initial and perturbed states. Using the X α exchange-correlation (XC) functional, we find an analytic solution for the first-order density and first- through third-order energies as a function of α , with and without a self-interaction correction. The fact that the XC Hessian is not positive definite plays an important role in the behavior of the occupation numbers.
Maier, K H; Grawe, H; Kluge, H
1981-01-01
The g-factor measurements of the ground state and an isomeric level in /sup 217/Ac using the DPAD method with alpha -decay are described. The results of gamma -ray g-factor measurements for the isomer and a tentative decay scheme produced by alpha - gamma and gamma - gamma coincidence experiments are also presented. An analysis of the alpha - particle angular distributions suggests that nuclear deformation affects the observed anisotropy. (13 refs).
Ooguri, H; Ooguri, Hirosi; Yin, Zheng
1996-01-01
These lecture notes are based on a course on string theories given by Hirosi Ooguri in the first week of TASI 96 Summer School at Boulder, Colorado. It is an introductory course designed to provide students with minimum knowledge before they attend more advanced courses on non-perturbative aspects of string theories in the School. The course consists of five lectures: 1. Bosonic String, 2. Toroidal Compactifications, 3. Superstrings, 4. Heterotic Strings, and 5. Orbifold Compactifications.
Covariant Bardeen perturbation formalism
Vitenti, S. D. P.; Falciano, F. T.; Pinto-Neto, N.
2014-05-01
In a previous work we obtained a set of necessary conditions for the linear approximation in cosmology. Here we discuss the relations of this approach with the so-called covariant perturbations. It is often argued in the literature that one of the main advantages of the covariant approach to describe cosmological perturbations is that the Bardeen formalism is coordinate dependent. In this paper we will reformulate the Bardeen approach in a completely covariant manner. For that, we introduce the notion of pure and mixed tensors, which yields an adequate language to treat both perturbative approaches in a common framework. We then stress that in the referred covariant approach, one necessarily introduces an additional hypersurface choice to the problem. Using our mixed and pure tensors approach, we are able to construct a one-to-one map relating the usual gauge dependence of the Bardeen formalism with the hypersurface dependence inherent to the covariant approach. Finally, through the use of this map, we define full nonlinear tensors that at first order correspond to the three known gauge invariant variables Φ, Ψ and Ξ, which are simultaneously foliation and gauge invariant. We then stress that the use of the proposed mixed tensors allows one to construct simultaneously gauge and hypersurface invariant variables at any order.
Asymptotic analysis of perturbed dust cosmologies to second order
Uggla, Claes; Wainwright, John
2013-08-01
Nonlinear perturbations of Friedmann-Lemaitre cosmologies with dust and a cosmological constant Λ >0 have recently attracted considerable attention. In this paper our first goal is to compare the evolution of the first and second order perturbations by determining their asymptotic behaviour at late times in ever-expanding models. We show that in the presence of spatial curvature K or a cosmological constant, the density perturbation approaches a finite limit both to first and second order, but the rate of approach depends on the model, being power law in the scale factor if Λ >0 but logarithmic if Λ =0 and K0 the decaying mode does not die away, i.e. it contributes on an equal footing as the growing mode to the asymptotic expression for the density perturbation. On the other hand, the future asymptotic regime of the Einstein-de Sitter universe (K=Λ =0) is completely different, as exemplified by the density perturbation which diverges; moreover, the second order perturbation diverges faster than the first order perturbation, which suggests that the Einstein-de Sitter universe is unstable to perturbations, and that the perturbation series do not converge towards the future. We conclude that the presence of spatial curvature or a cosmological constant stabilizes the perturbations. Our second goal is to derive an explicit expression for the second order density perturbation that can be used to study the effects of including a cosmological constant and spatial curvature.
Perturbation semigroup of matrix algebras
Neumann, N.; Suijlekom, W.D. van
2016-01-01
In this article we analyze the structure of the semigroup of inner perturbations in noncommutative geometry. This perturbation semigroup is associated to a unital associative *-algebra and extends the group of unitary elements of this *-algebra. We compute the perturbation semigroup for all matrix algebras.
Non-perturbative Heavy Quark Effective Theory
DEFF Research Database (Denmark)
Della Morte, Michele; Heitger, Jochen; Simma, Hubert;
2015-01-01
We review a lattice strategy how to non-perturbatively determine the coefficients in the HQET expansion of all components of the heavy-light axial and vector currents, including 1/m_h-corrections. We also discuss recent preliminary results on the form factors parameterizing semi-leptonic B-decays...
Non-perturbative Heavy Quark Effective Theory
DEFF Research Database (Denmark)
Della Morte, Michele; Heitger, Jochen; Simma, Hubert
2015-01-01
We review a lattice strategy how to non-perturbatively determine the coefficients in the HQET expansion of all components of the heavy-light axial and vector currents, including 1/m_h-corrections. We also discuss recent preliminary results on the form factors parameterizing semi-leptonic B-decays...
Beane, Silas R; Vuorinen, Aleksi
2009-01-01
We present a new formulation of effective field theory for nucleon-nucleon (NN) interactions which treats pion interactions perturbatively, and we offer evidence that the expansion converges satisfactorily to third order in the expansion, which we have computed analytically for s and d wave NN scattering. Starting with the Kaplan-Savage-Wise (KSW) expansion about the nontrivial fixed point corresponding to infinite NN scattering length, we cure the convergence problems with that theory by summing to all orders the singular short distance part of the pion tensor interaction. This method makes possible a host of high precision analytic few-body calculations in nuclear physics.
Non-Perturbative Renormalization
Mastropietro, Vieri
2008-01-01
The notion of renormalization is at the core of several spectacular achievements of contemporary physics, and in the last years powerful techniques have been developed allowing to put renormalization on a firm mathematical basis. This book provides a self-consistent and accessible introduction to the sophisticated tools used in the modern theory of non-perturbative renormalization, allowing an unified and rigorous treatment of Quantum Field Theory, Statistical Physics and Condensed Matter models. In particular the first part of this book is devoted to Constructive Quantum Field Theory, providi
Non-perturbative QCD and hadron physics
Cobos-Martínez, J. J.
2016-10-01
A brief exposition of contemporary non-perturbative methods based on the Schwinger-Dyson (SDE) and Bethe-Salpeter equations (BSE) of Quantum Chromodynamics (QCD) and their application to hadron physics is given. These equations provide a non-perturbative continuum formulation of QCD and are a powerful and promising tool for the study of hadron physics. Results on some properties of hadrons based on this approach, with particular attention to the pion distribution amplitude, elastic, and transition electromagnetic form factors, and their comparison to experimental data are presented.
Perturbative renormalization of the electric field correlator
Christensen, C
2016-01-01
The momentum diffusion coefficient of a heavy quark in a hot QCD plasma can be extracted as a transport coefficient related to the correlator of two colour-electric fields dressing a Polyakov loop. We determine the perturbative renormalization factor for a particular lattice discretization of this correlator within Wilson's SU(3) gauge theory, finding a ~12% NLO correction for values of the bare coupling used in the current generation of simulations. The impact of this result on existing lattice determinations is commented upon, and a possibility for non-perturbative renormalization through the gradient flow is pointed out.
Perturbative renormalization of the electric field correlator
Directory of Open Access Journals (Sweden)
C. Christensen
2016-04-01
Full Text Available The momentum diffusion coefficient of a heavy quark in a hot QCD plasma can be extracted as a transport coefficient related to the correlator of two colour-electric fields dressing a Polyakov loop. We determine the perturbative renormalization factor for a particular lattice discretization of this correlator within Wilson's SU(3 gauge theory, finding a ∼12% NLO correction for values of the bare coupling used in the current generation of simulations. The impact of this result on existing lattice determinations is commented upon, and a possibility for non-perturbative renormalization through the gradient flow is pointed out.
Perturbative renormalization of the electric field correlator
Christensen, C.; Laine, M.
2016-04-01
The momentum diffusion coefficient of a heavy quark in a hot QCD plasma can be extracted as a transport coefficient related to the correlator of two colour-electric fields dressing a Polyakov loop. We determine the perturbative renormalization factor for a particular lattice discretization of this correlator within Wilson's SU(3) gauge theory, finding a ∼ 12% NLO correction for values of the bare coupling used in the current generation of simulations. The impact of this result on existing lattice determinations is commented upon, and a possibility for non-perturbative renormalization through the gradient flow is pointed out.
Sudakov Safety in Perturbative QCD
Larkoski, Andrew J; Thaler, Jesse
2015-01-01
Traditional calculations in perturbative quantum chromodynamics (pQCD) are based on an order-by-order expansion in the strong coupling $\\alpha_s$. Observables that are calculable in this way are known as "safe". Recently, a class of unsafe observables was discovered that do not have a valid $\\alpha_s$ expansion but are nevertheless calculable in pQCD using all-orders resummation. These observables are called "Sudakov safe" since singularities at each $\\alpha_s$ order are regulated by an all-orders Sudakov form factor. In this letter, we give a concrete definition of Sudakov safety based on conditional probability distributions, and we study a one-parameter family of momentum sharing observables that interpolate between the safe and unsafe regimes. The boundary between these regimes is particularly interesting, as the resulting distribution can be understood as the ultraviolet fixed point of a generalized fragmentation function, yielding a leading behavior that is independent of $\\alpha_s$.
Gauge Invariant Cosmological Perturbation Theory
Durrer, R
1993-01-01
After an introduction to the problem of cosmological structure formation, we develop gauge invariant cosmological perturbation theory. We derive the first order perturbation equations of Einstein's equations and energy momentum ``conservation''. Furthermore, the perturbations of Liouville's equation for collisionless particles and Boltzmann's equation for Compton scattering are worked out. We fully discuss the propagation of photons in a perturbed Friedmann universe, calculating the Sachs--Wolfe effect and light deflection. The perturbation equations are extended to accommodate also perturbations induced by seeds. With these general results we discuss some of the main aspects of the texture model for the formation of large scale structure in the Universe (galaxies, clusters, sheets, voids). In this model, perturbations in the dark matter are induced by texture seeds. The gravitational effects of a spherically symmetric collapsing texture on dark matter, baryonic matter and photons are calculated in first orde...
Elementary Theorems Regarding Blue Isocurvature Perturbations
Chung, Daniel J H
2015-01-01
Blue CDM-photon isocurvature perturbations are attractive in terms of observability and may be typical from the perspective of generic mass relations in supergravity. We present and apply three theorems useful for blue isocurvature perturbations arising from linear spectator scalar fields. In the process, we give a more precise formula for the blue spectrum associated with the work of 0904.3800, which can in a parametric corner give a factor of O(10) correction. We explain how a conserved current associated with Peccei-Quinn symmetry plays a crucial role and explicitly plot several example spectra including the breaks in the spectra. We also resolve a little puzzle arising from a naive multiplication of isocurvature expression that sheds light on the gravitational imprint of the adiabatic perturbations on the fields responsible for blue isocurvature fluctuations.
Direct perturbation method for perturbed complex Burgers equation
Institute of Scientific and Technical Information of China (English)
Cheng Xue-Ping; Lin Ji; Yao Jian-Ming
2009-01-01
So far, Lou's direct perturbation method has been applied successfully to solve the nonlinear Schrōdinger equa-tion(NLSE) hierarchy, such as the NLSE, the coupled NLSE, the critical NLSE, and the derivative NLSE. But to our knowledge, this method for other types of perturbed nonlinear evolution equations has still been lacking. In this paper, Lou's direct perturbation method is applied to the study of perturbed complex Burgers equation. By this method, we calculate not only the zero-order adiabatic solution, but also the first order modification.
Introduction to perturbation methods
Holmes, M
1995-01-01
This book is an introductory graduate text dealing with many of the perturbation methods currently used by applied mathematicians, scientists, and engineers. The author has based his book on a graduate course he has taught several times over the last ten years to students in applied mathematics, engineering sciences, and physics. The only prerequisite for the course is a background in differential equations. Each chapter begins with an introductory development involving ordinary differential equations. The book covers traditional topics, such as boundary layers and multiple scales. However, it also contains material arising from current research interest. This includes homogenization, slender body theory, symbolic computing, and discrete equations. One of the more important features of this book is contained in the exercises. Many are derived from problems of up- to-date research and are from a wide range of application areas.
Applications of Cosmological Perturbation Theory
Christopherson, Adam J
2011-01-01
Cosmological perturbation theory is crucial for our understanding of the universe. The linear theory has been well understood for some time, however developing and applying the theory beyond linear order is currently at the forefront of research in theoretical cosmology. This thesis studies the applications of perturbation theory to cosmology and, specifically, to the early universe. Starting with some background material introducing the well-tested 'standard model' of cosmology, we move on to develop the formalism for perturbation theory up to second order giving evolution equations for all types of scalar, vector and tensor perturbations, both in gauge dependent and gauge invariant form. We then move on to the main result of the thesis, showing that, at second order in perturbation theory, vorticity is sourced by a coupling term quadratic in energy density and entropy perturbations. This source term implies a qualitative difference to linear order. Thus, while at linear order vorticity decays with the expan...
Applications Of Chiral Perturbation Theory
Mohta, V
2005-01-01
Effective field theory techniques are used to describe the spectrum and interactions of hadrons. The mathematics of classical field theory and perturbative quantum field theory are reviewed. The physics of effective field theory and, in particular, of chiral perturbation theory and heavy baryon chiral perturbation theory are also reviewed. The geometry underlying heavy baryon chiral perturbation theory is described in detail. Results by Coleman et. al. in the physics literature are stated precisely and proven. A chiral perturbation theory is developed for a multiplet containing the recently- observed exotic baryons. A small coupling expansion is identified that allows the calculation of self-energy corrections to the exotic baryon masses. Opportunities in lattice calculations are discussed. Chiral perturbation theory is used to study the possibility of two multiplets of exotic baryons mixed by quark masses. A new symmetry constraint on reduced partial widths is identified. Predictions in the literature based ...
Xu, Wen-Ping; Yi, Min; Li, Qian-Qian; Zhou, Wei-Ping; Cong, Wen-Ming; Yang, Yuan; Ning, Bei-Fang; Yin, Chuan; Huang, Zhao-Wei; Wang, Jian; Qian, Hui; Jiang, Cai-Feng; Chen, Yue-Xiang; Xia, Chun-Yan; Wang, Hong-Yang; Zhang, Xin; Xie, Wei-Fen
2013-12-01
MicroRNA 370 (miR-370) is located within the DLK1/DIO3 imprinting region on human chromosome 14, which has been identified as a cancer-associated genomic region. However, the role of miR-370 in malignances remains controversial. Here, we report that miR-370 was repressed in human hepatocellular carcinoma (HCC) tissues and hepatoma cell lines. Using gain-of-function and loss-of-function experiments, we demonstrated that miR-370 inhibited the malignant phenotype of HCC cells in vitro. Overexpression of miR-370 inhibited growth and metastasis of HCC cells in vivo. Moreover, the RNA-binding protein, LIN28A, was identified as a direct functional target of miR-370, which, in turn, blocked the biogenesis of miR-370 by binding to its precursor. LIN28A also mediated the suppressive effects of miR-370 on migration and invasion of HCC cells by post-transcriptionally regulating RelA/p65, which is an important effector of the canonical nuclear factor kappa B (NF-κB) pathway. Interleukin-6 (IL-6), a well-known NF-κB downstream inflammatory molecule, reduced miR-370 but increased LIN28A levels in HCC. Furthermore, miR-370 levels were inversely correlated with LIN28A and IL-6 messenger RNA (mRNA) levels, whereas LIN28A mRNA expression was positively correlated with IL-6 expression in human HCC samples. Interestingly, reduction of miR-370 expression was associated with the development of HCC in rats, as well as with aggressive tumor behavior and short survival in HCC patients. These data demonstrate the involvement of a novel regulatory circuit consisting of miR-370, LIN28A, RelA/p65 and IL-6 in HCC progression. Manipulating this feedback loop may have beneficial effect in HCC treatment. © 2013 by the American Association for the Study of Liver Diseases.
Cosmological perturbations in massive bigravity
Energy Technology Data Exchange (ETDEWEB)
Lagos, Macarena; Ferreira, Pedro G., E-mail: m.lagos13@imperial.ac.uk, E-mail: p.ferreira1@physics.ox.ac.uk [Astrophysics, University of Oxford, DWB, Keble road, Oxford OX1 3RH (United Kingdom)
2014-12-01
We present a comprehensive analysis of classical scalar, vector and tensor cosmological perturbations in ghost-free massive bigravity. In particular, we find the full evolution equations and analytical solutions in a wide range of regimes. We show that there are viable cosmological backgrounds but, as has been found in the literature, these models generally have exponential instabilities in linear perturbation theory. However, it is possible to find stable scalar cosmological perturbations for a very particular choice of parameters. For this stable subclass of models we find that vector and tensor perturbations have growing solutions. We argue that special initial conditions are needed for tensor modes in order to have a viable model.
Characterizing regulatory path motifs in integrated networks using perturbational data
Joshi, Anagha Madhusudan; Van Parys, Thomas; de Peer, Yves Van; Michoel, Tom
2010-01-01
We introduce Pathicular http://bioinformatics.psb.ugent.be/software/details/Pathicular, a Cytoscape plugin for studying the cellular response to perturbations of transcription factors by integrating perturbational expression data with transcriptional, protein-protein and phosphorylation networks. Pathicular searches for 'regulatory path motifs', short paths in the integrated physical networks which occur significantly more often than expected between transcription factors and their targets in...
Inversion of the perturbation series
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Colima, Colima (Mexico); Fernandez, Francisco M [INIFTA (Conicet, UNLP), Division Quimica Teorica, Diag 113 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2008-01-18
We investigate the inversion of the perturbation series and its resummation, and prove that it is related to a recently developed parametric perturbation theory. Results for some illustrative examples show that in some cases series reversion may improve the accuracy of the results.
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....
Path integral for inflationary perturbations
Prokopec, T.; Rigopoulos, G.
2010-01-01
The quantum theory of cosmological perturbations in single-field inflation is formulated in terms of a path integral. Starting from a canonical formulation, we show how the free propagators can be obtained from the well-known gauge-invariant quadratic action for scalar and tensor perturbations, and
Ma, Ai-Jun; Wang, Wen-Fei; Xiao, Zhen-Jun
2016-01-01
In this paper, we study the $B_{(s)} \\to (D_{(s)},\\bar{D}_{(s)}) \\rho \\to (D_{(s)}, \\bar{D}_{(s)})\\pi \\pi$ decays by employing a framework for the quasi-two-body decays in the perturbative QCD(PQCD) factorization approach. We use the two-pion distribution amplitudes $\\Phi_{\\pi\\pi}$, which contains both resonant and nonresonant contributions from the pion pair to explain the final-state interactions between the pions in the resonant regions. We found that (a) for the four $B\\to (\\bar{D}^0,D^-) \\rho \\to (\\bar{D}^0,D^-) \\pi\\pi$ and $B_s \\to D_s^- \\rho^+ \\to D_s^- \\pi^+\\pi^0$ decays, the PQCD predictions for their branching ratios can be as large as $10^{-4}-10^{-2}$; (b) for other ten considered decays, the PQCD predictions for their decay rates are around $10^{-8}$ to $10^{-5}$ mainly due to strong CKM suppressions; and (c) the PQCD predictions based on the quasi-two-body and the two-body framework agree well with each other, and also be consistent with currently available experimental measurements.
Junction conditions of cosmological perturbations
Tomita, K
2004-01-01
The behavior of perturbations is studied in cosmological models which consist of two different homogeneous regions connected in a spherical shell boundary. The junction conditions for the metric perturbations and the displacements of the shell boundary are analyzed and the surface densities of the perturbed energy and momentum in the shell are derived, using Mukohyama's gauge-invariant formalism and the Israel discontinuity condition. In both homogeneous regions the perturbations of scalar, vector and tensor types are expanded using the 3-dimensional harmonic functions, but the model coupling among them is caused in the shell by the inhomogeneity. By treating the perturbations with odd and even parities separately, it is found, however, that we can have consistent displacements and surface densities for given metric parturbations
Perturbations in Massive Gravity Cosmology
Crisostomi, Marco; Pilo, Luigi
2012-01-01
We study cosmological perturbations for a ghost free massive gravity theory formulated with a dynamical extra metric that is needed to massive deform GR. In this formulation FRW background solutions fall in two branches. In the dynamics of perturbations around the first branch solutions, no extra degree of freedom with respect to GR ispresent at linearized level, likewise what is found in the Stuckelberg formulation of massive gravity where the extra metric isflat and non dynamical. In the first branch, perturbations are probably strongly coupled. On the contrary, for perturbations around the second branch solutions all expected degrees of freedom propagate. While tensor and vector perturbations of the physical metric that couples with matter follow closely the ones of GR, scalars develop an exponential Jeans-like instability on sub-horizon scales. On the other hand, around a de Sitter background there is no instability. We argue that one could get rid of the instabilities by introducing a mirror dark matter ...
Multiplicative perturbations of local -semigroups
Indian Academy of Sciences (India)
Chung-Cheng Kuo
2015-02-01
In this paper, we establish some left and right multiplicative perturbation theorems concerning local -semigroups when the generator of a perturbed local -semigroup $S(\\cdot)$ may not be densely defined and the perturbation operator is a bounded linear operator from $\\overline{D(A)}$ into () such that = on $\\overline{D(A)}$, which can be applied to obtain some additive perturbation theorems for local -semigroups in which is a bounded linear operator from $[D(A)]$ into () such that = on $\\overline{D(A)}$. We also show that the perturbations of a (local) -semigroup $S(\\cdot)$ are exponentially bounded (resp., norm continuous, locally Lipschitz continuous, or exponentially Lipschitz continuous) if $S(\\cdot)$ is.
Non-perturbative quark mass renormalization
Capitani, S.; Luescher, M.; Sint, S.; Sommer, R.; Weisz, P.; Wittig, H.
1998-01-01
We show that the renormalization factor relating the renormalization group invariant quark masses to the bare quark masses computed in lattice QCD can be determined non-perturbatively. The calculation is based on an extension of a finite-size technique previously employed to compute the running coupling in quenched QCD. As a by-product we obtain the $\\Lambda$--parameter in this theory with completely controlled errors.
Combined perturbation bounds:Ⅱ.Polar decompositions
Institute of Scientific and Technical Information of China (English)
2007-01-01
In this paper,we study the perturbation bounds for the polar decomposition A=QH where Q is unitary and H is Hermitian.The optimal （asymptotic） bounds obtained in previous works for the unitary factor,the Hermitian factor and singular values of A areσr2||ΔQ||F2≤||ΔA||F2, 1/2||ΔH||F2≤||ΔA||F2 and ||Δ∑||F2≤||ΔA||F2,respectively,where∑=diag（σ1,σ2,...,σr,0,...,0） is the singular value matrix of A andσr denotes the smallest nonzero singular value.Here we present some new combined （asymptotic） perturbation boundsσr2||ΔQ||F2+1/2||ΔH||F2≤||ΔA||F2 andσr2||ΔQ||F2+||Δ∑||F2≤||ΔA||F2 which are optimal for each factor.Some corresponding absolute perturbation bounds are also given.
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.
Cylindrical Beam Propagation Modelling of Perturbed Whispering-Gallery Mode Microcavities
Shirazi, Mohammad Amin Cheraghi; Vincent, Serge; Lu, Tao
2013-01-01
We simulate light propagation in perturbed whispering-gallery mode microcavities using a two-dimensional finite-difference beam prop- agation method in a cylindrical coordinate system. Optical properties of whispering-gallery microcavities perturbed by polystyrene nanobeads are investigated through this formulation. The light perturbation as well as quality factor degradation arising from cavity ellipticity are also studied.
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.
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
Density perturbations with relativistic thermodynamics
Maartens, R
1997-01-01
We investigate cosmological density perturbations in a covariant and gauge- invariant formalism, incorporating relativistic causal thermodynamics to give a self-consistent description. The gradient of density inhomogeneities splits covariantly into a scalar part, a rotational vector part that is determined by the vorticity, and a tensor part that describes the shape. We give the evolution equations for these parts in the general dissipative case. Causal thermodynamics gives evolution equations for viswcous stress and heat flux, which are coupled to the density perturbation equation and to the entropy and temperature perturbation equations. We give the full coupled system in the general dissipative case, and simplify the system in certain cases.
Instabilities in mimetic matter perturbations
Firouzjahi, Hassan; Gorji, Mohammad Ali; Mansoori, Seyed Ali Hosseini
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.
Perturbation Theory of Embedded Eigenvalues
DEFF Research Database (Denmark)
Engelmann, Matthias
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...... 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...
Causal compensated perturbations in cosmology
Energy Technology Data Exchange (ETDEWEB)
Veeraraghavan, S.; Stebbins, A. (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (USA) California Univ., Berkeley (USA) Canadian Institute for Theoretical Astrophysics, Toronto (Canada))
1990-12-01
A theoretical framework is developed to calculate linear perturbations in the gravitational and matter fields which arise causally in response to the presence of stiff matter sources in a FRW cosmology. It is shown that, in order to satisfy energy and momentum conservation, the gravitational fields of the source must be compensated by perturbations in the matter and gravitational fields, and the role of such compensation in containing the initial inhomogeneities in their subsequent evolution is discussed. A complete formal solution is derived in terms of Green functions for the perturbations produced by an arbitrary source in a flat universe containing cold dark matter. Approximate Green function solutions are derived for the late-time density perturbations and late-time gravitational waves in a universe containing a radiation fluid. A cosmological energy-momentum pseudotensor is defined to clarify the nature of energy and momentum conservation in the expanding universe. 55 refs.
Dynamical Friction on extended perturbers
Esquivel, O
2008-01-01
Following a wave-mechanical treatment we calculate the drag force exerted by an infinite homogeneous background of stars on a perturber as this makes its way through the system. We recover Chandrasekhar's classical dynamical friction (DF) law with a modified Coulomb logarithm. We take into account a range of models that encompasses all plausible density distributions for satellite galaxies by considering the DF exerted on a Plummer sphere and a perturber having a Hernquist profile. It is shown that the shape of the perturber affects only the exact form of the Coulomb logarithm. The latter converges on small scales, because encounters of the test and field stars with impact parameters less than the size of the massive perturber become inefficient. We confirm this way earlier results based on the impulse approximation of small angle scatterings.
Review of chiral perturbation theory
Indian Academy of Sciences (India)
B Ananthanarayan
2003-11-01
A review of chiral perturbation theory and recent developments on the comparison of its predictions with experiment is presented. Some interesting topics with scope for further elaboration are touched upon.
Snakes and perturbed random walks
Basak, Gopal
2011-01-01
In this paper we study some properties of random walks perturbed at extrema, which are generalizations of the walks considered e.g., in Davis (1999). This process can also be viewed as a version of {\\em excited random walk}, studied recently by many authors. We obtain a few properties related to the range of the process with infinite memory. We also prove the Strong law, Central Limit Theorem, and the criterion for the recurrence of the perturbed walk with finite memory.
Perturbed Einstein field equations using Maple
De Campos, M
2003-01-01
We obtain the perturbed components of affine connection and Ricci tensor using algebraic computation. Naturally, the perturbed Einstein field equations for the vacuum can written. The method can be used to obtain perturbed equations of the superior order.
Resonant magnetic perturbations and divertor footprints in poloidally diverted tokamaks
Cahyna, Pavel
2010-01-01
General formula describing both the divertor strike point splitting and width of magnetic islands created by resonant magnetic perturbations (RMPs) in a poloidally diverted tokamak equilibrium is derived. Under the assumption that the RMP is produced by coils at the low-field side such as those used to control edge localized modes (ELMs) it is demonstrated that the width of islands on different magnetic surfaces at the edge and the amount of divertor splitting are related to each other. Explanation is provided of aligned maxima of the perturbation spectra with the safety factor profile - an effect empirically observed in models of many perturbation coil designs.
特纳综合征患者血清转化生长因子β的变化%Perturbation of the transforming growth factor β system in Turner syndrome
Institute of Scientific and Technical Information of China (English)
周键; Sruthi AREPALLI; Clara M. CHENG; Vladimir K. BAKALOV; Carolyn A. BONDY
2012-01-01
目的:观察转化生长因子β(transforming growth factor-beta,TGFβ)在特纳综合征(Turner syndrome,TS)患者血清中的变化及其与内分泌和心血管参数的关系.方法:选择TS患者和健康志愿者妇女(对照组)各40例,采用酶联免疫方法测定血清中的TGFβ1、TGFβ2及转化生长因子受体(endoglin).所有TS患者均行心血管系统磁共振和超声检查.结果:TS患者血清中TGFβ1和endoglin水平均高于对照组(P ＜0.000 1),而TGFβ2的水平则低于对照组(P ＜0.000 1).TGFβ的改变与年龄、血压、血小板、甲状腺功能、体重指数或心血管疾病的分型无关.结论:TS患者血清中TGFβ显著性改变对疾病的研究具有重要意义.%Objective:To measure components of the circulating transforming growth factor β (TGFβ)system in patients with Turner syndrome (TS) compared to relevant controls and to ascertain correlation with endocrine and cardiovascular parameters.Methods:TGFβ1,TGFβ2 and endoglin (a vascular TGF receptor component) were measured using enzyme-linked immunoassays in the sera of 40 subjects with TS and 40 healthy volunteer women.The cardiovascular phenotype in TS subjects was extensively characterized by cardiac magnetic resonance (MR) and echo.Results:TGFβ1 levels were about 3-fold higher in TS while TGFβ2 levels were about 3.5-fold higher in controls (P ＜0.000 1 for both).Soluble endoglin levels were 25％ higher in TS (P ＜0.000 1 ).Variation in TGFβ system components was not explained by age,blood pressure,platelet count,thyroid function,body proportions or cardiovascular phenotype.Conclusion:There is profound perturbation of the TGFβ system evident in the circulation of individuals with TS.
Perturbation growth in accreting filaments
Clarke, Seamus D; Hubber, David A
2016-01-01
We use smoothed particle hydrodynamic simulations to investigate the growth of perturbations in infinitely long, initially sub-critical but accreting filaments. The growth of these perturbations leads to filament fragmentation and the formation of cores. Most previous work on this subject has been confined to the growth and fragmentation of equilibrium filaments and has found that there exists a preferential fragmentation length scale which is roughly 4 times the filament's diameter. Our results show a more complicated dispersion relation with a series of peaks linking perturbation wavelength and growth rate. These are due to gravo-acoustic oscillations along the longitudinal axis during the sub-critical phase of growth. The positions of the peaks in growth rate have a strong dependence on both the mass accretion rate onto the filament and the temperature of the gas. When seeded with a multi-wavelength density power spectrum there exists a clear preferred core separation equal to the largest peak in the dispe...
Gravitational waves from perturbed stars
Ferrari, Valeria
2011-01-01
Non radial oscillations of neutron stars are associated with the emission of gravitational waves. The characteristic frequencies of these oscillations can be computed using the theory of stellar perturbations, and they are shown to carry detailed information on the internal structure of the emitting source. Moreover, they appear to be encoded in various radiative processes, as for instance in the tail of the giant flares of Soft Gamma Repeaters. Thus, their determination is central to the theory of stellar perturbation. A viable approach to the problem consists in formulating this theory as a problem of resonant scattering of gravitational waves incident on the potential barrier generated by the spacetime curvature. This approach discloses some unexpected correspondences between the theory of stellar perturbations and the theory of quantum mechanics, and allows us to predict new relativistic effects.
Physicochemical Perturbations of Phase Equilibriums
Dobruskin, Vladimir Kh
2010-01-01
The alternative approach to the displacement of gas/liquid equilibrium is developed on the basis of the Clapeyron equation. The phase transition in the system with well-established properties is taken as a reference process to search for the parameters of phase transition in the perturbed equilibrium system. The main equation, derived in the framework of both classical thermodynamics and statistical mechanics, establishes a correlation between variations of enthalpies of evaporation, \\Delta (\\Delta H), which is induced by perturbations, and the equilibrium vapor pressures. The dissolution of a solute, changing the surface shape, and the effect of the external field of adsorbents are considered as the perturbing actions on the liquid phase. The model provides the unified method for studying (1) solutions, (2) membrane separations (3) surface phenomena, and (4) effect of the adsorption field; it leads to the useful relations between \\Delta (\\Delta H), on the one hand, and the osmotic pressures, the Donnan poten...
Multi-field inflation and cosmological perturbations
Gong, Jinn-Ouk
2016-01-01
We provide a concise review on multi-field inflation and cosmological perturbations. We discuss convenient and physically meaningful bases in terms of which perturbations can be systematically studied. We give formal accounts on the gauge fixing conditions and present the perturbation action in two gauges. We also briefly review non-linear perturbations.
A Perturbative Window into Non-Perturbative Physics
Dijkgraaf, R; Dijkgraaf, Robbert; Vafa, Cumrun
2002-01-01
We argue that for a large class of N=1 supersymmetric gauge theories the effective superpotential as a function of the glueball chiral superfield is exactly given by a summation of planar diagrams of the same gauge theory. This perturbative computation reduces to a matrix model whose action is the tree-level superpotential. For all models that can be embedded in string theory we give a proof of this result, and we sketch an argument how to derive this more generally directly in field theory. These results are obtained without assuming any conjectured dualities and can be used as a systematic method to compute instanton effects: the perturbative corrections up to n-th loop can be used to compute up to n-instanton corrections. These techniques allow us to see many non-perturbative effects, such as the Seiberg-Witten solutions of N=2 theories, the consequences of Montonen-Olive S-duality in N=1* and Seiberg-like dualities for N=1 theories from a completely perturbative planar point of view in the same gauge theo...
Doppler peaks from active perturbations
Magueijo, J; Coulson, D; Ferreira, P; Magueijo, Joao; Albrecht, Andreas; Coulson, David; Ferreira, Pedro
1995-01-01
We examine how the qualitative structure of the Doppler peaks in the angular power spectrum of the cosmic microwave anisotropy depends on the fundamental nature of the perturbations which produced them. The formalism of Hu and Sugiyama is extended to treat models with cosmic defects. We discuss how perturbations can be ``active'' or ``passive'' and ``incoherent'' or ``coherent'', and show how causality and scale invariance play rather different roles in these various cases. We find that the existence of secondary Doppler peaks and the rough placing of the primary peak unambiguously reflect these basic properties.
B -> phi K decays in perturbative QCD approach
Mishima, S
2001-01-01
We calculate the branching ratios and CP asymmetries of the $B\\to \\phi K$ decays using perturbative QCD approach, which includes $k_T$ and threshold resummations. Our results of branching ratios are consistent with the experimental data and larger than those obtained from the naive factorization assumption and QCD-improved factorization approach.
The triple pomeron interaction in the perturbative QCD
Braun, M
1995-01-01
The triple pomeron interaction is studied in the perturbative approach of BFKL-Bartels. At finite momentum transfers \\sqrt{-t} the contribution factorizes in the standard manner with a triple-pomeron vertex proportional to 1/\\sqrt{-t}. At t=0 the contribution is finite, although it grows faster with energy than for finite t and does not factorize.
Explaining jet quenching with perturbative QCD alone
Zapp, Korinna C; Wiedemann, Urs A
2011-01-01
We present a new formulation of jet quenching in perturbative QCD beyond the eikonal approximation. Multiple scattering in the medium is modelled through infra-red-continued (2 -> 2) scattering matrix elements in QCD and the parton shower describing further emissions. The interplay between these processes is arranged in terms of a formation time constraint such that coherent emissions can be treated consistently. Emerging partons are hadronised by the Lund string model, tuned to describe LEP data in conjunction with the parton shower. Based on this picture we obtain a good description of the nuclear modification factor R_AA at RHIC and LHC.
Effects of thermal inflation on small scale density perturbations
Hong, Sungwook E; Lee, Young Jae; Stewart, Ewan D; Zoe, Heeseung
2015-01-01
In cosmological scenarios with thermal inflation, extra eras of moduli matter domination, thermal inflation and flaton matter domination exist between primordial inflation and the radiation domination of Big Bang nucleosynthesis. During these eras, cosmological perturbations on small scales can enter and re-exit the horizon, modifying the power spectrum on those scales. The largest modified scale, $k_\\mathrm{b}$, touches the horizon size when the expansion changes from deflation to inflation at the transition from moduli domination to thermal inflation. We analytically calculate the evolution of perturbations from moduli domination through thermal inflation and evaluate the curvature perturbation on the constant radiation density hypersurface at the end of thermal inflation to determine the late time curvature perturbation. Our resulting transfer function suppresses the power spectrum by a factor $\\sim 50$ at $k \\gg k_\\mathrm{b}$, with $k_\\mathrm{b}$ corresponding to anywhere from megaparsec to subparsec scal...
Cosmological perturbation theory and quantum gravity
Brunetti, Romeo; Hack, Thomas-Paul; Pinamonti, Nicola; Rejzner, Katarzyna
2016-01-01
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.
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.
Energy Technology Data Exchange (ETDEWEB)
Voigts-Rhetz, P von; Zink, K [Technische Hochschule Mittelhessen - University of Applied Sciences, Giessen, Hessen (Germany)
2014-06-01
Purpose: All present dosimetry protocols recommend well-guarded parallel-plate ion chambers for electron dosimetry. For the guard-less Markus chamber an energy dependent fluence perturbation correction pcav is given. This perturbation correction was experimentally determined by van der Plaetsen by comparison of the read-out of a Markus and a NACP chamber, which was assumed to be “perturbation-free”. Aim of the present study is a Monte Carlo based reiteration of this experiment. Methods: Detailed models of four parallel-plate chambers (Roos, Markus, NACP and Advanced Markus) were designed using the Monte Carlo code EGSnrc and placed in a water phantom. For all chambers the dose to the active volume filled with low density water was calculated for 13 clinical electron spectra (E{sub 0}=6-21 MeV) at the depth of maximum and at the reference depth under reference conditions. In all cases the chamber's reference point was positioned at the depth of measurement. Moreover, the dose to water DW was calculated in a small water voxel positioned at the same depth. Results: The calculated dose ratio D{sub NACP}/D{sub Markus}, which according to van der Plaetsen reflects the fluence perturbation correction of the Markus chamber, deviates less from unity than the values given by van der Plaetsen's but exhibits a similar energy dependence. The same holds for the dose ratios of the other well guarded chambers. But, in comparison to water, the Markus chamber reveals the smallest overall perturbation correction which is nearly energy independent at both investigated depths. Conclusion: The simulations principally confirm the energy dependence of the dose ratio D{sub NACP}/D{sub Markus} as published by van der Plaetsen. But, as shown by our simulations of the ratio D{sub W}/D{sub Markus}, the conclusion drawn in all dosimetry protocols is questionable: in contrast to all well-guarded chambers the guard-less Markus chamber reveals the smallest overall perturbation
Adaptation Strategies in Perturbed /s/
Brunner, Jana; Hoole, Phil; Perrier, Pascal
2011-01-01
The purpose of this work is to investigate the role of three articulatory parameters (tongue position, jaw position and tongue grooving) in the production of /s/. Six normal speakers' speech was perturbed by a palatal prosthesis. The fricative was recorded acoustically and through electromagnetic articulography in four conditions: (1) unperturbed,…
Basics of QCD perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Soper, D.E. [Univ. of Oregon, Eugene, OR (United States). Inst. of Theoretical Science
1997-06-01
This is an introduction to the use of QCD perturbation theory, emphasizing generic features of the theory that enable one to separate short-time and long-time effects. The author also covers some important classes of applications: electron-positron annihilation to hadrons, deeply inelastic scattering, and hard processes in hadron-hadron collisions. 31 refs., 38 figs.
Seven topics in perturbative QCD
Energy Technology Data Exchange (ETDEWEB)
Buras, A.J.
1980-09-01
The following topics of perturbative QCD are discussed: (1) deep inelastic scattering; (2) higher order corrections to e/sup +/e/sup -/ annihilation, to photon structure functions and to quarkonia decays; (3) higher order corrections to fragmentation functions and to various semi-inclusive processes; (4) higher twist contributions; (5) exclusive processes; (6) transverse momentum effects; (7) jet and photon physics.
Chiral Perturbation Theory and Unitarization
Ruiz-Arriola, E; Nieves, J; Peláez, J R
2000-01-01
We review our recent work on unitarization and chiral perturbation theory both in the $\\pi\\pi$ and the $\\pi N$ sectors. We pay particular attention to the Bethe-Salpeter and Inverse Amplitude unitarization methods and their recent applications to $\\pi\\pi$ and $\\pi N$ scattering.
Transport studies using perturbative experiments
Hogeweij, G. M. D.
2000-01-01
By inducing a small electron temperature perturbation in a plasma in steady state one can in principle determine the conductive and convective components of the electron heat flux, and the associated thermal diffusivity and convection velocity. The same can be done for other plasma parameters, like
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
Using qualitative analysis, we study perturbed Hamiltonian systems with different n-th order polynomial as perturbation terms. By numerical simulation, we show that these perturbed systems have the same distribution of limit cycles. Our results imply that these perturbed systems are equivalent in the sense of distribution of limit cycles. This is useful for studying limit cycles of perturbed systems.
Notes on Rank One Perturbed Resolvent. Perturbation of Isolated Eigenvalue.
Chorosavin, S A
2003-01-01
This paper is a didactic commentary (a transcription with variations) to the paper of S.R. Foguel {\\it Finite Dimensional Perturbations in Banach Spaces}. Addressed, mainly: postgraduates and related readers. Subject: Suppose we have two linear operators, A, B, so that B - A is rank one. Let \\lambda_o be an {\\it isolated} point of the spectrum of A. In addition, let \\lambda_o be an {\\it eigenvalue} of A: \\lambda_o \\in \\sigma_{pp}(A) . The question is: Is \\lambda_o an eigenvalue of B ? And, if so, is the multiplicity of \\lambda_o in \\sigma_{pp}(B) equal to the multiplicity of \\lambda_o in \\sigma_{pp}(A) ? -- or less? -- or greater? Keywords: M.G.Krein's Formula, Finite Rank Perturbation.
Vector perturbations of galaxy number counts
Durrer, Ruth; Tansella, Vittorio
2016-07-01
We derive the contribution to relativistic galaxy number count fluctuations from vector and tensor perturbations within linear perturbation theory. Our result is consistent with the the relativistic corrections to number counts due to scalar perturbation, where the Bardeen potentials are replaced with line-of-sight projection of vector and tensor quantities. Since vector and tensor perturbations do not lead to density fluctuations the standard density term in the number counts is absent. We apply our results to vector perturbations which are induced from scalar perturbations at second order and give numerical estimates of their contributions to the power spectrum of relativistic galaxy number counts.
Vector perturbations of galaxy number counts
Durrer, Ruth
2016-01-01
We derive the contribution to relativistic galaxy number count fluctuations from vector and tensor perturbations within linear perturbation theory. Our result is consistent with the the relativistic corrections to number counts due to scalar perturbation, where the Bardeen potentials are replaced with line-of-sight projection of vector and tensor quantities. Since vector and tensor perturbations do not lead to density fluctuations the standard density term in the number counts is absent. We apply our results to vector perturbations which are induced from scalar perturbations at second order and give numerical estimates of their contributions to the power spectrum of relativistic galaxy number counts.
Perturbatively improving RI-MOM renormalization constants
Energy Technology Data Exchange (ETDEWEB)
Constantinou, M.; Costa, M.; Panagopoulos, H. [Cyprus Univ. (Cyprus). Dept. of Physics; Goeckeler, M. [Regensburg Univ. (Germany). Institut fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics; Perlt, H.; Schiller, A. [Leipzig Univ. (Germany). Inst. fuer Theoretische Physik; Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Dept. of Mathematical Sciences; Schhierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2013-03-15
The determination of renormalization factors is of crucial importance in lattice QCD. They relate the observables obtained on the lattice to their measured counterparts in the continuum in a suitable renormalization scheme. Therefore, they have to be computed as precisely as possible. A widely used approach is the nonperturbative Rome-Southampton method. It requires, however, a careful treatment of lattice artifacts. In this paper we investigate a method to suppress these artifacts by subtracting one-loop contributions to renormalization factors calculated in lattice perturbation theory. We compare results obtained from a complete one-loop subtraction with those calculated for a subtraction of contributions proportional to the square of the lattice spacing.
Perturbatively improving RI-MOM renormalization constants
Energy Technology Data Exchange (ETDEWEB)
Constantinou, M.; Costa, M.; Panagopoulos, H. [Cyprus Univ. (Cyprus). Dept. of Physics; Goeckeler, M. [Regensburg Univ. (Germany). Institut fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics; Perlt, H.; Schiller, A. [Leipzig Univ. (Germany). Inst. fuer Theoretische Physik; Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Dept. of Mathematical Sciences; Schhierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2013-03-15
The determination of renormalization factors is of crucial importance in lattice QCD. They relate the observables obtained on the lattice to their measured counterparts in the continuum in a suitable renormalization scheme. Therefore, they have to be computed as precisely as possible. A widely used approach is the nonperturbative Rome-Southampton method. It requires, however, a careful treatment of lattice artifacts. In this paper we investigate a method to suppress these artifacts by subtracting one-loop contributions to renormalization factors calculated in lattice perturbation theory. We compare results obtained from a complete one-loop subtraction with those calculated for a subtraction of contributions proportional to the square of the lattice spacing.
Dipolar fluids under external perturbations
Energy Technology Data Exchange (ETDEWEB)
Klapp, Sabine H L [Stranski-Laboratorium fuer Physikalische und Theoretische Chemie Sekretariat TC7, Technische Universitaet Berlin, Strasse des 17. Juni 124, D-10623 Berlin (Germany)
2005-04-20
We discuss recent developments and present new findings on the structural and phase properties of dipolar model fluids influenced by various external perturbations. We concentrate on systems of spherical particles with permanent (point) dipole moments. Starting from what is known about the three-dimensional systems, particular emphasis is given to dipolar fluids in different confining situations involving both simple and complex (disordered) pore geometries. Further topics concern the effect of quenched positional disorder, the influence of external (electric or magnetic) fields, and the fluid-fluid phase behaviour of various dipolar mixtures. It is demonstrated that due to the translational-orientational coupling and due to the long range of dipolar interactions even simple perturbations such as hard walls can have a profound impact on the systems. (topical review)
BRST quantization of cosmological perturbations
Energy Technology Data Exchange (ETDEWEB)
Armendariz-Picon, Cristian [Physics Department, St. Lawrence University,Canton, NY 13617 (United States); Şengör, Gizem [Department of Physics, Syracuse University,Syracuse, NY 13244 (United States)
2016-11-08
BRST quantization is an elegant and powerful method to quantize theories with local symmetries. In this article we study the Hamiltonian BRST quantization of cosmological perturbations in a universe dominated by a scalar field, along with the closely related quantization method of Dirac. We describe how both formalisms apply to perturbations in a time-dependent background, and how expectation values of gauge-invariant operators can be calculated in the in-in formalism. Our analysis focuses mostly on the free theory. By appropriate canonical transformations we simplify and diagonalize the free Hamiltonian. BRST quantization in derivative gauges allows us to dramatically simplify the structure of the propagators, whereas Dirac quantization, which amounts to quantization in synchronous gauge, dispenses with the need to introduce ghosts and preserves the locality of the gauge-fixed action.
Back Reaction of Cosmological Perturbations
Brandenberger, R H
2000-01-01
The presence of cosmological perturbations affects the background metric and matter configuration in which the perturbations propagate. This effect, studied a long time ago for gravitational waves, also is operational for scalar gravitational fluctuations, inhomogeneities which are believed to be more important in inflationary cosmology. The back-reaction of fluctuations can be described by an effective energy-momentum tensor. The issue of coordinate invariance makes the analysis more complicated for scalar fluctuations than for gravitational waves. We show that the back-reaction of fluctuations can be described in a diffeomorphism-invariant way. In an inflationary cosmology, the back-reaction is dominated by infrared modes. We show that these modes give a contribution to the effective energy-momentum tensor of the form of a negative cosmological constant whose absolute value grows in time. We speculate that this may lead to a self-regulating dynamical relaxation mechanism for the cosmological constant. This ...
Perturbation analysis of Poisson processes
Last, Günter
2012-01-01
We consider a Poisson process $\\Phi$ on a general phase space. The expectation of a function of $\\Phi$ can be considered as a functional of the intensity measure $\\lambda$ of $\\Phi$. Extending ealier results of Molchanov and Zuyev (2000) on finite Poisson processes, we study the behaviour of this functional under signed (possibly infinite) perturbations of $\\lambda$. In particular we obtain general Margulis--Russo type formulas for the derivative with respect to non-linear transformations of the intensity measure depending on some parameter. As an application we study the behaviour of expectations of functions of multivariate pure jump L\\'evy processes under perturbations of the L\\'evy measure. A key ingredient of our approach is the explicit Fock space representation obtained in Last and Penrose (2011).
BRST Quantization of Cosmological Perturbations
Armendariz-Picon, Cristian
2016-01-01
BRST quantization is an elegant and powerful method to quantize theories with local symmetries. In this article we study the Hamiltonian BRST quantization of cosmological perturbations in a universe dominated by a scalar field, along with the closely related quantization method of Dirac. We describe how both formalisms apply to the perturbations in a time-dependent background, and how expectation values of gauge-invariant operators can be calculated in the in-in formalism. Our analysis focuses mostly on the free theory. By appropriate canonical transformations we simplify and diagonalize the free Hamiltonian. BRST quantization in derivative gauges allows us to dramatically simplify the structure of the propagators, whereas quantization in synchronous gauge, which amounts to Dirac quantization, dispenses with the need to introduce ghosts and preserves the locality of the gauge-fixed action.
Perturbations of Dark Matter Gravity
Maia, M D; Müller, D; 10.1142/S0218271809015072
2009-01-01
Until recently the study of the gravitational field of dark matter was primarily concerned with its local effects on the motion of stars in galaxies and galaxy clusters. On the other hand, the WMAP experiment has shown that the gravitational field produced by dark matter amplifies the higher acoustic modes of the CMBR power spectrum, more intensely than the gravitational field of baryons. Such a wide range of experimental evidences from cosmology to local gravity suggests the necessity of a comprehensive analysis of the dark matter gravitational field per se, regardless of any other attributes that dark matter may eventually possess. In this paper we introduce and apply Nash's theory of perturbative geometry to the study of the dark matter gravitational field alone, in a higher-dimensional framework. It is shown that the dark matter gravitational perturbations in the early universe can be explained by the extrinsic curvature of the standard cosmology. Together with the estimated presence of massive neutrinos,...
Perturbations in electromagnetic dark energy
Energy Technology Data Exchange (ETDEWEB)
Jiménez, Jose Beltrán; Maroto, Antonio L. [Departamento de Física Teórica, Universidad Complutense de Madrid, 28040 Madrid (Spain); Koivisto, Tomi S. [Institute for Theoretical Physics, University of Heidelberg, 69120 Heidelberg (Germany); Mota, David F., E-mail: jobeltra@fis.ucm.es, E-mail: T.Koivisto@thphys.uni-heidelberg.de, E-mail: maroto@fis.ucm.es, E-mail: d.f.mota@astro.uio.no [Institute of Theoretical Astrophysics, University of Oslo, 0315 Oslo (Norway)
2009-10-01
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.
Taming Landau singularities in QCD perturbation theory: The analytic approach
Stefanis, N G
2013-01-01
The aim of this topical article is to outline the fundamental ideas underlying the recently developed Fractional Analytic Perturbation Theory (FAPT) of QCD and present its main calculational tools. For this, it is first necessary to review previous methods to apply QCD perturbation theory at low spacelike momentum scales, where the influence of the Landau singularities becomes inevitable. Several concepts are considered and their limitations are pointed out. The usefulness of FAPT is discussed in terms of two characteristic hadronic quantities: the perturbatively calculable part of the pion's electromagnetic form factor in the spacelike region and the Higgs-boson decay into a b\\bar b pair in the timelike region. In the first case, the focus is on the optimization of the prediction with respect to the choice of the renormalization scheme and the dependence on the renormalization and the factorization scales. The second case serves to show that the application of FAPT to this reaction reaches already at the fou...
The bispectrum of matter perturbations from cosmic strings
Regan, Donough
2014-01-01
We present the first calculation of the bispectrum of the matter perturbations induced by cosmic strings. The calculation is performed in two different ways: the first uses the unequal time correlators (UETCs) of the string network - computed using a Gaussian model previously employed for cosmic string power spectra. The second approach uses the wake model, where string density perturbations are concentrated in sheet-like structures whose surface density grows with time. The qualitative and quantitative agreement of the two gives confidence to the results. An essential ingredient in the UETC approach is the inclusion of compensation factors in the integration with the Green's function of the matter and radiation fluids, and we show that these compensation factors must be included in the wake model also. We also present a comparison of the UETCs computed in the Gaussian model, and those computed in the unconnected segment model (USM) used by the standard cosmic string perturbation package CMBACT. We compare nu...
Perturbative Computation of Glueball Superpotentials
Dijkgraaf, R; Lam, C S; Vafa, C; Zanon, D
2003-01-01
Using N=1 superspace techniques in four dimensions we show how to perturbatively compute the superpotential generated for the glueball superfield upon integrating out massive charged fields. The technique applies to arbitrary gauge groups and representations. Moreover we show that for U(N) gauge theories admitting a large N expansion the computation dramatically simplifies and we prove the validity of the recently proposed recipe for computation of this quantity in terms of planar diagrams of matrix integrals.
Perturbative computation of glueball superpotentials
Dijkgraaf, R.; Grisaru, M. T.; Lam, C. S.; Vafa, C.; Zanon, D.
2003-10-01
Using N=1 superspace techniques in four dimensions we show how to perturbatively compute the superpotential generated for the glueball superfield upon integrating out massive charged fields. The technique applies to arbitrary gauge groups and representations. Moreover, we show that for U(N) gauge theories admitting a large N expansion the computation dramatically simplifies and we prove the validity of the recently proposed recipe for computation of this quantity in terms of planar diagrams of matrix integrals.
Perturbative computation of glueball superpotentials
Energy Technology Data Exchange (ETDEWEB)
Dijkgraaf, R.; Grisaru, M.T.; Lam, C.S.; Vafa, C.; Zanon, D
2003-10-30
Using N=1 superspace techniques in four dimensions we show how to perturbatively compute the superpotential generated for the glueball superfield upon integrating out massive charged fields. The technique applies to arbitrary gauge groups and representations. Moreover, we show that for U(N) gauge theories admitting a large N expansion the computation dramatically simplifies and we prove the validity of the recently proposed recipe for computation of this quantity in terms of planar diagrams of matrix integrals.
Perturbation growth in accreting filaments
Clarke, S. D.; Whitworth, A. P.; Hubber, D. A.
2016-05-01
We use smoothed particle hydrodynamic simulations to investigate the growth of perturbations in infinitely long filaments as they form and grow by accretion. The growth of these perturbations leads to filament fragmentation and the formation of cores. Most previous work on this subject has been confined to the growth and fragmentation of equilibrium filaments and has found that there exists a preferential fragmentation length-scale which is roughly four times the filament's diameter. Our results show a more complicated dispersion relation with a series of peaks linking perturbation wavelength and growth rate. These are due to gravo-acoustic oscillations along the longitudinal axis during the sub-critical phase of growth. The positions of the peaks in growth rate have a strong dependence on both the mass accretion rate onto the filament and the temperature of the gas. When seeded with a multiwavelength density power spectrum, there exists a clear preferred core separation equal to the largest peak in the dispersion relation. Our results allow one to estimate a minimum age for a filament which is breaking up into regularly spaced fragments, as well as an average accretion rate. We apply the model to observations of filaments in Taurus by Tafalla & Hacar and find accretion rates consistent with those estimated by Palmeirim et al.
Non-perturbative inputs for gluon distributions in the hadrons
Ermolaev, B. I.; Troyan, S. I.
2017-03-01
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.
Cosmological Perturbations: Vorticity, Isocurvature and Magnetic Fields
Christopherson, Adam J
2014-01-01
In this paper I review some recent, interlinked, work undertaken using cosmological perturbation theory -- a powerful technique for modelling inhomogeneities in the Universe. The common theme which underpins these pieces of work is the presence of non-adiabatic pressure, or entropy, perturbations. After a brief introduction covering the standard techniques of describing inhomogeneities in both Newtonian and relativistic cosmology, I discuss the generation of vorticity. As in classical fluid mechanics, vorticity is not present in linearized perturbation theory (unless included as an initial condition). Allowing for entropy perturbations, and working to second order in perturbation theory, I show that vorticity is generated, even in the absence of vector perturbations, by purely scalar perturbations, the source term being quadratic in the gradients of first order energy density and isocurvature, or non-adiabatic pressure perturbations. This generalizes Crocco's theorem to a cosmological setting. I then introduc...
Perturbation theory and renormalisation group equations
Litim, Daniel F; Litim, Daniel F.; Pawlowski, Jan M.
2002-01-01
We discuss the perturbative expansion of several one-loop improved renormalisation group equations. It is shown that in general the integrated renormalisation group flows fail to reproduce perturbation theory beyond one loop.
Data perturbation analysis of a linear model
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The linear model features were carefully studied in the cases of data perturbation and mean shift perturbation.Some important features were also proved mathematically. The results show that the mean shift perturbation is equivalentto the data perturbation, that is, adding a parameter to an observation equation means that this set of data is deleted fromthe data set. The estimate of this parameter is its predicted residual in fact
Perturbative versus non-perturbative decoupling of heavy quarks
Energy Technology Data Exchange (ETDEWEB)
Knechtli, Francesco [Wuppertal Univ. (Germany). Dept. of Physics; Bruno, Mattia [Brookhaven National Laboratory, Upton, NY (United States); Finkenrath, Jacob [CaSToRC, Cyl Athalassa Campus, Nicosia (Cyprus); Leder, Bjoern [Humboldt Univ. Berlin (Germany). Inst. fuer Physik; Sommer, Rainer [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Collaboration: ALPHA Collaboration
2015-11-15
We simulate a theory with N{sub f}=2 heavy quarks of mass M. At energies much smaller than M the heavy quarks decouple and the theory can be described by an effective theory which is a pure gauge theory to leading order in 1/M. We present results for the mass dependence of ratios such as t{sub 0}(M)/t{sub 0}(0). We compute these ratios from simulations and compare them to the perturbative prediction. The latter relies on a factorisation formula for the ratios which is valid to leading order in 1/M.
Transients from Initial Conditions A Perturbative Analysis
Scoccimarro, R
1998-01-01
The standard procedure to generate initial conditions (IC) in numerical simulations is to use the Zel'dovich approximation (ZA). Although the ZA correctly reproduces the linear growing modes of density and velocity perturbations, non-linear growth is inaccurately represented because of the ZA failure to conserve momentum. This implies that it takes time for the actual dynamics to establish the correct statistical properties of density and velocity fields. We extend perturbation theory (PT) to include transients as non-linear excitations of decaying modes caused by the IC. We focus on higher-order statistics of the density contrast and velocity divergence, characterized by the S_p and T_p parameters. We find that the time-scale of transients is determined, at a given order p, by the spectral index n. The skewness factor S_3 (T_3) attains 10% accuracy only after a=6 (a=15) for n=0, whereas higher (lower) n demands more (less) expansion away from the IC. These requirements become much more stringent as p increas...
Tensorial Perturbations in an Accelerating Universe
De Campos, M
2002-01-01
We study tensorial perturbations (gravitational waves) in a universe with particle production (OSC). The background of gravitational waves produces a perturbation in the redshift observed from distant sources. The modes for the perturbation in the redshift (induced redshift) are calculated in a universe with particle production.
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.
Matrix perturbations: bounding and computing eigenvalues
Reis da Silva, R.J.
2011-01-01
Despite the somewhat negative connotation of the word, not every perturbation is a bad perturbation. In fact, while disturbing the matrix entries, many perturbations still preserve useful properties such as the orthonormality of the basis of eigenvectors or the Hermicity of the original matrix. In t
Geometric Hamiltonian structures and perturbation theory
Energy Technology Data Exchange (ETDEWEB)
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.
Perturbative Transport Studies in Fusion Plasmas
Cardozo, N. J. L.
1995-01-01
Studies of transport in fusion plasmas using perturbations of an equilibrium state reviewed. Essential differences between steady-state and perturbative transport studies are pointed out. Important transport issues that can be addressed with perturbative experiments are identified as: (i) Are the tr
PYESSENCE: Generalized Coupled Quintessence Linear Perturbation Python Code
Leithes, Alexander
2016-09-01
PYESSENCE evolves linearly perturbed coupled quintessence models with multiple (cold dark matter) CDM fluid species and multiple DE (dark energy) scalar fields, and can be used to generate quantities such as the growth factor of large scale structure for any coupled quintessence model with an arbitrary number of fields and fluids and arbitrary couplings.
Directory of Open Access Journals (Sweden)
G. Sun
2011-11-01
Full Text Available Human activities and climate change are important factors that affect grassland ecosystems. A new optimization approach, the approach of conditional nonlinear optimal perturbation (CNOP related to initial and parameter perturbations, is employed to explore the nonlinearly combined impacts of human activities and climate change on a grassland ecosystem using a theoretical grassland model. In our study, it is assumed that the initial perturbations and parameter perturbations are regarded as human activities and climate change, respectively. Numerical results indicate that the climate changes causing the maximum effect in the grassland ecosystem are different under disparate intensities of human activities. This implies the pattern of climate change is very critical to the maintenance or degradation of grassland ecosystem in light of high intensity of human activities and that the grassland ecosystem should be rationally managed when the moisture index decreases. The grassland ecosystem influenced by the nonlinear combination of human activities and climate change undergoes abrupt change, while the grassland ecosystem affected by other types of human activities and climate change fails to show the abrupt change under a certain range of perturbations with the theoretical model. The further numerical analyses also indicate that the growth of living biomass and the evaporation from soil surface shaded by the wilted biomass may be crucial factors contributing to the abrupt change of the grassland equilibrium state within the theoretical model.
Threshold Effects And Perturbative Unification
Bastero-Gil, M; Pérez-Mercader, J
1995-01-01
We discuss the effect of the renormalization procedure in the computation of the unification point for running coupling constants. We explore the effects of threshold--crossing on the $\\beta$--functions. We compute the running of the coupling constants of the Standard Model, between $m_Z$ and $M_P$, using a mass dependent subtraction procedure, and then compare the results with $\\bar{MS}$, and with the $\\theta$-- function approximation. We also do this for the Minimal Supersymmetric extension of the Standard Model. In the latter, the bounds on susy masses that one obtains by requiring perturbative unification are dependent, to some extent, on the procedure.
Perturbation analyses of intermolecular interactions
Koyama, Yohei M.; Kobayashi, Tetsuya J.; Ueda, Hiroki R.
2011-08-01
Conformational fluctuations of a protein molecule are important to its function, and it is known that environmental molecules, such as water molecules, ions, and ligand molecules, significantly affect the function by changing the conformational fluctuations. However, it is difficult to systematically understand the role of environmental molecules because intermolecular interactions related to the conformational fluctuations are complicated. To identify important intermolecular interactions with regard to the conformational fluctuations, we develop herein (i) distance-independent and (ii) distance-dependent perturbation analyses of the intermolecular interactions. We show that these perturbation analyses can be realized by performing (i) a principal component analysis using conditional expectations of truncated and shifted intermolecular potential energy terms and (ii) a functional principal component analysis using products of intermolecular forces and conditional cumulative densities. We refer to these analyses as intermolecular perturbation analysis (IPA) and distance-dependent intermolecular perturbation analysis (DIPA), respectively. For comparison of the IPA and the DIPA, we apply them to the alanine dipeptide isomerization in explicit water. Although the first IPA principal components discriminate two states (the α state and PPII (polyproline II) + β states) for larger cutoff length, the separation between the PPII state and the β state is unclear in the second IPA principal components. On the other hand, in the large cutoff value, DIPA eigenvalues converge faster than that for IPA and the top two DIPA principal components clearly identify the three states. By using the DIPA biplot, the contributions of the dipeptide-water interactions to each state are analyzed systematically. Since the DIPA improves the state identification and the convergence rate with retaining distance information, we conclude that the DIPA is a more practical method compared with the
Eikonal perturbation theory in photoionization
Cajiao Vélez, F.; Krajewska, K.; Kamiński, J. Z.
2016-02-01
The eikonal perturbation theory is formulated and applied to photoionization by strong laser pulses. A special emphasis is put on the first order approximation with respect to the binding potential, which is known as the generalized eikonal approximation [2015 Phys. Rev. A 91 053417]. The ordinary eikonal approximation and its domain of applicability is derived from the generalized eikonal approximation. While the former approach is singular for the electron trajectories which return to the potential center, the generalized eikonal avoids this problem. This property makes it a promising tool for further investigations of rescattering and high-order harmonic generation processes.
Perturbative QCD analysis of $B \\to \\phi K^* $ decays
Chen Chuan Hung; Li, H; Chen, Chuan-Hung; Keum, Yong-Yeon; Li, Hsiang-nan
2002-01-01
We study the first observed charmless $B\\to VV$ modes, the $B\\to\\phi K^*$ decays, in perturbative QCD formalism. The obtained branching ratios $B(B\\to\\phi K^*)\\sim 15 \\times 10^{-6}$ are larger than $\\sim 9\\times 10^{-6}$ from QCD factorization. The comparison of the predicted magnitudes and phases of the different helicity amplitudes, and branching ratios with experimental data can test the power counting rules, the evaluation of annihilation contributions, and the mechanism of dynamical penguin enhancement in perturbative QCD, respectively.
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.
Testing gauge-invariant perturbation theory
Törek, Pascal
2016-01-01
Gauge-invariant perturbation theory for theories with a Brout-Englert-Higgs effect, as developed by Fr\\"ohlich, Morchio and Strocchi, starts out from physical, exactly gauge-invariant quantities as initial and final states. These are composite operators, and can thus be considered as bound states. In case of the standard model, this reduces almost entirely to conventional perturbation theory. This explains the success of conventional perturbation theory for the standard model. However, this is due to the special structure of the standard model, and it is not guaranteed to be the case for other theories. Here, we review gauge-invariant perturbation theory. Especially, we show how it can be applied and that it is little more complicated than conventional perturbation theory, and that it is often possible to utilize existing results of conventional perturbation theory. Finally, we present tests of the predictions of gauge-invariant perturbation theory, using lattice gauge theory, in three different settings. In ...
Spatially Heterogeneous Perturbations Homogenize the Regulation of Insect Herbivores.
Harvey, Eric; MacDougall, Andrew S
2015-11-01
Anthropogenic influences on resources and consumers can affect food web regulation, with impacts on trophic structure and ecosystem processes. Identifying how these impacts unfold is challenging because alterations to one or both resources and consumers can similarly transform community structure, especially for intermediate consumers. To date, empirical testing of perturbations on trophic regulation has been limited by the difficulty in separating the direct effect of perturbations on species composition and diversity from those unfolding indirectly via altered feeding pathways. Moreover, disentangling the independent and interactive impacts of covarying stressors that characterize human-altered systems has been an ongoing analytical challenge. We used a large-scale metacommunity experiment in grasslands to test how resource inputs, stand perturbation, and spatial factors affect regulation of insect herbivores in tritrophic grassland food webs. Using path-model comparisons, we observed significant simplification of food web regulation on insect herbivores, shifting from mixed predator-resource regulation in unaltered mainland areas to strictly resource-based regulation with landscape perturbation and fragmentation. Most changes were attributed to homogenization of plant community caused by landscape fragmentation and the deterministic influence of eutrophication that reduced among-patch beta diversity. This led to a simplified food web dominated by fewer but more abundant herbivore taxa. Our work implies that anthropogenic perturbation relating to resources and spatial isolation can transform the regulation of food web diversity, structure, and function.
Nonspherical Szekeres models in the language of cosmological perturbations
Sussman, Roberto A.; Hidalgo, Juan Carlos; Delgado Gaspar, Ismael; Germán, Gabriel
2017-03-01
We study the differences and equivalences between the nonperturbative description of the evolution of cosmic structure furnished by the Szekeres dust models (a nonspherical exact solution of Einstein's equations) and the dynamics of cosmological perturbation theory (C P T ) for dust sources in a Λ CDM background. We show how the dynamics of Szekeres models can be described by evolution equations given in terms of "exact fluctuations" that identically reduce (at all orders) to evolution equations of C P T in the comoving isochronous gauge. We explicitly show how Szekeres linearized exact fluctuations are specific (deterministic) realizations of standard linear perturbations of C P T given as random fields, but, as opposed to the latter perturbations, they can be evolved exactly into the full nonlinear regime. We prove two important results: (i) the conservation of the curvature perturbation (at all scales) also holds for the appropriate linear approximation of the exact Szekeres fluctuations in a Λ CDM background, and (ii) the different collapse morphologies of Szekeres models yields, at nonlinear order, different functional forms for the growth factor that follows from the study of redshift space distortions. The metric-based potentials used in linear C P T are computed in terms of the parameters of the linearized Szekeres models, thus allowing us to relate our results to linear C P T results in other gauges. We believe that these results provide a solid starting stage to examine the role of non-perturbative general relativity in current cosmological research.
Asymptotic analysis of perturbed dust cosmologies to second order
Uggla, Claes
2013-01-01
Nonlinear perturbations of Friedmann-Lemaitre cosmologies with dust and a positive cosmological constant have recently attracted considerable attention. In this paper our first goal is to compare the evolution of the first and second order perturbations by determining their asymptotic behaviour at late times in ever-expanding models. We show that in the presence of spatial curvature K or a positive cosmological constant, the density perturbation approaches a finite limit both to first and second order, but the rate of approach depends on the model, being power law in the scale factor if the cosmological constant is positive but logarithmic if it is zero and and K<0. Scalar perturbations in general contain a growing and a decaying mode. We find, somewhat surprisingly, that if the cosmological constant is positive the decaying mode does not die away, i.e. it contributes on an equal footing as the growing mode to the asymptotic expression for the density perturbation. On the other hand, the future asymptotic ...
Integrability and non-perturbative effects in the AdS/CFT correspondence
Gómez, C; Gómez, César; Hernández, Rafael
2007-01-01
We present a non-perturbative resummation of the asymptotic strong-coupling expansion for the dressing phase factor of the AdS_5xS^5 string S-matrix. The non-perturbative resummation provides a general form for the coefficients in the weak-coupling expansion, in agreement with crossing symmetry and transcendentality. The ambiguities of the non-perturbative prescription are discussed together with the similarities with the non-perturbative definition of the c=1 matrix model.
Díez, A; Largo, J; Solana, J R
2006-08-21
Computer simulations have been performed for fluids with van der Waals potential, that is, hard spheres with attractive inverse power tails, to determine the equation of state and the excess energy. On the other hand, the first- and second-order perturbative contributions to the energy and the zero- and first-order perturbative contributions to the compressibility factor have been determined too from Monte Carlo simulations performed on the reference hard-sphere system. The aim was to test the reliability of this "exact" perturbation theory. It has been found that the results obtained from the Monte Carlo perturbation theory for these two thermodynamic properties agree well with the direct Monte Carlo simulations. Moreover, it has been found that results from the Barker-Henderson [J. Chem. Phys. 47, 2856 (1967)] perturbation theory are in good agreement with those from the exact perturbation theory.
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.
Detector dose response in megavoltage small photon beams. II. Pencil beam perturbation effects
Energy Technology Data Exchange (ETDEWEB)
Bouchard, Hugo, E-mail: hugo.bouchard@npl.co.uk; Duane, Simon [Acoustics and Ionising Radiation Team, National Physical Laboratory, Hampton Road, Teddington TW11 0LW (United Kingdom); Kamio, Yuji [Centre hospitalier de l’Université de Montréal (CHUM), 1560 Sherbrooke Est, Montréal, Québec H2L 4M1 (Canada); Palmans, Hugo [Acoustics and Ionising Radiation Team, National Physical Laboratory, Hampton Road, Teddington TW11 0LW (United Kingdom); Medical Physics, EBG MedAustron GmbH, Wiener Neustadt A-2700 (Austria); Seuntjens, Jan [Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4 (Canada)
2015-10-15
Purpose: To quantify detector perturbation effects in megavoltage small photon fields and support the theoretical explanation on the nature of quality correction factors in these conditions. Methods: In this second paper, a modern approach to radiation dosimetry is defined for any detector and applied to small photon fields. Fano’s theorem is adapted in the form of a cavity theory and applied in the context of nonstandard beams to express four main effects in the form of perturbation factors. The pencil-beam decomposition method is detailed and adapted to the calculation of perturbation factors and quality correction factors. The approach defines a perturbation function which, for a given field size or beam modulation, entirely determines these dosimetric factors. Monte Carlo calculations are performed in different cavity sizes for different detection materials, electron densities, and extracameral components. Results: Perturbation effects are detailed with calculated perturbation functions, showing the relative magnitude of the effects as well as the geometrical extent to which collimating or modulating the beam impacts the dosimetric factors. The existence of a perturbation zone around the detector cavity is demonstrated and the approach is discussed and linked to previous approaches in the literature to determine critical field sizes. Conclusions: Monte Carlo simulations are valuable to describe pencil beam perturbation effects and detail the nature of dosimetric factors in megavoltage small photon fields. In practice, it is shown that dosimetric factors could be avoided if the field size remains larger than the detector perturbation zone. However, given a detector and beam quality, a full account for the detector geometry is necessary to determine critical field sizes.
Production of scalar and tensor perturbations in inflationary models
Turner, Michael S.
1993-10-01
Scalar (density) and tensor (gravity-wave) perturbations provide the basis for the fundamental observable consequences of inflation, including CBR anisotropy and the formation of structure in the Universe. These perturbations are nearly scale invariant (Harrison-Zel'dovich spectrum), though a slight deviation from scale invariance (``tilt'') can have significant consequences for both CBR anisotropy and structure formation. In particular, a slightly tilted spectrum of scalar perturbations may improve the agreement of the cold dark matter scenario with the observational data. The amplitude and spectrum of the scalar and tensor perturbations depend upon the shape of the inflationary potential in the small interval where the scalar field responsible for inflation was between about 46 and 54 e-folds before the end of inflation. By expanding the inflationary potential in a Taylor series over this interval we show that the amplitudes of the perturbations and the power-law slopes of their spectra can be expressed in terms of the value of the potential 50 e-folds before the end of inflation, V50, its steepness x50≡mPlV'50/V50, and the rate of change of its steepness, x'50 (a prime denotes a derivative with respect to the scalar field). In addition, the power-law index of the cosmic-scale factor at this time is q50≡[dlnR/dlnt]50~=16π/x250. (Formally, our results for the perturbation amplitudes and spectral indices are accurate to lowest order in the deviation from scale invariance.) In general, the deviation from scale invariance is such to enhance fluctuations on large scales, and is only significant for steep potentials, large x50, or potentials with rapidly changing steepness, large x'50. In the latter case, only the spectrum of scalar perturbations is significantly tilted. Steep potentials are characterized by a large tensor-mode contribution to the quadrupole CBR temperature anisotropy, a similar tilt in both scalar and tensor perturbations, and a slower expansion
Inflationary Perturbations and Precision Cosmology
Habib, S; Heitmann, K; Jungman, G; Habib, Salman; Heinen, Andreas; Heitmann, Katrin; Jungman, Gerard
2005-01-01
Inflationary cosmology provides a natural mechanism for the generation of primordial perturbations which seed the formation of observed cosmic structure and lead to specific signals of anisotropy in the cosmic microwave background radiation. In order to test the broad inflationary paradigm as well as particular models against precision observations, it is crucial to be able to make accurate predictions for the power spectrum of both scalar and tensor fluctuations. We present detailed calculations of these quantities utilizing direct numerical approaches as well as error-controlled uniform approximations, comparing with the (uncontrolled) traditional slow-roll approach. A simple extension of the leading-order uniform approximation yields results for the power spectra amplitudes, the spectral indices, and the running of spectral indices, with accuracy of the order of 0.1% - approximately the same level at which the transfer functions are known. Several representative examples are used to demonstrate these resul...
World-line perturbation theory
van Holten, Jan-Willem
2016-01-01
The motion of a compact body in space and time is commonly described by the world line of a point representing the instantaneous position of the body. In General Relativity such a world-line formalism is not quite straightforward because of the strict impossibility to accommodate point masses and rigid bodies. In many situations of practical interest it can still be made to work using an effective hamiltonian or energy-momentum tensor for a finite number of collective degrees of freedom of the compact object. Even so exact solutions of the equations of motion are often not available. In such cases families of world lines of compact bodies in curved space-times can be constructed by a perturbative procedure based on generalized geodesic deviation equations. Examples for simple test masses and for spinning test bodies are presented.
Perturbativity in the seesaw mechanism
Directory of Open Access Journals (Sweden)
Takehiko Asaka
2016-02-01
Full Text Available 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.
Initial conditions for cosmological perturbations
Ashtekar, Abhay
2016-01-01
Penrose proposed that the big bang singularity should be constrained by requiring that the Weyl curvature vanishes there. The idea behind this past hypothesis is attractive because it constrains the initial conditions for the universe in geometric terms and is not confined to a specific early universe paradigm. However, the precise statement of Penrose's hypothesis is tied to classical space-times and furthermore restricts only the gravitational degrees of freedom. These are encapsulated only in the tensor modes of the commonly used cosmological perturbation theory. Drawing inspiration from the underlying idea, we propose a quantum generalization of Penrose's hypothesis using the Planck regime in place of the big bang, and simultaneously incorporating tensor as well as scalar modes. Initial conditions selected by this generalization constrain the universe to be as homogeneous and isotropic in the Planck regime \\emph{as permitted by the Heisenberg uncertainty relations}.
Perturbations of vortex ring pairs
Gubser, Steven S; Parikh, Sarthak
2015-01-01
We study pairs of co-axial vortex rings starting from the action for a classical bosonic string in a three-form background. We complete earlier work on the phase diagram of classical orbits by explicitly considering the case where the circulations of the two vortex rings are equal and opposite. We then go on to study perturbations, focusing on cases where the relevant four-dimensional transfer matrix splits into two-dimensional blocks. When the circulations of the rings have the same sign, instabilities are mostly limited to wavelengths smaller than a dynamically generated length scale at which single-ring instabilities occur. When the circulations have the opposite sign, larger wavelength instabilities can occur.
Noncommutative Fluid and Cosmological Perturbations
Das, Praloy
2016-01-01
In the present paper we have developed a Non-Commutative (NC) generalization of perfect fluid model from first principles, in a Hamiltonian framework. The noncommutativity is introduced at the Lagrangian (particle) coordinate space brackets and the induced NC fluid bracket algebra for the Eulerian (fluid) field variables is derived. Together with a Hamiltonian this NC algebra generates the generalized fluid dynamics that satisfies exact local conservation laws for mass and energy thereby maintaining mass and energy conservation. However, nontrivial NC correction terms appear in charge and energy fluxes. Other non-relativistic spacetime symmetries of the NC fluid are also discussed in detail. This constitutes the NC fluid dynamics and kinematics. In the second part we construct an extension of Friedmann-Robertson-Walker (FRW) cosmological model based on the NC fluid dynamics presented here. We outline the way in which NC effects generate cosmological perturbations bringing in anisotropy and inhomogeneity in th...
Boosted perturbations at the end of inflation
Zaballa, Ignacio
2009-01-01
We study the effect on the primordial cosmological perturbations of a sharp transition from inflationary to a radiation and matter dominated epoch respectively. We assume that the perturbations are generated by the vacuum fluctuations of a scalar field slowly rolling down its potential, and that the transition into the subsequent epoch takes place much faster than a Hubble time. The behaviour of the superhorizon perturbations corresponding to cosmological scales in this case is well known. However, it is not clear how perturbations on scales of and smaller than the Hubble horizon scale at the end of inflation may evolve through such a transition. We derive the evolution equation for the gravitational potential $\\Psi$, which allows us to study the evolution of the perturbations on all scales under these circumstances. We show that for a certain range of scales inside the horizon at the end of inflation, the amplitude of the perturbations are enhanced relative to the superhorizon scales. This enhancement may le...
Transient dynamics of perturbations in astrophysical disks
Razdoburdin, Dmitry N
2015-01-01
This paper reviews some aspects of one of the major unsolved problems in understanding astrophysical (in particular, accretion) disks: whether the disk interiors may be effectively viscous in spite of the absence of marnetorotational instability? In this case a rotational homogeneous inviscid flow with a Keplerian angular velocity profile is spectrally stable, making the transient growth of perturbations a candidate mechanism for energy transfer from the regular motion to perturbations. Transient perturbations differ qualitatively from perturbation modes and can grow substantially in shear flows due to the nonnormality of their dynamical evolution operator. Since the eigenvectors of this operator, alias perturbation modes, are mutually nonorthogonal, they can mutually interfere, resulting in the transient growth of their linear combinations. Physically, a growing transient perturbation is a leading spiral whose branches are shrunk as a result of the differential rotation of the flow. This paper discusses in d...
Dynamics of Cosmological Perturbations in Position Space
Bashinsky, S V; Bashinsky, Sergei; Bertschinger, Edmund
2002-01-01
We show that the linear dynamics of cosmological perturbations can be described by coupled wave equations, allowing their efficient numerical and, in certain limits, analytical integration directly in position space. The linear evolution of any perturbation can then be analyzed with the Green's function method. Prior to hydrogen recombination, assuming tight coupling between photons and baryons, neglecting neutrino perturbations, and taking isentropic (adiabatic) initial conditions, the obtained Green's functions for all metric, density, and velocity perturbations vanish beyond the acoustic horizon. At the acoustic wavefronts, a positive gravitational potential perturbation produces narrow photon-baryon density spikes, which provide one of the major contributions to the observed cosmic microwave background radiation anisotropy on all scales. The gravitational interaction between cold dark matter and baryons causes a dip in the observed temperature of the radiation at the center of the initial perturbation. We...
Newtonian Limits of the Relativistic Cosmological Perturbations
Hwang, J
1997-01-01
Relativistic cosmological perturbation analyses can be made based on several different fundamental gauge conditions. In the pressureless limit the variables in certain gauge conditions show the correct Newtonian behaviors. We consider the general curvature and the cosmological constant in the background medium. The perturbed density in the comoving gauge, and the perturbed velocity and the perturbed potential in the zero-shear gauge show the same behavior as the Newtonian ones in a general scale. Far inside horizon, except for the uniform-density gauge, density perturbations in all the fundamental gauge conditions show the correct Newtonian behavior. In this paper we elaborate these Newtonian correspondences. We also present the relativistic results considering general pressures in the background and perturbation.
Threshold resummation in SCET vs. perturbative QCD. An analytic comparison
Energy Technology Data Exchange (ETDEWEB)
Bonvini, Marco [Genoa Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Genoa (Italy); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Forte, Stefano [Milano Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Milan (Italy); Ghezzi, Margherita [Milano Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Milan (Italy); Rome Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Rome (Italy); Ridolfi, Giovanni [Genoa Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Genoa (Italy)
2012-01-15
We compare threshold resummation in QCD, as performed using soft-collinear effective theory (SCET), to the standard perturbative QCD formalism based on factorization and resummation of Mellin moments of partonic cross-sections. We consider various forms of the SCET result, which correspond to different choices of the soft scale {mu}{sub s} that characterizes this approach. We derive a master formula that relates the SCET resummation to the QCD result for any choice of {mu}{sub s}. We then use it first, to show that if SCET resummation is performed in N-Mellin moment space by suitable choice of {mu}{sub s} it is equivalent to the standard perturbative approach. Next, we show that if SCET resummation is performed by choosing for {mu}{sub s} a partonic momentum variable, the perturbative result for partonic resummed cross-sections is again reproduced, but like its standard perturbative counterpart it is beset by divergent behaviour at the endpoint. Finally, using the master formula we show that when {mu}{sub s} is chosen as a hadronic momentum variable the SCET and standard approach are related through a multiplicative (convolutive) factor, which contains the dependence on the Landau pole and associated divergence. This factor depends on the luminosity in a non-universal way; it lowers by one power of log the accuracy of the resummed result, but it is otherwise subleading if one assumes the luminosity not to contain logarithmically enhanced terms. Therefore, the SCET approach can be turned into a prescription to remove the Landau pole from the perturbative result, but the price to pay for this is the reduction by one logarithmic power of the accuracy at each order and the need to make assumptions on the parton luminosity. (orig.)
Eldumiati, I. I.; Haddad, G. I.
1972-01-01
Cavity perturbation techniques offer a very sensitive and highly versatile means for studying the complex microwave conductivity of a bulk material. A knowledge of the cavity coupling factor in the absence of perturbation, together with the change in the reflected power and the cavity resonance frequency shift, are adequate for the determination of the material properties. This eliminates the need to determine the Q-factor change with perturbation which may lead to appreciable error, especially in the presence of mismatch loss. The measurement accuracy can also be improved by a proper choice of the cavity coupling factor prior to the perturbation.
Approximation of pressure perturbations by FEM
Bichir, Cătălin - Liviu
2011-01-01
In the mathematical problem of linear hydrodynamic stability for shear flows against Tollmien-Schlichting perturbations, the continuity equation for the perturbation of the velocity is replaced by a Poisson equation for the pressure perturbation. The resulting eigenvalue problem, an alternative form for the two - point eigenvalue problem for the Orr - Sommerfeld equation, is formulated in a variational form and this one is approximated by finite element method (FEM). Possible applications to concrete cases are revealed.
Cosmological perturbations in a noncommutative braneworld inflation
Institute of Scientific and Technical Information of China (English)
Kourosh Nozari; Siamak Akhshabi
2012-01-01
We use the smeared,coherent state picture of noncommutativity to study evolution of perturbations in a noncommutative braneworld scenario.Within the standard procedure of studying braneworld cosmological perturbations,we study the evolution of the Bardeen metric potential and curvature perturbations in this model.We show that in this setup,the early stage of the universe's evolution has a transient phantom evolution with imaginary effective sound speed.
Non-Perturbative Theory of Dispersion Interactions
Boström, M; Persson, C; Parsons, D F; Buhmann, S Y; Brevik, I; Sernelius, Bo E
2015-01-01
Some open questions exist with fluctuation-induced forces between extended dipoles. Conventional intuition derives from large-separation perturbative approximations to dispersion force theory. Here we present a full non-perturbative theory. In addition we discuss how one can take into account finite dipole size corrections. It is of fundamental value to investigate the limits of validity of the perturbative dispersion force theory.
On adiabatic perturbations in the ekpyrotic scenario
Linde, A.; Mukhanov, V.; Vikman, A.
2010-02-01
In a recent paper, Khoury and Steinhardt proposed a way to generate adiabatic cosmological perturbations with a nearly flat spectrum in a contracting Universe. To produce these perturbations they used a regime in which the equation of state exponentially rapidly changed during a short time interval. Leaving aside the singularity problem and the difficult question about the possibility to transmit these perturbations from a contracting Universe to the expanding phase, we will show that the methods used in Khoury are inapplicable for the description of the cosmological evolution and of the process of generation of perturbations in this scenario.
On adiabatic perturbations in the ekpyrotic scenario
Linde, A; Vikman, A
2009-01-01
In a recent paper arXiv:0910.2230, Khoury and Steinhardt proposed a way to generate adiabatic cosmological perturbations with a nearly flat spectrum in a contracting Universe. To produce these perturbations they used a regime in which the equation of state exponentially rapidly changed during a short time interval. Leaving aside the singularity problem and the difficult question about the possibility to transmit these perturbations from a contracting Universe to the expanding phase, we will show that the methods used in arXiv:0910.2230 are inapplicable for the description of the cosmological evolution and of the process of generation of perturbations in this scenario.
Kato expansion in quantum canonical perturbation theory
Nikolaev, A S
2015-01-01
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 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. The corresponding computational algorithm is more efficient for high perturbative orders than the algorithms of Van Vleck and Magnus methods.
Superhorizon Perturbations and the Cosmic Microwave Background
Erickcek, Adrienne L; Kamionkowski, Marc
2008-01-01
Superhorizon perturbations induce large-scale temperature anisotropies in the cosmic microwave background (CMB) via the Grishchuk-Zel'dovich effect. We analyze the CMB temperature anisotropies generated by a single-mode adiabatic superhorizon perturbation. We show that an adiabatic superhorizon perturbation in a LCDM universe does not generate a CMB temperature dipole, and we derive constraints to the amplitude and wavelength of a superhorizon potential perturbation from measurements of the CMB quadrupole and octupole. We also consider constraints to a superhorizon fluctuation in the curvaton field, which was recently proposed as a source of the hemispherical power asymmetry in the CMB.
Perturbative spacetimes from Yang-Mills theory
Luna, Andrés; Nicholson, Isobel; Ochirov, Alexander; O'Connell, Donal; Westerberg, Niclas; White, Chris D.
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.
Kato expansion in quantum canonical perturbation theory
Nikolaev, Andrey
2016-06-01
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.
Perturbative spacetimes from Yang-Mills theory
Luna, Andres; Nicholson, Isobel; Ochirov, Alexander; O'Connell, Donal; Westerberg, Niclas; White, Chris D.
2016-01-01
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.
Controlling Disorder in Traffic Flow by Perturbation
Institute of Scientific and Technical Information of China (English)
LIKe-Ping; GAOZi-You; CHENTian-Lun
2004-01-01
We propose a new technique for controlling disorder in traffic system. A kind of control signal which can be considered as a perturbation has been designated at a given site (perturbation point) of the single-lane highway. When a vehicle passes the perturbation point at a time, the velocity of the vehicle will be changed at the next time by the perturbation. This technique is tested for the deterministic NaSch traffic model. The simulation results indicate that the traffic system can be transited from the disorder states to the order states, such as fixed-point, periodic motion, etc.
Study on ETKF-Based Initial Perturbation Scheme for GRAPES Global Ensemble Prediction
Institute of Scientific and Technical Information of China (English)
MA Xulin; XUE Jishan; LU Weisong
2009-01-01
Initial perturbation scheme is one of the important problems for ensemble prediction. In this paper,ensemble initial perturbation scheme for Global/Regional Assimilation and PrEdiction System (GRAPES)global ensemble prediction is developed in terms of the ensemble transform Kalman filter (ETKF) method.A new GRAPES global ensemble prediction system (GEPS) is also constructed. The spherical simplex 14-member ensemble prediction experiments, using the simulated observation network and error character-lstics of simulated observations and innovation-based inflation, are carried out for about two months. The structure characters and perturbation amplitudes of the ETKF initial perturbations and the perturbation growth characters are analyzed, and their qualities and abilities for the ensemble initial perturbations are given.The preliminary experimental results indicate that the ETKF-based GRAPES ensemble initial perturba- tions could identify main normal structures of analysis error variance and reflect the perturbation amplitudes.The initial perturbations and the spread are reasonable. The initial perturbation variance, which is approx-imately equal to the forecast error variance, is found to respond to changes in the observational spatial variations with simulated observational network density. The perturbations generated through the simplex method are also shown to exhibit a very high degree of consistency between initial analysis and short-range forecast perturbations. The appropriate growth and spread of ensemble perturbations can be maintained up to 96-h lead time. The statistical results for 52-day ensemble forecasts show that the forecast scores of ensemble average for the Northern Hemisphere are higher than that of the control forecast. Provided that using more ensemble members, a real-time observational network and a more appropriate inflation factor,better effects of the ETKF-based initial scheme should be shown.
Perturbation theory in light-cone quantization
Energy Technology Data Exchange (ETDEWEB)
Langnau, A.
1992-01-01
A thorough investigation of light-cone properties which are characteristic for higher dimensions is very important. The easiest way of addressing these issues is by analyzing the perturbative structure of light-cone field theories first. Perturbative studies cannot be substituted for an analysis of problems related to a nonperturbative approach. However, in order to lay down groundwork for upcoming nonperturbative studies, it is indispensable to validate the renormalization methods at the perturbative level, i.e., to gain control over the perturbative treatment first. A clear understanding of divergences in perturbation theory, as well as their numerical treatment, is a necessary first step towards formulating such a program. The first objective of this dissertation is to clarify this issue, at least in second and fourth-order in perturbation theory. The work in this dissertation can provide guidance for the choice of counterterms in Discrete Light-Cone Quantization or the Tamm-Dancoff approach. A second objective of this work is the study of light-cone perturbation theory as a competitive tool for conducting perturbative Feynman diagram calculations. Feynman perturbation theory has become the most practical tool for computing cross sections in high energy physics and other physical properties of field theory. Although this standard covariant method has been applied to a great range of problems, computations beyond one-loop corrections are very difficult. Because of the algebraic complexity of the Feynman calculations in higher-order perturbation theory, it is desirable to automatize Feynman diagram calculations so that algebraic manipulation programs can carry out almost the entire calculation. This thesis presents a step in this direction. The technique we are elaborating on here is known as light-cone perturbation theory.
Perturbative Chern-Simons theory revisited
DEFF Research Database (Denmark)
McLellan, Brendan Donald Kenneth
2013-01-01
We reconsider perturbative Chern-Simons theory on a closed and oriented three-manifold with a choice of contact structure following C. Beasley and E. Witten. Closed three manifolds that admit a Sasakian structure are explicitly computed to first order in perturbation in terms of their Seifert dat...
Double soft theorem for perturbative gravity
Saha, Arnab Priya
2016-09-01
Following up on the recent work of Cachazo, He and Yuan [1], we derive the double soft graviton theorem in perturbative gravity. We show that the double soft theorem derived using CHY formula precisely matches with the perturbative computation involving Feynman diagrams. In particular, we find how certain delicate limits of Feynman diagrams play an important role in obtaining this equivalence.
Identifying influential multinomial observations by perturbation
Nyangoma, S.O.; Fung, W.-K.; Jansen, R.C.
2006-01-01
The assessment of the influence of individual observations on the outcome of the analysis by perturbation has received a lot of attention for situations in which the observations are independent and identically distributed. However, no methods based on minor perturbations for carrying out such asses
Tokamak Transport Studies Using Perturbation Analysis
Cardozo, N. J. L.; Dehaas, J. C. M.; Hogeweij, G. M. D.; Orourke, J.; Sips, A.C.C.; Tubbing, B. J. D.
1990-01-01
Studies of the transport properties of tokamak plasmas using perturbation analysis are discussed. The focus is on experiments with not too large perturbations, such as sawtooth induced heat and density pulse propagation, power modulation and oscillatory gas-puff experiments. The approximations made
ADDITIVE FUNCTIONALS AND PERTURBATION OF SEMIGROUP
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The perturbation of semigroup by a multiplicative functional with bounded variation is investigated in the frame of weak duality. The strong continuity and Schrodinger type equation of the perturbated semigroup are discussed. A few switching identities and formulae conerning dual additive functionals and Revuz measures are given.
ADDITIVE FUNCTIONALS AND PERTURBATION OF SEMIGROUP
Institute of Scientific and Technical Information of China (English)
JINMENGWEI; YINGJIANGANG
2001-01-01
The perturbation of semigroup by a multiplicative functional with bounded variation is investigated in the frame of weak duality. The strong continuity and SchrSdinger type equation of the perturbated semigroup are discussed. A few switching identities and formulae conerning dual additive functionais and Revuz measures are given.
Perturbation of eigenvalues embedded at a threshold
DEFF Research Database (Denmark)
Jensen, Arne; Melgaard, Michael
2002-01-01
Results are obtained on perturbation of eigenvalues and half-bound states (zero-resonances) embedded at a threshold. The results are obtained in a two-channel framework for small off-diagonal perturbations. The results are based on given asymptotic expansions of the component Hamiltonians....
Tokamak Transport Studies Using Perturbation Analysis
Cardozo, N. J. L.; Dehaas, J. C. M.; Hogeweij, G. M. D.; Orourke, J.; Sips, A.C.C.; Tubbing, B. J. D.
1990-01-01
Studies of the transport properties of tokamak plasmas using perturbation analysis are discussed. The focus is on experiments with not too large perturbations, such as sawtooth induced heat and density pulse propagation, power modulation and oscillatory gas-puff experiments. The approximations made
Perturbative expansion of Chern-Simons theory
SAWON, Justin
2005-01-01
An overview of the perturbative expansion of the Chern--Simons path integral is given. The main goal is to describe how trivalent graphs appear: as they already occur in the perturbative expansion of an analogous finite-dimensional integral, we discuss this case in detail.
Relevant Perturbation of Entanglement Entropy and Stationarity
Nishioka, Tatsuma
2014-01-01
A relevant perturbation of the entanglement entropy of a sphere is examined holographically near the UV fixed point. Varying the conformal dimension of the relevant operator, we obtain three different sectors: 1) the entanglement entropy is stationary and the perturbative expansion is well-defined with respect to the relevant coupling, 2) the entropy is stationary, but the perturbation fails, 3) the entropy is neither stationary nor perturbative. We compare our holographic results with the numerical calculation for a free massive scalar field in three-dimensions, and find a qualitative agreement between them. We argue that these statements hold for any relevant perturbation in any quantum field theory invariant under the Poincare symmetry.
Perturbative stability of catenoidal soap films
Jana, Soumya
2013-01-01
The perturbative stability of catenoidal soap films formed between parallel, equal radii, coaxial rings is studied using analytical and semi-analytical methods. Using a theorem on the nature of eigenvalues for a class of Sturm--Liouville operators, we show that for the given boundary conditions, azimuthally asymmetric perturbations are stable, while symmetric perturbations lead to an instability--a result demonstrated in Ben Amar et. al [7] using numerics and experiment. Further, we show how to obtain the lowest real eigenvalue of perturbations, using the semi-analytical Asymptotic Iteration Method (AIM). Conclusions using AIM support the analytically obtained result as well as the results in [7]. Finally, we compute the eigenfunctions and show, pictorially, how the perturbed soap film evolves in time.
Metric perturbations in Einstein-Cartan Cosmology
Garcia de Andrade, L C
2002-01-01
Metric perturbations the stability of solution of Einstein-Cartan cosmology (ECC) are given. The first addresses the stability of solutions of Einstein-Cartan (EC) cosmological model against Einstein static universe background. In this solution we show that the metric is stable against first-order perturbations and correspond to acoustic oscillations. The second example deals with the stability of de Sitter metric also against first-order perturbations. Torsion and shear are also computed in these cases. The resultant perturbed anisotropic spacetime with torsion is only de Sitter along one direction or is unperturbed along one direction and perturbed against the other two. Cartan torsion contributes to the frequency of oscillations in the model. Therefore gravitational waves could be triggered by the spin-torsion scalar density .
Perturbative photon production in a dispersive medium
Belgiorno, Francesco; Piazza, Francesco Dalla
2014-01-01
We investigate photon pair-creation in a dispersive dielectric medium induced by the presence of a spacetime varying dielectric constant. Our aim is to examine the possibility to observe new phenomena of pair creation induced by travelling dielectric perturbations e.g. created by laser pulses by means of the Kerr effect. In this perspective, we adopt a semi-phenomenological version of the Hopfield model in which a space-time dependent dielectric susceptibility appears. We focus our attention on perturbation theory, and provide general formulas for the photon production induced by a local but arbitrarily spacetime dependent refractive index perturbation. As an example, we further explore the case of an uniformly travelling perturbation, and provide examples of purely time-dependent perturbations.
Adiabatic density-functional perturbation theory
Gonze, Xavier
1995-08-01
The treatment of adiabatic perturbations within density-functional theory is examined, at arbitrary order of the perturbation expansion. Due to the extremal property of the energy functional, standard variation-perturbation theorems can be used. The different methods (Sternheimer equation, extremal principle, Green's function, and sum over state) for obtaining the perturbation expansion of the wave functions are presented. The invariance of the Hilbert space of occupied wave functions with respect to a unitary transformation leads to the definition of a ``parallel-transport-gauge'' and a ``diagonal-gauge'' perturbation expansion. Then, the general expressions are specialized for the second, third, and fourth derivative of the energy, with an example of application of the method up to third order.
Non-Perturbative Quantum Dynamics of a New Inflation Model
Boyanovsky, D; De Vega, H J; Holman, R; Kumar, S P
1998-01-01
We consider an O(N) model coupled self-consistently to gravity in the semiclassical approximation, where the field is subject to `new inflation' type initial conditions. We study the dynamics self-consistently and non-perturbatively with non-equilibrium field theory methods in the large N limit. We find that spinodal instabilities drive the growth of non-perturbatively large quantum fluctuations which shut off the inflationary growth of the scale factor. We find that a very specific combination of these large fluctuations plus the inflaton zero mode assemble into a new effective field. This new field behaves classically and it is the object which actually rolls down. We show how this reinterpretation saves the standard picture of how metric perturbations are generated during inflation and that the spinodal growth of fluctuations dominates the time dependence of the Bardeen variable for superhorizon modes during inflation. We compute the amplitude and index for the spectrum of scalar density and tensor perturb...
Unsafe but Calculable: Ratios of Angularities in Perturbative QCD
Larkoski, Andrew J
2013-01-01
Infrared- and collinear-safe (IRC-safe) observables have finite cross sections to each fixed-order in perturbative QCD. Generically, ratios of IRC-safe observables are themselves not IRC safe and do not have a valid fixed-order expansion. Nevertheless, in this paper we present an explicit method to calculate the cross section for a ratio observable in perturbative QCD with the help of resummation. We take the IRC-safe jet angularities as an example and consider the ratio formed from two angularities with different angular exponents. While the ratio observable is not IRC safe, it is "Sudakov safe", meaning that the perturbative Sudakov factor exponentially suppresses the singular region of phase space. At leading logarithmic (LL) order, the distribution is finite but has a peculiar expansion in the square root of the strong coupling constant, a consequence of IRC unsafety. The accuracy of the LL distribution can be further improved with higher-order resummation and fixed-order matching. Non-perturbative effect...
BaF2 TIME DIFFERENTIAL PERTURBED ANGULAR DISTRIBUTION SPECTROMETER
Institute of Scientific and Technical Information of China (English)
朱升云; 勾振辉; 等
1994-01-01
A BaF2 time differential perturbed angular distribution spectrometer has been established at the HI-13 tandem accelerator in CIAE.The time resolution of the spectrometer is 195ps and the nonlinearity is less than 2%.The spectrometer works very stably and no time drift is found over a period of experimental runs.This spectrometer has been successfully used in the g-factor measurement of 43Sc(19/2-,3.1232MeV).
Nakamura, Yousuke; Taniguchi, Yusuke; Collaboration, for CP-PACS
2007-01-01
We present non-perturbative renormalization factors for $\\Delta S=2$ four-quark operators in quenched domain-wall QCD using the Schroedinger functional method. Non-perturbative renormalization factor for $B_K$ is evaluated at hadronic scale. Combined with the non-perturbative RG running obtained by the Alpha collaboration, our result yields renormalization factor which converts lattice bare $B_K$ to the renormalization group invariant one. We apply the renormalization factor to bare $B_K$ pre...
Building a non-perturbative quark-gluon vertex from a perturbative one
Bermudez, Rocio
2016-10-01
The quark-gluon vertex describes the electromagnetic and the strong interaction among these particles. The description of this interaction at high precision in both regimes, perturbative and non-perturbative, continues being a matter of interest in the context of QCD and Hadron Physics. There exist very helpful models in the literature that explain perturbative aspects of the theory but they fail describing non-perturbative phenomena, as confinement and dynamic chiral symmetry breaking. In this work we study the structure of the quark-gluon vertex in a non-perturbative regime examining QCD, checking results with QED, and working in the Schwinger-Dyson formalism.
Energy Technology Data Exchange (ETDEWEB)
Weber, Christopher R. [Univ. of Wisconsin, Madison, WI (United States); Cook, Andrew W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bonazza, Riccardo [Univ. of Wisconsin, Madison, WI (United States)
2013-05-14
Here we derive a growth-rate model for the Richtmyer–Meshkov mixing layer, given arbitrary but known initial conditions. The initial growth rate is determined by the net mass flux through the centre plane of the perturbed interface immediately after shock passage. The net mass flux is determined by the correlation between the post-shock density and streamwise velocity. The post-shock density field is computed from the known initial perturbations and the shock jump conditions. The streamwise velocity is computed via Biot–Savart integration of the vorticity field. The vorticity deposited by the shock is obtained from the baroclinic torque with an impulsive acceleration. Using the initial growth rate and characteristic perturbation wavelength as scaling factors, the model collapses the growth-rate curves and, in most cases, predicts the peak growth rate over a range of Mach numbers (1.1 ≤M_{i}≤1.9), Atwood numbers (₋0.73 ≤ A ≤ ₋0.35 and 0.22 ≤ A ≤ 0.73), adiabatic indices (1.40/1.67≤γ_{1}/γ_{2}≤1.67/1.09) and narrow-band perturbation spectra. Lastly, the mixing layer at late times exhibits a power-law growth with an average exponent of θ=0.24.
Yalley, Akua; Schill, Daniel; Hatta, Mitsutoki; Johnson, Nicole; Cirillo, Lisa Ann
2016-04-15
FoxO1 binds to insulin response elements located in the promoters of insulin-like growth factor-binding protein 1 (IGFBP1) and glucose-6-phosphatase (G6Pase), activating their expression. Insulin-mediated phosphorylation of FoxO1 promotes cytoplasmic translocation, inhibiting FoxO1-mediated transactivation. We have previously demonstrated that FoxO1 opens and remodels chromatin assembled from the IGFBP1 promoter via a highly conserved winged helix motif. This finding, which established FoxO1 as a "pioneer" factor, suggested a model whereby FoxO1 chromatin remodeling at regulatory targets facilitates binding and recruitment of additional regulatory factors. However, the impact of FoxO1 phosphorylation on its ability to bind chromatin and the effect of FoxO1 loss on recruitment of neighboring transcription factors at its regulatory targets in liver chromatin is unknown. In this study, we demonstrate that an amino acid substitution that mimics insulin-mediated phosphorylation of a serine in the winged helix DNA binding motif curtails FoxO1 nucleosome binding. We also demonstrate that shRNA-mediated loss of FoxO1 binding to the IGFBP1 and G6Pase promoters in HepG2 cells significantly reduces binding of RNA polymerase II and the pioneer factors FoxA1/A2. Knockdown of FoxA1 similarly reduced binding of RNA polymerase II and FoxO1. Reduction in acetylation of histone H3 Lys-27 accompanies loss of FoxO1 and FoxA1/A2 binding. Interdependent binding of FoxO1 and FoxA1/A2 possibly entails cooperative binding because FoxO1 and FoxA1/A2 facilitate one another's binding to IGFPB1 promoter DNA. These results illustrate how transcription factors can nucleate transcriptional events in chromatin in response to signaling events and suggest a model for regulation of hepatic glucose metabolism through interdependent FoxO/FoxA binding.
Quantitative methods in classical perturbation theory.
Giorgilli, A.
Poincaré proved that the series commonly used in Celestial mechanics are typically non convergent, although their usefulness is generally evident. Recent work in perturbation theory has enlightened this conjecture of Poincaré, bringing into evidence that the series of perturbation theory, although non convergent in general, furnish nevertheless valuable approximations to the true orbits for a very large time, which in some practical cases could be comparable with the age of the universe. The aim of the author's paper is to introduce the quantitative methods of perturbation theory which allow to obtain such powerful results.
Density perturbation growth in teleparallel cosmology
Energy Technology Data Exchange (ETDEWEB)
Geng, Chao-Qiang [College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing, 400065 (China); Wu, Yi-Peng, E-mail: geng@phys.nthu.edu.tw, E-mail: s9822508@m98.nthu.edu.tw [Department of Physics, National Tsing Hua University, Hsinchu, 300 Taiwan (China)
2013-04-01
We study the cosmological perturbations in teleparallel dark energy models in which there is a dynamical scalar field with a non-minimal coupling to gravity. We find that the propagating degrees of freedom are the same as in quintessence cosmology despite that variables of the perturbed vierbein field are greater than those in metric theories. We numerically show some evident discrepancy from general relativity in the evolutions of the perturbations on all scales of the universe. We also demonstrate that the gravitational interactions are enhanced during the unique tracker evolutions in these models.
HIV-associated memory B cell perturbations.
Hu, Zhiliang; Luo, Zhenwu; Wan, Zhuang; Wu, Hao; Li, Wei; Zhang, Tong; Jiang, Wei
2015-05-21
Memory B-cell depletion, hyperimmunoglobulinemia, and impaired vaccine responses are the hallmark of B cell perturbations inhuman immunodeficiency virus (HIV) disease. Although B cells are not the targets for HIV infection, there is evidence for B cell, especially memory B cell dysfunction in HIV disease mediated by other cells or HIV itself. This review will focus on HIV-associated phenotypic and functional alterations in memory B cells. Additionally, we will discuss the mechanism underlying these perturbations and the effect of anti-retroviral therapy (ART) on these perturbations.
Perturbative Semiclassical Trace Formulae for Harmonic Oscillators
DEFF Research Database (Denmark)
Møller-Andersen, Jakob; Ögren, Magnus
2015-01-01
In this article we extend previous semiclassical studies by including more general perturbative potentials of the harmonic oscillator in arbitrary spatial dimensions. Our starting point is a radial harmonic potential with an arbitrary even monomial perturbation, which we use to study the resulting...... U(D) to O(D) symmetry breaking. We derive the gross structure of the semiclassical spectrum from periodic orbit theory, in the form of a perturbative (ħ → 0) trace formula. We then show how to apply the results to even-order polynomial potentials, possibly including mean-field terms. We have drawn...
Asymptotic stability of singularly perturbed differential equations
Artstein, Zvi
2017-02-01
Asymptotic stability is examined for singularly perturbed ordinary differential equations that may not possess a natural split into fast and slow motions. Rather, the right hand side of the equation is comprised of a singularly perturbed component and a regular one. The limit dynamics consists then of Young measures, with values being invariant measures of the fast contribution, drifted by the slow one. Relations between the asymptotic stability of the perturbed system and the limit dynamics are examined, and a Lyapunov functions criterion, based on averaging, is established.
EMG feedback tasks reduce reflexive stiffness during force and position perturbations.
Forbes, Patrick A; Happee, Riender; van der Helm, Frans C T; Schouten, Alfred C
2011-08-01
Force and position perturbations are widely applied to identify muscular and reflexive contributions to posture maintenance of the arm. Both task instruction (force vs. position) and the inherently linked perturbation type (i.e., force perturbations-position task and position perturbations-force tasks) affect these contributions and their mutual balance. The goal of this study is to explore the modulation of muscular and reflexive contributions in shoulder muscles using EMG biofeedback. The EMG biofeedback provides a harmonized task instruction to facilitate the investigation of perturbation type effects irrespective of task instruction. External continuous force and position perturbations with a bandwidth of 0.5-20 Hz were applied at the hand while subjects maintained prescribed constant levels of muscular co-activation using visual feedback of an EMG biofeedback signal. Joint admittance and reflexive impedance were identified in the frequency domain, and parametric identification separated intrinsic muscular and reflexive feedback properties. In tests with EMG biofeedback, perturbation type (position and force) had no effect on joint admittance and reflexive impedance, indicating task as the dominant factor. A reduction in muscular and reflexive stiffness was observed when performing the EMG biofeedback task relative to the position task. Reflexive position feedback was effectively suppressed during the equivalent EMG biofeedback task, while velocity and acceleration feedback were both decreased by approximately 37%. This indicates that force perturbations with position tasks are a more effective paradigm to investigate complete dynamic motor control of the arm, while EMG tasks tend to reduce the reflexive contribution.
Filossofov, D V; Korolev, N A; Egorov, V G; Lebedev, N A; Akselrod, Z Z; Brockmann, J; Rösch, F
2001-01-01
A new method of the perturbed angular \\gamma\\gamma-correlation (PAC) measurements was developed using one detector only. For the perturbation factor quantification the relation of the summing peak composed of two cascade \\gamma-rays of study (the perturbation-affected parameter) to the summing peak composed of one \\gamma-ray and X-ray (the perturbation non-affected parameter) was used. This method was demonstrated for the ^{111}In and ^{111m}Cd radionuclides.
Performance optimization of queueing systems with perturbation realization
Xia, Li
2012-04-01
After the intensive studies of queueing theory in the past decades, many excellent results in performance analysis have been obtained, and successful examples abound. However, exploring special features of queueing systems directly in performance optimization still seems to be a territory not very well cultivated. Recent progresses of perturbation analysis (PA) and sensitivity-based optimization provide a new perspective of performance optimization of queueing systems. PA utilizes the structural information of queueing systems to efficiently extract the performance sensitivity information from a sample path of system. This paper gives a brief review of PA and performance optimization of queueing systems, focusing on a fundamental concept called perturbation realization factors, which captures the special dynamic feature of a queueing system. With the perturbation realization factors as building blocks, the performance derivative formula and performance difference formula can be obtained. With performance derivatives, gradient-based optimization can be derived, while with performance difference, policy iteration and optimality equations can be derived. These two fundamental formulas provide a foundation for performance optimization of queueing systems from a sensitivity-based point of view. We hope this survey may provide some inspirations on this promising research topic. © 2011 Elsevier B.V. All rights reserved.
Picturing perturbative parton cascades in QCD matter
Directory of Open Access Journals (Sweden)
Aleksi Kurkela
2015-01-01
Full Text Available Based on parametric reasoning, we provide a simple dynamical picture of how a perturbative parton cascade, in interaction with a QCD medium, fills phase space as a function of time.
Perturbative Analysis of Gauged Matrix Models
Dijkgraaf, R; Kazakov, V A; Vafa, C; Dijkgraaf, Robbert; Gukov, Sergei; Kazakov, Vladimir A.; Vafa, Cumrun
2003-01-01
We analyze perturbative aspects of gauged matrix models, including those where classically the gauge symmetry is partially broken. Ghost fields play a crucial role in the Feynman rules for these vacua. We use this formalism to elucidate the fact that non-perturbative aspects of N=1 gauge theories can be computed systematically using perturbative techniques of matrix models, even if we do not possess an exact solution for the matrix model. As examples we show how the Seiberg-Witten solution for N=2 gauge theory, the Montonen-Olive modular invariance for N=1*, and the superpotential for the Leigh-Strassler deformation of N=4 can be systematically computed in perturbation theory of the matrix model/gauge theory (even though in some of these cases the exact answer can also be obtained by summing up planar diagrams of matrix models).
Simple Perturbation Example for Quantum Chemistry.
Goodfriend, P. L.
1985-01-01
Presents a simple example that illustrates various aspects of the Rayleigh-Schrodinger perturbation theory. The example is a particularly good one because it is straightforward and can be compared with both the exact solution and with experimental data. (JN)
Creating Statistically Anisotropic and Inhomogeneous Perturbations
Armendariz-Picon, C
2007-01-01
In almost all structure formation models, primordial perturbations are created within a homogeneous and isotropic universe, like the one we observe. Because their ensemble averages inherit the symmetries of the spacetime in which they are seeded, cosmological perturbations then happen to be statistically isotropic and homogeneous. Certain anomalies in the cosmic microwave background on the other hand suggest that perturbations do not satisfy these statistical properties, thereby challenging perhaps our understanding of structure formation. In this article we relax this tension. We show that if the universe contains an appropriate triad of scalar fields with spatially constant but non-zero gradients, it is possible to generate statistically anisotropic and inhomogeneous primordial perturbations, even though the energy momentum tensor of the triad itself is invariant under translations and rotations.
Gauge and motion in perturbation theory
Pound, Adam
2015-01-01
Through second order in perturbative general relativity, a small compact object in an external vacuum spacetime obeys a generalized equivalence principle: although it is accelerated with respect to the external background geometry, it is in free fall with respect to a certain \\emph{effective} vacuum geometry. However, this single principle takes very different mathematical forms, with very different behaviors, depending on how one treats perturbed motion. Furthermore, any description of perturbed motion can be altered by a gauge transformation. In this paper, I clarify the relationship between two treatments of perturbed motion and the gauge freedom in each. I first show explicitly how one common treatment, called the Gralla-Wald approximation, can be derived from a second, called the self-consistent approximation. I next present a general treatment of smooth gauge transformations in both approximations, in which I emphasise that the approximations' governing equations can be formulated in an invariant manner...
Perturbations of spiky strings in flat spacetimes
Bhattacharya, Soumya; Panigrahi, Kamal L
2016-01-01
Perturbations of a class of semiclassical strings known today as spiky strings, are studied using the well-known Jacobi equations for small normal deformations of an embedded timelike surface. It is shown that there exists finite normal perturbations of the spiky string worldsheets embedded in a $2+1$ dimensional flat spacetime. Such perturbations lead to a rounding off the spikes, which, in a way, demonstrates the stable nature of the unperturbed worldsheet. The same features appear for the dual spiky string solution and in the spiky as well as their dual solutions in $3+1$ dimensional flat spacetime. Our results are based on exact solutions of the corresponding Jacobi equations which we obtain and use while constructing the profiles of the perturbed configurations.
THE EIGENVALUE PERTURBATION BOUND FOR ARBITRARY MATRICES
Institute of Scientific and Technical Information of China (English)
Wen Li; Jian-xin Chen
2006-01-01
In this paper we present some new absolute and relative perturbation bounds for the eigenvalue for arbitrary matrices, which improves some recent results. The eigenvalue inclusion region is also discussed.
Cosmological perturbations in mimetic Horndeski gravity
Arroja, Frederico; Karmakar, Purnendu; Matarrese, Sabino
2016-01-01
We study linear scalar perturbations around a flat FLRW background in mimetic Horndeski gravity. In the absence of matter, we show that the Newtonian potential satisfies a second-order differential equation with no spatial derivatives. This implies that the sound speed for scalar perturbations is exactly zero on this background. We also show that in mimetic $G^3$ theories the sound speed is equally zero. We obtain the equation of motion for the comoving curvature perturbation (first order differential equation) and solve it to find that the comoving curvature perturbation is constant on all scales in mimetic Horndeski gravity. We find solutions for the Newtonian potential evolution equation in two simple models. Finally we show that the sound speed is zero on all backgrounds and therefore the system does not have any wave-like scalar degrees of freedom.
Rolling axions during inflation: perturbativity and signatures
Peloso, Marco; Unal, Caner
2016-01-01
The motion of a pseudo-scalar field $X$ during inflation naturally induces a significant amplification of the gauge fields to which it is coupled. The amplified gauge fields can source characteristic scalar and tensor primordial perturbations. Several phenomenological implications have been discussed in the cases in which (i) $X$ is the inflation, and (ii) $X$ is a field different from the inflation, that experiences a temporary speed up during inflation. In this second case, visible sourced gravitational waves (GW) can be produced at the CMB scales without affecting the scalar perturbations, even if the scale of inflation is several orders of magnitude below what is required to produce a visible vacuum GW signal. Perturbativity considerations can be used to limit the regime in which these results are under perturbative control. We revised limits recently claimed for the case (i), and we extend these considerations to the case (ii). We show that, in both cases, these limits are satisfied by the applications t...
Effective Field Theory of Cosmological Perturbations
Piazza, Federico
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 to write down the most general Lagrangian---and of the Stueckelberg "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 ana...
General degeneracy in density functional perturbation theory
Palenik, Mark C.; Dunlap, Brett I.
2017-07-01
Degenerate perturbation theory from quantum mechanics is inadequate in density functional theory (DFT) because of nonlinearity in the Kohn-Sham potential. Herein, we develop the fully general perturbation theory for open-shell, degenerate systems in Kohn-Sham DFT, without assuming the presence of symmetry or equal occupation of degenerate orbitals. To demonstrate the resulting methodology, we apply it to the iron atom in the central field approximation, perturbed by an electric quadrupole. This system was chosen because it displays both symmetry required degeneracy, between the five 3 d orbitals, as well as accidental degeneracy, between the 3 d and 4 s orbitals. The quadrupole potential couples the degenerate 3 d and 4 s states, serving as an example of the most general perturbation.
Collision orbits in the presence of perturbations
Energy Technology Data Exchange (ETDEWEB)
Diaz-Cano, A. [Departamento de Algebra, Facultad de CC. Matematicas, Universidad Complutense de Madrid, Madrid (Spain)]. E-mail: antonio_diazcano@mat.ucm.es; Gonzalez-Gascon, F. [Departamento de Fisica Teorica II, Facultad de CC. Fisicas, Universidad Complutense de Madrid, Madrid (Spain)
2006-10-16
It is shown that for particles moving in a plane under the action of attracting central potentials and a perturbing force (potential but not central), orbits representing the falling down of the particle to the center of force exist.
Cosmological perturbations in teleparallel Loop Quantum Cosmology
Haro, Jaime
2013-01-01
Cosmological perturbations in Loop Quantum Cosmology (LQC) could be studied from two totally different ways. The first one, called holonomy corrected LQC, is performed in the Hamiltonian framework, where the Asthekar connection is replaced by a suitable sinus function (holonomy correction), in order to have a well-defined quantum analogue. The alternative approach is based in the fact that isotropic LQC could be also obtained as a particular case of teleparallel $F(T)$ gravity (teleparallel LQC). Then, working in the Lagrangian framework and using the well-know perturbation equations in $F(T)$ gravity, we have obtained, in teleparallel LQC, the equations for scalar and tensor perturbations, and the corresponding Mukhanov-Sasaki equations. For scalar perturbations, our equation only differs from the one obtained by holonomy corrections in the velocity of sound, leading both formulations, essentially to the same scale invariant power spectrum when a matter-dominated universe is considered. However for tensor pe...
Microwave Background Anisotropies from Scaling Seed Perturbations
Durrer, R; Durrer, Ruth; Sakellariadou, Mairi
1997-01-01
We study microwave background anisotropies induced by scaling seed perturbations in a universe dominated by cold dark matter. Using a gauge invariant linear perturbation analysis, we solve the perturbation equations on super-horizon scales, for CMB anisotropies triggered by generic gravitational seeds. We find that perturbations induced by seeds -- under very mild restrictions -- are nearly isocurvature. Thus, compensation, which is mainly the consequence of physically sensible initial conditions, is very generic. We then restrict our study to the case of scaling sources, motivated by global scalar fields. We parameterize the energy momentum tensor of the source by ``seed functions'' and calculate the Sachs-Wolfe and acoustic contributions to the CMB anisotropies. We discuss the dependence of the anisotropy spectrum on the parameters of the model considered. Even within the restricted class of models investigated in this work, we find a surprising variety of results for the position and height of the first ac...
Adiabatic perturbations in coupled scalar field cosmologies
Beyer, Joschka
2014-01-01
We present a comprehensive and gauge invariant treatment of perturbations around cosmological scaling solutions for two canonical scalar fields coupled through a common potential in the early universe, in the presence of neutrinos, photons and baryons, but excluding cold dark matter. This setup is relevant for analyzing cosmic perturbations in scalar field models of dark matter with a coupling to a quintessence field. We put strong restrictions on the shape of the common potential and adopt a matrix-eigensystem approach to determine the dominant perturbations modes in such models. Similar to recent results in scenarios where standard cold dark matter couples to quintessence, we show that the stability of the adiabatic perturbation mode can be an issue for this class of scalar field dark matter models, but only for specific choices of the common potential. For an exponential coupling potential, a rather common shape arising naturally in many instances, this problem can be avoided. We explicitly calculate the d...
Chiral perturbation theory of muonic hydrogen Lamb shift: polarizability contribution
Alarcón, Jose Manuel; Pascalutsa, Vladimir
2013-01-01
The proton polarizability effect in the muonic-hydrogen Lamb shift comes out as a prediction of baryon chiral perturbation theory at leading order and our calculation yields for it: $\\Delta E^{(\\mathrm{pol})} (2P-2S) = 8^{+3}_{-1}\\, \\mu$eV. This result is consistent with most of evaluations based on dispersive sum rules, but is about a factor of two smaller than the recent result obtained in {\\em heavy-baryon} chiral perturbation theory. We also find that the effect of $\\Delta(1232)$-resonance excitation on the Lamb-shift is suppressed, as is the entire contribution of the magnetic polarizability; the electric polarizability dominates. Our results reaffirm the point of view that the proton structure effects, beyond the charge radius, are too small to resolve the `proton radius puzzle'.
Tidal satellite perturbations and the Lense-Thirring effect
Iorio, L; Iorio, Lorenzo; Pavlis, Erricos C.
2001-01-01
The tiny general relativistic Lense-Thirring effect can be measured by means of a suitable combination of the orbital residuals of the nodes of LAGEOS and LAGEOS II and the perigee of LAGEOS II. This observable is affected, among other factors, by the Earth' s solid and ocean tides. They induce long-period orbital perturbations that, over observational periods of few years, may alias the detection of the gravitomagnetic secular trend of interest. In this paper we calculate explicitly the most relevant tidal perturbations acting upon LAGEOSs and assess their influence on the detection of the Lense-Thirring effect. The present day level of knowledge of the solid and ocean tides allow us to conclude that their influence on it ranges from almost 4% over 4 years to less than 2% over 7 years.
Fidelity under isospectral perturbations: a random matrix study
Leyvraz, F.; García, A.; Kohler, H.; Seligman, T. H.
2013-07-01
The set of Hamiltonians generated by all unitary transformations from a single Hamiltonian is the largest set of isospectral Hamiltonians we can form. Taking advantage of the fact that the unitary group can be generated from Hermitian matrices we can take the ones generated by the Gaussian unitary ensemble with a small parameter as small perturbations. Similarly, the transformations generated by Hermitian antisymmetric matrices from orthogonal matrices form isospectral transformations among symmetric matrices. Based on this concept we can obtain the fidelity decay of a system that decays under a random isospectral perturbation with well-defined properties regarding time-reversal invariance. If we choose the Hamiltonian itself also from a classical random matrix ensemble, then we obtain solutions in terms of form factors in the limit of large matrices.
Dark matter perturbations and viscosity: a causal approach
Acquaviva, Giovanni; Pénin, Aurélie
2016-01-01
The inclusion of dissipative effects in cosmic fluids modifies their clustering properties and could have observable effects on the formation of large scale structures. We analyse the evolution of density perturbations of cold dark matter endowed with causal bulk viscosity. The perturbative analysis is carried out in the Newtonian approximation and the bulk viscosity is described by the causal Israel-Stewart (IS) theory. In contrast to the non-causal Eckart theory, we obtain a third order evolution equation for the density contrast that depends on three free parameters. For certain parameter values, the density contrast and growth factor in IS mimic their behaviour in $\\Lambda$CDM when $z \\geq 1$. Interestingly, and contrary to intuition, certain sets of parameters lead to an increase of the clustering.
Fast spectral source integration in black hole perturbation calculations
Hopper, Seth; Osburn, Thomas; Evans, Charles R
2015-01-01
This paper presents a new technique for achieving spectral accuracy and fast computational performance in a class of black hole perturbation and gravitational self-force calculations involving extreme mass ratios and generic orbits. Called \\emph{spectral source integration} (SSI), this method should see widespread future use in problems that entail (i) point-particle description of the small compact object, (ii) frequency domain decomposition, and (iii) use of the background eccentric geodesic motion. Frequency domain approaches are widely used in both perturbation theory flux-balance calculations and in local gravitational self-force calculations. Recent self-force calculations in Lorenz gauge, using the frequency domain and method of extended homogeneous solutions, have been able to accurately reach eccentricities as high as $e \\simeq 0.7$. We show here SSI successfully applied to Lorenz gauge. In a double precision Lorenz gauge code, SSI enhances the accuracy of results and makes a factor of three improvem...
Observing Quantum Tunneling in Perturbation Series
Suzuki, H; Suzuki, Hiroshi; Yasuta, Hirofumi
1997-01-01
It is well-known that the quantum tunneling makes conventional perturbation series non-Borel summable. We use this fact reversely and attempt to extract the decay width of the false-vacuum from the actual perturbation series of the vacuum energy density (vacuum bubble diagrams). It is confirmed that, at least in quantum mechanical examples, our proposal provides a complimentary approach to the the conventional instanton calculus in the strong coupling region.
Alternative perturbation approaches in classical mechanics
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Colima, Colima (Mexico); Raya, Alfredo [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Colima, Colima (Mexico); Fernandez, Francisco M [INIFTA (Conicet, UNLP), Blvd. 113 y 64 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2005-11-01
We discuss two alternative methods, based on the Lindstedt-Poincare technique, for the removal of secular terms from the equations of perturbation theory. We calculate the period of an anharmonic oscillator by means of both approaches and show that one of them is more accurate for all values of the coupling constant. We believe that present discussion and comparison may be a suitable exercise for teaching perturbation theory in advanced undergraduate courses on classical mechanics.
Double Soft Theorem for Perturbative Gravity
Saha, Arnab Priya
2016-01-01
Following up on the recent work of Cachazo, He and Yuan \\cite{arXiv:1503.04816 [hep-th]}, we derive the double soft graviton theorem in perturbative gravity. We show that the double soft theorem derived using CHY formula precisely matches with the perturbative computation involving Feynman diagrams. In particular, we find how certain delicate limits of Feynman diagrams play an important role in obtaining this equivalence.
Reflection and transmission of conformal perturbation defects
Brunner, Ilka
2015-01-01
We consider reflection and transmission of interfaces which implement renormalisation group flows between conformal fixed points in two dimensions. Such an RG interface is constructed from the identity defect in the ultraviolet CFT by perturbing the theory on one side of the defect line. We compute reflection and transmission coefficients in perturbation theory to third order in the coupling constant and check our calculations against exact constructions of RG interfaces between coset models.
Density Perturbation Growth in Teleparallel Cosmology
Geng, Chao-Qiang
2012-01-01
We study the cosmological perturbations in teleparallel dark energy models in which there is a dynamical scalar field with a non-minimal coupling to gravity. We find that the propagating degrees of freedom are the same as in quintessence cosmology despite that variables of the perturbed vierbein field are greater than those in metric theories. The resulting growth evolution shows that gravitational interactions are enhanced during the unique tracker evolution of teleparallel dark energy models.
Non-perturbative renormalization in kaon decays
Donini, Andrea; Martinelli, G; Rossi, G C; Talevi, M; Testa, M; Vladikas, A
1996-01-01
We discuss the application of the MPSTV non-perturbative method \\cite{NPM} to the operators relevant to kaon decays. This enables us to reappraise the long-standing question of the $\\Delta I=1/2$ rule, which involves power-divergent subtractions that cannot be evaluated in perturbation theory. We also study the mixing with dimension-six operators and discuss its implications to the chiral behaviour of the $B_K$ parameter.
Cosmological scalar field perturbations can grow
Alcubierre, Miguel; Diez-Tejedor, Alberto; Torres, José M
2015-01-01
It has been argued that the small perturbations in the energy density to the homogeneous and isotropic configurations of a canonical scalar field in an expanding universe do not grow. We show that this is not true in general, and clarify the root of the misunderstanding. We revisit a simple model in which the linear perturbations grow like those in the standard cold dark matter scenario, but with the Jeans length at the scale of the Compton wavelength of the scalar particle.
Perturbative partition function for squashed S^5
Imamura, Yosuke
2012-01-01
We compute the index of 6d N=(1,0) theories on S^5xR containing vector and hypermultiplets. We only consider the perturbative sector without instantons. By compactifying R to S^1 with a twisted boundary condition and taking the small radius limit, we derive the perturbative partition function on a squashed S^5. The 1-loop partition function is represented in a simple form with the triple sine function.
General degeneracy in density functional perturbation theory
Palenik, Mark C
2016-01-01
Degenerate perturbation theory from quantum mechanics is inadequate in density functional theory (DFT) because of nonlinearity in the Kohn-Sham potential. We develop the fully general degenerate perturbation theory for DFT without assuming that the degeneracy is required by symmetry. The resulting methodology is applied to the iron atom ground state in order to demonstrate the effects of degeneracy that appears both due to symmetry requirements and accidentally, between different representations of the symmetry group.
PRIMAL PERTURBATION SIMPLEX ALGORITHMS FOR LINEAR PROGRAMMING
Institute of Scientific and Technical Information of China (English)
Ping-qi Pan
2000-01-01
In this paper, we propose two new perturbation simplex variants. Solving linear programming problems without introducing artificial variables, each of the two uses the dual pivot rule to achieve primal feasibility, and then the primal pivot rule to achieve optimality. The second algorithm, a modification of the first, is designed to handle highly degenerate problems more etficiently. Some interesting results concerning merit of the perturbation are established. Numerical results from preliminary tests are also reported.
Gauge and motion in perturbation theory
Pound, Adam
2015-08-01
Through second order in perturbative general relativity, a small compact object in an external vacuum spacetime obeys a generalized equivalence principle: although it is accelerated with respect to the external background geometry, it is in free fall with respect to a certain effective vacuum geometry. However, this single principle takes very different mathematical forms, with very different behaviors, depending on how one treats perturbed motion. Furthermore, any description of perturbed motion can be altered by a gauge transformation. In this paper, I clarify the relationship between two treatments of perturbed motion and the gauge freedom in each. I first show explicitly how one common treatment, called the Gralla-Wald approximation, can be derived from a second, called the self-consistent approximation. I next present a general treatment of smooth gauge transformations in both approximations, in which I emphasize that the approximations' governing equations can be formulated in an invariant manner. All of these analyses are carried through second perturbative order, but the methods are general enough to go to any order. Furthermore, the tools I develop, and many of the results, should have broad applicability to any description of perturbed motion, including osculating-geodesic and two-timescale descriptions.
Dielectric loss determination using perturbation
Andrawis, Madeleine Y.
1991-01-01
A dielectric filled cavity structure is currently being used to estimate the dielectric constant and loss factor over a wide range of frequencies of a dielectric material which fills the cavity structure [Saed, 1987]. A full field analysis is used to compute the effective complex permittivity of the sample material based on reflection coefficient measurements of the cavity structure and associated geometrical dimensions. The method has previously been used successfully to de...
Desoer, C. A.; Kabuli, M. G.
1989-01-01
The authors consider a linear (not necessarily time-invariant) stable unity-feedback system, where the plant and the compensator have normalized right-coprime factorizations. They study two cases of nonlinear plant perturbations (additive and feedback), with four subcases resulting from: (1) allowing exogenous input to Delta P or not; 2) allowing the observation of the output of Delta P or not. The plant perturbation Delta P is not required to be stable. Using the factorization approach, the authors obtain necessary and sufficient conditions for all cases in terms of two pairs of nonlinear pseudostate maps. Simple physical considerations explain the form of these necessary and sufficient conditions. Finally, the authors obtain the characterization of all perturbations Delta P for which the perturbed system remains stable.
Hajian, K; Sheikh-Jabbari, M M
2014-01-01
In arXiv:1310.3727 we formulated and derived the three universal laws governing Near Horizon Extremal Geometries (NHEG). In this work we focus on the Entropy Perturbation Law (EPL) which, similarly to the first law of black hole thermodynamics, relates perturbations of the charges labeling perturbations around a given NHEG to the corresponding entropy perturbation. We show that field perturbations governed by the linearized equations of motion and symmetry conditions which we carefully specify, satisfy the EPL. We also show that these perturbations are limited to those coming from difference of two NHEG solutions (i.e. variations on the NHEG solution parameter space). Our analysis and discussions shed light on the "no-dynamics" statements of arXiv:0906.2380 and arXiv:0906.2376.
SOLVABILITY FOR NONLINEAR ELLIPTIC EQUATION WITH BOUNDARY PERTURBATION
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The solvability of nonlinear elliptic equation with boundary perturbation is considered. The perturbed solution of original problem is obtained and the uniformly valid expansion of solution is proved.
Perturbations of ultralight vector field dark matter
Cembranos, J. A. R.; Maroto, A. L.; Núñez Jareño, S. J.
2017-02-01
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}^2≪ Hma, we have a particle-like behaviour indistinguishable from cold dark matter, whereas for modes with {k}^2≫ Hma, we get a wave-like behaviour in which the sound speed is non-vanishing and of order c s 2 ≃ k 2/ m 2 a 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 s 2 . Moreover in this regime the amplitude of the tensor to scalar ratio of the scalar-tensor modes is also h/ Φ ˜ c s 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.
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.
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 F2, H2O2, C2H6, and N2 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 (ΔST=ET-ES) of 9,10-anthracyne. At the DSRG-MRPT3 level of theory, our best estimate of the adiabatic ΔST is 3.9 kcal mol(-1), a value that is within 0.1 kcal mol(-1) from multireference coupled cluster results.
Rolling axions during inflation: perturbativity and signatures
Peloso, Marco; Sorbo, Lorenzo; Unal, Caner
2016-09-01
The motion of a pseudo-scalar field X during inflation naturally induces a significant amplification of the gauge fields to which it is coupled. The amplified gauge fields can source characteristic scalar and tensor primordial perturbations. Several phenomenological implications have been discussed in the cases in which (i) X is the inflaton, and (ii) X is a field different from the inflaton, that experiences a temporary speed up during inflation. In this second case, visible sourced gravitational waves (GW) can be produced at the CMB scales without affecting the scalar perturbations, even if the scale of inflation is several orders of magnitude below what is required to produce a visible vacuum GW signal. Perturbativity considerations can be used to limit the regime in which these results are under perturbative control. We revised limits recently claimed for the case (i), and we extend these considerations to the case (ii). We show that, in both cases, these limits are satisfied by the applications that generate signals at CMB scales. Applications that generate gravitational waves and primordial black holes at much smaller scales are at the limit of the validity of this perturbativity analysis, so we expect those results to be valid up to possibly order one corrections.
Cosmological perturbations on the Phantom brane
Bag, Satadru; Shtanov, Yuri; Sahni, Varun
2016-01-01
We obtain a closed system of equations for scalar perturbations in a multi-component braneworld. Our braneworld possesses a phantom-like equation of state at late times, $w_{\\rm eff} < -1$, but no big-rip future singularity. In addition to matter and radiation, the braneworld possesses a new effective degree of freedom - the 'Weyl fluid' or 'dark radiation'. Setting initial conditions on super-Hubble spatial scales at the epoch of radiation domination, we evolve perturbations of radiation, pressureless matter and the Weyl fluid until the present epoch. We observe a gradual decrease in the amplitude of the Weyl-fluid perturbations after Hubble-radius crossing, which results in a negligible effect of the Weyl fluid on the evolution of matter perturbations on spatial scales relevant for structure formation. Consequently, the quasi-static approximation of Koyama and Maartens provides a good fit to the exact results during the matter-dominated epoch. We find that the late-time growth of density perturbations on...
Four-Dimensional Spin Foam Perturbation Theory
Directory of Open Access Journals (Sweden)
João Faria Martins
2011-10-01
Full Text Available We define a four-dimensional spin-foam perturbation theory for the BF-theory with a B∧B potential term defined for a compact semi-simple Lie group G on a compact orientable 4-manifold M. This is done by using the formal spin foam perturbative series coming from the spin-foam generating functional. We then regularize the terms in the perturbative series by passing to the category of representations of the quantum group U_q(g where g is the Lie algebra of G and q is a root of unity. The Chain-Mail formalism can be used to calculate the perturbative terms when the vector space of intertwiners Λ⊗Λ→A, where A is the adjoint representation of g, is 1-dimensional for each irrep Λ. We calculate the partition function Z in the dilute-gas limit for a special class of triangulations of restricted local complexity, which we conjecture to exist on any 4-manifold M. We prove that the first-order perturbative contribution vanishes for finite triangulations, so that we define a dilute-gas limit by using the second-order contribution. We show that Z is an analytic continuation of the Crane-Yetter partition function. Furthermore, we relate Z to the partition function for the F∧F theory.
Local perturbations perturb—exponentially–locally
Energy Technology Data Exchange (ETDEWEB)
De Roeck, W., E-mail: wojciech.deroeck@fys.kuleuven.be; Schütz, M., E-mail: marius.schutz@fys.kuleuven.be [Instituut voor Theoretische Fysica, K. U. Leuven, Celestijnenlaan 200D, B-3001 Heverlee (Belgium)
2015-06-15
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.
Perturbative analysis of gauged matrix models
Dijkgraaf, Robbert; Gukov, Sergei; Kazakov, Vladimir A.; Vafa, Cumrun
2003-08-01
We analyze perturbative aspects of gauged matrix models, including those where classically the gauge symmetry is partially broken. Ghost fields play a crucial role in the Feynman rules for these vacua. We use this formalism to elucidate the fact that nonperturbative aspects of N=1 gauge theories can be computed systematically using perturbative techniques of matrix models, even if we do not possess an exact solution for the matrix model. As examples we show how the Seiberg-Witten solution for N=2 gauge theory, the Montonen-Olive modular invariance for N=1*, and the superpotential for the Leigh-Strassler deformation of N=4 can be systematically computed in perturbation theory of the matrix model or gauge theory (even though in some of these cases an exact answer can also be obtained by summing up planar diagrams of matrix models).
Perturbation calculation of thermodynamic density of states.
Brown, G; Schulthess, T C; Nicholson, D M; Eisenbach, M; Stocks, G M
2011-12-01
The density of states g (ε) is frequently used to calculate the temperature-dependent properties of a thermodynamic system. Here a derivation is given for calculating the warped density of states g*(ε) resulting from the addition of a perturbation. The method is validated for a classical Heisenberg model of bcc Fe and the errors in the free energy are shown to be second order in the perturbation. Taking the perturbation to be the difference between a first-principles quantum-mechanical energy and a corresponding classical energy, this method can significantly reduce the computational effort required to calculate g(ε) for quantum systems using the Wang-Landau approach.
Non-perturbative quantum geometry III
Krefl, Daniel
2016-08-01
The Nekrasov-Shatashvili limit of the refined topological string on toric Calabi-Yau manifolds and the resulting quantum geometry is studied from a non-perturbative perspective. The quantum differential and thus the quantum periods exhibit Stokes phenomena over the combined string coupling and quantized Kähler moduli space. We outline that the underlying formalism of exact quantization is generally applicable to points in moduli space featuring massless hypermultiplets, leading to non-perturbative band splitting. Our prime example is local ℙ1 + ℙ1 near a conifold point in moduli space. In particular, we will present numerical evidence that in a Stokes chamber of interest the string based quantum geometry reproduces the non-perturbative corrections for the Nekrasov-Shatashvili limit of 4d supersymmetric SU(2) gauge theory at strong coupling found in the previous part of this series. A preliminary discussion of local ℙ2 near the conifold point in moduli space is also provided.
Cosmic Perturbations Through the Cyclic Ages
Erickson, J K; Steinhardt, P J; Turok, N G; Erickson, Joel K.; Gratton, Steven; Steinhardt, Paul J.; Turok, Neil
2006-01-01
We analyze the evolution of cosmological perturbations in the cyclic model, paying particular attention to their behavior and interplay over multiple cycles. Our key results are: (1) galaxies and large scale structure present in one cycle are generated by the quantum fluctuations in the preceding cycle without interference from perturbations or structure generated in earlier cycles and without interfering with structure generated in later cycles; (2) the ekpyrotic phase, an epoch of gentle contraction with equation of state $w\\gg 1$ preceding the hot big bang, makes the universe homogeneous, isotropic and flat within any given observer's horizon; and, (3) although the universe is uniform within each observer's horizon, the global structure of the cyclic universe is more complex, owing to the effects of superhorizon length perturbations, and cannot be described in a uniform Friedmann-Robertson-Walker picture. In particular, we show that the ekpyrotic phase is so effective in smoothing, flattening and isotropiz...
Chiral Perturbation Theory With Lattice Regularization
Ouimet, P P A
2005-01-01
In this work, alternative methods to regularize chiral perturbation theory are discussed. First, Long Distance Regularization will be considered in the presence of the decuplet of the lightest spin 32 baryons for several different observables. This serves motivation and introduction to the use of the lattice regulator for chiral perturbation theory. The mesonic, baryonic and anomalous sectors of chiral perturbation theory will be formulated on a lattice of space time points. The consistency of the lattice as a regulator will be discussed in the context of the meson and baryon masses. Order a effects will also be discussed for the baryon masses, sigma terms and magnetic moments. The work will close with an attempt to derive an effective Wess-Zumino-Witten Lagrangian for Wilson fermions at non-zero a. Following this discussion, there will be a proposal for a phenomenologically useful WZW Lagrangian at non-zero a.
Non-Perturbative Quantum Geometry III
Krefl, Daniel
2016-01-01
The Nekrasov-Shatashvili limit of the refined topological string on toric Calabi-Yau manifolds and the resulting quantum geometry is studied from a non-perturbative perspective. The quantum differential and thus the quantum periods exhibit Stockes phenomena over the combined string coupling and quantized Kaehler moduli space. We outline that the underlying formalism of exact quantization is generally applicable to points in moduli space featuring massless hypermultiplets, leading to non-perturbative band splitting. Our prime example is local P1xP1 near a conifold point in moduli space. In particular, we will present numerical evidence that in a Stockes chamber of interest the string based quantum geometry reproduces the non-perturbative corrections for the Nekrasov-Shatashvili limit of 4d supersymmetric SU(2) gauge theory at strong coupling found in the previous part of this series. A preliminary discussion of local P2 near the conifold point in moduli space is also provided.
Gaugeon Formalism for Perturbative Quantum Gravity
Upadhyay, Sudhaker
2014-01-01
In this paper we investigate the Yokoyama gaugeon formalism for perturbative quantum gravity in general curved spacetime. Within the gaugeon formalism, we extend the configuration space by introducing vector gaugeon fields describing quantum gauge freedom. Such extended theory of perturbative gravity admits quantum gauge transformations leading to an natural shift in the gauge parameter. Further we impose the Gupta-Bleuler type subsidiary condition to remove the unphysical gaugeon modes. To replace the Gupta-Bleuler type condition by more acceptable Kugo-Ojima type subsidiary condition we analyse the BRST symmetric gaugeon formalism. Further, the physical Hilbert space is constructed for the perturbative quantum gravity which remains invariant under both the BRST symmetry and quantum gauge transformations.
Cosmological Perturbations in Extended Massive Gravity
Gumrukcuoglu, A Emir; Lin, Chunshan; Mukohyama, Shinji; Trodden, Mark
2013-01-01
We study cosmological perturbations around self-accelerating solutions to two extensions of nonlinear massive gravity: the quasi-dilaton theory and the mass-varying theory. We examine stability of the cosmological solutions, and the extent to which the vanishing of the kinetic terms for scalar and vector perturbations of self-accelerating solutions in massive gravity is generic when the theory is extended. We find that these kinetic terms are in general non-vanishing in both extensions, though there are constraints on the parameters and background evolution from demanding that they have the correct sign. In particular, the self-accelerating solutions of the quasi-dilaton theory are always unstable to scalar perturbations with wavelength shorter than the Hubble length.
Note on the semiclassicality of cosmological perturbations
Donà, Pietro; Marcianò, Antonino
2016-12-01
Moving from the consideration that matter fields must be treated in terms of their fundamental quantum counterparts, we show straightforward arguments, within the framework of ordinary quantum mechanics and quantum field theory, in order to convince readers that cosmological perturbations must be addressed in term of the semiclassical limit of the expectation value of quantum fields. We first take into account cosmological perturbations originated by a quantum scalar field, and then extend our treatment in order to account for the expectation values of bilinears of Dirac fermion fields. The latter can indeed transform as scalar quantities under diffeomorphisms, as well as all the other bilinear of the Dirac fields that belong to the Clifford algebra. This is the first of a series of works that is intended to prove that cosmological quantum perturbations can actually be accounted for in terms of Dirac fermion fields, which must be treated as fundamental quantum objects, and their dynamics.
Cosmological Perturbations with Multiple Fluids and Fields
Hwang, J
2002-01-01
We consider the evolution of perturbed cosmological spacetime with multiple fluid and field system in Einstein gravity. Equations are presented in gauge-ready forms, and are presented using the adiabatic and isocurvature perturbation variables. We present equations in the general background with $K$ and $\\Lambda$. We also clarify the conditions for conserved adiabatic and isocurvature perturbations in the large-scale limit. One interesting conclusion is that, for ideal fluid system, although the isocurvature modes can seed the adiabatic mode in the large-scale limit, the isocurvature modes decouple from the adiabatic one which is not the case for the field system. Useful sets of equations readily applicable to the quintessence models and the warm inflation scenario can be found in this work. An application to the scaling regime with an exponential field potential is made in the Appendix.
Operator Decomposition Framework for Perturbation Theory
Energy Technology Data Exchange (ETDEWEB)
Abdel-Khalik, Hany S.; Wang, Congjian; Bang, Young Suk [North Carolina State University, Raleigh (United States)
2012-05-15
This summary describes a new framework for perturbation theory intended to improve its performance, in terms of the associated computational cost and the complexity of implementation, for routine reactor calculations in support of design, analysis, and regulation. Since its first introduction in reactor analysis by Winger, perturbation theory has assumed an aura of sophistication with regard to its implementation and its capabilities. Only few reactor physicists, typically mathematically proficient, have contributed to its development, with the general body of the nuclear engineering community remaining unaware of its current status, capabilities, and challenges. Given its perceived sophistication and the small body of community users, the application of perturbation theory has been limited to investigatory analyses only. It is safe to say that the nuclear community is split into two groups, a small one which understands the theory and, and a much bigger group with the perceived notion that perturbation theory is nothing but a fancy mathematical approach that has very little use in practice. Over the past three years, research has demonstrated two goals. First, reduce the computational cost of perturbation theory in order to enable its use for routine reactor calculations. Second, expose some of the myth about perturbation theory and present it in a form that is simple and relatable in order to stimulate the interest of nuclear practitioners, especially those who are currently working on the development of next generation reactor design and analysis tools. The operator decomposition approach has its roots in linear algebra and can be easily understood by code developers, especially those involved in the design of iterative numerical solution strategies
Evolution of perturbed accelerating relativistic shock waves
Palma, G; Vietri, M; Del Zanna, L
2008-01-01
We study the evolution of an accelerating hyperrelativistic shock under the presence of upstream inhomogeneities wrinkling the discontinuity surface. The investigation is conducted by means of numerical simulations using the PLUTO code for astrophysical fluid dynamics. The reliability and robustness of the code are demonstrated against well known results coming from the linear perturbation theory. We then follow the nonlinear evolution of two classes of perturbing upstream atmospheres and conclude that no lasting wrinkle can be preserved indefinitely by the flow. Finally we derive analytically a description of the geometrical effects of a turbulent upstream ambient on the discontinuity surface.
Scalar and tensor perturbation in vacuum inflation
Huang, Zhiqiang
2016-01-01
It was recently proposed that a small true vacuum universe can inflate spontaneously, in principle. In this paper, this model is completed with experimental results. There should be matter creation in vacuum inflation due to quantum fluctuations, and the matter created will influence the inflation simultaneously. We derive cosmological perturbations in this vacuum inflation model and express them with Hubble flow-functions. By comparing the perturbations with the experimental results, we can determine all the parameters in this model. Finally, we calculate the evolution of the matter density with the determined parameters and show that the matter produced in inflation roughly fits the observations at present.
Matter Density Perturbations in Modified Teleparallel Theories
Wu, Yi-Peng
2012-01-01
We study the matter density perturbations in modified teleparallel gravity theories, where extra degrees of freedom arise from the local Lorentz violation in the tangent space. We formulate a vierbein perturbation with variables addressing all the 16 components of the vierbein field. By assuming the perfect fluid matter source, we examine the cosmological implication of the 6 unfamiliar new degrees of freedom in modified $f(T)$ gravity theories. We find that despite the new modes in the vierbein scenario provide no explicit significant effect in the small-scale regime, they exhibit some deviation from the standard general relativity results in super-horizon scales.
Robustness of braneworld scenarios against tensorial perturbations
Bazeia, D; Menezes, R; Olmo, Gonzalo J; Rubiera-Garcia, D
2015-01-01
Inspired by the peculiarities of the effective geometry of crystalline structures, we reconsider thick brane scenarios from a metric-affine perspective. We show that for a rather general family of theories of gravity, whose Lagrangian is an arbitrary function of the metric and the Ricci tensor, the background and scalar field equations can be written in first-order form, and tensorial perturbations have a non negative definite spectrum, which makes them stable under linear perturbations regardless of the form of the gravity Lagrangian. We find, in particular, that the tensorial zero modes are exactly the same as predicted by Einstein's theory regardless of the scalar field and gravitational Lagrangians.
Cosmological perturbations from an inhomogeneous phase transition
Energy Technology Data Exchange (ETDEWEB)
Matsuda, Tomohiro, E-mail: matsuda@sit.ac.j [Laboratory of Physics, Saitama Institute of Technology, Fusaiji, Okabe-machi, Saitama 369-0293 (Japan)
2009-07-21
A mechanism for generating metric perturbations in inflationary models is considered. Long-wavelength inhomogeneities of light scalar fields in a decoupled sector may give rise to superhorizon fluctuations of couplings and masses in the low-energy effective action. Cosmological phase transitions may then occur that are not simultaneous in space, but occur with time lags in different Hubble patches that arise from the long-wavelength inhomogeneities. Here an interesting model in which cosmological perturbations may be created at the electroweak phase transition is considered. The results show that phase transitions may be a generic source of non-Gaussianity.
Vector Meson Masses in Chiral Perturbation Theory
Bijnens, J; Talavera, P
1997-01-01
We discuss the vector meson masses within the context of Chiral Perturbation Theory performing an expansion in terms of the momenta, quark masses and 1/Nc. We extend the previous analysis to include isospin breaking effects and also include up to order p^4. We discuss vector meson chiral perturbation theory in some detail and present a derivation from a relativistic lagrangian. The unknown coefficients are estimated in various ways. We also discuss the relevance of electromagnetic corrections and the implications of the present calculation for the determination of quark masses.
Perturbations of C*-algebraic Invariants
DEFF Research Database (Denmark)
Christensen, Erik; Sinclair, Allan M.; Smith, Roger R.;
2010-01-01
The setting of the article is the so-called theory of perturbations of algebras of operators. It is shown that several of the properties a C*-algebra may have are preseved under pertubations. The main result states that Pisier's concept finite length is a stasble property.......The setting of the article is the so-called theory of perturbations of algebras of operators. It is shown that several of the properties a C*-algebra may have are preseved under pertubations. The main result states that Pisier's concept finite length is a stasble property....
A generalized perturbation program for CANDU reactor
Energy Technology Data Exchange (ETDEWEB)
Kim, Do Heon; Kim, Jong Kyung [Hanyang University, Seoul (Korea, Republic of); Choi, Hang Bok; Roh, Gyu Hong [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of); Yang, Won Sik [Chosun University, Kwangju (Korea, Republic of)
1998-12-31
A generalized perturbation program has been developed for the purpose of estimating zonal power variation of a CANDU reactor upon refueling operation. The forward and adjoint calculation modules of RFSP code were used to construct the generalized perturbation program. The numerical algorithm for the generalized adjoint flux calculation was verified by comparing the zone power estimates upon refueling with those of forward calculation. It was, however, noticed that the truncation error from the iteration process of the generalized adjoint flux is not negligible. 2 refs., 1 figs., 1 tab. (Author)
Taming perturbative divergences in asymptotically safe gravity
Energy Technology Data Exchange (ETDEWEB)
Benedetti, Dario, E-mail: dbenedetti@perimeterinstitute.c [Perimeter Institute for Theoretical Physics, 31 Caroline St. N, N2L 2Y5, Waterloo ON (Canada); Machado, Pedro F., E-mail: p.f.machado@uu.n [Institute for Theoretical Physics, Utrecht University, 3508 TD Utrecht (Netherlands); Saueressig, Frank, E-mail: Frank.Saueressig@cea.f [Institut de Physique Theorique, CEA Saclay, F-91191 Gif-Sur-Yvette Cedex (France); CNRS URA 2306, F-91191 Gif-Sur-Yvette Cedex (France)
2010-01-01
We use functional renormalization group methods to study gravity minimally coupled to a free scalar field. This setup provides the prototype of a gravitational theory which is perturbatively non-renormalizable at one-loop level, but may possess a non-trivial renormalization group fixed point controlling its UV behavior. We show that such a fixed point indeed exists within the truncations considered, lending strong support to the conjectured asymptotic safety of the theory. In particular, we demonstrate that the counterterms responsible for its perturbative non-renormalizability have no qualitative effect on this feature.
Death to perturbative QCD in exclusive processes?
Energy Technology Data Exchange (ETDEWEB)
Eckardt, R.; Hansper, J.; Gari, M.F. [Institut fuer Theoretische Physik, Bochum (Germany)
1994-04-01
The authors discuss the question of whether perturbative QCD is applicable in calculations of exclusive processes at available momentum transfers. They show that the currently used method of determining hadronic quark distribution amplitudes from QCD sum rules yields wave functions which are completely undetermined because the polynomial expansion diverges. Because of the indeterminacy of the wave functions no statement can be made at present as to whether perturbative QCD is valid. The authors emphasize the necessity of a rigorous discussion of the subject and the importance of experimental data in the range of interest.
Perturbative approach to Markovian open quantum systems.
Li, Andy C Y; Petruccione, F; Koch, Jens
2014-05-08
The exact treatment of Markovian open quantum systems, when based on numerical diagonalization of the Liouville super-operator or averaging over quantum trajectories, is severely limited by Hilbert space size. Perturbation theory, standard in the investigation of closed quantum systems, has remained much less developed for open quantum systems where a direct application to the Lindblad master equation is desirable. We present such a perturbative treatment which will be useful for an analytical understanding of open quantum systems and for numerical calculation of system observables which would otherwise be impractical.
Perturbative QCD at finite temperature and density
Niégawa, A
1997-01-01
This is a comprehensive review on the perturbative hot QCD including the recent developments. The main body of the review is concentrated upon dealing with physical quantities like reaction rates. Contents: \\S1. Introduction, \\S2. Perturbative thermal field theory: Feynman rules, \\S3. Reaction-rate formula, \\S4. Hard-thermal-loop resummation scheme in hot QCD, \\S5. Effective action, \\S6. Hard modes with $|P^2| \\leq O (g^2 T^2)$, hard-thermal-loop resummation scheme, \\S9. Conclusions.
Perturbation of Wavelet and Gabor Frames
Institute of Scientific and Technical Information of China (English)
Ivana Carrizo; Sergio Favier
2003-01-01
In this work two aspects of theory of frames are presented: a side necessary condition on irregular wavelet frames is obtained, another perturbation of wavelet and Gabor frames is considered. Specifically,we present the results obtained on frame stability when one disturbs the mother of wavelet frame, or the parameter of dilatation, and in Gabor frames when the generating function or the parameter of translation are perturbed. In all cases we work without demanding compactness of the support, neither on the generating function, nor on its Fourier transform.
Perturbative and nonperturbative renormalization in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Institut fuer Theoretische Physik; Horsley, R. [University of Edinburgh (United Kingdom). School of Physics and Astronomy; Perlt, H. [Leipzig Univ. (DE). Institut fuer Theoretische Physik] (and others)
2010-03-15
We investigate the perturbative and nonperturbative renormalization of composite operators in lattice QCD restricting ourselves to operators that are bilinear in the quark fields (quark-antiquark operators). These include operators which are relevant to the calculation of moments of hadronic structure functions. The nonperturbative computations are based on Monte Carlo simulations with two flavors of clover fermions and utilize the Rome-Southampton method also known as the RI-MOM scheme. We compare the results of this approach with various estimates from lattice perturbation theory, in particular with recent two-loop calculations. (orig.)
$K_{\\ell3}$ decays in Chiral Perturbation Theory
Bijnens, J; Bijnens, Johan; Talavera, Pere
2003-01-01
The process $K_{\\ell3}$ is calculated to two-loop order ($p^6$) in Chiral Perturbation Theory (ChPT) in the isospin conserved case. We use expressions suitable for use with previous work in two-loop CHPT where the order $p^4$ parameters ($L_i^r$) were determined from experiment. We point out that all the order $p^6$ parameters ($C_i^r$) that appear in the value of $f_+(0)$ relevant for the determination of $|V_{us}|$ can be determined from $K_{\\ell3}$ measurements via the slope and the curvature of the scalar form-factor.
Fingerprints of Primordial Universe Paradigms as Features in Density Perturbations
Chen, Xingang
2011-01-01
Experimentally distinguishing different primordial universe paradigms that lead to the Big Bang model is an outstanding challenge in modern cosmology and astrophysics. We show that a generic type of signals that exist in primordial universe models can be used for such purpose. These signals are induced by tiny oscillations of massive fields and manifest as features in primordial density perturbations. They are capable of recording the time-dependence of the scale factor of the primordial universe, and therefore provide direct evidence for specific paradigm.
Standard Clock in Primordial Density Perturbations and Cosmic Microwave Background
Chen, Xingang
2014-01-01
Standard Clocks in the primordial epoch leave a special type of features in the primordial perturbations, which can be used to directly measure the scale factor of the primordial universe as a function of time a(t), thus discriminating between inflation and alternatives. We have started to search for such signals in the Planck 2013 data using the key predictions of the Standard Clock. In this Letter, we present an interesting candidate with the inflation fingerprint. Motivated by this candidate, we construct and compute full Standard Clock models and use the more complete prediction to make more extensive comparison with data.
Waveform Perturbations os Spherical Transiet Waves Propagating in a Random Medium
Wenzel, Alan R.
1996-01-01
Of those aspects of sonic-boom propagation that are not yet fully understood, one of the more important is that which relates to the perturbations of the waveform. This phenomenon, which arises also in connection with the propagation of other types of transient waves in real media, generally take the form, in the case of sonic-boom N-waves, of a random high-frequency structure (sometimes called fine structure) that is most prominent in the regions immediately behind each of the shocks. The perturbations in those regions can be large, occasionally attaining magnitudes comparable to that of th incident wave itself. Such magnitudes, in combination with the high-frequency character of the perturbations, can lead to a considerable increase in the perceived noisiness of the sonic boom. Waveform perturbations are consequently an important factor as regards the question of sonic-boom acceptability. On the basis of observations, and some early theoretical studies, it is now generally accepted that perturbations of sonic-boom waveforms are a manifestation of the effect on the propagating wave of relatively small-scale variations in the acoustic properties of the atmosphere- variations that are usually associated with turbulence. Although the mechanism underlying perturbations of sonic-boom waveforms seems thus to be well understood, no fully-satisfactory theory of such perturbations has emerged. Indeed, even for the relatively simple case of an incident step-function pulse, no theory of waveform perturbations, formulated in a realistic three-dimensional context, has been advanced that is valid in the region of strongest perturbations; viz., the region immediately behind, and including, the wave front. The work reported herein represents an attempt to develop such a theory.
Manifestly Covariant Gauge-invariant Cosmological Perturbation Theory
Miedema, P G
2010-01-01
It is shown that a first-order cosmological perturbation theory for the open, flat and closed Friedmann-Lemaitre-Robertson-Walker universes admits one, and only one, gauge-invariant variable which describes the perturbation to the energy density and which becomes equal to the usual Newtonian energy density in the non-relativistic limit. The same holds true for the perturbation to the particle number density. Using these two new variables, a new manifestly gauge-invariant cosmological perturbation theory has been developed. Density perturbations evolve diabatically. Perturbations in the total energy density are gravitationally coupled to perturbations in the particle number density, irrespective of the nature of the particles. There is, in first-order, no back-reaction of perturbations to the global expansion of the universe. Small-scale perturbations in the radiation-dominated era oscillate with an increasing amplitude, whereas in older, less precise treatments, oscillating perturbations are found with a decr...
On Self-adjustment of Social Conventions to Small Perturbations
Institute of Scientific and Technical Information of China (English)
JIANG Yi-Chuan
2008-01-01
@@ We present a model for self-adjustment of social conventions to small perturbations, and investigate how pertur-bations can influence the convergence of social convention in different situations.The experimental results show that the sensitivity of social conventions is determined by not only the perturbations themselves but also the agent adjustment functions for the perturbations; and social conventions are more sensitive to the outlier agent number than to the strategy fluctuation magnitudes and localities of perturbations.
Reduction of some perturbed Keplerian problems
Energy Technology Data Exchange (ETDEWEB)
Inarrea, Manuel [Universidad de La Rioja, Area de Fisica, 26006 Logrono (Spain); Lanchares, Victor [Universidad de La Rioja, Departamento de Matematicas y Computacion, 26004 Logrono (Spain)] e-mail: vlancha@dmc.unirioja.es; Palacian, Jesus F. [Universidad Publica de Navarra, Departamento de Matematica e Informatica, 31006 Pamplona (Spain); Pascual, Ana I. [Universidad de La Rioja, Departamento de Matematicas y Computacion, 26004 Logrono (Spain); Salas, J. Pablo [Universidad de La Rioja, Area de Fisica, 26006 Logrono (Spain); Yanguas, Patricia [Universidad Publica de Navarra, Departamento de Matematica e Informatica, 31006 Pamplona (Spain)
2006-01-01
Perturbed Hamiltonian Keplerian systems enjoying some discrete and continuous symmetries can be brought to a one degree of freedom system containing the main qualitative features of the original one. This reduced system is defined in a compact set of the plane where the qualitative dynamics can be studied in a systematic way.
Homological Perturbation Theory and Mirror Symmetry
Institute of Scientific and Technical Information of China (English)
Jian ZHOU
2003-01-01
We explain how deformation theories of geometric objects such as complex structures,Poisson structures and holomorphic bundle structures lead to differential Gerstenhaber or Poisson al-gebras. We use homological perturbation theory to construct A∞ algebra structures on the cohomology,and their canonically defined deformations. Such constructions are used to formulate a version of A∞algebraic mirror symmetry.
Characterizing heterogeneous cellular responses to perturbations.
Slack, Michael D; Martinez, Elisabeth D; Wu, Lani F; Altschuler, Steven J
2008-12-01
Cellular populations have been widely observed to respond heterogeneously to perturbation. However, interpreting the observed heterogeneity is an extremely challenging problem because of the complexity of possible cellular phenotypes, the large dimension of potential perturbations, and the lack of methods for separating meaningful biological information from noise. Here, we develop an image-based approach to characterize cellular phenotypes based on patterns of signaling marker colocalization. Heterogeneous cellular populations are characterized as mixtures of phenotypically distinct subpopulations, and responses to perturbations are summarized succinctly as probabilistic redistributions of these mixtures. We apply our method to characterize the heterogeneous responses of cancer cells to a panel of drugs. We find that cells treated with drugs of (dis-)similar mechanism exhibit (dis-)similar patterns of heterogeneity. Despite the observed phenotypic diversity of cells observed within our data, low-complexity models of heterogeneity were sufficient to distinguish most classes of drug mechanism. Our approach offers a computational framework for assessing the complexity of cellular heterogeneity, investigating the degree to which perturbations induce redistributions of a limited, but nontrivial, repertoire of underlying states and revealing functional significance contained within distinct patterns of heterogeneous responses.
Electromagnetic Nondestructive Testing by Perturbation Homotopy Method
Directory of Open Access Journals (Sweden)
Liang Ding
2014-01-01
Full Text Available Now electromagnetic nondestructive testing methods have been applied to many fields of engineering. But traditional electromagnetic methods (usually based on least square and local iteration just roughly give the information of location, scale, and quality. In this paper we consider inverse electromagnetic problem which is concerned with the estimation of electric conductivity of Maxwell's equations (2D and 3D. A perturbation homotopy method combined with damping Gauss-Newton methods is applied to the inverse electromagnetic problem. This method differs from traditional homotopy method. The structure of homotopy function is similar to Tikhonov functional. Sets of solutions are produced by perturbation for every homotopy parameter λ=λi, i=0,…,L. At each iterative step of the algorithm, we add stochastic perturbation to numerical solutions. The previous solution and perturbation solution are regarded as the initial value in the next iteration. Although the number of solution in set increased, it increased the likelihood of obtaining correct solution. Results exhibits clear advantages over damping Gauss-Newton method and testify that it is an available method, especially on aspects of wide convergence and precision.
The Kepler Problem with Anisotropic Perturbations
Diacu, Florin; Santoprete, Manuele
2009-01-01
We study a 2-body problem given by the sum of the Newtonian potential and an anisotropic perturbation that is a homogeneous function of degree $-\\beta$, $\\beta\\ge 2$. For $\\beta>2$, the sets of initial conditions leading to collisions/ejections and the one leading to escapes/captures have positive measure. For $\\beta>2$ and $\\beta\
Perturbations of ultralight vector field dark matter
Cembranos, J A R; Jareño, S J Núñez
2016-01-01
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 $k^2\\ll {\\cal H}ma$, we have a particle-like behaviour indistinguishable from cold dark matter, whereas for modes with $k^2\\gg {\\cal H}ma$, we get a wave-like behaviour in which the sound speed is non-vanishing and of order $c_s^2\\simeq k^2/m^2a^2$. 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 o...
Geometric singular perturbation theory in biological practice
Hek, G.
2010-01-01
Geometric singular perturbation theory is a useful tool in the analysis of problems with a clear separation in time scales. It uses invariant manifolds in phase space in order to understand the global structure of the phase space or to construct orbits with desired properties. This paper explains an
Cosmological perturbations from the Standard Model Higgs
Energy Technology Data Exchange (ETDEWEB)
Simone, Andrea De [SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Riotto, Antonio, E-mail: andrea.desimone@sissa.it, E-mail: antonio.riotto@unige.ch [Department of Theoretical Physics and Center for Astroparticle Physics (CAP), 24 quai E. Ansermet, CH-1211 Geneva 4 (Switzerland)
2013-02-01
We propose that the Standard Model (SM) Higgs is responsible for generating the cosmological perturbations of the universe by acting as an isocurvature mode during a de Sitter inflationary stage. In view of the recent ATLAS and CMS results for the Higgs mass, this can happen if the Hubble rate during inflation is in the range (10{sup 10}−10{sup 14}) GeV (depending on the SM parameters). Implications for the detection of primordial tensor perturbations through the B-mode of CMB polarization via the PLANCK satellite are discussed. For example, if the Higgs mass value is confirmed to be m{sub h} = 125.5 GeV and m{sub t},α{sub s} are at their central values, our mechanism predicts tensor perturbations too small to be detected in the near future. On the other hand, if tensor perturbations will be detected by PLANCK through the B-mode of CMB, then there is a definite relation between the Higgs and top masses, making the mechanism predictive and falsifiable.
Quenched chiral perturbation theory to one loop
Colangelo, Gilberto; Pallante, Elisabetta
1998-01-01
We calculate the divergences of the generating functional of quenched chiral perturbation theory at one loop, and renormalize the theory by an appropriate definition of the counterterms. We show that the quenched chiral logarithms can be accounted for by defining a renormalized B0 parameter which, a
Quenched Chiral Perturbation Theory to one loop
Colangelo, G.; Pallante, E.
1998-01-01
The divergences of the generating functional of quenched Chiral Perturbation theory (qCHPT) to one loop are computed in closed form. We show how the quenched chiral logarithms can be reabsorbed in the renormalization of the B0 parameter of the leading order Lagrangian. Finally, we do the chiral powe
Volume reduction through perturbative Wilson loops
Perez, Margarita Garcia; Okawa, Masanori
2016-01-01
We derive the perturbative expansion of Wilson loops to order g^4 in a SU(N) lattice gauge theory with twisted boundary conditions. Our expressions show that the thermodynamic limit is attained at infinite N for any number of lattice sites and allow to quantify the deviations from volume independence at finite large N as a function of the twist.
Un convoi exceptionnel perturbe la circulation
Duraffourd, C
2004-01-01
"Le passage d'un convoi exceptionnel hier après-midi dans le secteur de Bellegarde en direction de Cessy aura causé d'importantes perturbations. Entre la deux fois deux voies obturée et les routes secondaires bouclées, les automobilistes ont dû prendre leur mal en patience" (1 page)
Perturbation theory for intermolecular forces including exchange
Lekkerkerker, H.N.W.; Laidlaw, W.G.
1970-01-01
Generalized solutions to the Kisenschitz and London perturbation equations are derived. It is pointed out that the results obtained in the formalisms proposed by Hirschfelder (HAV), by Hirschfelder and Silbey, by Murrell and Shaw, and by Musher and Amos are special cases of the generalized treatment
Perturbed bifurcations in the BCS gap equation
DEFF Research Database (Denmark)
Spathis, P. N.; Sørensen, Mads Peter; Lazarides, Nickos
1992-01-01
. The transitions from d- or s- to mixed s- and d-wave solutions result from pitchfork bifurcations. In the case of slightly different pairing strength in the x and y directions, perturbed pitchfork bifurcations emerge, leading to a dramatic change in the physical properties of the superconducting state....
Scalar perturbations from brane-world inflation
Koyama, K; Maartens, R; Wands, D
2004-01-01
We investigate the scalar metric perturbations about a de Sitter brane universe in a 5-dimensional anti de Sitter bulk. We compare the master-variable formalism, describing metric perturbations in a 5-dimensional longitudinal gauge, with results in a Gaussian normal gauge. For a vacuum brane (with constant brane tension) there is a continuum of normalizable Kaluza-Klein modes, with m>3H/2, which remain in the vacuum state. A light radion mode, with m=\\sqrt{2}H, satisfies the boundary conditions for two branes but is not normalizable in the single-brane case. When matter is introduced (as a test field) on the brane, this mode, together with the zero-mode and an infinite ladder of discrete tachyonic modes, become normalizable. However, the boundary condition requires the self-consistent 4-dimensional evolution of scalar field perturbations on the brane and the dangerous growing modes are not excited. These normalizable discrete modes introduce corrections at first-order to the scalar field perturbations compute...
Toward controlling perturbations in robotic sensor networks
Banerjee, Ashis G.; Majumder, Saikat R.
2014-06-01
Robotic sensor networks (RSNs), which consist of networks of sensors placed on mobile robots, are being increasingly used for environment monitoring applications. In particular, a lot of work has been done on simultaneous localization and mapping of the robots, and optimal sensor placement for environment state estimation1. The deployment of RSNs, however, remains challenging in harsh environments where the RSNs have to deal with significant perturbations in the forms of wind gusts, turbulent water flows, sand storms, or blizzards that disrupt inter-robot communication and individual robot stability. Hence, there is a need to be able to control such perturbations and bring the networks to desirable states with stable nodes (robots) and minimal operational performance (environment sensing). Recent work has demonstrated the feasibility of controlling the non-linear dynamics in other communication networks like emergency management systems and power grids by introducing compensatory perturbations to restore network stability and operation2. In this paper, we develop a computational framework to investigate the usefulness of this approach for RSNs in marine environments. Preliminary analysis shows promising performance and identifies bounds on the original perturbations within which it is possible to control the networks.
Second order perturbation theory for embedded eigenvalues
DEFF Research Database (Denmark)
Faupin, Jeremy; Møller, Jacob Schach; Skibsted, Erik
2011-01-01
We study second order perturbation theory for embedded eigenvalues of an abstract class of self-adjoint operators. Using an extension of the Mourre theory, under assumptions on the regularity of bound states with respect to a conjugate operator, we prove upper semicontinuity of the point spectrum...
Suppressing Super-Horizon Curvature Perturbations
Sloth, M S
2006-01-01
We consider the possibility of suppressing superhorizon curvature perturbations after the end of the ordinary slow-roll inflationary stage. This is the opposite of the curvaton limit. We assume that large curvature perturbations are created by the inflaton and investigate to which extent they can be diluted or suppressed by a second very homogeneous field which starts to dominate the energy density of the universe shortly after the end of inflation. The suppression is non-trivial to achieve, but we demonstrate two examples where it works. The mechanism is shown to work if the decay rate of the second field has a certain time-dependence leading to an intrinsic non-adiabatic energy transfer or if the second field is an axion field with a very non-linear periodic potential leading to a non-vanishing intrinsic non-adiabatic pressure perturbation. This opens the possibility of having much larger inflaton perturbations created during inflation than normally allowed by the COBE bound. It relaxes the upper bound on t...
Homotopy Perturbation Method for a Modified
Directory of Open Access Journals (Sweden)
E. Hesameddini
2009-06-01
Full Text Available In this article, the Homotopy Perturbation Method (HPM is employed to approximate solutions of a modified Lotka - Volterra equation. HPM has been introduced by He to solve approximately linear or nonlinear differential equations. Approximate polynomials have also been constructed to find approximate solutions of a modified Lotka - Volterra system. Numerical comparisons are made between HPM and maple numerical results
Privacy Is Become with, Data Perturbation
Singh, Er. Niranjan; Singhai, Niky
2011-06-01
Privacy is becoming an increasingly important issue in many data mining applications that deal with health care, security, finance, behavior and other types of sensitive data. Is particularly becoming important in counterterrorism and homeland security-related applications. We touch upon several techniques of masking the data, namely random distortion, including the uniform and Gaussian noise, applied to the data in order to protect it. These perturbation schemes are equivalent to additive perturbation after the logarithmic Transformation. Due to the large volume of research in deriving private information from the additive noise perturbed data, the security of these perturbation schemes is questionable Many artificial intelligence and statistical methods exist for data analysis interpretation, Identifying and measuring the interestingness of patterns and rules discovered, or to be discovered is essential for the evaluation of the mined knowledge and the KDD process as a whole. While some concrete measurements exist, assessing the interestingness of discovered knowledge is still an important research issue. As the tool for the algorithm implementations we chose the language of choice in industrial world MATLAB.
Gravitational Perturbation in Topological Phonon Space
Institute of Scientific and Technical Information of China (English)
李芳昱; 罗俊; 唐孟希
1994-01-01
The effect of gravitational wave (GW) on phonon in crystal lattice space with spiral dislocation is expressed as a gravitational perturbation in topological phonon space with background of the spiral dislocation.This is a new-type effect form of the GW field to the phonon.The corresponding phonon solutions are given.
Transport Studies in Fusion Plasmas - Perturbative Experiments
Cardozo, N. J. L.
1994-01-01
By subjecting a plasma in steady state to small perturbations and measuring the response, it is possible to determine elements of the matrix of transport coefficients. Experimentally this is difficult, and results are mainly limited to tranpsport driven by the pressure and temperature gradients. Imp
Transport studies in fusion plasmas: Perturbative experiments
Cardozo, N. J. L.
1996-01-01
By subjecting a plasma in steady state to small perturbations and measuring the response, it is possible to determine elements of the matrix of transport coefficients. Experimentally this is difficult, and results are mainly limited to tranpsport driven by the pressure and temperature gradients. Imp
Transport studies in fusion plasmas: Perturbative experiments
Cardozo, N. L.
1998-01-01
By inducing in a small temperature perturbation in a plasma in a steady state one can determine the conductive and convective components of the heat flux, and the associated thermal diffusivity and convection velocity. The same can be done for the density, and in principle also other plasma paramete
Perturbative Odderon in the Dipole Model
Kovchegov, Yu V; Wallon, S; Kovchegov, Yuri V.; Szymanowski, Lech; Wallon, Samuel
2003-01-01
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,\
Perturbations of normally solvable nonlinear operators, I
Directory of Open Access Journals (Sweden)
William O. Ray
1985-01-01
Full Text Available Let X and Y be Banach spaces and let ℱ and be Gateaux differentiable mappings from X to Y In this note we study when the operator ℱ+ is surjective for sufficiently small perturbations of a surjective operator ℱ The methods extend previous results in the area of normal solvability for nonlinear operators.
Jentschura; Becher; Weniger; Soff
2000-09-18
We propose a method for the resummation of divergent perturbative expansions in quantum electrodynamics and related field theories. The method is based on a nonlinear sequence transformation and uses as input data only the numerical values of a finite number of perturbative coefficients. The results obtained in this way are for alternating series superior to those obtained using Pade approximants. The nonlinear sequence transformation fulfills an accuracy-through-order relation and can be used to predict perturbative coefficients. In many cases, these predictions are closer to available analytic results than predictions obtained using the Pade method.
DEFF Research Database (Denmark)
Sadegh, Payman; Spall, J. C.
1998-01-01
The simultaneous perturbation stochastic approximation (SPSA) algorithm has attracted considerable attention for challenging optimization problems where it is difficult or impossible to obtain a direct gradient of the objective (say, loss) function. The approach is based on a highly efficient...... 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...
DEFF Research Database (Denmark)
Sadegh, Payman; Spall, J. C.
1997-01-01
The simultaneous perturbation stochastic approximation (SPSA) algorithm has recently attracted considerable attention for optimization problems where it is difficult or impossible to obtain a direct gradient of the objective (say, loss) function. The approach is based on a highly efficient...... 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...
Pure annihilation type $ D\\to PP(V)$ decays in the perturbative QCD approach
Zou, Zhi-Tian; Lü, Cai-Dian
2013-01-01
The annihilation type diagrams are difficult to calculate in any kind of models or method. Encouraged by the the successful calculation of pure annihilation type B decays in the perturbative QCD factorization approach, we calculate the pure annihilation type $D\\to PP(V)$ decays in the perturbative QCD approach based on the $k_T$ factorization. Although the expansion parameter $1/m_D$ is not very small, our leading order numerical results agree with the existing experiment data for most channels. We expect the more accurate observation from experiments, which can help us learn about the dynamics of $D$ meson weak decays.
Resonance model for non-perturbative inputs to gluon distributions in the hadrons
Ermolaev, B I; Troyan, S I
2015-01-01
We construct non-perturbative inputs for the elastic gluon-hadron scattering amplitudes in the forward kinematic region for both polarized and non-polarized hadrons. We use the optical theorem to relate invariant scattering amplitudes to the gluon distributions in the hadrons. By analyzing the structure of the UV and IR divergences, we can determine theoretical conditions on the non-perturbative inputs, and use these to construct the results in a generalized Basic Factorization framework using a simple Resonance Model. These results can then be related to the K_T and Collinear Factorization expressions, and the corresponding constrains can be extracted.
Heavy-Light Semileptonic Decays in Staggered Chiral Perturbation Theory
Aubin, C
2007-01-01
We calculate the form factors for the semileptonic decays of heavy-light pseudoscalar mesons in partially quenched staggered chiral perturbation theory (\\schpt), working to leading order in $1/m_Q$, where $m_Q$ is the heavy quark mass. We take the light meson in the final state to be a pseudoscalar corresponding to the exact chiral symmetry of staggered quarks. The treatment assumes the validity of the standard prescription for representing the staggered ``fourth root trick'' within \\schpt by insertions of factors of 1/4 for each sea quark loop. Our calculation is based on an existing partially quenched continuum chiral perturbation theory calculation with degenerate sea quarks by Becirevic, Prelovsek and Zupan, which we generalize to the staggered (and non-degenerate) case. As a by-product, we obtain the continuum partially quenched results with non-degenerate sea quarks. We analyze the effects of non-leading chiral terms, and find a relation among the coefficients governing the analytic valence mass depende...
Perturbative corrections to zero recoil inclusive B decay sum rules
Kapustin, A A; Wise, M B; Grinstein, B; Kapustin, Anton; Ligeti, Zoltan; Wise, Mark B; Grinstein, Benjamin
1996-01-01
Comparing the result of inserting a complete set of physical states in a time ordered product of b decay currents with the operator product expansion gives a class of zero recoil sum rules. They sum over physical states with excitation energies less than \\Delta, where \\Delta is much greater than the QCD scale and much less than the heavy charm and bottom quark masses. These sum rules have been used to derive an upper bound on the zero recoil limit of the B\\to D^* form-factor, and on the matrix element of the kinetic energy operator between B meson states. Perturbative corrections to the sum rules of order \\alpha_s(\\Delta) \\Delta^2/m_{c,b}^2 have previously been computed. We calculate the corrections of order \\alpha_s(\\Delta) and \\alpha_s^2(\\Delta) \\beta_0 keeping all orders in \\Delta/m_{c,b}, and show that these perturbative QCD corrections suppressed by powers of \\Delta/m_{c,b} significantly weaken the upper bound on the zero recoil B\\to D^* form-factor, and also on the kinetic energy operator's matrix eleme...
Enea Romano, Antonio; Sanes Negrete, Sergio; Sasaki, Misao; Starobinsky, Alexei A.
2014-06-01
We study effects on the luminosity distance of a local inhomogeneity seeded by primordial curvature perturbations of the type predicted by the inflationary scenario and constrained by the cosmic microwave background radiation. We find that a local underdensity originated from a one, two or three standard deviations peaks of the primordial curvature perturbations field can induce corrections to the value of a cosmological constant of the order of 0.6{%},1{%},1.5{%} , respectively. These effects cannot be neglected in the precision cosmology era in which we are entering. Our results can be considered an upper bound for the effect of the monopole component of the local non-linear structure which can arise from primordial curvature perturbations and requires a fully non-perturbative relativistic treatment.
Kuo, Fang-Chuan; Hong, Chang-Zern; Lai, Chung-Liang; Tan, Shih-Hsin
2011-05-01
Cross-sectional study. To investigate the automatic balance correction related to anticipatory perturbation (AP) and quick backward perturbation in adolescent idiopathic scoliosis (AIS). Most previous studies on AIS patients focused on posture sway and lacked analysis of muscle activated patterns in dynamic standing control. Thirty-two AIS patients and 23 age-matched normal subjects received perturbation balance tests on an unstable platform. The tilting angle of the platform and the muscle activity of the bilateral lumbar multifidi, gluteus medii, and gastrocnemii muscles were recorded. Electromyographic (EMG) amplitude, onset latencies, and duration were calculated with software accompanied with machine. The AIS group had less posture tilting but higher muscle activities than normal subjects under both perturbation conditions (P posture control patterns between AIS and normal subjects. AIS subjects have asymmetric habitual muscle activities for AP, whereas when coping with sudden balance threats, they react with synchronized recruitment of bilateral postural muscles.
Hansmann, Marcel
2015-01-01
In the first part of this paper we provide a self-contained introduction to (regularized) perturbation determinants for operators in Banach spaces. In the second part, we use these determinants to derive new bounds on the discrete eigenvalues of compactly perturbed operators, broadly extending some recent results by Demuth et al. In addition, we also establish new bounds on the discrete eigenvalues of generators of $C_0$-semigroups.
Evolution of the curvature perturbations during warm inflation
Energy Technology Data Exchange (ETDEWEB)
Matsuda, Tomohiro, E-mail: matsuda@sit.ac.jp [Laboratory of Physics, Saitama Institute of Technology, Fusaiji, Okabe-machi, Saitama 369-0293 (Japan)
2009-06-15
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.
Evolution of the curvature perturbations during warm inflation
Matsuda, Tomohiro
2009-06-01
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.
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.
Determination of the sediment carrying capacity based on perturbed theory.
Ni, Zhi-hui; Zeng, Qiang; Li-chun, Wu
2014-01-01
According to the previous studies of sediment carrying capacity, a new method of sediment carrying capacity on perturbed theory was proposed. By taking into account the average water depth, average flow velocity, settling velocity, and other influencing factors and introducing the median grain size as one main influencing factor in deriving the new formula, we established a new sediment carrying capacity formula. The coefficients were determined by the principle of dimensional analysis, multiple linear regression method, and the least square method. After that, the new formula was verified through measuring data of natural rivers and flume tests and comparing the verified results calculated by Cao Formula, Zhang Formula, Li Formula, Engelung-Hansen Formula, Ackers-White Formula, and Yang Formula. According to the compared results, it can be seen that the new method is of high accuracy. It could be a useful reference for the determination of sediment carrying capacity.
Gauge theories in local causal perturbation theory
Boas, F M
1999-01-01
In this thesis quantum gauge theories are considered in the framework of local, causal perturbation theory. Gauge invariance is described in terms of the BRS formalism. Local interacting field operators are constructed perturbatively and field equations are established. A nilpotent BRS transformation is defined on the local algebra of fields. It allows the definition of the algebra of local observables as an operator cohomology. This algebra of local observables can be represented in a Hilbert space. The interacting field operators are defined in terms of time ordered products of free field operators. For the results above to hold the time ordered products must satisfy certain normalization conditions. To formulate these conditions also for field operators that contain a spacetime derivative a suitable mathematical description of time ordered products is developed. Among the normalization conditions are Ward identities for the ghost current and the BRS current. The latter are generalizations of a normalizatio...
Stochastic multireference Epstein-Nesbet perturbation theory
Sharma, Sandeep; Jeanmairet, Guillaume; Alavi, Ali; Umrigar, C J
2016-01-01
We extend the recently proposed heat-bath configuration interaction (HCI) method [Holmes, Tubman, Umrigar, J. Chem. Theory Comput. 12, 3674 (2016)], by introducing a stochastic algorithm for performing multireference Epstein-Nesbet perturbation theory, in order to completely eliminate the severe memory bottleneck of the original method. The proposed stochastic algorithm has several attractive features. First, there is no sign problem that plagues several quantum Monte Carlo methods. Second, instead of using Metropolis-Hastings sampling, we use the Alias method to directly sample determinants from the reference wavefunction, thus avoiding correlations between consecutive samples. Third, in addition to removing the memory bottleneck, stochastic-HCI (s-HCI) is faster than the deterministic variant for most systems if a stochastic error of 0.1 mHa is acceptable. Fourth, within the s-HCI algorithm one can trade memory for a modest increase in computer time. Fifth, the perturbative calculation is embarrassingly par...
A primer for Chiral Perturbative Theory
Energy Technology Data Exchange (ETDEWEB)
Scherer, Stefan [Mainz Univ. (Germany). Inst. fuer Kernphysik; Schindler, Matthias R. [South Carolina Univ., Columbia, SC (United States). Dept. of Physics; George Washington Univ., Washington, DC (United States). Dept. of Physics
2012-07-01
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.)
A Perturbation Result for Dynamical Contact Problems
Institute of Scientific and Technical Information of China (English)
Corinna Klapproth; Peter Deuflhard; Anton Schiela
2009-01-01
This paper is intended to be a first step towards the continuous dependence of dynamical contact problems on the initial data as well as the uniqueness of a solution. Moreover, it provides the basis for a proof of the convergence of popular time integration schemes as the Newmark method. We study a frictionless dynamical contact problem between both linearly elastic and viscoelastic bodies which is formulated via the Signorini contact conditions. For viscoelastic materials fulfilling the Kelvin-Voigt constitutive law, we find a characterization of the class of problems which satisfy a perturbation result in a non-trivial mix of norms in function space. This characterization is given in the form of a stability condition on the contact stresses at the contact boundaries. Furthermore, we present perturbation results for two well-established approximations of the classical Signorini condition: The Signorini condition formulated in velocities and the model of normal compliance, both satisfying even a sharper version of our stability condition.
Nonlinear Acoustics -- Perturbation Theory and Webster's Equation
Jorge, Rogério
2013-01-01
Webster's horn equation (1919) offers a one-dimensional approximation for low-frequency sound waves along a rigid tube with a variable cross-sectional area. It can be thought as a wave equation with a source term that takes into account the nonlinear geometry of the tube. In this document we derive this equation using a simplified fluid model of an ideal gas. By a simple change of variables, we convert it to a Schr\\"odinger equation and use the well-known variational and perturbative methods to seek perturbative solutions. As an example, we apply these methods to the Gabriel's Horn geometry, deriving the first order corrections to the linear frequency. An algorithm to the harmonic modes in any order for a general horn geometry is derived.
Revisiting perturbations in extended quasidilaton massive gravity
Heisenberg, Lavinia
2015-04-01
In this work we study the theory of extended quasidilaton massive gravity together with the presence of matter fields. After discussing the homogeneous and isotropic fully dynamical background equations, which governs the exact expansion history of the universe, we consider small cosmological perturbations around these general FLRW solutions. The stability of tensor, vector and scalar perturbations on top of these general background solutions give rise to slightly different constraints on the parameters of the theory than those obtained in the approximative assumption of the late-time asymptotic form of the expansion history, which does not correspond to our current epoch. This opens up the possibility of stable FLRW solutions to be compared with current data on cosmic expansion with the restricted parameter space based on theoretical ground.
Quasi-periodic oscillations of perturbed tori
Parthasarathy, Varadarajan; Kluzniak, Wlodek
2015-01-01
We performed axisymmetric hydrodynamic simulations of perturbed tori orbiting a black hole. The tori in equilibrium were constructed with a constant distribution of angular momentum in a pseudo-Newtonian potential (Klu{\\'z}niak-Lee). Epicyclic motions were triggered by adding sub-sonic velocity fields: radial, vertical and diagonal to the tori in equilibrium. As the perturbed tori evolved in time, we measured $L_{2}$ norm of density and obtained the power spectrum of $L_{2}$ norm which manifested eigenfrequencies of tori modes. We observe a pair of modes which occur in an approximate 3:2 ratio. Results from our simulations are relevant in the context of high-frequency quasi-periodic oscillations (HF QPOs) observed in stellar-mass black hole binaries.
Gluonic Lorentz violation and chiral perturbation theory
Noordmans, J. P.
2017-04-01
By applying chiral-perturbation-theory methods to the QCD sector of the Lorentz-violating Standard-Model Extension, we investigate Lorentz violation in the strong interactions. In particular, we consider the C P T -even pure-gluon operator of the minimal Standard-Model Extension. We construct the lowest-order chiral effective Lagrangian for three as well as two light quark flavors. We develop the power-counting rules and construct the heavy-baryon chiral-perturbation-theory Lagrangian, which we use to calculate Lorentz-violating contributions to the nucleon self-energy. Using the constructed effective operators, we derive the first stringent limits on many of the components of the relevant Lorentz-violating parameter. We also obtain the Lorentz-violating nucleon-nucleon potential. We suggest that this potential may be used to obtain new limits from atomic-clock or deuteron storage-ring experiments.
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.
On counterterms in cosmological perturbation theory
Goswami, Gaurav
2014-01-01
Cosmological perturbation theory is the theory of fluctuations (scalar as well as tensor) around the inflationary cosmological background solution. It is important to understand the details of the process of renormalization in this theory. In more familiar applications of quantum field theory, the dependence on the external momenta of the dimensionally regulated expression of the one-loop contribution to a correlator determines the number of counter terms (and their forms) required to renormalize it. In this work, it is pointed out that in cosmological perturbation theory, though this still happens, it happens in a completely different way such that in the late time limit, the information about the number and forms of counter terms required gets erased. This is to be compared with what happens in spontaneous symmetry breaking where the use of fluctuation fields around a chosen vacuum seems to suggest that more counter terms shall be needed to renormalize the theory than are actually required. We also comment ...
Coupled Oscillator Model for Nonlinear Gravitational Perturbations
Yang, Huan; Green, Stephen R; Lehner, Luis
2015-01-01
Motivated by the gravity/fluid correspondence, we introduce a new method for characterizing nonlinear gravitational interactions. Namely we map the nonlinear perturbative form of the Einstein equation to the equations of motion of a collection of nonlinearly-coupled harmonic oscillators. These oscillators correspond to the quasinormal or normal modes of the background spacetime. We demonstrate the mechanics and the utility of this formalism within the context of perturbed asymptotically anti-de Sitter black brane spacetimes. We confirm in this case that the boundary fluid dynamics are equivalent to those of the hydrodynamic quasinormal modes of the bulk spacetime. We expect this formalism to remain valid in more general spacetimes, including those without a fluid dual. In other words, although borne out of the gravity/fluid correspondence, the formalism is fully independent and it has a much wider range of applicability. In particular, as this formalism inspires an especially transparent physical intuition, w...
Non-Perturbative Flat Direction Decay
Basboll, A; Riva, F; West, S M; Basboll, Anders; Maybury, David; Riva, Francesco; West, Stephen M.
2007-01-01
We argue that supersymmetric flat direction vevs can decay non-perturbatively via preheating. Considering the case of a single flat direction, we explicitly calculate the scalar potential in the unitary gauge for a U(1) theory and show that the mass matrix for excitations around the flat direction has non-diagonal entries which vary with the phase of the flat direction vev. Furthermore, this mass matrix has 2 zero eigenvalues (associated with the excitations along the flat direction) whose eigenstates change with time. We show that these 2 light degrees of freedom are produced copiously in the non-perturbative decay of the flat direction vev. We also comment on the application of these results to the MSSM flat direction H_uL.
Linear Density Perturbations in Multifield Coupled Quintessence
Leithes, Alexander; Mulryne, David J; Nunes, Nelson J
2016-01-01
We study the behaviour of linear perturbations in multifield coupled quintessence models. Using gauge invariant linear cosmological perturbation theory we provide the full set of governing equations for this class of models, and solve the system numerically. We apply the numerical code to generate growth functions for various examples, and compare these both to the standard $\\Lambda$CDM model and to current and future observational bounds. Finally, we examine the applicability of the "small scale approximation", often used to calculate growth functions in quintessence models, in light of upcoming experiments such as SKA and Euclid. We find the deviation of the full equation results for large k modes from the approximation exceeds the experimental uncertainty for these future surveys. The numerical code, PYESSENCE, written in Python will be publicly available.
Revisiting perturbations in extended quasidilaton massive gravity
Heisenberg, Lavinia
2015-01-01
In this work we study the theory of extended quasidilaton massive gravity together with the presence of matter fields. After discussing the homogeneous and isotropic fully dynamical background equations, which governs the exact expansion history of the universe, we consider small cosmological perturbations around these general FLRW solutions. The stability of tensor, vector and scalar perturbations on top of these general background solutions give rise to slightly different constraints on the parameters of the theory than those obtained in the approximative assumption of the late-time asymptotic form of the expansion history, which does not correspond to our current epoch. This opens up the possibility of stable FLRW solutions to be compared with current data on cosmic expansion with the restricted parameter space based on theoretical ground.
Cosmological perturbations on the phantom brane
Bag, Satadru; Viznyuk, Alexander; Shtanov, Yuri; Sahni, Varun
2016-07-01
We obtain a closed system of equations for scalar perturbations in a multi-component braneworld. Our braneworld possesses a phantom-like equation of state at late times, weff Consequently, the quasi-static approximation of Koyama and Maartens provides a good fit to the exact results during the matter-dominated epoch. We find that the late-time growth of density perturbations on the brane proceeds at a faster rate than in ΛCDM. Additionally, the gravitational potentials Φ and Ψ evolve differently on the brane than in ΛCDM, for which Φ = Ψ. On the brane, by contrast, the ratio Φ/Ψ exceeds unity during the late matter-dominated epoch (z lesssim 50). These features emerge as smoking gun tests of phantom brane cosmology and allow predictions of this scenario to be tested against observations of galaxy clustering and large-scale structure.
Nucleophilicity index from perturbed electrostatic potentials.
Cedillo, A; Contreras, R; Galván, M; Aizman, A; Andrés, J; Safont, V S
2007-03-29
We introduce and test a nucleophilicity index as a new descriptor of chemical reactivity. The index is derived from a perturbation model for the interaction between the nucleophile and a positive test charge. The computational implementation of the model uses an isoelectronic process involving the minimum values of the electronic part of the perturbed molecular electrostatic potential. The working expression defining the nucleophilicity index encompasses both the electrostatic contributions and the second-order polarization effects in a form which is consistent with the empirical scales previously proposed. The index is validated for a series of neutral nucleophiles in the gas phase for which the nucleophilicity pattern has been experimentally established within a spectroscopic scale.
Massive perturbers in the galactic center
Perets, H B; Alexander, T; Perets, Hagai B.; Hopman, Clovis; Alexander, Tal
2006-01-01
We investigate the role of massive perturbers, such as giant molecular clouds or stellar clusters, in supplying low-angular momentum stars that pass very close to the central massive black hole (MBH) or fall into it. We show that massive pe rturbers can play an important role in supplying both binaries and single stars to the vicinity of the MBH. We discuss possible implications for the ejection of high velocity stars; for the capture of stars on tight orbits around the MBH; for the emission of gravitational waves from low-eccentricity inspiraling stars; and for the origin of the young main sequence B stars observed very near the Gal actic MBH. Massive perturbers may also enhance the the growth rate of MBHs, and may accelerate the dynamical orbital decay of coalescing binary MBHs.
SPT 2004: Symmetry and Perturbation Theory
Prinari, Barbara; Rauch-Wojciechowski, Stefan; Terracini, Susanna
2005-01-01
This proceedings volume is a collection of papers presented at the International Conference on SPT2004 focusing on symmetry, perturbation theory, and integrability. The book provides an updated overview of the recent developments in the various different fields of nonlinear dynamics, covering both theory and applications. Special emphasis is given to algebraic and geometric integrability, solutions to the N-body problem of the “choreography” type, geometry and symmetry of dynamical systems, integrable evolution equations, various different perturbation theories, and bifurcation analysis. The contributors to this volume include some of the leading scientists in the field, among them: I Anderson, D Bambusi, S Benenti, S Bolotin, M Fels, W Y Hsiang, V Matveev, A V Mikhailov, P J Olver, G Pucacco, G Sartori, M A Teixeira, S Terracini, F Verhulst and I Yehorchenko.
Molecular Cluster Perturbation Theory. I. Formalism
Byrd, Jason N; Molt,, Robert W; Bartlett, Rodney J; Sanders, Beverly A; Lotrich, Victor F
2014-01-01
We present second-order molecular cluster perturbation theory (MCPT(2)), a methodology to calculate arbitrarily large systems with explicit calculation of individual wavefunctions in a coupled cluster framework. This new MCPT(2) framework uses coupled cluster perturbation theory and an expansion in terms of molecular dimer interactions to obtain molecular wavefunctions that are infinite order in both the electronic fluctuation operator and all possible dimer (and products of dimers) interactions. The MCPT(2) framework has been implemented in the new SIA/ACES parallel architecture, making use of the advanced dynamic memory control and fine grained parallelism to perform very large explicit molecular cluster calculations. To illustrate the power of this method, we have computed energy shifts and lattice site dipole moments for the polar and non-polar configurations of solid hydrogen fluoride by scaling an explicit lattice to the bulk limit. The explicit lattice size without periodic boundary conditions was scal...
General Analysis Tool Box for Controlled Perturbation
Osbild, Ralf
2012-01-01
The implementation of reliable and efficient geometric algorithms is a challenging task. The reason is the following conflict: On the one hand, computing with rounded arithmetic may question the reliability of programs while, on the other hand, computing with exact arithmetic may be too expensive and hence inefficient. One solution is the implementation of controlled perturbation algorithms which combine the speed of floating-point arithmetic with a protection mechanism that guarantees reliability, nonetheless. This paper is concerned with the performance analysis of controlled perturbation algorithms in theory. We answer this question with the presentation of a general analysis tool box. This tool box is separated into independent components which are presented individually with their interfaces. This way, the tool box supports alternative approaches for the derivation of the most crucial bounds. We present three approaches for this task. Furthermore, we have thoroughly reworked the concept of controlled per...
Cosmological perturbations in mimetic matter model
Matsumoto, Jiro; Sushkov, Sergey V
2015-01-01
We investigate the cosmological evolution of mimetic matter model with arbitrary scalar potential. The cosmological reconstruction is explicitly done for different choices of potential. The cases that mimetic matter model shows the evolution as Cold Dark Matter(CDM), wCDM model, dark matter and dark energy with dynamical $Om(z)$ or phantom dark energy with phantom-non-phantom crossing are presented in detail. The cosmological perturbations for such evolution are studied in mimetic matter model. For instance, the evolution behavior of the matter density contrast which is different from usual one, i.e. $\\ddot \\delta + 2 H \\dot \\delta - \\kappa ^2 \\rho \\delta /2 = 0$ is investigated. The possibility of peculiar evolution of $\\delta$ in the model under consideration is shown. Special attention is paid to the behavior of matter density contrast near to future singularity where decay of perturbations may occur much earlier the singularity.
Cosmological perturbations in transient phantom inflation scenarios
Energy Technology Data Exchange (ETDEWEB)
Richarte, Martin G. [Universidade Federal do Parana, Departamento de Fisica, Caixa Postal 19044, Curitiba (Brazil); Universidad de Buenos Aires, Ciudad Universitaria 1428, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina); Kremer, Gilberto M. [Universidade Federal do Parana, Departamento de Fisica, Caixa Postal 19044, Curitiba (Brazil)
2017-01-15
We present a model of inflation where the inflaton is accommodated as a phantom field which exhibits an initial transient pole behavior and then decays into a quintessence field which is responsible for a radiation era. We must stress that the present unified model only deals with a single field and that the transition between the two eras is achieved in a smooth way, so the model does not suffer from the eternal inflation issue. We explore the conditions for the crossing of the phantom divide line within the inflationary era along with the structural stability of several critical points. We study the behavior of the phantom field within the slow-climb approximation along with the necessary conditions to have sufficient inflation. We also examine the model at the level of classical perturbations within the Newtonian gauge and determine the behavior of the gravitational potential, contrast density and perturbed field near the inflation stage and the subsequent radiation era. (orig.)
Quantum Cosmological Perturbations of Multiple Fluids
Peter, Patrick; Vitenti, Sandro Dias Pinto
2015-01-01
The formalism to treat quantization and evolution of cosmological perturbations of multiple fluids is described. We first construct the Lagrangian for both the gravitational and matter parts, providing the necessary relevant variables and momenta leading to the quadratic Hamiltonian describing linear perturbations. The final Hamiltonian is obtained without assuming any equations of motions for the background variables. This general formalism is applied to the special case of two fluids, having in mind the usual radiation and matter mix which made most of our current Universe history. Quantization is achieved using an adiabatic expansion of the basis functions. This allows for an unambiguous definition of a vacuum state up to the given adiabatic order. Using this basis, we show that particle creation is well defined for a suitable choice of vacuum and canonical variables, so that the time evolution of the corresponding quantum fields is unitary. This provides constraints for setting initial conditions for an a...
Improving perturbation theory with cactus diagrams
Constantinou, M; Skouroupathis, A; Constantinou, Martha; Panagopoulos, Haralambos; Skouroupathis, Apostolos
2006-01-01
We study a systematic improvement of perturbation theory for gauge fields on the lattice [hep-lat/0606001]; the improvement entails resumming, to all orders in the coupling constant, a dominant subclass of tadpole diagrams. This method, originally proposed for the Wilson gluon action, is extended here to encompass all possible gluon actions made of closed Wilson loops; any fermion action can be employed as well. The effect of resummation is to replace various parameters in the action (coupling constant, Symanzik and clover coefficient) by ``dressed'' values; the latter are solutions to certain coupled integral equations, which are easy to solve numerically. Some positive features of this method are: a) It is gauge invariant, b) it can be systematically applied to improve (to all orders) results obtained at any given order in perturbation theory, c) it does indeed absorb in the dressed parameters the bulk of tadpole contributions. Two different applications are presented: The additive renormalization of fermio...
Gauge Invariant Perturbations of the Schwarzschild Spacetime
Chen, Hector; Whiting, Bernard F
2016-01-01
Beginning with the pioneering work of Regge and Wheeler (Phys. Rev. 108, 1957), there have been many studies of perturbations away from the Schwarzschild spacetime background. In particular several authors (e.g. Moncrief, Ann. Phys 88, 1974) have investigated gauge invariant quantities of the Regge-Wheeler (RW) gauge. Steven Detweiler also investigated perturbations of Schwarzschild in his own gauge, which he denoted the "easy (EZ) gauge", and which he was in the process of adapting for use in the second-order self-force problem. We present here a compilation of some of his working results, arising from notes for which there seems to have been no manuscript in preparation. In particular, we list the gauge invariant quantities used by Detweiler, as well as explain the process by which he found them.
Co cycle Perturbation on Banach Algebras
Institute of Scientific and Technical Information of China (English)
Shi Luo-yi; Wu Yu-jing
2014-01-01
Letαbe a flow on a Banach algebra B, and t 7→ut a continuous function from R into the group of invertible elements of B such that usαs(ut)=us+t, s, t∈R. Then βt =Adut◦αt, t∈R is also a flow on B, where Adut(B) , utBu-1t for any B ∈ B. β is said to be a cocycle perturbation of α. We show that if α, β are two flows on a nest algebra (or quasi-triangular algebra), thenβ is a cocycle perturbation ofα. And the flows on a nest algebra (or quasi-triangular algebra) are all uniformly continuous.
A Perturbative Realization of Miransky Scaling
DEFF Research Database (Denmark)
Antipin, O.; Di Chiara, S.; Mojaza, M.;
2012-01-01
fixed points of which one is all directions stable in the infrared. An interesting feature of the model is that this fixed point is lost, within the perturbatively trustable regime, by merging with another fixed point when varying the number of quark flavors. We show the emergence of the Miransky......Near conformal dynamics is employed in different extensions of the standard model of particle interactions as well as in cosmology. Many of its interesting properties are either conjectured or determined using model computations. We introduce a relevant four dimensional gauge theory template...... allowing us to investigate such dynamics perturbatively. The gauge theory we consider is quantum chromodynamics with the addition of a meson-like scalar degree of freedom as well as an adjoint Weyl fermion. At the two-loop level, and in the Veneziano limit, we firmly establish the existence of several...
Intelligent perturbation algorithms for space scheduling optimization
Kurtzman, Clifford R.
1990-01-01
The optimization of space operations is examined in the light of optimization heuristics for computer algorithms and iterative search techniques. Specific attention is given to the search concepts known collectively as intelligent perturbation algorithms (IPAs) and their application to crew/resource allocation problems. IPAs iteratively examine successive schedules which become progressively more efficient, and the characteristics of good perturbation operators are listed. IPAs can be applied to aerospace systems to efficiently utilize crews, payloads, and resources in the context of systems such as Space-Station scheduling. A program is presented called the MFIVE Space Station Scheduling Worksheet which generates task assignments and resource usage structures. The IPAs can be used to develop flexible manifesting and scheduling for the Industrial Space Facility.
Observing Quantum Tunneling in Perturbation Series
Suzuki, H; Suzuki, Hiroshi; Yasuta, Hirofumi
1996-01-01
We apply Borel resummation method to the conventional perturbation series of ground state energy in a metastable potential, $V(x)=x^2/2-gx^4/4$. We observe numerically that the discontinuity of Borel transform reproduces the imaginary part of energy eigenvalue, i.e., total decay width due to the quantum tunneling. The agreement with the exact numerical value is remarkable in the whole tunneling regime $0
Capillary and viscous perturbations to Helmholtz flows
Moore, M. R.
2014-02-21
Inspired by recent calculations by Thoraval et al. (Phys. Rev. Lett., vol. 108, 2012, p.Â 264506) relating to droplet impact, this paper presents an analysis of the perturbations to the free surface caused by small surface tension and viscosity in steady Helmholtz flows. In particular, we identify the regimes in which appreciable vorticity can be shed from the boundary layer to the bulk flow. © 2014 Cambridge University Press.
Double parton scattering for perturbative transverse momenta
Buffing, Maarten G A; Kasemets, Tomas
2016-01-01
The cross section for transverse momentum dependent double parton scattering involves transverse momentum dependent double parton distributions (DTMDs). In the region of perturbative transverse momentum the DTMDs can be matched onto collinear double parton distributions. We present the framework and results for this matching, as well as the evolution equations for DTMDs in the region of large distance between the two partons. We discuss explicit results for one-loop matching coefficients and evolution kernels.
Strongly Nonlinear Transverse Perturbations in Phononic Crystals
Directory of Open Access Journals (Sweden)
S. Nikitenkova
2014-01-01
Full Text Available The dynamics of the surface heterogeneities formation in low-dimensional phononic crystals is studied. It is shown that phononic transverse perturbations in this medium are highly nonlinear. They can be described with the help of the Riemann wave and may form stable wave structures of the finite amplitude. The Riemann wave deformation is described analytically. The Riemann wave time existence up to the beginning of the gradient catastrophe is calculated.
Profiling DNA damage response following mitotic perturbations
DEFF Research Database (Denmark)
S Pedersen, Ronni; Karemore, Gopal; Gudjonsson, Thorkell
2016-01-01
Genome integrity relies on precise coordination between DNA replication and chromosome segregation. Whereas replication stress attracted much attention, the consequences of mitotic perturbations for genome integrity are less understood. Here, we knockdown 47 validated mitotic regulators to show...... phenotypes. To demonstrate the potential of this resource, we show that DNA breakage after cytokinesis failure is preceded by replication stress, which mounts during consecutive cell cycles and coincides with decreased proliferation. Together, our results provide a resource to gauge the magnitude...
Geometric perturbation theory and plasma physics
Energy Technology Data Exchange (ETDEWEB)
Omohundro, S.M.
1985-04-04
Modern differential geometric techniques are used to unify the physical asymptotics underlying mechanics, wave theory and statistical mechanics. The approach gives new insights into the structure of physical theories and is suited to the needs of modern large-scale computer simulation and symbol manipulation systems. A coordinate-free formulation of non-singular perturbation theory is given, from which a new Hamiltonian perturbation structure is derived and related to the unperturbed structure. The theory of perturbations in the presence of symmetry is developed, and the method of averaging is related to reduction by a circle group action. The pseudo-forces and magnetic Poisson bracket terms due to reduction are given a natural asymptotic interpretation. Similar terms due to changing reference frames are related to the method of variation of parameters, which is also given a Hamiltonian formulation. These methods are used to answer a question about nearly periodic systems. The answer leads to a new secular perturbation theory that contains no ad hoc elements. Eikonal wave theory is given a Hamiltonian formulation that generalizes Whitham's Lagrangian approach. The evolution of wave action density on ray phase space is given a Hamiltonian structure using a Lie-Poisson bracket. The relationship between dissipative and Hamiltonian systems is discussed. A new type of attractor is defined which attracts both forward and backward in time and is shown to occur in infinite-dimensional Hamiltonian systems with dissipative behavior. The theory of Smale horseshoes is applied to gyromotion in the neighborhood of a magnetic field reversal and the phenomenon of reinsertion in area-preserving horseshoes is introduced. The central limit theorem is proved by renormalization group techniques. A natural symplectic structure for thermodynamics is shown to arise asymptotically from the maximum entropy formalism.
Understanding Theoretical Uncertainties in Perturbative QCD Computations
DEFF Research Database (Denmark)
Jenniches, Laura Katharina
effective field theories and perturbative QCD to predict the effect of New Physics on measurements at the LHC and at other future colliders. We use heavy-quark, heavy-scalar and soft-collinear effective theory to calculate a three-body cascade decay at NLO QCD in the expansion-by-regions formalism...... discuss an extension of the Cacciari-Houdeau approach to observables with hadrons in the initial state....
Property (ωˊ) and Its Perturbation
Institute of Scientific and Technical Information of China (English)
Yan Hua ZHANG; Xiao Hong CAO
2011-01-01
In this note we define the property (ωˊ),a variant of Weyl's theorem,and establish for a bounded linear operator defined on a Hilbert space the necessary and sufficient conditions for which property (ωˊ) holds by means of the variant of the essential approximate point spectrum σ1(.) and the spectrum defined in view of the property of consistency in Fredholm and index.In addition,the perturbation of property (ωˊ) is discussed.
Perturbative calculation of quasi-normal modes
Siopsis, G
2005-01-01
I discuss a systematic method of analytically calculating the asymptotic form of quasi-normal frequencies. In the case of a four-dimensional Schwarzschild black hole, I expand around the zeroth-order approximation to the wave equation proposed by Motl and Neitzke. In the case of a five-dimensional AdS black hole, I discuss a perturbative solution of the Heun equation. The analytical results are in agreement with the results from numerical analysis.
Perturbational analysis of plasmon decay in jellium
Bachlechner, Martina E.; Macke, Wilhelm; Miesenböck, Helga M.; Schinner, Andreas
1991-02-01
Plasmon damping in the three-dimensional homogeneous electron gas is investigated within second order perturbation theory for the density-density response function. The equivalence of several existing approaches that take into account lowest order two-pair excitations is shown explicitly. Finally, a complete Monte-Carlo analysis of the multi-dimensional integrals for the dielectric function is made for arbitrary densities.
Linguistic Structure as Composition and Perturbation
De Marcken, C
1996-01-01
This paper discusses the problem of learning language from unprocessed text and speech signals, concentrating on the problem of learning a lexicon. In particular, it argues for a representation of language in which linguistic parameters like words are built by perturbing a composition of existing parameters. The power of this representation is demonstrated by several examples in text segmentation and compression, acquisition of a lexicon from raw speech, and the acquisition of mappings between text and artificial representations of meaning.
Perturbation theory for solitons in optical fibers
Kaup, D. J.
1990-11-01
Using a singular perturbation expansion, we study the evolution of a Raman loss compensated soliton in an optical fiber. Our analytical results agree quite well with the numerical results of Mollenauer, Gordon, and Islam [IEEE J. Quantum Electron. QE-22, 157 (1986)]. However, there are some differences in that our theory predicts an additional structure that was only partially seen in the numerical calculations. Our analytical results do give a quite good qualitative and quantitative check of the numerical results.
Perturbations Involving nu1 of NCCN.
Maki; Klee
1999-01-01
From high-resolution infrared spectra of 14N12C12C14N, 14N13C13C14N, and 15N12C12C15N, we find that the levels 1000(0)0(0), 1000(0)1(1), 1000(0)2(0,2), and 1000(0)3(1,3) have very pronounced perturbations. Our analysis shows that these perturbations are due to a vibrational resonance among the levels 1000(0)0(0), 0102(0)2(0), and 0102(0)2(2) in the one case, and equivalent levels with one or more additional quanta of nu5 in the other three cases. The resonance constant for the perturbation involving nu1 is 0.25 cm-1. It has the dependence on v5 and l5 that is expected for the sextic potential constant, K124455, although it seems too large for such a high-order constant. The Deltal (or Deltak) = 2 interaction between, for instance, 1000(0)0(0) and 0102(0)2(2e) is shown to be primarily due to the l-type resonance mixing of the 0102(0)2(0) and 0102(0)2(2e) states. The resonance is nearly "turned off" for the 1000(0)2(0,2) and 1000(0)3(1,3) states of 14N13C13C14N because there are no level crossings between the interacting states and the band centers are too far away to have an obvious effect, although careful analysis shows that the perturbation can be seen in their effective centrifugal distortion constants. The spectrum of 15N12C12C15N shows level crossings only in the case of the 1000(0)1(1), 1000(0)2(0,2), and 1000(0)3(1,3) states. Copyright 1999 Academic Press.
Perturbations of Kantowski-Sachs models
Bradley, Michael; Keresztes, Zoltán; Gergely, László Á; Dunsby, Peter K S
2013-01-01
Perturbations of Kantowski-Sachs models with a positive cosmological constant are considered in a harmonic decomposition, in the framework of gauge invariant 1+3 and 1+1+2 covariant splits of spacetime. Scalar, vector and tensor modes are allowed, however they remain vorticity-free and of perfect fluid type. The dynamics is encompassed in six evolution equations for six harmonic coefficients.
Higher representations on the lattice: perturbative studies
Del Debbio, Luigi; Panagopoulos, Haralambos; Sannino, Francesco
2008-01-01
We present analytical results to guide numerical simulations with Wilson fermions in higher representations of the colour group. The ratio of $\\Lambda$ parameters, the additive renormalization of the fermion mass, and the renormalization of fermion bilinears are computed in perturbation theory, including cactus resummation. We recall the chiral Lagrangian for the different patterns of symmetry breaking that can take place with fermions in higher representations, and discuss the possibility of an Aoki phase as the fermion mass is reduced at finite lattice spacing.
Stability of SIRS system with random perturbations
Lu, Qiuying
2009-09-01
Epidemiological models with bilinear incidence rate λSI usually have an asymptotically stable trivial equilibrium corresponding to the disease-free state, or an asymptotically stable non-trivial equilibrium (i.e. interior equilibrium) corresponding to the endemic state. In this paper, we consider an epidemiological model, which is an SIRS model with or without distributed time delay influenced by random perturbations. We present the stability conditions of the disease-free equilibrium of the associated stochastic SIRS system.
Magnetic field homogeneity perturbations in finite Halbach dipole magnets.
Turek, Krzysztof; Liszkowski, Piotr
2014-01-01
Halbach hollow cylinder dipole magnets of a low or relatively low aspect ratio attract considerable attention due to their applications, among others, in compact NMR and MRI systems for investigating small objects. However, a complete mathematical framework for the analysis of magnetic fields in these magnets has been developed only for their infinitely long precursors. In such a case the analysis is reduced to two-dimensions (2D). The paper details the analysis of the 3D magnetic field in the Halbach dipole cylinders of a finite length. The analysis is based on three equations in which the components of the magnetic flux density Bx, By and Bz are expanded to infinite power series of the radial coordinate r. The zeroth term in the series corresponds to a homogeneous magnetic field Bc, which is perturbed by the higher order terms due to a finite magnet length. This set of equations is supplemented with an equation for the field profile B(z) along the magnet axis, presented for the first time. It is demonstrated that the geometrical factors in the coefficients of particular powers of r, defined by intricate integrals are the coefficients of the Taylor expansion of the homogeneity profile (B(z)-Bc)/Bc. As a consequence, the components of B can be easily calculated with an arbitrary accuracy. In order to describe perturbations of the field due to segmentation, two additional equations are borrowed from the 2D theory. It is shown that the 2D approach to the perturbations generated by the segmentation can be applied to the 3D Halbach structures unless r is not too close to the inner radius of the cylinder ri. The mathematical framework presented in the paper was verified with great precision by computations of B by a highly accurate integration of the magnetostatic Coulomb law and utilized to analyze the inhomogeneity of the magnetic field in the magnet with the accuracy better than 1 ppm.
Supersymmetric Perturbations of the M5 brane
Niarchos, Vasilis
2014-01-01
We study long-wavelength supersymmetric deformations of brane solutions in supergravity using an extension of previous ideas within the general scheme of the blackfold approach. As a concrete example, we consider long-wavelength perturbations of the planar M2-M5 bound state solution in eleven-dimensional supergravity. We propose a specific ansatz for the first order deformation of the supergravity fields and explore how this deformation perturbs the Killing spinor equations. We find that a special part of these equations gives a projection equation on the Killing spinors that has the same structure as the $\\kappa$-symmetry condition of the abelian M5 brane theory. Requiring a match between supergravity and gauge theory implies a specific non-linear gauge-gravity map between the bosonic fields of the abelian M5 brane theory and the gravity-induced fluid-like degrees of freedom of the blackfold equations that control the perturbative gravity solution. This observation sheds new light on the SUGRA/DBI correspond...
Circumstellar Debris Disks: Diagnosing the Unseen Perturber
Nesvold, Erika R; Vican, Laura; Farr, Will M
2016-01-01
The first indication of the presence of a circumstellar debris disk is usually the detection of excess infrared emission from the population of small dust grains orbiting the star. This dust is short-lived, requiring continual replenishment, and indicating that the disk must be excited by an unseen perturber. Previous theoretical studies have demonstrated that an eccentric planet orbiting interior to the disk will stir the larger bodies in the belt and produce dust via interparticle collisions. However, motivated by recent observations, we explore another possible mechanism for heating a debris disk: a stellar-mass perturber orbiting exterior to and inclined to the disk and exciting the disk particles' eccentricities and inclinations via the Kozai-Lidov mechanism. We explore the consequences of an exterior perturber on the evolution of a debris disk using secular analysis and collisional N-body simulations. We demonstrate that a Kozai-Lidov excited disk can generate a dust disk via collisions and we compare t...
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.)
Harmonic gauge perturbations of the Schwarzschild metric
Berndtson, Mark V
1996-01-01
The satellite observatory LISA will be capable of detecting gravitational waves from extreme mass ratio inspirals (EMRIs), such as a small black hole orbiting a supermassive black hole. The gravitational effects of the much smaller mass can be treated as the perturbation of a known background metric, here the Schwarzschild metric. The perturbed Einstein field equations form a system of ten coupled partial differential equations. We solve the equations in the harmonic gauge, also called the Lorentz gauge or Lorenz gauge. Using separation of variables and Fourier transforms, we write the frequency domain solutions in terms of six radial functions which satisfy decoupled ordinary differential equations. The six functions are the Zerilli and five generalized Regge-Wheeler functions of spin 2,1,0. We use the solutions to calculate the gravitational self-force for circular orbits. The self-force gives the first order perturbative corrections to the equations of motion. Section 1.2 of the thesis has a more detailed ...
Cosmological scalar field perturbations can grow
Alcubierre, Miguel; de la Macorra, Axel; Diez-Tejedor, Alberto; Torres, José M.
2015-09-01
It has been argued that the small perturbations to the homogeneous and isotropic configurations of a canonical scalar field in an expanding universe do not grow. We show that this is not true in general, and clarify the root of the misunderstanding. We revisit a simple model in which the zero mode of a free scalar field oscillates with high frequency around the minimum of the potential. Under this assumption the linear perturbations grow like those in the standard cold dark matter scenario, but with a Jeans length at the scale of the Compton wavelength of the scalar particle. Contrary to previous analyses in the literature our results do not rely on time averages and/or fluid identifications, and instead we solve both analytically (in terms of a well-defined series expansion) and numerically the linearized Einstein-Klein-Gordon system. Also, we use gauge-invariant fields, which makes the physical analysis more transparent and simplifies the comparison with previous works carried out in different gauges. As a byproduct of this study we identify a time-dependent modulation of the different physical quantities associated to the background as well as the perturbations with potential observational consequences in dark matter models.
Linear perturbations of spatially locally homogeneous spacetimes
Tanimoto, M
2003-01-01
Methods and properties regarding the linear perturbations are discussed for some spatially closed (vacuum) solutions of Einstein's equation. The main focus is on two kinds of spatially locally homogeneous solution; one is the Bianchi III (Thurston's H^2 x R) type, while the other is the Bianchi II (Thurston's Nil) type. With a brief summary of previous results on the Bianchi III perturbations, asymptotic solutions for the gauge-invariant variables for the Bianchi III are shown, with which (in)stability of the background solution is also examined. The issue of linear stability for a Bianchi II solution is still an open problem. To approach it, appropriate eigenfunctions are presented for an explicitly compactified Bianchi II manifold and based on that, some field equations on the Bianchi II background spacetime are studied. Differences between perturbation analyses for Bianchi class B (to which Bianchi III belongs) and class A (to which Bianchi II belongs) are stressed for an intention to be helpful for applic...
Perturbative Critical Behavior from Spacetime Dependent Couplings
Energy Technology Data Exchange (ETDEWEB)
Dong, Xi; Horn, Bart; Silverstein, Eva; Torroba, Gonzalo
2012-08-03
We find novel perturbative fixed points by introducing mildly spacetime-dependent couplings into otherwise marginal terms. In four-dimensional QFT, these are physical analogues of the small-{epsilon} Wilson-Fisher fixed point. Rather than considering 4-{epsilon} dimensions, we stay in four dimensions but introduce couplings whose leading spacetime dependence is of the form {lambda}x{sup {kappa}}{mu}{sup {kappa}}, with a small parameter {kappa} playing a role analogous to {epsilon}. We show, in {phi}{sup 4} theory and in QED and QCD with massless flavors, that this leads to a critical theory under perturbative control over an exponentially wide window of spacetime positions x. The exact fixed point coupling {lambda}{sub *}(x) in our theory is identical to the running coupling of the translationally invariant theory, with the scale replaced by 1/x. Similar statements hold for three-dimensional {phi}{sup 6} theories and two-dimensional sigma models with curved target spaces. We also describe strongly coupled examples using conformal perturbation theory.
Non-perturbative study of QCD correlators
Lokhov, A Y
2006-01-01
This PhD dissertation is devoted to a non-perturbative study of QCD correlators. The main tool that we use is lattice QCD. We concentrated our efforts on the study of the main correlators of the pure Yang - Mills theory in the Landau gauge, namely the ghost and the gluon propagators. We are particularly interested in determining the $\\Lqcd$ parameter. It is extracted by means of perturbative predictions available up to NNNLO. The related topic is the influence of non-perturbative effects that show up as appearance of power-corrections to the low-momentum behaviour of the Green functions. A new method of removing these power corrections allows a better estimate of $\\Lqcd$. Our result is $\\Lambda^{n_f=0}_{\\ms} = 269(5)^{+12}_{-9}$ MeV. Another question that we address is the infrared behaviour of Green functions, at momenta of order and below $\\Lqcd$. At low energy the momentum dependence of the propagators changes considerably, and this is probably related to confinement. The lattice approach allows to check t...
Hamiltonian formalism for Perturbed Black Hole Spacetimes
Mihaylov, Deyan; Gair, Jonathan
2017-01-01
Present and future gravitational wave observations provide a new mechanism to probe the predictions of general relativity. Observations of extreme mass ratio inspirals with millihertz gravitational wave detectors such as LISA will provide exquisite constraints on the spacetime structure outside astrophysical black holes, enabling tests of the no-hair property that all general relativistic black holes are described by the Kerr metric. Previous work to understand what constraints LISA observations will be able to place has focussed on specific alternative theories of gravity, or generic deviations that preserve geodesic separability. We describe an alternative approach to this problem--a technique that employs canonical perturbations of the Hamiltonian function describing motion in the Kerr metric. We derive this new approach and demonstrate its application to the cases of a slowly rotating Kerr black hole which is viewed as a perturbation of a Schwarzschild black hole, of coupled perturbations of black holes in the second-order Chern-Simons modified gravity theory, and several more indicative scenarios. Deyan Mihaylov is funded by STFC.
TMDs, universality and factorization
D'Alesio, Umberto
2011-01-01
We present a short overview on transverse momentum dependent parton distribution and fragmentation functions, giving their partonic interpretation and ways to access them. We then discuss the issue of their universality and its connection to factorization in perturbative QCD.
Approximate Generalized Conditional Symmetries for Perturbed Evolution Equations
Institute of Scientific and Technical Information of China (English)
ZHANG Shun-Li; WANG Yong; LOU Sen-Yue
2007-01-01
The concept of approximate generalized conditional symmetry (AGCS) for the perturbed evolution equations is introduced, and how to derive approximate conditional invariant solutions to the perturbed equations via their AGCSs is illustrated with examples.
Global Bifurcation of a Perturbed Double-Homoclinic Loop
Institute of Scientific and Technical Information of China (English)
Desheng SHANG; Maoan HAN
2006-01-01
This paper deals with a kind of fourth degree systems with perturbations. By using the method of multi-parameter perturbation theory and qualitative analysis, it is proved that the system can have six limit cycles.
Zhou, Hao-Jun; Fan, Xiao-Qiang; Li, Zheng-Hong; Pu, Yi-Kang
2015-01-01
The perturbation method is proposed to obtain the effective delayed neutron fraction (\\b{eta}eff) of a cylindrical highly enriched uranium reactor. Based on the reactivity measurements with and without a sample at a designable position using the positive periodic technique, the reactor reactivity perturbation {\\Delta}\\r{ho} of the sample in \\b{eta}eff units is measured. The simulation of the perturbation experiments are performed by MCNP program. The PERT card is used to provide the difference dk of effective neutron multiplication factors with and without the sample inside the reactor. Based on the relationship between the effective multiplication factor and the reactivity, the equation \\b{eta}eff =dk/{\\Delta}\\r{ho} is derived. In this paper, the reactivity perturbations of 13 metal samples at the designable position of the reactor are measured and calculated. The average \\b{eta}eff value of the reactor is given as 0.00645, and the standard uncertainty is 3.0%. Additionally, the perturbation experiments for ...
Zhou, Hao-Jun; Yin, Yan-Peng; Fan, Xiao-Qiang; Li, Zheng-Hong; Pu, Yi-Kang
2016-06-01
A perturbation method is proposed to obtain the effective delayed neutron fraction β eff of a cylindrical highly enriched uranium reactor. Based on reactivity measurements with and without a sample at a specified position using the positive period technique, the reactor reactivity perturbation Δρ of the sample in β eff units is measured. Simulations of the perturbation experiments are performed using the MCNP program. The PERT card is used to provide the difference dk of effective neutron multiplication factors with and without the sample inside the reactor. Based on the relationship between the effective multiplication factor and the reactivity, the equation β eff = dk/Δρ is derived. In this paper, the reactivity perturbations of 13 metal samples at the designable position of the reactor are measured and calculated. The average β eff value of the reactor is given as 0.00645, and the standard uncertainty is 3.0%. Additionally, the perturbation experiments for β eff can be used to evaluate the reliabilities of the delayed neutron parameters. This work shows that the delayed neutron data of 235U and 238U from G.R. Keepin’s publication are more reliable than those from ENDF-B6.0, ENDF-B7.0, JENDL3.3 and CENDL2.2. Supported by Foundation of Key Laboratory of Neutron Physics, China Academy of Engineering Physics (2012AA01, 2014AA01), National Natural Science Foundation (11375158, 91326104)
Sakamoto, Hiroki; Yamamoto, Toshihiro
2017-09-01
This paper presents improvement and performance evaluation of the ;perturbation source method;, which is one of the Monte Carlo perturbation techniques. The formerly proposed perturbation source method was first-order accurate, although it is known that the method can be easily extended to an exact perturbation method. A transport equation for calculating an exact flux difference caused by a perturbation is solved. A perturbation particle representing a flux difference is explicitly transported in the perturbed system, instead of in the unperturbed system. The source term of the transport equation is defined by the unperturbed flux and the cross section (or optical parameter) changes. The unperturbed flux is provided by an ;on-the-fly; technique during the course of the ordinary fixed source calculation for the unperturbed system. A set of perturbation particle is started at the collision point in the perturbed region and tracked until death. For a perturbation in a smaller portion of the whole domain, the efficiency of the perturbation source method can be improved by using a virtual scattering coefficient or cross section in the perturbed region, forcing collisions. Performance is evaluated by comparing the proposed method to other Monte Carlo perturbation methods. Numerical tests performed for a particle transport in a two-dimensional geometry reveal that the perturbation source method is less effective than the correlated sampling method for a perturbation in a larger portion of the whole domain. However, for a perturbation in a smaller portion, the perturbation source method outperforms the correlated sampling method. The efficiency depends strongly on the adjustment of the new virtual scattering coefficient or cross section.
A perturbative and gauge invariant treatment of gravitational wave memory
Bieri, Lydia
2013-01-01
We present a perturbative treatment of gravitational wave memory. The coordinate invariance of Einstein's equations leads to a type of gauge invariance in perturbation theory. As with any gauge invariant theory, results are more clear when expressed in terms of manifestly gauge invariant quantities. Therefore we derive all our results from the perturbed Weyl tensor rather than the perturbed metric. We derive gravitational wave memory for the Einstein equations coupled to a general energy-momentum tensor that reaches null infinity.
On the Interface between Perturbative and Nonperturbative QCD
Deur, A; de Teramond, G F
2016-01-01
The QCD running coupling $\\alpha_s(Q^2)$ sets the strength of the interactions of quarks and gluons as a function of the momentum transfer $Q$. The $Q^2$ dependence of the coupling is required to describe hadronic interactions at both large and short distances. In this article we adopt the light-front holographic approach to strongly-coupled QCD, a formalism which incorporates confinement, predicts the spectroscopy of hadrons composed of light quarks, and describes the low-$Q^2$ analytic behavior of the strong coupling $\\alpha_s(Q^2)$. The high-$Q^2$ dependence of the coupling $\\alpha_s(Q^2)$ is specified by perturbative QCD and its renormalization group equation. The matching of the high and low $Q^2$ regimes of $\\alpha_s(Q^2)$ then determines the scale $Q_0$ which sets the interface between perturbative and nonperturbative hadron dynamics. The value of $Q_0$ can be used to set the factorization scale for DGLAP evolution of hadronic structure functions and the ERBL evolution of distribution amplitudes. We di...
A Scale-Dependent Power Asymmetry from Isocurvature Perturbations
Erickcek, Adrienne L; Kamionkowski, Marc
2009-01-01
If the hemispherical power asymmetry observed in the cosmic microwave background (CMB) on large angular scales is attributable to a superhorizon curvaton fluctuation, then the simplest model predicts that the primordial density fluctuations should be similarly asymmetric on all smaller scales. The distribution of high-redshift quasars was recently used to constrain the power asymmetry on scales k ~ 1.5h/Mpc, and the upper bound on the amplitude of the asymmetry was found to be a factor of six smaller than the amplitude of the asymmetry in the CMB. We show that it is not possible to generate an asymmetry with this scale dependence by changing the relative contributions of the inflaton and curvaton to the adiabatic power spectrum. Instead, we consider curvaton scenarios in which the curvaton decays after dark matter freezes out, thus generating isocurvature perturbations. If there is a superhorizon fluctuation in the curvaton field, then the rms amplitude of these perturbations will be asymmetric, and the asymm...
A NOTE ON DELTA-PERTURBATION EXPANSION METHOD
Institute of Scientific and Technical Information of China (English)
何吉欢
2002-01-01
The Delta-perturbation expansion method, a kind of new perturbation technique depending upon an artificial parameter Delta was studied. The study reveals that the method exits some advantages, but also exits some limitations. To overcome the limitations, the socalled linearized perturbation method proposed by HE Ji-huan can be powerfully applied.
On spectral perturbation caused by bounded variation of potential
Energy Technology Data Exchange (ETDEWEB)
Ismagilov, R S [N.E. Bauman Moscow State Technical University, Moscow (Russian Federation)
2014-01-31
The harmonic oscillator operator is perturbed by an arbitrary bounded continuous term. This results in the perturbation of the spectrum. The map sending the first of these perturbations into the second is examined. Its approximation by a linear map is studied. Bibliography: 2 titles.
Energy corrections and persistent perturbation effects in continuous spectra
Hove, Léon van
1955-01-01
The quantum-mechanical perturbation theory of continuous energy spectra is investigated for a special class of perturbations possessing some of the formal properties of the familiar interaction energies of field theory. These formal properties entail the inapplicability of the familiar perturbation
Perturbation Theory of the Cosmological Log-Density Field
DEFF Research Database (Denmark)
Wang, Xin; Neyrinck, Mark; Szapudi, István
2011-01-01
, motivating an analytic study of it. In this paper, we develop cosmological perturbation theory for the power spectrum of this field. Our formalism is developed in the context of renormalized perturbation theory, which helps to regulate the convergence behavior of the perturbation series, and of the Taylor...
Distributed Capacitance of Coaxial Line With Perturbed Walls
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Perturbation method of boundary geometry(PMOBG) used in Laplacian problems is dealt with and the three-term perturbation expression of distributed capacitance of a coaxial line with perturbed walls is obtained. As an example,four-order expression of distributed capacitance of a elliptic coaxial line with small eccentricity is given.
The reconstruction property in Banach spaces and a perturbation theorem
DEFF Research Database (Denmark)
Casazza, P.G.; Christensen, Ole
2008-01-01
Perturbation theory is a fundamental tool in Banach space theory. However, the applications of the classical results are limited by the fact that they force the perturbed sequence to be equivalent to the given sequence. We will develop a more general perturbation theory that does not force equiva...
On spectral perturbation caused by bounded variation of potential
Ismagilov, R. S.
2014-01-01
The harmonic oscillator operator is perturbed by an arbitrary bounded continuous term. This results in the perturbation of the spectrum. The map sending the first of these perturbations into the second is examined. Its approximation by a linear map is studied. Bibliography: 2 titles.
Perturbative Approach to the Quasinormal Modes of Dirty Black Holes
Leung, P T; Suen, W M; Tam, C Y; Young, K
1999-01-01
Using a recently developed perturbation theory for uasinormal modes (QNM's), we evaluate the shifts in the real and imaginary parts of the QNM frequencies due to a quasi-static perturbation of the black hole spacetime. We show the perturbed QNM spectrum of a black hole can have interesting features using a simple model based on the scalar wave equation.
The reconstruction property in Banach spaces and a perturbation theorem
DEFF Research Database (Denmark)
Casazza, P.G.; Christensen, Ole
2008-01-01
Perturbation theory is a fundamental tool in Banach space theory. However, the applications of the classical results are limited by the fact that they force the perturbed sequence to be equivalent to the given sequence. We will develop a more general perturbation theory that does not force...
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.
Bogdan, V. M.; Bond, V. B.
1980-01-01
The deviation of the solution of the differential equation y' = f(t, y), y(O) = y sub O from the solution of the perturbed system z' = f(t, z) + g(t, z), z(O) = z sub O was investigated for the case where f and g are continuous functions on I x R sup n into R sup n, where I = (o, a) or I = (o, infinity). These functions are assumed to satisfy the Lipschitz condition in the variable z. The space Lip(I) of all such functions with suitable norms forms a Banach space. By introducing a suitable norm in the space of continuous functions C(I), introducing the problem can be reduced to an equivalent problem in terminology of operators in such spaces. A theorem on existence and uniqueness of the solution is presented by means of Banach space technique. Norm estimates on the rate of growth of such solutions are found. As a consequence, estimates of deviation of a solution due to perturbation are obtained. Continuity of the solution on the initial data and on the perturbation is established. A nonlinear perturbation of the harmonic oscillator is considered a perturbation of equations of the restricted three body problem linearized at libration point.
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.
CONVERGENCE RESULTS OF RUNGE-KUTTA METHODS FOR MULTIPLY-STIFF SINGULAR PERTURBATION PROBLEMS
Institute of Scientific and Technical Information of China (English)
Ai-guo Xiao
2002-01-01
The main purpose of this paper is to present some convergence results for algebraically stable Runge-Kutta methods applied to some classes of one- and two-parameter multiplystiff singular perturbation problems whose stiffness is caused by small parameters and some other factors. A numerical example confirms our results.
The Feynman-Schwinger (world-line) representation in perturbative QCD
Simonov, Yu. A.; Tjon, J. A.
2002-01-01
Abstract: The proper time path integral representation is derived explicitly for an arbitrary $n$-point amplitude in QCD. In the standard perturbation theory the formalism allows to sum up the leading subseries, e.g. yielding double-logarithm Sudakov asymptotics for form factors. Correspondence with
Chiral perturbation theory study of the axial $N\\to\\Delta(1232)$ transition
Geng, L S; Alvarez-Ruso, L; Vacas, M J Vicente
2008-01-01
We have performed a theoretical study of the axial Nucleon to Delta(1232) ($N\\to\\Delta$) transition form factors up to one-loop order in covariant baryon chiral perturbation theory within a formalism in which the unphysical spin-1/2 components of the $\\Delta$ fields are decoupled.
Non-perturbative Heavy Quark Effective Theory: An application to semi-leptonic B-decays
Della Morte, Michele; Simma, Hubert; Sommer, Rainer
2015-01-01
We review a lattice strategy how to non-perturbatively determine the coefficients in the HQET expansion of all components of the heavy-light axial and vector currents, including 1/m_h-corrections. We also discuss recent preliminary results on the form factors parameterizing semi-leptonic B-decays at the leading order in 1/m_h.
Chishtie, F A
2002-01-01
Pade approximants (PA) have been widely applied in practically all areas of physics. This thesis focuses on developing PA as tools for both perturbative and non- perturbative quantum field theory (QFT). In perturbative QFT, we systematically estimate higher (unknown) loop terms via the asymptotic formula devised by Samuel et al. This algorithm, generally denoted as the asymptotic Pade approximation procedure (APAP), has greatly enhanced scope when it is applied to renormalization-group-(RG-) invariant quantities. A presently-unknown higher-loop quantity can then be matched with the approximant over the entire momentum region of phenomenological interest. Furthermore, the predicted value of the RG coefficients can be compared with the RG-accessible coefficients (at the higher-loop order), allowing a clearer indication of the accuracy of the predicted RG-inaccessible term. This methodology is applied to hadronic Higgs decay rates (H → bb¯ and H → gg, both within the Standard Model and...
The perturbative ghost propagator in Landau gauge from numerical stochastic perturbation theory
Di Renzo, F; Perlt, H; Schiller, A; Torrero, C
2008-01-01
We present one- and two-loop results for the ghost propagator in Landau gauge calculated in Numerical Stochastic Perturbation Theory (NSPT). The one-loop results are compared with available standard Lattice Perturbation Theory in the infinite-volume limit. We discuss in detail how to perform the different necessary limits in the NSPT approach and discuss a recipe to treat logarithmic terms by introducing ``finite-lattice logs''. We find agreement with the one-loop result from standard Lattice Perturbation Theory and estimate, from the non-logarithmic part of the ghost propagator in two-loop order, the unknown constant contribution to the ghost self-energy in the RI'-MOM scheme in Landau gauge. That constant vanishes within our numerical accuracy.
Transfer function analysis of thermospheric perturbations
Mayr, H. G.; Harris, I.; Varosi, F.; Herrero, F. A.; Spencer, N. W.
1986-01-01
Applying perturbation theory, a spectral model in terms of vectors spherical harmonics (Legendre polynomials) is used to describe the short term thermospheric perturbations originating in the auroral regions. The source may be Joule heating, particle precipitation or ExB ion drift-momentum coupling. A multiconstituent atmosphere is considered, allowing for the collisional momentum exchange between species including Ar, O2, N2, O, He and H. The coupled equations of energy, mass and momentum conservation are solved simultaneously for the major species N2 and O. Applying homogeneous boundary conditions, the integration is carred out from the Earth's surface up to 700 km. In the analysis, the spherical harmonics are treated as eigenfunctions, assuming that the Earth's rotation (and prevailing circulation) do not significantly affect perturbations with periods which are typically much less than one day. Under these simplifying assumptions, and given a particular source distribution in the vertical, a two dimensional transfer function is constructed to describe the three dimensional response of the atmosphere. In the order of increasing horizontal wave numbers (order of polynomials), this transfer function reveals five components. To compile the transfer function, the numerical computations are very time consuming (about 100 hours on a VAX for one particular vertical source distribution). However, given the transfer function, the atmospheric response in space and time (using Fourier integral representation) can be constructed with a few seconds of a central processing unit. This model is applied in a case study of wind and temperature measurements on the Dynamics Explorer B, which show features characteristic of a ringlike excitation source in the auroral oval. The data can be interpreted as gravity waves which are focused (and amplified) in the polar region and then are reflected to propagate toward lower latitudes.
Scalar cosmological perturbations from inflationary black holes
Energy Technology Data Exchange (ETDEWEB)
Prokopec, Tomislav; Reska, Paul, E-mail: t.prokopec@uu.nl, E-mail: p.m.reska@uu.nl [Spinoza Institute and Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht (Netherlands)
2011-03-01
We study the correction to the scale invariant power spectrum of a scalar field on de Sitter space from small black holes that formed during a pre-inflationary matter dominated era. The formation probability of such black holes is estimated from primordial Gaussian density fluctuations. We determine the correction to the spectrum of scalar cosmological perturbations from the Keldysh propagator of a massless scalar field on Schwarzschild-de Sitter space. Our results suggest that the effect is strong enough to be tested — and possibly even ruled out — by observations.
Large Field Cutoffs Make Perturbative Series Converge
Meurice, Y
2002-01-01
For lambda phi^4 problems, convergent perturbative series can be obtained by cutting off the large field configurations. The modified series converge to values exponentially close to the exact ones. For lambda larger than some critical value, the method outperforms Pade approximants and Borel summations. We discuss some aspects of the semi-classical methods used to calculate the modified Feynman rules and estimate the error associated with the procedure. We provide a simple numerical example where the procedure works despite the fact that the Borel sum has singularities on the positive real axis.
Large field cutoffs make perturbative series converge
Meurice, Yannick
2002-03-01
For λφ 4 problems, convergent perturbative series can be obtained by cutting off the large field configurations. The modified series converge to values exponentially close to the exact ones. For λ larger than some critical value, the method outperforms Padé approximants and Borel summations. We discuss some aspects of the semi-classical methods used to calculate the modified Feynman rules and estimate the error associated with the procedure. We provide a simple numerical example where the procedure works despite the fact that the Borel sum has singularities on the positive real axis.
Light-Front Perturbation Without Spurious Singularities
Przeszowski, Jerzy A.; Dzimida-Chmielewska, Elżbieta; Żochowski, Jan
2016-07-01
A new form of the light front Feynman propagators is proposed. It contains no energy denominators. Instead the dependence on the longitudinal subinterval x^2_L = 2 x+ x- is explicit and a new formalism for doing the perturbative calculations is invented. These novel propagators are implemented for the one-loop effective potential and various 1-loop 2-point functions for a massive scalar field. The consistency with results for the standard covariant Feynman diagrams is obtained and no spurious singularities are encountered at all. Some remarks on the calculations with fermion and gauge fields in QED and QCD are added.
Metastability of exponentially perturbed Markov chains
Institute of Scientific and Technical Information of China (English)
陈大岳; 冯建峰; 钱敏平
1996-01-01
A family of irreducible Markov chains on a finite state space is considered as an exponential perturbation of a reducible Markov chain. This is a generalization of the Freidlin-Wentzell theory, motivated by studies of stochastic Ising models, neural network and simulated annealing. It is shown that the metastability is a universal feature for this wide class of Markov chains. The metastable states are simply those recurrent states of the reducible Markov chain. Higher level attractors, related attractive basins and their pyramidal structure are analysed. The logarithmic asymptotics of the hitting time of various sets are estimated. The hitting time over its mean converges in law to the unit exponential distribution.
Tests of Chiral perturbation theory with COMPASS
Directory of Open Access Journals (Sweden)
Friedrich Jan M.
2014-06-01
Full Text Available The COMPASS experiment at CERN accesses pion-photon reactions via the Primakoff effect., where high-energetic pions react with the quasi-real photon field surrounding the target nuclei. When a single real photon is produced, pion Compton scattering is accessed and from the measured cross-section shape, the pion polarisability is determined. The COMPASS measurement is in contradiction to the earlier dedicated measurements, and rather in agreement with the theoretical expectation from ChPT. In the same experimental data taking, reactions with neutral and charged pions in the final state are measured and analyzed in the context of chiral perturbation theory.
Perturbations in some models of tachyonic inflation
G., Iván E Sánchez
2015-01-01
In the present work an inflationary tachyon field model of the early universe in the braneworld scenario is considered. Several cosmological effects produced by a particular potential in this tachyonic era are studied, under the approximation of slow-roll inflation. In particular, the evolution of the spectral index $n_s$ with time is obtained. The equations for the cosmological scalar perturbations are analytically solved in order to show that the power spectrum for small $k$ values is $P_{\\zeta}\\sim 1/k^{\\frac{1}{2}+\
Eigenvector dynamics under perturbation of modular networks
Sarkar, Somwrita; Robinson, Peter A; Fortunato, Santo
2015-01-01
Rotation dynamics of eigenvectors of modular network adjacency matrices under random perturbations are presented. In the presence of $q$ communities, the number of eigenvectors corresponding to the $q$ largest eigenvalues form a "community" eigenspace and rotate together, but separately from that of the "bulk" eigenspace spanned by all the other eigenvectors. Using this property, the number of modules or clusters in a network can be estimated in an algorithm-independent way. A general derivation for the theoretical detectability limit for sparse modular networks with $q$ communities is presented, beyond which modularity persists in the system but cannot be detected, and estimation results are shown to hold right to this limit.
Superspace Dynamics and Perturbations Around "Emptiness"
Soo, C P; Soo, Chopin; Chang, Lay Nam
1994-01-01
Superspace parametrized by gauge potentials instead of metric three-geometries is discussed in the context of the Ashtekar variables. Among other things, an "internal clock" for the full theory can be identified. Gauge-fixing conditions which lead to the natural geometrical separation of physical from gauge modes are derived with the use of the metric in connection-superspace. A perturbation scheme about an unconventional background which is inaccessible to conventional variables is presented. The resultant expansion retains much of the simplicity of Ashtekar's formulation of General Relativity.
Visual Vection does not Perturb Squatting Posture
Directory of Open Access Journals (Sweden)
Dietrich Gilles
2011-12-01
Full Text Available Vision contributes fundamentally to the control of the standing posture. The illusion of self motion falsely perceived (vection increases postural sway while standing. In this paper we examine the effect of vection on both standing and deep squatting with the hypothesis that the squatting posture should not be disturbed by the conflict of sensory information due to vection. The results show that standing posture only was affected by the visual stimuli. The widespread use of squatting for work as well as rest could be due in part to this lack of effect of sensory perturbation on postural stability.
Dynamical entropy for systems with stochastic perturbation
Ostruszka, A; Slomczynski, W; Zyczkowski, K; Ostruszka, Andrzej; Pakonski, Prot; Slomczynski, Wojciech; Zyczkowski, Karol
1999-01-01
Dynamics of deterministic systems perturbed by random additive noise is characterized quantitatively. Since for such systems the KS-entropy diverges we analyse the difference between the total entropy of a noisy system and the entropy of the noise itself. We show that this quantity is non negative and in the weak noise limit is conjectured to tend to the KS-entropy of the deterministic system. In particular, we consider one-dimensional systems with noise described by a finite-dimensional kernel, for which the Frobenius-Perron operator can be represented by a finite matrix.
Bonding charge density from atomic perturbations.
Wang, Yi; Wang, William Yi; Chen, Long-Qing; Liu, Zi-Kui
2015-05-15
Charge transfer among individual atoms is the key concept in modern electronic theory of chemical bonding. In this work, we present a first-principles approach to calculating the charge transfer. Based on the effects of perturbations of an individual atom or a group of atoms on the electron charge density, we determine unambiguously the amount of electron charge associated with a particular atom or a group of atoms. We computed the topological electron loss versus gain using ethylene, graphene, MgO, and SrTiO3 as examples. Our results verify the nature of chemical bonds in these materials at the atomic level.
Amplification of curvature perturbations in cyclic cosmology
Zhang, Jun; Liu, Zhi-Guo; Piao, Yun-Song
2010-12-01
We analytically and numerically show that through the cycles with nonsingular bounce, the amplitude of curvature perturbation on a large scale will be amplified and the power spectrum will redden. In some sense, this amplification will eventually destroy the homogeneity of the background, which will lead to the ultimate end of cycles of the global universe. We argue that for the model with increasing cycles, it might be possible that a fissiparous multiverse will emerge after one or several cycles, in which the cycles will continue only at corresponding local regions.
Perturbative Higgs CP violation, unitarity and phenomenology
Englert, Christoph; Sakurai, Kazuki; Spannowsky, Michael
2016-01-01
Perturbative probability conservation provides a strong constraint on the presence of new interactions of the Higgs boson. In this work we consider CP violating Higgs interactions in conjunction with unitarity constraints in the gauge-Higgs and fermion-Higgs sectors. Injecting signal strength measurements of the recently discovered Higgs boson allows us to make concrete and correlated predictions of how CP-violation in the Higgs sector can be directly constrained through collider searches for either characteristic new states or tell-tale enhancements in multi-Higgs processes.
On causality, unitarity and perturbative expansions
Energy Technology Data Exchange (ETDEWEB)
Danilkin, Igor; Gasparyan, Ashot; Lutz, Matthias [GSI, Planck Str. 1, 64291 Darmstadt (Germany)
2011-07-01
We present a pedagogical case study how to combine micro-causality and unitarity based on a perturbative approach. The method we advocate constructs an analytic extrapolation of partial-wave scattering amplitudes that is constrained by the unitarity condition. Suitably constructed conformal mappings help to arrive at a systematic approximation of the scattering amplitude. The technique is illustrated at hand of a Yukawa interaction. The typical case of a superposition of strong short-range and weak long-range forces is investigated.
On causality, unitarity and perturbative expansions
Energy Technology Data Exchange (ETDEWEB)
Danilkin, I.V.; Gasparyan, A.M. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Planck Str. 1, 64291 Darmstadt (Germany); Institute for Theoretical and Experimental Physics, 117259, B. Cheremushkinskaya 25, Moscow (Russian Federation); Lutz, M.F.M., E-mail: m.lutz@gsi.d [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Planck Str. 1, 64291 Darmstadt (Germany)
2011-02-28
We present a pedagogical case study how to combine micro-causality and unitarity based on a perturbative approach. The method we advocate constructs an analytic extrapolation of partial-wave scattering amplitudes that is constrained by the unitarity condition. Suitably constructed conformal mappings help to arrive at a systematic approximation of the scattering amplitude in a quantum-field theoretical context. The technique is illustrated at hand of a Yukawa interaction. The typical case of a superposition of strong short-range and weak long-range forces is investigated.
Homotopy Perturbation Method with an Auxiliary Term
Directory of Open Access Journals (Sweden)
Ji-Huan He
2012-01-01
Full Text Available The two most important steps in application of the homotopy perturbation method are to construct a suitable homotopy equation and to choose a suitable initial guess. The homotopy equation should be such constructed that when the homotopy parameter is zero, it can approximately describe the solution property, and the initial solution can be chosen with an unknown parameter, which is determined after one or two iterations. This paper suggests an alternative approach to construction of the homotopy equation with an auxiliary term; Dufing equation is used as an example to illustrate the solution procedure.
Non-perturbative monodromies in N=2 heterotic string vacua
Lópes-Cardoso, G; Mohaupt, T; Cardoso, Gabriel Lopes; Lust, Dieter; Mohaupt, Thomas
1995-01-01
We address non-perturbative effects and duality symmetries in N=2 heterotic string theories in four dimensions. Specifically, we consider how each of the four lines of enhanced gauge symmetries in the perturbative moduli space of N=2 T_2 compactifications is split into 2 lines where monopoles and dyons become massless. This amounts to considering non-perturbative effects originating from enhanced gauge symmetries at the microscopic string level. We show that the perturbative and non-perturbative monodromies consistently lead to the results of Seiberg-Witten upon identication of a consistent truncation procedure from local to rigid N=2 supersymmetry.
Direct Perturbation Method for Derivative Nonlinear Schrodinger Equation
Institute of Scientific and Technical Information of China (English)
CHENG Xue-Ping; LIN Ji; HAN Ping
2008-01-01
We extend Lou's direct perturbation method for solving the nonlinear SchrSdinger equation to the case of the derivative nonlinear Schrodinger equation (DNLSE). By applying this method, different types of perturbation solutions axe obtained. Based on these approximate solutions, the analytical forms of soliton parameters, such as the velocity, the width and the initial position, are carried out and the effects of perturbation on solitons are analyzed at the same time. A numerical simulation of perturbed DNLSE finally verifies the results of the perturbation method.
Comparison of electroglottographic and acoustic analysis of pitch perturbation.
LaBlance, G R; Maves, M D; Scialfa, T M; Eitnier, C M; Steckol, K F
1992-11-01
Pitch perturbation is a measure of the cycle-to-cycle variation in vocal fold vibration. Perturbation can be assessed by means of electroglottographic or acoustic signals. The purpose of this study was to determine if these two analysis techniques are equivalent measures. The Laryngograph, an electroglottograph, and the Visi-Pitch, an acoustic analyzer, were used to measure pitch perturbation in 80 dysphonic subjects. Both instruments use Koike's formula to calculate relative average perturbation. While intra-subject variability appeared erratic, statistical analysis of intersubject data indicated that the two instruments provided an equivalent measure of pitch perturbation.
Saleh, Mahamat; Bouetou, Bouetou Thomas; Kofane, Timoleon Crepin
2016-04-01
In this work, quasinormal modes (QNMs) of the Schwarzschild black hole are investigated by taking into account the quantum fluctuations. Gravitational and Dirac perturbations were considered for this case. The Regge-Wheeler gauge and the Dirac equation were used to derive the perturbation equations of the gravitational and Dirac fields respectively and the third order Wentzel-Kramers-Brillouin (WKB) approximation method is used for the computing of the quasinormal frequencies. The results show that due to the quantum fluctuations in the background of the Schwarzschild black hole, the QNMs of the black hole damp more slowly when increasing the quantum correction factor (a), and oscillate more slowly.
Balance training enhances motor coordination during a perturbed side-step cutting task
DEFF Research Database (Denmark)
Oliveira, Anderson Souza; Silva, Priscila de Brito; Lund, Morten Enemark
2017-01-01
, and ground reaction forces. Motor modules were extracted from the EMG by non-negative matrix factorization. External knee abduction moments were calculated using inverse dynamics equations. Results BTR resulted in a reduction of the external knee abduction moment (33 ± 25%, p2)=0.......725), and increased the activation of trunk and proximal hip muscles in specific motor modules during perturbed cutting. BTR also increased burst duration for the motor module related to landing early in the perturbation phase (23 ± 11%, p2)=0.532). Conclusion BTR resulted in altered motor coordination...
Saleh, Mahamat; Crépin, Kofané Timoléon
2016-01-01
In this work, quasinormal modes (QNMs) of the Schwarzschild black hole are investigated by taking into account the quantum fluctuations. Gravitational and Dirac perturbations were considered for this case. The Regge-Wheeler gauge and the Dirac equation were used to derive the perturbation equations of the gravitational and Dirac fields respectively and the third order Wentzel-Kramers-Brillouin (WKB) approximation method is used for the computing of the quasinormal frequencies. The results show that due to the quantum fluctuations in the background of the Schwarzschild black hole, the QNMs of the black hole damp more slowly when increasing the quantum correction factor (a), and oscillate more slowly.
Institute of Scientific and Technical Information of China (English)
Jingsun Yao; Jiaqi Mo
2005-01-01
The nonlinear nonlocal singularly perturbed initial boundary value problems for reaction diffusion equations with a boundary perturbation is considered. Under suitable conditions, the outer solution of the original problem is obtained. Using the stretched variable, the composing expansion method and the expanding theory of power series the initial layer is constructed. And then using the theory of differential inequalities the asymptotic behavior of solution for the initial boundary value problems is studied. Finally the existence and uniqueness of solution for the original problem and the uniformly valid asymptotic estimation are discussed.
Perturbative QCD analysis of $B \\to \\phi K$ decays
Chen Chuan Hung; Li, H; Chen, Chuan-Hung; Keum, Yong-Yoen; Li, Hsiang-nan
2001-01-01
We investigate exclusive nonleptonic $B$ meson decays $B\\to\\phi K$ in perturbative QCD formalism. It is shown that the end-point (logarithmic and linear) singularities in decay amplitudes do not exist, after $k_T$ and threshold resummations are included. Power counting for emission and annihilation topologies of diagrams, including both factorizable and nonfactorizable ones, is discussed with Sudakov effects taken into account. Our predictions for the branching ratios $B(B\\to\\phi K)\\sim 10 \\times 10^{-6}$ are larger than those ($\\sim 4 \\times 10^{-6}$) from the factorization approach because of dynamical enhancement of penguin contributions. Whether this enhancement is essential for penguin-dominated modes can be justified by experimental data.
Renormalisation and off-shell improvement in lattice perturbation theory
Capitani, S; Horsley, R; Perlt, H; Rakow, P E L; Schierholz, G; Schiller, A
2001-01-01
We discuss the improvement of flavour non-singlet point and one-link lattice quark operators, which describe the quark currents and the first moment of the DIS structure functions respectively. Suitable bases of improved operators are given, and the corresponding renormalisation factors and improvement coefficients are calculated in one-loop lattice perturbation theory, using the Sheikholeslami-Wohlert (clover) action. To this order we achieve off-shell improvement by eliminating the effect of contact terms. We use massive fermions, and our calculations are done keeping all terms up to first order in the lattice spacing, for arbitrary m^2/p^2, in a general covariant gauge. We also compare clover fermions with fermions satisfying the Ginsparg-Wilson relation, and show how to remove O(a) effects off-shell in this case too, and how this is in many aspects simpler than for clover fermions. Finally, tadpole improvement is also considered.
Metabolic and Transcriptional Response to Cofactor Perturbations in Escherichia coli
DEFF Research Database (Denmark)
Holm, Anders Koefoed; Blank, L.M.; Oldiges, M.
2010-01-01
to lower the level of NADH and ATP, respectively. We used a global interaction network, comprising of protein interactions, transcriptional regulation, and metabolic networks, to integrate data from transcription profiles, metabolic fluxes, and the metabolite levels. We identified high-scoring networks...... for the two strains. The results revealed a smaller, but denser network for perturbations of ATP level, compared with that of NADH level. The action of many global transcription factors such as ArcA, Fnr, CRP, and IHF commonly involved both NADH and ATP, whereas others responded to either ATP or NADH....... Overexpressing NADH oxidase invokes response in widespread aspects of metabolism involving the redox cofactors (NADH and NADPH), whereas ATPase has a more focused response to restore ATP level by enhancing proton translocation mechanisms and repressing biosynthesis. Interestingly, NADPH played a key role...
The Operator Product Expansion Beyond Perturbation Theory in QCD
Dominguez, C A
2010-01-01
The Operator Product Expansion (OPE) of current correlators at short distances beyond perturbation theory in QCD, together with Cauchy's theorem in the complex energy plane, are the pillars of the method of QCD sum rules. This technique provides an analytic tool to relate QCD with hadronic physics at low and intermediate energies. It has been in use for over thirty years to determine hadronic parameters, form factors, and QCD parameters such as the quark masses, and the running strong coupling at the scale of the $\\tau$-lepton. QCD sum rules provide a powerful complement to numerical simulations of QCD on the lattice. In this talk a short review of the method is presented for non experts, followed by three examples of recent applications.
Infrared singularities of scattering amplitudes in perturbative QCD
Energy Technology Data Exchange (ETDEWEB)
Becher, Thomas [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Neubert, Matthias [Johannes Gutenberg-Universitaet Mainz, Mainz (Germany)
2013-11-01
An exact formula is derived for the infrared singularities of dimensionally regularized scattering amplitudes in massless QCD with an arbitrary number of legs, valid at any number of loops. It is based on the conjecture that the anomalous-dimension matrix of n-jet operators in soft-collinear effective theory contains only a single non-trivial color structure, whose coefficient is the cusp anomalous dimension of Wilson loops with light-like segments. Its color-diagonal part is characterized by two anomalous dimensions, which are extracted to three-loop order from known perturbative results for the quark and gluon form factors. This allows us to predict the three-loop coefficients of all 1/epsilon^k poles for an arbitrary n-parton scattering amplitudes, generalizing existing two-loop results.
Perturbation Theory for Parent Hamiltonians of Matrix Product States
Szehr, Oleg; Wolf, Michael M.
2015-05-01
This article investigates the stability of the ground state subspace of a canonical parent Hamiltonian of a Matrix product state against local perturbations. We prove that the spectral gap of such a Hamiltonian remains stable under weak local perturbations even in the thermodynamic limit, where the entire perturbation might not be bounded. Our discussion is based on preceding work by Yarotsky that develops a perturbation theory for relatively bounded quantum perturbations of classical Hamiltonians. We exploit a renormalization procedure, which on large scale transforms the parent Hamiltonian of a Matrix product state into a classical Hamiltonian plus some perturbation. We can thus extend Yarotsky's results to provide a perturbation theory for parent Hamiltonians of Matrix product states and recover some of the findings of the independent contributions (Cirac et al in Phys Rev B 8(11):115108, 2013) and (Michalakis and Pytel in Comm Math Phys 322(2):277-302, 2013).
Lie transform Hamiltonian perturbation theory for limit cycle systems
Shah, Tirth; Chakraborty, Sagar
2016-01-01
Usage of a Hamiltonian perturbation theory for nonconservative system is counterintuitive and in general, a technical impossibility by definition. However, the dual (time independent) Hamiltonian formalism for nonconservative systems have opened the door for using various Hamiltonian (and hence, Lagrangian) perturbation theories for investigating the dynamics of such systems. Following the recent extension of the canonical perturbation theory that brings Li\\'enard systems possessing limit cycles under its scope, here we show that the Lie transform Hamiltonian perturbation theory can also be generalized to find perturbative solutions for similar systems. The Lie transform perturbation theories are comparatively easier while seeking higher order corrections in the perturbative series for the solutions and they are also numerically implementable using any symbolic algebra package. For the sake of concreteness, we have illustrated the methodology using the important example of the van der Pol oscillator. While th...
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.)
Pire, B
2009-01-01
QCD is the theory of strong interactions and non-perturbative methods have been developed to address the confinement property of QCD. Many experimental measurements probe the confining dynamics, and it is well-known that hard scattering processes allow the extraction of non perturbative hadronic matrix elements. To study exclusive hard processes, such as electromagnetic form factors and reactions like gamma* N -> gamma N', gamma* N -> pi N', gamma* gamma -> pi pi, antiproton proton ->gamma* pi in particular kinematics (named as generalized Bjorken regime), one introduces specific non-perturbative objects, namely generalized parton distributions (GPDs), distribution amplitudes (DA) and transition distribution amplitudes (TDA), which are Fourier transformed non-diagonal matrix elements of non-local operators on the light-cone. We review here a selected sample of exclusive amplitudes in which the quark and gluon content of hadrons is probed, and emphasize that much remains to be done to successfully compute thei...
On the perturbative renormalization of four-quark operators for new physics
Energy Technology Data Exchange (ETDEWEB)
Papinutto, M. [Roma Univ. (Italy). Dipt. di Fisica; INFN, Sezione di Roma (Italy); Pena, C. [Univ. Autonoma de Madrid (Spain). Dept. de Fisica Teorica; Univ. Autonoma de Madrid (Spain). Inst. de Fisica Teorica UAM-CSIC; Preti, D. [Univ. Autonoma de Madrid (Spain). Inst. de Fisica Teorica UAM-CSIC
2017-06-15
We discuss the renormalization properties of the full set of ΔF = 2 operators involved in BSM processes, including the definition of RGI versions of operators that exhibit mixing under RG transformations. As a first step for a fully non-perturbative determination of the scale-dependent renormalization factors and their runnings, we introduce a family of appropriate Schroedinger Functional schemes, and study them in perturbation theory. This allows, in particular, to determine the NLO anomalous dimensions of all ΔF = 1,2 operators in these schemes. Finally, we discuss the systematic uncertainties related to the use of NLO perturbation theory for the RG running of four-quark operators to scales in the GeV range, in both our SF schemes and standard MS and RI-MOM schemes. Large truncation effects are found for some of the operators considered. (orig.)
Nguyen, Jennifer; Hayakawa, Carole K; Mourant, Judith R; Venugopalan, Vasan; Spanier, Jerome
2016-05-01
We present a polarization-sensitive, transport-rigorous perturbation Monte Carlo (pMC) method to model the impact of optical property changes on reflectance measurements within a discrete particle scattering model. The model consists of three log-normally distributed populations of Mie scatterers that approximate biologically relevant cervical tissue properties. Our method provides reflectance estimates for perturbations across wavelength and/or scattering model parameters. We test our pMC model performance by perturbing across number densities and mean particle radii, and compare pMC reflectance estimates with those obtained from conventional Monte Carlo simulations. These tests allow us to explore different factors that control pMC performance and to evaluate the gains in computational efficiency that our pMC method provides.
Kemmeren, Patrick; Sameith, Katrin; van de Pasch, Loes A L; Benschop, Joris J; Lenstra, Tineke L; Margaritis, Thanasis; O'Duibhir, Eoghan; Apweiler, Eva; van Wageningen, Sake; Ko, Cheuk W; van Heesch, Sebastiaan; Kashani, Mehdi M; Ampatziadis-Michailidis, Giannis; Brok, Mariel O; Brabers, Nathalie A C H; Miles, Anthony J; Bouwmeester, Diane; van Hooff, Sander R; van Bakel, Harm; Sluiters, Erik; Bakker, Linda V; Snel, Berend; Lijnzaad, Philip; van Leenen, Dik; Groot Koerkamp, Marian J A; Holstege, Frank C P
2014-04-24
To understand regulatory systems, it would be useful to uniformly determine how different components contribute to the expression of all other genes. We therefore monitored mRNA expression genome-wide, for individual deletions of one-quarter of yeast genes, focusing on (putative) regulators. The resulting genetic perturbation signatures reflect many different properties. These include the architecture of protein complexes and pathways, identification of expression changes compatible with viability, and the varying responsiveness to genetic perturbation. The data are assembled into a genetic perturbation network that shows different connectivities for different classes of regulators. Four feed-forward loop (FFL) types are overrepresented, including incoherent type 2 FFLs that likely represent feedback. Systematic transcription factor classification shows a surprisingly high abundance of gene-specific repressors, suggesting that yeast chromatin is not as generally restrictive to transcription as is often assumed. The data set is useful for studying individual genes and for discovering properties of an entire regulatory system.
Running vacuum cosmological models: linear scalar perturbations
Perico, E. L. D.; Tamayo, D. A.
2017-08-01
In cosmology, phenomenologically motivated expressions for running vacuum are commonly parameterized as linear functions typically denoted by Λ(H2) or Λ(R). Such models assume an equation of state for the vacuum given by bar PΛ = - bar rhoΛ, relating its background pressure bar PΛ with its mean energy density bar rhoΛ ≡ Λ/8πG. This equation of state suggests that the vacuum dynamics is due to an interaction with the matter content of the universe. Most of the approaches studying the observational impact of these models only consider the interaction between the vacuum and the transient dominant matter component of the universe. We extend such models by assuming that the running vacuum is the sum of independent contributions, namely bar rhoΛ = Σibar rhoΛi. Each Λ i vacuum component is associated and interacting with one of the i matter components in both the background and perturbation levels. We derive the evolution equations for the linear scalar vacuum and matter perturbations in those two scenarios, and identify the running vacuum imprints on the cosmic microwave background anisotropies as well as on the matter power spectrum. In the Λ(H2) scenario the vacuum is coupled with every matter component, whereas the Λ(R) description only leads to a coupling between vacuum and non-relativistic matter, producing different effects on the matter power spectrum.
Testing gravity theories using tensor perturbations
Lin, Weikang; Ishak-Boushaki, Mustapha B.
2017-01-01
Primordial gravitational waves constitute a promising probe of the very early universe physics and the laws of gravity. We study the changes to tensor-mode perturbations that can arise in various modified gravity theories. These include a modified friction and a nonstandard dispersion relation. We introduce a physically motivated parametrization of these effects and use current data to obtain excluded parameter spaces. Taking into account the foreground subtraction, we then perform a forecast analysis focusing on the tensor-mode modified-gravity parameters as constrained by future experiments COrE, Stage-IV and PIXIE. For the tensor-to-scalar ratio r=0.01, we find the minimum detectible modified-gravity effects. In particular, the minimum detectable graviton mass is about 7.8˜9.7×10-33 eV, which is of the same order of magnitude as the graviton mass that allows massive gravity to produce late-time cosmic acceleration. Finally, we study the tensor-mode perturbations in modified gravity during inflation. We find that, the tensor spectral index would be additionally related to the friction parameter ν0 by nT=-3ν0-r/8. In some cases, the future experiments will be able to distinguish this relation from the standard one. In sum, primordial gravitational waves provide a complementary avenue to test gravity theories.
Perceived timing of a postural perturbation.
Lupo, Julian; Barnett-Cowan, Michael
2017-02-03
Falling down is a common event that threatens the survival of an organism. Simple, yet sophisticated neural mechanisms allow for rapid detection of a fall as well as the generation of compensatory reflexes designed to prevent a fall. Fall awareness and preventative alerting devices could potentially mitigate the likelihood of a fall, however, relatively little is known about the perceived timing of a fall. Common anecdotal reports suggest that humans often describe distortions in their perception of time with very little recollection of what occurred during the fall. Previous research has also found that the vestibular system is perceptually slow compared to the other senses (45-160ms delay), indicating that vestibular stimuli must occur prior to other sensory stimuli in order for it to be perceived as synchronous. Here we examine whether fall perception is similarly slow. Participants made temporal order judgments identifying whether fall or sound onset came first to measure the point of subjective simultaneity. Results show that fall perception is slow, where the onset of a perturbation has to precede an auditory stimulus by ∼44 ms to appear coincident with the fall. We suggest that the central nervous system's rapid detection and response capabilities are restricted to reflexive behaviour, with conscious awareness of a fall being prioritized less. The additional lead times for detecting perturbation onset constrain possible fall detection and alert systems that have been proposed to inform a user to prevent falls and may also help explain the increased likelihood for fall incidence in the elderly.
Gauge-invariant perturbations of Schwarzschild spacetime
Shah, Abhay G; Aksteiner, Steffen; Andersson, Lars; Bäckdahl, Thomas
2016-01-01
We study perturbations of Schwarzschild spacetime in a coordinate-free, covariant form. The GHP formulation, having the advantage of not only being covariant but also tetrad-rotation invariant, is used to write down the previously known odd- and even-parity gauge-invariants and the equations they satisfy. Additionally, in the even-parity sector, a new invariant and the second order hyperbolic equation it satisfies are presented. Chandrasekhar's work on transformations of solutions for perturbation equations on Schwarzschild spacetime is translated into the GHP form, i.e., solutions for the equations of the even- and odd-parity invariants are written in terms of one another, and the extreme Weyl scalars; and solutions for the equations of these latter invariants are also written in terms of one another. Recently, further gauge invariants previously used by Steven Detweiler have been described. His method is translated into GHP form and his basic invariants are presented here. We also show how these invariants ...
Orbital perturbations due to massive rings
Iorio, Lorenzo
2012-01-01
We analytically work out the long-term orbital perturbations induced by a homogeneous circular ring of radius Rr and mass mr on the motion of a test particle in the cases (I): r > R_r and (II): r < R_r. In order to extend the validity of our analysis to the orbital con?gurations of, e.g., some proposed spacecraftbased mission for fundamental physics like LISA and ASTROD, of possible annuli around the supermassive black hole in Sgr A* coming from tidal disruptions of incoming gas clouds, and to the e?ect of arti?cial space debris belts around the Earth, we do not restrict ourselves to the case in which the ring and the orbit of the perturbed particle lie just in the same plane. From the corrections to the standard secular perihelion precessions, recently determined by a team of astronomers for some planets of the Solar System, we infer upper bounds on mr for various putative and known annular matter distributions of natural origin (close circumsolar ring with R_r = 0.02-0.13 au, dust ring with R_r = 1 au, m...
Nonlinearly perturbed semi-Markov processes
Silvestrov, Dmitrii
2017-01-01
The book presents new methods of asymptotic analysis for nonlinearly perturbed semi-Markov processes with a finite phase space. These methods are based on special time-space screening procedures for sequential phase space reduction of semi-Markov processes combined with the systematical use of operational calculus for Laurent asymptotic expansions. Effective recurrent algorithms are composed for getting asymptotic expansions, without and with explicit upper bounds for remainders, for power moments of hitting times, stationary and conditional quasi-stationary distributions for nonlinearly perturbed semi-Markov processes. These results are illustrated by asymptotic expansions for birth-death-type semi-Markov processes, which play an important role in various applications. The book will be a useful contribution to the continuing intensive studies in the area. It is an essential reference for theoretical and applied researchers in the field of stochastic processes and their applications that will cont...
Bounded relative motion under zonal harmonics perturbations
Baresi, Nicola; Scheeres, Daniel J.
2017-04-01
The problem of finding natural bounded relative trajectories between the different units of a distributed space system is of great interest to the astrodynamics community. This is because most popular initialization methods still fail to establish long-term bounded relative motion when gravitational perturbations are involved. Recent numerical searches based on dynamical systems theory and ergodic maps have demonstrated that bounded relative trajectories not only exist but may extend up to hundreds of kilometers, i.e., well beyond the reach of currently available techniques. To remedy this, we introduce a novel approach that relies on neither linearized equations nor mean-to-osculating orbit element mappings. The proposed algorithm applies to rotationally symmetric bodies and is based on a numerical method for computing quasi-periodic invariant tori via stroboscopic maps, including extra constraints to fix the average of the nodal period and RAAN drift between two consecutive equatorial plane crossings of the quasi-periodic solutions. In this way, bounded relative trajectories of arbitrary size can be found with great accuracy as long as these are allowed by the natural dynamics and the physical constraints of the system (e.g., the surface of the gravitational attractor). This holds under any number of zonal harmonics perturbations and for arbitrary time intervals as demonstrated by numerical simulations about an Earth-like planet and the highly oblate primary of the binary asteroid (66391) 1999 KW4.
Localized Perturbations in Saturn's C Ring
Spitale, Joseph N.; Tiscareno, Matthew S.
2016-10-01
Years of high-resolution imaging of Saturn's rings have revealed many examples of perturbations arising from local causes. For example, the presence of 100-m-scale and smaller moonlets is inferred in the A ring based on the propeller-shaped disturbances that they create (Tiscareno et al. 2006, 2010); the F ring is shaped by regular collisions with its shepherd Prometheus, as well as with other smaller bodies orbiting in the vicinity (Murray et al. 2005, 2008); the "wisps" on the outer edge of the Keeler gap (Porco et al. 2005) may mark the locations of small moonlets that have emerged from the A ring (Tiscareno and Arnault 2015); wakes in the Huygens ringlet imply the presence of two multi-km bodies, and the irregular shape of its inner edge suggests the presence of many smaller bodies (Spitale and Hahn 2016); based on shadow measurements, the B ring contains an embedded 300-m object that produces a small propeller-shaped disturbance (Spitale and Porco 2010; Spitale and Tiscareno 2012).Here, we present evidence for localized perturbations in the C ring. The ringlet embedded in the Bond gap, near 1.470 Saturn radii, shows discrete clumps orbiting at the Keplerian rate in images spanning about eight years. The clumps are not detected in all image sequences at the expected longitudes. The Dawes ringlet, near 1.495 Saturn radii, has an irregular edge that does not appear as a simple superposition of low-wavenumber normal modes.
Solitary magnetic perturbations at the ELM onset
Wenninger, RP; Boom, JE; Burckhart, A; Dunne, MG; Dux, R; Eich, T; Fischer, R; Fuchs, C; Garcia-Munoz, M; Igochine, V; Hoelzl, M; Luhmann, NC; Lunt, T; Maraschek, M; Mueller, HW; Park, HK; Schneider, PA; Sommer, F; Suttrop, W; Viezzer, E
2012-01-01
Edge localised modes (ELMs) allow maintaining sufficient purity of tokamak H-mode plasmas and thus enable stationary H-mode. On the other hand in a future device ELMs may cause divertor power flux densities far in excess of tolerable material limits. The size of the energy loss per ELM is determined by saturation effects in the non-linear phase of the ELM, which at present is hardly understood. Solitary magnetic perturbations (SMPs) are identified as dominant features in the radial magnetic fluctuations below 100kHz. They are typically observed close (+-0.1ms) to the onset of pedestal erosion. SMPs are field aligned structures rotating in the electron diamagnetic drift direction with perpendicular velocities of about 10km/s. A comparison of perpendicular velocities suggests that the perturbation evoking SMPs is located at or inside the separatrix. Analysis of very pronounced examples showed that the number of peaks per toroidal turn is 1 or 2, which is clearly lower than corresponding numbers in linear stabil...
Perturbative quantum gravity in double field theory
Boels, Rutger H.; Horst, Christoph
2016-04-01
We study perturbative general relativity with a two-form and a dilaton using the double field theory formulation which features explicit index factorisation at the Lagrangian level. Explicit checks to known tree level results are performed. In a natural covariant gauge a ghost-like scalar which contributes even at tree level is shown to decouple consistently as required by perturbative unitarity. In addition, a lightcone gauge is explored which bypasses the problem altogether. Using this gauge to study BCFW on-shell recursion, we can show that most of the D-dimensional tree level S-matrix of the theory, including all pure graviton scattering amplitudes, is reproduced by the double field theory. More generally, we argue that the integrand may be reconstructed from its single cuts and provide limited evidence for off-shell cancellations in the Feynman graphs. As a straightforward application of the developed technology double field theory-like expressions for four field string corrections are derived.