Quantum thermodynamics: a nonequilibrium Green's function approach.
Esposito, Massimiliano; Ochoa, Maicol A; Galperin, Michael
2015-02-27
We establish the foundations of a nonequilibrium theory of quantum thermodynamics for noninteracting open quantum systems strongly coupled to their reservoirs within the framework of the nonequilibrium Green's functions. The energy of the system and its coupling to the reservoirs are controlled by a slow external time-dependent force treated to first order beyond the quasistatic limit. We derive the four basic laws of thermodynamics and characterize reversible transformations. Stochastic thermodynamics is recovered in the weak coupling limit.
Nonequilibrium Green function techniques applied to hot electron quantum transport
International Nuclear Information System (INIS)
Jauho, A.P.
1989-01-01
During the last few years considerable effort has been devoted to deriving quantum transport equations for semiconductors under extreme conditions (high electric fields, spatial quantization in one or two directions). Here we review the results obtained with nonequilibrium Green function techniques as formulated by Baym and Kadanoff, or by Keldysh. In particular, the following topics will be discussed: (i) Systematic approaches to reduce the transport equation governing the correlation function to a transport equation for the Wigner function; (ii) Approximations reducing the nonmarkovian quantum transport equation to a numerically tractable form, and results for model semiconductors; (iii) Recent progress in extending the formalism to inhomogeneous systems; and (iv) Nonequilibrium screening. In all sections we try to direct the reader's attention to points where the present understanding is (at best) incomplete, and indicate possible lines for future work. (orig.)
Directory of Open Access Journals (Sweden)
P.Kostrobii
2006-01-01
Full Text Available Nonequilibrium properties of an inhomogeneous electron gas are studied using the method of the nonequilibrium statistical operator by D.N. Zubarev. Generalized transport equations for the mean values of inhomogeneous operators of the electron number density, momentum density, and total energy density for weakly and strongly nonequilibrium states are obtained. We derive a chain of equations for the Green's functions, which connects commutative time-dependent Green's functions "density-density", "momentum-momentum", "enthalpy-enthalpy" with reduced Green's functions of the generalized transport coefficients and with Green's functions for higher order memory kernels in the case of a weakly nonequilibrium spatially inhomogeneous electron gas.
Nonequilibrium Green's function method for quantum thermal transport
Wang, Jian-Sheng; Agarwalla, Bijay Kumar; Li, Huanan; Thingna, Juzar
2014-12-01
This review deals with the nonequilibrium Green's function (NEGF) method applied to the problems of energy transport due to atomic vibrations (phonons), primarily for small junction systems. We present a pedagogical introduction to the subject, deriving some of the well-known results such as the Laudauer-like formula for heat current in ballistic systems. The main aim of the review is to build the machinery of the method so that it can be applied to other situations, which are not directly treated here. In addition to the above, we consider a number of applications of NEGF, not in routine model system calculations, but in a few new aspects showing the power and usefulness of the formalism. In particular, we discuss the problems of multiple leads, coupled left-right-lead system, and system without a center. We also apply the method to the problem of full counting statistics. In the case of nonlinear systems, we make general comments on the thermal expansion effect, phonon relaxation time, and a certain class of mean-field approximations. Lastly, we examine the relationship between NEGF, reduced density matrix, and master equation approaches to thermal transport.
Electron systems out of equilibrium: nonequilibrium Green's function approach
Czech Academy of Sciences Publication Activity Database
Špička, Václav; Velický, Bedřich; Kalvová, Anděla
2014-01-01
Roč. 28, č. 23 (2014), "1430013-1"-"1430013-103" ISSN 0217-9792 R&D Projects: GA ČR GAP204/12/0897 Institutional support: RVO:68378271 Keywords : nonequilibrium statistical physics * transients * quantum transport the ory Subject RIV: BE - The oretical Physics Impact factor: 0.937, year: 2014
International Nuclear Information System (INIS)
Zhao, Peiji; Horing, Norman J.M.; Woolard, Dwight L.; Cui, H.L.
2003-01-01
We present a nonequilibrium Green's function formulation of many-body quantum transport theory for multi-band semiconductor systems with a phonon bath. The equations are expressed exactly in terms of single particle nonequilibrium Green's functions and self-energies, treating the open electron-hole system in weak interaction with the bath. A decoupling technique is employed to separate the individual band Green's function equations of motion from one another, with the band-band interaction effects embedded in ''cross-band'' self-energies. This nonequilibrium Green's function formulation of quantum transport theory is amenable to solution by parallel computing because of its formal decoupling with respect to inter-band interactions. Moreover, this formulation also permits coding the simulator of an n-band semiconductor in terms of that for an (n-1)-band system, in step with the current tendency and development of programming technology. Finally, the focus of these equations on individual bands provides a relatively direct route for the determination of carrier motion in energy bands, and to delineate the influence of intra- and inter-band interactions. A detailed description is provided for three-band semiconductor systems
Replacing leads by self-energies using non-equilibrium Green's functions
International Nuclear Information System (INIS)
Michael, Fredrick; Johnson, M.D.
2003-01-01
Open quantum systems consist of semi-infinite leads which transport electrons to and from the device of interest. We show here that within the non-equilibrium Green's function technique for continuum systems, the leads can be replaced by simple c-number self-energies. Our starting point is an approach for continuum systems developed by Feuchtwang. The reformulation developed here is simpler to understand and carry out than the somewhat unwieldly manipulations typical in the Feuchtwang method. The self-energies turn out to have a limited variability: the retarded self-energy Σ r depends on the arbitrary choice of internal boundary conditions, but the non-equilibrium self-energy or scattering function Σ which determines transport is invariant for a broad class of boundary conditions. Expressed in terms of these self-energies, continuum non-equilibrium transport calculations take a particularly simple form similar to that developed for discrete systems
Papior, Nick Rübner; Lorente, Nicolás; Frederiksen, Thomas; García, Alberto; Brandbyge, Mads
2017-01-01
We present novel methods implemented within the non-equilibrium Green function code (NEGF) TRANSIESTA based on density functional theory (DFT). Our flexible, next-generation DFT–NEGF code handles devices with one or multiple electrodes (Ne≥1) with individual chemical potentials and electronic temperatures. We describe its novel methods for electrostatic gating, contour optimizations, and assertion of charge conservation, as well as the newly implemented algorithms for optimized and scalable m...
Nonequilibrium Green's function theory for nonadiabatic effects in quantum electron transport
Kershaw, Vincent F.; Kosov, Daniel S.
2017-12-01
We develop nonequilibrium Green's function-based transport theory, which includes effects of nonadiabatic nuclear motion in the calculation of the electric current in molecular junctions. Our approach is based on the separation of slow and fast time scales in the equations of motion for Green's functions by means of the Wigner representation. Time derivatives with respect to central time serve as a small parameter in the perturbative expansion enabling the computation of nonadiabatic corrections to molecular Green's functions. Consequently, we produce a series of analytic expressions for non-adiabatic electronic Green's functions (up to the second order in the central time derivatives), which depend not solely on the instantaneous molecular geometry but likewise on nuclear velocities and accelerations. An extended formula for electric current is derived which accounts for the non-adiabatic corrections. This theory is concisely illustrated by the calculations on a model molecular junction.
The non-equilibrium Green's function method for nanoscale device simulation
Pourfath, Mahdi
2014-01-01
For modeling the transport of carriers in nanoscale devices, a Green-function formalism is the most accurate approach. Due to the complexity of the formalism, one should have a deep understanding of the underlying principles and use smart approximations and numerical methods for solving the kinetic equations at a reasonable computational time. In this book the required concepts from quantum and statistical mechanics and numerical methods for calculating Green functions are presented. The Green function is studied in detail for systems both under equilibrium and under nonequilibrium conditions. Because the formalism enables rigorous modeling of different scattering mechanisms in terms of self-energies, but an exact evaluation of self-energies for realistic systems is not possible, their approximation and inclusion in the quantum kinetic equations of the Green functions are elaborated. All the elements of the kinetic equations, which are the device Hamiltonian, contact self-energies, and scattering self-energie...
International Nuclear Information System (INIS)
Do, Van-Nam
2014-01-01
We review fundamental aspects of the non-equilibrium Green function method in the simulation of nanometer electronic devices. The method is implemented into our recently developed computer package OPEDEVS to investigate transport properties of electrons in nano-scale devices and low-dimensional materials. Concretely, we present the definition of the four real-time Green functions, the retarded, advanced, lesser and greater functions. Basic relations among these functions and their equations of motion are also presented in detail as the basis for the performance of analytical and numerical calculations. In particular, we review in detail two recursive algorithms, which are implemented in OPEDEVS to solve the Green functions defined in finite-size opened systems and in the surface layer of semi-infinite homogeneous ones. Operation of the package is then illustrated through the simulation of the transport characteristics of a typical semiconductor device structure, the resonant tunneling diodes. (review)
The photon Green's function for bounded media: Splitting property and nonequilibrium radiation laws
International Nuclear Information System (INIS)
Richter, F; Semkat, D; Henneberger, K
2010-01-01
The presence of a medium boundary has been a major obstacle for the theoretical description of the propagation, emission and absorption of light due to the loss of translational invariance. We present a nonequilibrium photon Green's function theory that is valid for bounded (i.e., spatially inhomogeneous) media systems and also yields an energy flow law which can be seen as a generalization of the Kirchhoff and Planck laws to nonequilibrium. With the help of this law, we discuss mechanisms of emission and optical signatures of quantum condensates. An important finding is that the D>< components of the photon GF, which describe field-field fluctuations, decompose universally into two parts related to medium kinetics and external light sources. Thanks to their specific structure, the propagation of arbitrary (even nonclassical) light can be analyzed straightforwardly. These properties are used to demonstrate the energy flux and scattering of squeezed light incident on the medium.
Progress in Non-equilibrium Green's Functions (PNGF VI)
International Nuclear Information System (INIS)
2016-01-01
The sixth interdisciplinary conference 'Progress in Non-equilibrium Green's Functions' (PNGF6) took place at Lund University, Sweden, on 17-21 August 2015. The conference was attended by 60 scientists, from Europe and overseas, sharing an interest in Green's function methods and/or non-equilibrium phenomena. At the conference, 34 invited and contributed talks were given, together with a poster session with 17 contributions. As its predecessors (Rostock 1999, Dresden 2002, Kiel 2005, Glasgow 2009, Jyväskylä 2012) did, the conference succeeded in gathering different communities for the exchange of recent developments and results. Among the topics of the conference, we mention approaches for strongly correlated systems, improvements of existing perturbative many-body schemes, electron-phonon/-photon interactions in time-dependent treatments, numerical scalability of NEGF approaches, connections with other non-equilibrium methods and concrete physical applications. For the latter, we mention quantum transport, semiconductor kinetics, multiply excited states in atoms and ions, nuclear reactions, high energy physics, quantum cascade lasers, strongly correlated model systems, graphene-nanostructures, optoelectronics, superconductors, spin-dynamics, photovoltaics, excitations in atoms and ions and time-resolved spectroscopy. The present volume contains 20 articles from participants of PNGF6, devoted to these topics. Compared to previous conferences, a completely novel and successful aspect of PNGF6 was the participation of experimentalists among the invited speakers, to establish a connection between emerging experimental techniques (for example, time-dependent spectroscopies) and the theoretical NEGF community. As at the previous PNGF conferences, the atmosphere was friendly and exciting at the same time, favoring vivid and stimulating discussions among experienced scientists, young researchers and students. The conference would not have been
International Nuclear Information System (INIS)
Harbola, U.; Mukamel, S.
2008-01-01
Nonequilibrium Green's functions provide a powerful tool for computing the dynamical response and particle exchange statistics of coupled quantum systems. We formulate the theory in terms of the density matrix in Liouville space and introduce superoperator algebra that greatly simplifies the derivation and the physical interpretation of all quantities. Expressions for various observables are derived directly in real time in terms of superoperator nonequilibrium Green's functions (SNGF), rather than the artificial time-loop required in Schwinger's Hilbert-space formulation. Applications for computing interaction energies, charge densities, average currents, current induced fluorescence, electroluminescence and current fluctuation (electron counting) statistics are discussed
Non-equilibrium Green's functions method: Non-trivial and disordered leads
Energy Technology Data Exchange (ETDEWEB)
He, Yu, E-mail: heyuyhe@gmail.com; Wang, Yu; Klimeck, Gerhard; Kubis, Tillmann [Network for Computational Nanotechnology, Purdue University, West Lafayette, Indiana 47907 (United States)
2014-11-24
The non-equilibrium Green's function algorithm requires contact self-energies to model charge injection and extraction. All existing approaches assume infinitely periodic leads attached to a possibly quite complex device. This contradicts today's realistic devices in which contacts are spatially inhomogeneous, chemically disordered, and impacting the overall device characteristics. This work extends the complex absorbing potentials method for arbitrary, ideal, or non-ideal leads in atomistic tight binding representation. The algorithm is demonstrated on a Si nanowire with periodic leads, a graphene nanoribbon with trumpet shape leads, and devices with leads of randomly alloyed Si{sub 0.5}Ge{sub 0.5}. It is found that alloy randomness in the leads can reduce the predicted ON-state current of Si{sub 0.5}Ge{sub 0.5} transistors by 45% compared to conventional lead methods.
Non-equilibrium Green's functions method: Non-trivial and disordered leads
He, Yu; Wang, Yu; Klimeck, Gerhard; Kubis, Tillmann
2014-11-01
The non-equilibrium Green's function algorithm requires contact self-energies to model charge injection and extraction. All existing approaches assume infinitely periodic leads attached to a possibly quite complex device. This contradicts today's realistic devices in which contacts are spatially inhomogeneous, chemically disordered, and impacting the overall device characteristics. This work extends the complex absorbing potentials method for arbitrary, ideal, or non-ideal leads in atomistic tight binding representation. The algorithm is demonstrated on a Si nanowire with periodic leads, a graphene nanoribbon with trumpet shape leads, and devices with leads of randomly alloyed Si0.5Ge0.5. It is found that alloy randomness in the leads can reduce the predicted ON-state current of Si0.5Ge0.5 transistors by 45% compared to conventional lead methods.
General Retarded Contact Self-energies in and beyond the Non-equilibrium Green's Functions Method
Kubis, Tillmann; He, Yu; Andrawis, Robert; Klimeck, Gerhard
2016-03-01
Retarded contact self-energies in the framework of nonequilibrium Green's functions allow to model the impact of lead structures on the device without explicitly including the leads in the actual device calculation. Most of the contact self-energy algorithms are limited to homogeneous or periodic, semi-infinite lead structures. In this work, the complex absorbing potential method is extended to solve retarded contact self-energies for arbitrary lead structures, including irregular and randomly disordered leads. This method is verified for regular leads against common approaches and on physically equivalent, but numerically different irregular leads. Transmission results on randomly alloyed In0.5Ga0.5As structures show the importance of disorder in the leads. The concept of retarded contact self-energies is expanded to model passivation of atomically resolved surfaces without explicitly increasing the device's Hamiltonian.
Non-equilibrium Green's functions method: Non-trivial and disordered leads
International Nuclear Information System (INIS)
He, Yu; Wang, Yu; Klimeck, Gerhard; Kubis, Tillmann
2014-01-01
The non-equilibrium Green's function algorithm requires contact self-energies to model charge injection and extraction. All existing approaches assume infinitely periodic leads attached to a possibly quite complex device. This contradicts today's realistic devices in which contacts are spatially inhomogeneous, chemically disordered, and impacting the overall device characteristics. This work extends the complex absorbing potentials method for arbitrary, ideal, or non-ideal leads in atomistic tight binding representation. The algorithm is demonstrated on a Si nanowire with periodic leads, a graphene nanoribbon with trumpet shape leads, and devices with leads of randomly alloyed Si 0.5 Ge 0.5 . It is found that alloy randomness in the leads can reduce the predicted ON-state current of Si 0.5 Ge 0.5 transistors by 45% compared to conventional lead methods
Zhang, Zu-Quan; Lü, Jing-Tao
2017-09-01
Using the nonequilibrium Green's function method, we consider heat transport in an insulating ferromagnetic spin chain model with spin-phonon interaction under an external magnetic field. Employing the Holstein-Primakoff transformation to the spin system, we treat the resulted magnon-phonon interaction within the self-consistent Born approximation. We find the magnon-phonon coupling can change qualitatively the magnon thermal conductance in the high-temperature regime. At a spectral mismatched ferromagnetic-normal insulator interface, we also find thermal rectification and negative differential thermal conductance due to the magnon-phonon interaction. We show that these effects can be effectively tuned by the external applied magnetic field, a convenient advantage absent in anharmonic phonon and electron-phonon systems studied before.
Panahi, S F K S; Namiranian, Afshin; Soleimani, Maryam; Jamaati, Maryam
2018-02-07
We investigate the electronic transport properties of two types of junction based on single polyaromatic hydrocarbons (PAHs) and PAHs embedded in boron nitride (h-BN) nanoribbons, using nonequilibrium Green's functions (NEGF) and density functional theory (DFT). In the PAH junctions, a Fano resonance line shape at the Fermi energy in the transport feature can be clearly seen. In hybrid junctions, structural asymmetries enable interactions between the electronic states, leading to observation of interface-based transport. Our findings reveal that the interface of PAH/h-BN strongly affects the transport properties of the structures.
International Nuclear Information System (INIS)
Kurniawan, O; Bai, P; Li, E
2009-01-01
A ballistic calculation of a full quantum mechanical system is presented to study 2D nanoscale devices. The simulation uses the nonequilibrium Green's function (NEGF) approach to calculate the transport properties of the devices. While most available software uses the finite difference discretization technique, our work opts to formulate the NEGF calculation using the finite element method (FEM). In calculating a ballistic device, the FEM gives some advantages. In the FEM, the floating boundary condition for ballistic devices is satisfied naturally. This paper gives a detailed finite element formulation of the NEGF calculation applied to a double-gate MOSFET device with a channel length of 10 nm and a body thickness of 3 nm. The potential, electron density, Fermi functions integrated over the transverse energy, local density of states and the transmission coefficient of the device have been studied. We found that the transmission coefficient is significantly affected by the top of the barrier between the source and the channel, which in turn depends on the gate control. This supports the claim that ballistic devices can be modelled by the transport properties at the top of the barrier. Hence, the full quantum mechanical calculation presented here confirms the theory of ballistic transport in nanoscale devices.
Papior, Nick; Lorente, Nicolás; Frederiksen, Thomas; García, Alberto; Brandbyge, Mads
2017-03-01
We present novel methods implemented within the non-equilibrium Green function code (NEGF) TRANSIESTA based on density functional theory (DFT). Our flexible, next-generation DFT-NEGF code handles devices with one or multiple electrodes (Ne ≥ 1) with individual chemical potentials and electronic temperatures. We describe its novel methods for electrostatic gating, contour optimizations, and assertion of charge conservation, as well as the newly implemented algorithms for optimized and scalable matrix inversion, performance-critical pivoting, and hybrid parallelization. Additionally, a generic NEGF "post-processing" code (TBTRANS/PHTRANS) for electron and phonon transport is presented with several novelties such as Hamiltonian interpolations, Ne ≥ 1 electrode capability, bond-currents, generalized interface for user-defined tight-binding transport, transmission projection using eigenstates of a projected Hamiltonian, and fast inversion algorithms for large-scale simulations easily exceeding 106 atoms on workstation computers. The new features of both codes are demonstrated and bench-marked for relevant test systems.
DEFF Research Database (Denmark)
Stradi, Daniele; Martinez, Umberto; Blom, Anders
2016-01-01
Metal-semiconductor contacts are a pillar of modern semiconductor technology. Historically, their microscopic understanding has been hampered by the inability of traditional analytical and numerical methods to fully capture the complex physics governing their operating principles. Here we introduce...... an atomistic approach based on density functional theory and nonequilibrium Green's function, which includes all the relevant ingredients required to model realistic metal-semiconductor interfaces and allows for a direct comparison between theory and experiments via I-Vbias curve simulations. We apply...... interfaces as it neglects electron tunneling, and that finite-size atomistic models have problems in describing these interfaces in the presence of doping due to a poor representation of space-charge effects. Conversely, the present method deals effectively with both issues, thus representing a valid...
Yasuda, H.; Kubis, T.; Hosako, I.; Hirakawa, K.
2012-04-01
We theoretically investigated GaN-based resonant phonon terahertz-quantum cascade laser (QCL) structures for possible high-temperature operation by using the non-equilibrium Green's function method. It was found that the GaN-based THz-QCL structures do not necessarily have a gain sufficient for lasing, even though the thermal backfilling and the thermally activated phonon scattering are effectively suppressed. The main reason for this is the broadening of the subband levels caused by a very strong interaction between electrons and longitudinal optical (LO) phonons in GaN.
General Retarded Contact Self-energies in and beyond the Non-equilibrium Green's Functions Method
International Nuclear Information System (INIS)
Kubis, Tillmann; He, Yu; Andrawis, Robert; Klimeck, Gerhard
2016-01-01
Retarded contact self-energies in the framework of nonequilibrium Green's functions allow to model the impact of lead structures on the device without explicitly including the leads in the actual device calculation. Most of the contact self-energy algorithms are limited to homogeneous or periodic, semi-infinite lead structures. In this work, the complex absorbing potential method is extended to solve retarded contact self-energies for arbitrary lead structures, including irregular and randomly disordered leads. This method is verified for regular leads against common approaches and on physically equivalent, but numerically different irregular leads. Transmission results on randomly alloyed In 0.5 Ga 0.5 As structures show the importance of disorder in the leads. The concept of retarded contact self-energies is expanded to model passivation of atomically resolved surfaces without explicitly increasing the device's Hamiltonian. (paper)
Levy, Tal J; Rabani, Eran
2013-04-28
We study steady state transport through a double quantum dot array using the equation-of-motion approach to the nonequilibrium Green functions formalism. This popular technique relies on uncontrolled approximations to obtain a closure for a hierarchy of equations; however, its accuracy is questioned. We focus on 4 different closures, 2 of which were previously proposed in the context of the single quantum dot system (Anderson impurity model) and were extended to the double quantum dot array, and develop 2 new closures. Results for the differential conductance are compared to those attained by a master equation approach known to be accurate for weak system-leads couplings and high temperatures. While all 4 closures provide an accurate description of the Coulomb blockade and other transport properties in the single quantum dot case, they differ in the case of the double quantum dot array, where only one of the developed closures provides satisfactory results. This is rationalized by comparing the poles of the Green functions to the exact many-particle energy differences for the isolate system. Our analysis provides means to extend the equation-of-motion technique to more elaborate models of large bridge systems with strong electronic interactions.
International Nuclear Information System (INIS)
Hermanns, S; Bonitz, M; Balzer, K
2013-01-01
The nonequilibrium description of quantum systems requires, for more than two or three particles, the use of a reduced description to be numerically tractable. Two possible approaches are based on either reduced density matrices or nonequilibrium Green functions (NEGF). Both concepts are formulated in terms of hierarchies of coupled equations—the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy for the reduced density operators and the Martin-Schwinger-hierarchy (MS) for the Green functions, respectively. In both cases, similar approximations are introduced to decouple the hierarchy, yet still many questions regarding the correspondence of both approaches remain open. Here we analyze this correspondence by studying the generalized Kadanoff–Baym ansatz (GKBA) that reduces the NEGF to a single-time theory. Starting from the BBGKY-hierarchy we present the approximations that are necessary to recover the GKBA result both, with Hartree-Fock propagators (HF-GKBA) and propagators in second Born approximation. To test the quality of the HF-GKBA, we study the dynamics of a 4-electron Hubbard nanocluster starting from a strong nonequilibrium initial state and compare to exact results and the Wang-Cassing approximation to the BBGKY hierarchy presented recently by Akbari et al. [1].
Density-functional method for nonequilibrium electron transport
DEFF Research Database (Denmark)
Brandbyge, Mads; Mozos, J.L.; Ordejon, P.
2002-01-01
the contact and the electrodes on the same footing. The effect of the finite bias (including self-consistency and the solution of the electrostatic problem) is taken into account using nonequilibrium Green's functions. We relate the nonequilibrium Green's function expressions to the more transparent scheme...... wires connected to aluminum electrodes with extended or finite cross section, (ii) single atom gold wires, and finally (iii) large carbon nanotube systems with point defects....
DEFF Research Database (Denmark)
Palsgaard, Mattias Lau Nøhr; Crovetto, Andrea; Gunst, Tue
2016-01-01
In this paper we present a method to obtain the band offset of semiconductor heterointerfaces from Density Functional Theory together with the nonequilibrium Green's function method. Band alignment and detailed properties of the interface between Cu2ZnSnSe4 and CdS are extracted directly from first...... principles simulations. The interface is important for photovoltaics applications where in particular the band offsets are important for efficiency. The band bending pose a problem for accurate atomistic simulations of band offsets due to its long range. Here we investigate two different methods for dealing...... with band bending directly. One involves doping the materials to induce a shorter screening length. The other method is to apply a voltage bias across the interface to correct for the band bending. The calculated band offsets agree well with previous experimental and theoretical studies and, interestingly...
DEFF Research Database (Denmark)
De Souza, Fabricio; Jauho, Antti-Pekka; Egues, J.C.
2008-01-01
Using nonequilibrium Green's functions we calculate the spin-polarized current and shot noise in a ferromagnet-quantum-dot-ferromagnet system. Both parallel (P) and antiparallel (AP) magnetic configurations are considered. Coulomb interaction and coherent spin flip (similar to a transverse magnetic...... field) are taken into account within the dot. We find that the interplay between Coulomb interaction and spin accumulation in the dot can result in a bias-dependent current polarization p. In particular, p can be suppressed in the P alignment and enhanced in the AP case depending on the bias voltage....... The coherent spin flip can also result in a switch of the current polarization from the emitter to the collector lead. Interestingly, for a particular set of parameters it is possible to have a polarized current in the collector and an unpolarized current in the emitter lead. We also found a suppression...
International Nuclear Information System (INIS)
Horing, Norman J Morgenstern; Popov, Vyacheslav V
2006-01-01
Recent experimental observations by X.G. Peralta and S.J. Allen, et al. of dc photoconductivity resonances in steady source-drain current subject to terahertz radiation in a grid-gated double-quantum well FET suggested an association with plasmon resonances. This association was definitively confirmed for some parameter ranges in our detailed electrodynamic absorbance calculations. In this paper we propose that the reason that the dc photoconductance resonances match the plasmon resonances in semiconductors is based on a nonlinear dynamic screening mechanism. In this, we employ a shielded potential approximation that is nonlinear in the terahertz field to determine the nonequilibrium Green's function and associated density perturbation that govern the nonequilibrium dielectric polarization of the medium. This 'conditioning' of the system by the incident THz radiation results in resonant polarization response at the plasmon frequencies which, in turn, causes a sharp drop of the resistive shielded impurity scattering potentials and attendant increase of the dc source-drain current. This amounts to disabling the impurity scattering mechanism by plasmon resonant behavior in nonlinear screening
International Nuclear Information System (INIS)
Eslami, Leila; Esmaeilzadeh, Mahdi
2014-01-01
Spin-dependent electron transport in an open double quantum ring, when each ring is made up of four quantum dots and threaded by a magnetic flux, is studied. Two independent and tunable gate voltages are applied to induce Rashba spin-orbit effect in the quantum rings. Using non-equilibrium Green's function formalism, we study the effects of electron-electron interaction on spin-dependent electron transport and show that although the electron-electron interaction induces an energy gap, it has no considerable effect when the bias voltage is sufficiently high. We also show that the double quantum ring can operate as a spin-filter for both spin up and spin down electrons. The spin-polarization of transmitted electrons can be tuned from −1 (pure spin-down current) to +1 (pure spin-up current) by changing the magnetic flux and/or the gates voltage. Also, the double quantum ring can act as AND and NOR gates when the system parameters such as Rashba coefficient are properly adjusted
Liu, Tao; Kubis, Tillmann; Jie Wang, Qi; Klimeck, Gerhard
2012-03-01
The nonequilibrium Green's function approach is applied to the design of three-well indirect pumping terahertz (THz) quantum cascade lasers (QCLs) based on a resonant phonon depopulation scheme. The effects of the anticrossing of the injector states and the dipole matrix element of the laser levels on the optical gain of THz QCLs are studied. The results show that a design that results in a more pronounced anticrossing of the injector states will achieve a higher optical gain in the indirect pumping scheme compared to the traditional resonant-tunneling injection scheme. This offers in general a more efficient coherent resonant-tunneling transport of electrons in the indirect pumping scheme. It is also shown that, for operating temperatures below 200 K and low lasing frequencies, larger dipole matrix elements, i.e., vertical optical transitions, offer a higher optical gain. In contrast, in the case of high lasing frequencies, smaller dipole matrix elements, i.e., diagonal optical transitions are better for achieving a higher optical gain.
Arefinia, Zahra; Orouji, Ali A.
2009-02-01
The concept of dual-material gate (DMG) is applied to the carbon nanotube field-effect transistor (CNTFET) with doped source and drain extensions, and the features exhibited by the resulting new structure, i.e., the DMG-CNTFET structure, have been examined for the first time by developing a two-dimensional (2D) full quantum simulation. The simulations have been done by the self-consistent solution of 2D Poisson-Schrödinger equations, within the nonequilibrium Green's function (NEGF) formalism. The results show DMG-CNTFET decreases significantly leakage current and drain conductance and increases on-off current ratio and voltage gain as compared to the single material gate counterparts CNTFET. It is seen that short channel effects in this structure are suppressed because of the perceivable step in the surface potential profile, which screens the drain potential. Moreover, these unique features can be controlled by engineering the workfunction and length of the gate metals. Therefore, this work provides an incentive for further experimental exploration.
International Nuclear Information System (INIS)
Salazar, Ramon B.; Appenzeller, Joerg; Ilatikhameneh, Hesameddin; Rahman, Rajib; Klimeck, Gerhard
2015-01-01
A new compact modeling approach is presented which describes the full current-voltage (I-V) characteristic of high-performance (aggressively scaled-down) tunneling field-effect-transistors (TFETs) based on homojunction direct-bandgap semiconductors. The model is based on an analytic description of two key features, which capture the main physical phenomena related to TFETs: (1) the potential profile from source to channel and (2) the elliptic curvature of the complex bands in the bandgap region. It is proposed to use 1D Poisson's equations in the source and the channel to describe the potential profile in homojunction TFETs. This allows to quantify the impact of source/drain doping on device performance, an aspect usually ignored in TFET modeling but highly relevant in ultra-scaled devices. The compact model is validated by comparison with state-of-the-art quantum transport simulations using a 3D full band atomistic approach based on non-equilibrium Green's functions. It is shown that the model reproduces with good accuracy the data obtained from the simulations in all regions of operation: the on/off states and the n/p branches of conduction. This approach allows calculation of energy-dependent band-to-band tunneling currents in TFETs, a feature that allows gaining deep insights into the underlying device physics. The simplicity and accuracy of the approach provide a powerful tool to explore in a quantitatively manner how a wide variety of parameters (material-, size-, and/or geometry-dependent) impact the TFET performance under any bias conditions. The proposed model presents thus a practical complement to computationally expensive simulations such as the 3D NEGF approach
Mahfouzi, Farzad
Current and future technological needs increasingly motivate the intensive scientific research of the properties of materials at the nano-scale. One of the most important domains in this respect at present concerns nano-electronics and its diverse applications. The great interest in this domain arises from the potential reduction of the size of the circuit components, maintaining their quality and functionality, and aiming at greater efficiency, economy, and storage characteristics for the corresponding physical devices. The aim of this thesis is to present a contribution to the analysis of the electronic charge and spin transport phenomena that occur at the quantum level in nano-structures. This thesis spans the areas of quantum transport theory through time-dependent systems, electron-boson interacting systems and systems of interest to spintronics. A common thread in the thesis is to develop the theoretical foundations and computational algorithms to numerically simulate such systems. In order to optimize the numerical calculations I resort to different techniques (such as graph theory in finding inverse of a sparse matrix, adaptive grids for integrations and programming languages (e.g., MATLAB and C++) and distributed computing tools (MPI, CUDA). Outline of the Thesis: After giving an introduction to the topics covered in this thesis in Chapter 1, I present the theoretical foundations to the field of non-equilibrium quantum statistics in Chapter 2. The applications of this formalism and the results are covered in the subsequent chapters as follows: Spin and charge quantum pumping in time-dependent systems: Covered in Chapters 3, 4 and 5, this topics was initially motivated by experiments on measuring voltage signal from a magnetic tunnel junction (MTJ) exposed to a microwave radiation in ferromagnetic resonance (FMR) condition. In Chapter 3 we found a possible explanation for the finite voltage signal measured from a tunnel junction consisting of only a single
Quantum distribution function of nonequilibrium system
International Nuclear Information System (INIS)
Sogo, Kiyoshi; Fujimoto, Yasushi.
1990-03-01
A path integral representation is derived for the Wigner distribution function of a nonequilibrium system coupled with heat bath. Under appropriate conditions, the Wigner distribution function approaches an equilibrium distribution, which manifests shifting and broadening of spectral lines due to the interaction with heat bath. It is shown that the equilibrium distribution becomes the quantum canonical distribution in the vanishing coupling constant limit. (author)
Introduction to the nonequilibrium functional renormalization group
International Nuclear Information System (INIS)
Berges, J.; Mesterházy, D.
2012-01-01
In these lectures we introduce the functional renormalization group out of equilibrium. While in thermal equilibrium typically a Euclidean formulation is adequate, nonequilibrium properties require real-time descriptions. For quantum systems specified by a given density matrix at initial time, a generating functional for real-time correlation functions can be written down using the Schwinger-Keldysh closed time path. This can be used to construct a nonequilibrium functional renormalization group along similar lines as for Euclidean field theories in thermal equilibrium. Important differences include the absence of a fluctuation-dissipation relation for general out-of-equilibrium situations. The nonequilibrium renormalization group takes on a particularly simple form at a fixed point, where the corresponding scale-invariant system becomes independent of the details of the initial density matrix. We discuss some basic examples, for which we derive a hierarchy of fixed point solutions with increasing complexity from vacuum and thermal equilibrium to nonequilibrium. The latter solutions are then associated to the phenomenon of turbulence in quantum field theory.
Czech Academy of Sciences Publication Activity Database
Kalvová, Anděla; Velický, B.; Špička, Václav
2017-01-01
Roč. 30, č. 3 (2017), s. 807-811 ISSN 1557-1939 Institutional support: RVO:68378271 Keywords : non-equilibrium * initial conditions * transient currents * molecular islands Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.180, year: 2016
Many-Body Green Function of Degenerate Systems
International Nuclear Information System (INIS)
Brouder, Christian; Panati, Gianluca; Stoltz, Gabriel
2009-01-01
A rigorous nonperturbative adiabatic approximation of the evolution operator in the many-body physics of degenerate systems is derived. This approximation is used to solve the long-standing problem of the choice of the initial states of H 0 leading to eigenstates of H 0 +V for degenerate systems. These initial states are eigenstates of P 0 VP 0 , where P 0 is the projection onto a degenerate eigenspace of H 0 . This result is used to give the proper definition of the Green function, the statistical Green function and the nonequilibrium Green function of degenerate systems. The convergence of these Green functions is established.
International Nuclear Information System (INIS)
Hyldgaard, P
2012-01-01
The standard formulation of tunneling transport rests on an open-boundary modeling. There, conserving approximations to nonequilibrium Green function or quantum statistical mechanics provide consistent but computational costly approaches; alternatively, the use of density-dependent ballistic-transport calculations (e.g., Lang 1995 Phys. Rev. B 52 5335), here denoted ‘DBT’, provides computationally efficient (approximate) atomistic characterizations of the electron behavior but has until now lacked a formal justification. This paper presents an exact, variational nonequilibrium thermodynamic theory for fully interacting tunneling and provides a rigorous foundation for frozen-nuclei DBT calculations as a lowest-order approximation to an exact nonequilibrium thermodynamic density functional evaluation. The theory starts from the complete electron nonequilibrium quantum statistical mechanics and I identify the operator for the nonequilibrium Gibbs free energy which, generally, must be treated as an implicit solution of the fully interacting many-body dynamics. I demonstrate a minimal property of a functional for the nonequilibrium thermodynamic grand potential which thus uniquely identifies the solution as the exact nonequilibrium density matrix. I also show that the uniqueness-of-density proof from a closely related Lippmann-Schwinger collision density functional theory (Hyldgaard 2008 Phys. Rev. B 78 165109) makes it possible to express the variational nonequilibrium thermodynamic description as a single-particle formulation based on universal electron-density functionals; the full nonequilibrium single-particle formulation improves the DBT method, for example, by a more refined account of Gibbs free energy effects. I illustrate a formal evaluation of the zero-temperature thermodynamic grand potential value which I find is closely related to the variation in the scattering phase shifts and hence to Friedel density oscillations. This paper also discusses the
Green function on product networks
Arauz Lombardía, Cristina; Carmona Mejías, Ángeles; Encinas Bachiller, Andrés Marcos
2012-01-01
Our objective is to determine the Green function of product networks in terms of the Green function of one of the factor networks and the eigenvalues and eigenfunctions of the Schr odinger operator of the other factor network, which we consider that are known. Moreover, we use these results to obtain the Green function of spider networks in terms of Green functions over cicles and paths. Peer Reviewed
Harmonic supergraphs. Green functions
International Nuclear Information System (INIS)
Galperin, A.; Ivanov, E.; Gievetsky, V.; Sokatchev, E.
1985-01-01
The quantization procedure in the harmonic superspace approach is worked out. Harmonic distributions are introduced and are used to construct the analytic superspace delta-functions and the Green functions for the hypermultiplet and the N=2 Yang-Mills superfields. The gauge fixing is described and the relevant Faddeev-Popov ghosts are defined. The corresponding BRST transformations are found. The harmonic superspace quantization of the N=2 gauge theory turns out to be rather simple and has many parallels with that for the standard (N=0) Yang-Mills theory. In particular, no ghosts-forghosts are needed
Green's functions in quantum physics
Economou, Eleftherios N
2006-01-01
The main part of this book is devoted to the simplest kind of Green's functions, namely the solutions of linear differential equations with a -function source. It is shown that these familiar Green's functions are a powerful tool for obtaining relatively simple and general solutions of basic problems such as scattering and bound-level information. The bound-level treatment gives a clear physical understanding of "difficult" questions such as superconductivity, the Kondo effect, and, to a lesser degree, disorder-induced localization. The more advanced subject of many-body Green's functions is presented in the last part of the book.
Green functions of vortex operators
International Nuclear Information System (INIS)
Polchinski, J.; California Univ., Berkeley
1981-01-01
We study the euclidean Green functions of the 't Hooft vortex operator, primarly for abelian gauge theories. The operator is written in terms of elementary fields, with emphasis on a form in which it appears as the exponential of a surface integral. We explore the requirement that the Green functions depend only on the boundary of this surface. The Dirac veto problem appears in a new guise. We present a two-dimensional solvable model of a Dirac string, which suggests a new solution of the veto problem. The renormalization of the Green functions of the abelian Wilson loop and abelian vortex operator is studied with the aid of the operator product expansion. In each case, an overall multiplication of the operator makes all Green functions finite; a surprising cancellation of divergences occurs with the vortex operator. We present a brief discussion of the relation between the nature of the vacuum and the cluster properties of the Green functions of the Wilson and vortex operators, for a general gauge theory. The surface-like cluster property of the vortex operator in an abelian Higgs theory is explored in more detail. (orig.)
International Nuclear Information System (INIS)
Erpenbeck, J.J.
1987-01-01
We apply the so-called ''synthetic'' nonequilibrium molecular-dynamics method to the calculation of the self-diffusion constant of a Lennard-Jones fluid at a number density of 0.85/σ 3 and a temperature of 1.08 epsilon-c/k/sub B/ (where epsilon-c and σ are the energy and length parameters of the potential and k/sub B/ is the Boltzmann constant). By comparing with the Green-Kubo calculation for the same state of the system and for the same number of particles, N, we find the latter calculation to yield more precise values of the self-diffusion constant for a given number of molecular-dynamics time steps. Even at small values of the diffusion current, a nontrivial time is needed for the nonequilibrium calculation to reach the steady state. For larger values of the driving force, the steady-state flow appears to become unstable and evidence of a secondary flow pattern is presented. The presence of these instabilities acts as a limit to the range of the driving force for which the steady-state method can be applied. With increasing N the range of stable values of the diffusion current density decreases. For the Green-Kubo calculations, the N dependence of the self-diffusion constant is found to be anomalous for N = 108, with the 1/N dependence only exhibited for at least 500 particles. The nonequilibrium results, while approximately independent of N for 108 and 500 particles, are found to have a similar anomalous N dependence when we extend the calculations to 1372 particles, thereby bringing the Green-Kubo and nonequilibrium results into agreement in the large-system limit
Fragmentation function in non-equilibrium QCD using closed-time path integral formalism
International Nuclear Information System (INIS)
Nayak, Gouranga C.
2009-01-01
In this paper we implement the Schwinger-Keldysh closed-time path integral formalism in non-equilibrium QCD in accordance to the definition of the Collins-Soper fragmentation function. We consider a high-p T parton in QCD medium at initial time τ 0 with an arbitrary non-equilibrium (non-isotropic) distribution function f(vector (p)) fragmenting to a hadron. We formulate the parton-to-hadron fragmentation function in non-equilibrium QCD in the light-cone quantization formalism. It may be possible to include final-state interactions with the medium via a modification of the Wilson lines in this definition of the non-equilibrium fragmentation function. This may be relevant to the study of hadron production from a quark-gluon plasma at RHIC and LHC. (orig.)
A hybrid method for the parallel computation of Green's functions
International Nuclear Information System (INIS)
Petersen, Dan Erik; Li Song; Stokbro, Kurt; Sorensen, Hans Henrik B.; Hansen, Per Christian; Skelboe, Stig; Darve, Eric
2009-01-01
Quantum transport models for nanodevices using the non-equilibrium Green's function method require the repeated calculation of the block tridiagonal part of the Green's and lesser Green's function matrices. This problem is related to the calculation of the inverse of a sparse matrix. Because of the large number of times this calculation needs to be performed, this is computationally very expensive even on supercomputers. The classical approach is based on recurrence formulas which cannot be efficiently parallelized. This practically prevents the solution of large problems with hundreds of thousands of atoms. We propose new recurrences for a general class of sparse matrices to calculate Green's and lesser Green's function matrices which extend formulas derived by Takahashi and others. We show that these recurrences may lead to a dramatically reduced computational cost because they only require computing a small number of entries of the inverse matrix. Then, we propose a parallelization strategy for block tridiagonal matrices which involves a combination of Schur complement calculations and cyclic reduction. It achieves good scalability even on problems of modest size.
Closed forms for conformally flat Green's functions
International Nuclear Information System (INIS)
Brown, M.R.; Grove, P.G.; Ottewill, A.C.
1981-01-01
A closed form is obtained for the massless scalar Green's function on Rindler space. This is related by conformal transformation to the Green's function for a massless, conformally coupled scalar field on the open Einstein universe. A closed form is also obtained for the corresponding Green's function on the Einstein static universe. (author)
Dynamics of mesoscopic systems: Non-equilibrium Green's functions approach
Czech Academy of Sciences Publication Activity Database
Špička, Václav; Kalvová, Anděla; Velický, B.
2010-01-01
Roč. 42, č. 3 (2010), s. 525-538 ISSN 1386-9477 R&D Projects: GA ČR GA202/08/0361 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z10100521 Keywords : mesoscopic systems * NGF * initial condition * correlations * Ward identities * transients Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.304, year: 2010
Green's functions, states and renormalisation
International Nuclear Information System (INIS)
Brown, M.R.; Ottewill, A.C.
1982-01-01
The significance that is to be attached to different operator orderings of free quantum field theories in curved space-time is examined. It is hoped thus to elucidate the renormalization of such theories. It is argued that as in flat space, these theories should be rendered finite by normal ordering with respect to a local geometrical vacuum state. Flat space is considered first, then an analogous local, geometrical Green's function for curved space-time is defined. Examples given are the Einstein static universe, the open Einstein universe and the de Sitter universe. It is observed that normalization provides some insight into the nature of vacuum stress. (U.K.)
Partition Function and Configurational Entropy in Non-Equilibrium States: A New Theoretical Model
Directory of Open Access Journals (Sweden)
Akira Takada
2018-03-01
Full Text Available A new model of non-equilibrium thermodynamic states has been investigated on the basis of the fact that all thermodynamic variables can be derived from partition functions. We have thus attempted to define partition functions for non-equilibrium conditions by introducing the concept of pseudo-temperature distributions. These pseudo-temperatures are configurational in origin and distinct from kinetic (phonon temperatures because they refer to the particular fragments of the system with specific energies. This definition allows thermodynamic states to be described either for equilibrium or non-equilibrium conditions. In addition; a new formulation of an extended canonical partition function; internal energy and entropy are derived from this new temperature definition. With this new model; computational experiments are performed on simple non-interacting systems to investigate cooling and two distinct relaxational effects in terms of the time profiles of the partition function; internal energy and configurational entropy.
Lyapunov Functions, Stationary Distributions, and Non-equilibrium Potential for Reaction Networks
DEFF Research Database (Denmark)
Anderson, David F; Craciun, Gheorghe; Gopalkrishnan, Manoj
2015-01-01
We consider the relationship between stationary distributions for stochastic models of reaction systems and Lyapunov functions for their deterministic counterparts. Specifically, we derive the well-known Lyapunov function of reaction network theory as a scaling limit of the non-equilibrium potent...
The Green functions in curved spacetime
International Nuclear Information System (INIS)
Buchbinder, I.L.; Kirillova, E.N.; Odinstov, S.D.
1987-01-01
The theory of a free scalar field with conformal coupling in curved spacetime with some special metrics is considered. The integral representations for the green function G-tilde in the form of integrals with Schwinger-De Witt kernel over contours in the complex plane of proper time are obtained. It is shown how the transitions from a unique Green function in Euclidean space to different Green functions in Minkowski space and vice versa can be carried out. (author)
Green functions in an external electric field
International Nuclear Information System (INIS)
Gavrilov, S.P.; Gitman, D.M.; Shvartsman, Sh.M.
1979-01-01
In the framework of scalar quantum electrodynamics, when vacuum is unstable as to the birth of electron-positron couples, calculated have been Green functions for the case of stable homogeneous electric field. By summing corresponding solutions of the Klein-Gordon equation of the Green function are obtained in the form of contour integrals according to the proper time. Operation representations of all the calculated Green functions in the mentioned field are presented
Green's functions of solitons in heat bath
International Nuclear Information System (INIS)
Smilga, A.V.
1989-01-01
Soliton Green's functions at nonzero temperature are studied. Considering various model example it is shown that the Green's function pole position does not coincide generally speaking with free energy of a soliton. The Froelich polaron and the t'Hooft-Polyakov monopole the Green's function for which is in general a poorly defined concept as it involves an infinite imaginary part connected to the infinite total cross section of monopole scattering by electric charge are discussed. The pole position of the Green's function of the collective sphaleron excitation in the Glashow-Weinberg-Salem model does not as well coincide with the sphaleron free energy. 24 refs.; 9 figs
The closed time-path Green function formalism in many-body theory
International Nuclear Information System (INIS)
Guang-zhao Zhou; Zhao-bin Su; Bai-lin Hao; Lu Yu.
1983-09-01
The closed time-path Green function formalism, developed by our group during recent years, is briefly reviewed. The generating functional technique, the coupled equations for the order parameter and the elementary excitations as well as the systematic loop expansion are outlined. The applications to critical dynamics, quenched random systems, nonlinear response theory, superconductivity, laser system and quasi-one-dimensional conductors are described. The theoretical approach developed can be applied to both equilibrium and non-equilibrium many-body systems. (author)
Long and short time quantum dynamics: I. Between Green's functions and transport equations
Czech Academy of Sciences Publication Activity Database
Špička, Václav; Velický, Bedřich; Kalvová, Anděla
2005-01-01
Roč. 29, - (2005), s. 154-174 ISSN 1386-9477 R&D Projects: GA ČR(CZ) GA202/04/0585; GA AV ČR(CZ) IAA1010404 Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z10100520 Keywords : non-equilibrium * Green functions * quantum transport * density functional the ory Subject RIV: BE - The oretical Physics Impact factor: 0.946, year: 2005
Energy Technology Data Exchange (ETDEWEB)
Hofmann, Felix
2016-07-05
The self-energy functional theory (SFT) is extended to the nonequilibrium case and applied to the real-time dynamics of strongly correlated lattice-fermions. Exploiting the basic structure of the well established equilibrium theory the entire formalism is reformulated in the language of Keldysh-Matsubara Green's functions. To this end, a functional of general nonequilibrium self-energies is constructed which is stationary at the physical point where it moreover yields the physical grand potential of the initial thermal state. Nonperturbative approximations to the full self-energy can be constructed by reducing the original lattice problem to smaller reference systems and varying the functional on the space of the respective trial self-energies, which are parametrized by the reference system's one-particle parameters. Approximations constructed in this way can be shown to respect the macroscopic conservation laws related to the underlying symmetries of the original lattice model. Assuming thermal equilibrium, the original SFT is recovered from the extended formalism. However, in the general case, the nonequilibrium variational principle comprises functional derivatives off the physical parameter space. These can be carried out analytically to derive inherently causal conditional equations for the optimal physical parameters of the reference system and a computationally realizable propagation scheme is set up. As a benchmark for the numerical implementation the variational cluster approach is applied to the dynamics of a dimerized Hubbard model after fast ramps of its hopping parameters. Finally, the time-evolution of a homogeneous Hubbard model after sudden quenches and ramps of the interaction parameter is studied by means of a dynamical impurity approximation with a single bath site. Sharply separated by a critical interaction at which fast relaxation to a thermal final state is observed, two differing response regimes can be distinguished, where the
International Nuclear Information System (INIS)
Ness, H.; Dash, L. K.
2014-01-01
We study the non-equilibrium (NE) fluctuation-dissipation (FD) relations in the context of quantum thermoelectric transport through a two-terminal nanodevice in the steady-state. The FD relations for the one- and two-particle correlation functions are derived for a model of the central region consisting of a single electron level. Explicit expressions for the FD relations of the Green's functions (one-particle correlations) are provided. The FD relations for the current-current and charge-charge (two-particle) correlations are calculated numerically. We use self-consistent NE Green's functions calculations to treat the system in the absence and in the presence of interaction (electron-phonon) in the central region. We show that, for this model, there is no single universal FD theorem for the NE steady state. There are different FD relations for each different class of problems. We find that the FD relations for the one-particle correlation function are strongly dependent on both the NE conditions and the interactions, while the FD relations of the current-current correlation function are much less dependent on the interaction. The latter property suggests interesting applications for single-molecule and other nanoscale transport experiments
Green's functions potential fields on surfaces
Melnikov, Yuri A
2017-01-01
This book is comprehensive in its classical mathematical physics presentation, providing the reader with detailed instructions for obtaining Green's functions from scratch. Green's functions is an instrument easily accessible to practitioners who are engaged in design and exploitation of machines and structures in modern engineering practice. To date, there are no books available on the market that are devoted to the Green's function formalism for equations covered in this volume. The reader, with an undergraduate background in applied mathematics, can become an active user of the Green's function approach. For the first time, Green's functions are discussed for a specific class of problems dealing with potential fields induced in thin-wall structures and therefore, the reader will have first-hand access to a novel issue. This Work is accessible to researchers in applied mathematics, mechanics, and relevant disciplines such as engineering, as well as to upper level undergraduates and graduate students.
Energy Technology Data Exchange (ETDEWEB)
Chen Yong; Chen Xi; Qian Minping [School of Mathematical Sciences, Peking University, Beijing 100871 (China)
2006-03-17
A general form of the Green-Kubo formula, which describes the fluctuations pertaining to all the steady states whether equilibrium or non-equilibrium, for a system driven by a finite Markov chain with continuous time (briefly, MC) {l_brace}{xi}{sub t}{r_brace}, is shown. The equivalence of different forms of the Green-Kubo formula is exploited. We also look at the differences in terms of the autocorrelation function and the fluctuation spectrum between the equilibrium state and the non-equilibrium steady state. Also, if the MC is in the non-equilibrium steady state, we can always find a complex function {psi}, such that the fluctuation spectrum of {l_brace}{phi}({xi}{sub t}){r_brace} is non-monotonous in [0, + {infinity})
International Nuclear Information System (INIS)
Chen Yong; Chen Xi; Qian Minping
2006-01-01
A general form of the Green-Kubo formula, which describes the fluctuations pertaining to all the steady states whether equilibrium or non-equilibrium, for a system driven by a finite Markov chain with continuous time (briefly, MC) {ξ t }, is shown. The equivalence of different forms of the Green-Kubo formula is exploited. We also look at the differences in terms of the autocorrelation function and the fluctuation spectrum between the equilibrium state and the non-equilibrium steady state. Also, if the MC is in the non-equilibrium steady state, we can always find a complex function ψ, such that the fluctuation spectrum of {φ(ξ t )} is non-monotonous in [0, + ∞)
Carrier transport in THz quantum cascade lasers: Are Green's functions necessary?
International Nuclear Information System (INIS)
Matyas, A; Jirauschek, C; Kubis, T; Lugli, P
2009-01-01
We have applied two different simulation models for the stationary carrier transport and optical gain analysis in resonant phonon depopulation THz Quantum Cascade Lasers (QCLs), based on the semiclassical ensemble Monte Carlo (EMC) and fully quantum mechanical non-equilibrium Green's functions (NEGF) method, respectively. We find in the incoherent regime near and above the threshold current a qualitative and quantitative agreement of both methods. Therefore, we show that THz-QCLs can be successfully optimized utilizing the numerically efficient EMC method.
Scalar field Green functions on causal sets
International Nuclear Information System (INIS)
Nomaan Ahmed, S; Surya, Sumati; Dowker, Fay
2017-01-01
We examine the validity and scope of Johnston’s models for scalar field retarded Green functions on causal sets in 2 and 4 dimensions. As in the continuum, the massive Green function can be obtained from the massless one, and hence the key task in causal set theory is to first identify the massless Green function. We propose that the 2d model provides a Green function for the massive scalar field on causal sets approximated by any topologically trivial 2-dimensional spacetime. We explicitly demonstrate that this is indeed the case in a Riemann normal neighbourhood. In 4d the model can again be used to provide a Green function for the massive scalar field in a Riemann normal neighbourhood which we compare to Bunch and Parker’s continuum Green function. We find that the same prescription can also be used for de Sitter spacetime and the conformally flat patch of anti-de Sitter spacetime. Our analysis then allows us to suggest a generalisation of Johnston’s model for the Green function for a causal set approximated by 3-dimensional flat spacetime. (paper)
Thermodynamic Green functions in theory of superconductivity
Directory of Open Access Journals (Sweden)
N.M.Plakida
2006-01-01
Full Text Available A general theory of superconductivity is formulated within the thermodynamic Green function method for various types of pairing mediated by phonons, spin fluctuations, and strong Coulomb correlations in the Hubbard and t-J models. A rigorous Dyson equation for matrix Green functions is derived in terms of a self-energy as a many-particle Green function. By applying the noncrossing approximation for the self-energy, a closed self-consistent system of equations is obtained, similar to the conventional Eliashberg equations. A brief discussion of superconductivity mediated by kinematic interaction with an estimation of a superconducting transition temperature in the Hubbard model is given.
Green functions in Bianci-type spaces
International Nuclear Information System (INIS)
Bukhbinder, I.L.; Kirillova, E.N.
1988-01-01
The theory of free scalar field with conformal connection in distorted space - time with Bianci 1 type metrics is considered. The presentation of the Green functions G-tilde approximately in in in the form of integral from the Schwinger - De Witt kernel over the contour in the plane of complex values of eigentime is obtained. The way, in which the transfer from the Green function in space with Euclidean signature to the Green functions in space with Minkowski signature and vice versa is realized, has been shown
Nonequilibrium statistical averages and thermo field dynamics
International Nuclear Information System (INIS)
Marinaro, A.; Scarpetta, Q.
1984-01-01
An extension of thermo field dynamics is proposed, which permits the computation of nonequilibrium statistical averages. The Brownian motion of a quantum oscillator is treated as an example. In conclusion it is pointed out that the procedure proposed to computation of time-dependent statistical average gives the correct two-point Green function for the damped oscillator. A simple extension can be used to compute two-point Green functions of free particles
THE GREEN'S FUNCTIONS OF SUPERCONDUCTIVITY- A REVIEW
African Journals Online (AJOL)
users
2013-02-21
Feb 21, 2013 ... We present some basic Green's functions of superconductivity, ... show that the Gorkov interaction under a certain condition sustains .... We may then apply Wick's theorem(Lifshitz and Pitayevsky,1980) to the eqn(18) to have.
Multiconfigurational Green's function approaches in quantum chemistry
International Nuclear Information System (INIS)
Yeager, D.L.
1984-01-01
The author discusses multiconfigurational Green's function techniques and generalizations. In particular he is interested in developing and applying these techniques for isolated atoms and small molecules. Furthermore, he develops formalisms that are fairly clear, accurate, and capable of being applied to open-shell and highly-correlated systems as well as to closed-shell systems with little electronic correlation. The two kinds of Green's functions that this article discusses are the single-particle Green's function and the retarded two-time Green's function in the energy representation. The poles of the former give the ionization potentials and electron affinities while the poles of the latter give the excitation energies. The multiconfigurational approximations are known as the multiconfigurational electron propagator (MCEP) and the multiconfigurational time-dependent Hartree-Fock (MCTDHF) (also known as the multiconfigurational random phase approximation (MCRPA) or the multiconfigurational linear response), respectively. 44 references
Axioms for Euclidean Green's functions. Pt. 2
International Nuclear Information System (INIS)
Osterwalder, K.; Schrader, R.
1975-01-01
We give new (necessary and) sufficient conditions for Euclidean Green's functions to have analytic continuations to a relativistic field theory. These results extend and correct a previous paper. (orig.) [de
Worldline Green functions for multiloop diagrams
International Nuclear Information System (INIS)
Schmidt, M.G.; Heidelberg Univ.; Schubert, C.
1994-03-01
We propose a multiloop generalization of the Bern-Kosower formalism, based on Strassler's approach of evaluating worldline path integrals by worldline Green functions. Those Green functions are explicitly constructed for the basic two-loop graph, and for a loop with an arbitrary number of propagator insertions. For scalar and abelian gauge theories, the resulting integral representations allow to combine whole classes of Feynman diagrams into compact expressions. (orig.)
A Green function of neutron transport equation
International Nuclear Information System (INIS)
Simovic, R.
1993-01-01
In this paper the angularly dependent Green function of the neutron transport equation is derived analytically and approximately. By applying the analytical FDPN approximation up to eighth order, numerical values of the Green functions are obtained with the accuracy of six significant figures in the whole range of parameter c, angle cosine μ and distances x up to the ten optical lengths from the neutron source. (author)
Binary operators and their Green's functions
International Nuclear Information System (INIS)
Sheff, J.R.
1982-01-01
Three topics are considered. First, the Langevin approach to neutron noise is used as a basis and guide to develop solutions and solution techniques for the ChapmanKolmogorov forward equation approach to neutron noise. The approach followed throughout this first part is that of solution by means of Green's functions. A particular form for the binary operator Green's function was picked on the basis of the Langevin method. Second, the basic solution technique using the particular Green's function form mentioned above is proven to be a correct and a general result. It is proven that the binary operator is always separable and that the Green's function could be written as the product of two single operator Green's functions. This is a new result. Third and finally, the forward equation approach of Chapman-Kolmogorov is generalized to include time allowing differential equations for second and higher order correlation functions to be developed directly. The principal result of the last section, the differential equation for correlation function of the neutron density, is new. Its derivation is really outside of or broader than the scope indicated by the title of the paper
Two-proton correlation functions for equilibrium and non-equilibrium emission
International Nuclear Information System (INIS)
Gong, W.G.; Gelbke, C.K.; Carlin, N.; De Souza, R.T.; Kim, Y.D.; Lynch, W.G.; Murakami, T.; Poggi, G.; Sanderson, D.; Tsang, M.B.; Xu, H.M.; Michigan State Univ., East Lansing; Fields, D.E.; Kwiatkowski, K.; Planeta, R.; Viola, V.E. Jr.; Yennello, S.J.; Indiana Univ., Bloomington; Indiana Univ., Bloomington; Pratt, S.
1990-01-01
Two-proton correlation functions are compared for equilibrium and non-equilibrium emission processes investigated, respectively, in ''reverse kinematics'' for the reactions 129 Xe+ 27 Al and 129 Xe+ 122 Sn at E/A=31 MeV and in ''forward kinematics'' for the reaction 14 N+ 197 Au at E/A=75 MeV. Observed differences in the shapes of the correlation functions are understood in terms of the different time scales for equilibrium and preequilibrium emission. Transverse and longitudinal correlation functions are very similar. (orig.)
Semiclassical initial value approximation for Green's function.
Kay, Kenneth G
2010-06-28
A semiclassical initial value approximation is obtained for the energy-dependent Green's function. For a system with f degrees of freedom the Green's function expression has the form of a (2f-1)-dimensional integral over points on the energy surface and an integral over time along classical trajectories initiated from these points. This approximation is derived by requiring an integral ansatz for Green's function to reduce to Gutzwiller's semiclassical formula when the integrations are performed by the stationary phase method. A simpler approximation is also derived involving only an (f-1)-dimensional integral over momentum variables on a Poincare surface and an integral over time. The relationship between the present expressions and an earlier initial value approximation for energy eigenfunctions is explored. Numerical tests for two-dimensional systems indicate that good accuracy can be obtained from the initial value Green's function for calculations of autocorrelation spectra and time-independent wave functions. The relative advantages of initial value approximations for the energy-dependent Green's function and the time-dependent propagator are discussed.
Green's functions in quantum physics. 3. ed.
International Nuclear Information System (INIS)
Economou, E.N.
2006-01-01
The new edition of a standard reference will be of interest to advanced students wishing to become familiar with the method of Green's functions for obtaining simple and general solutions to basic problems in quantum physics. The main part is devoted to the simplest kind of Green's functions, namely the solutions of linear differential equations with a -function source. It is shown that these familiar Green's functions are a powerful tool for obtaining relatively simple and general solutions of basic problems such as scattering and bound level information. The bound-level treatment gives a clear physical understanding of ''difficult'' questions such as superconductivity, the Kondo effect, and, to a lesser degree, disorder-induced localization. The more advanced subject of many-body Green's functions is presented in the last part of the book. This third edition is 50% longer than the previous and offers end-of-chapter problems and solutions (40% are solved) and additional appendices to help it is to serve as an effective self-tutorial and self-sufficient reference. Throughout, it demonstrates the powerful and unifying formalism of Green's functions across many applications, including transport properties, carbon nanotubes, and photonics and photonic crystals. (orig.)
Functional equations and Green's functions for augmented scalar fields
International Nuclear Information System (INIS)
Klauder, J.R.
1977-01-01
Certain noncanonical self-coupled scalar quantum field theories, previously formulated by means of functional integration, are herein recast into the form of functional differential equations for the Green's functional. From these expressions the set of coupled equations relating the Green's functions is obtained. The new equations are compared with those of the conventional formulation, and are proposed as alternatives, especially for nonrenormalizable models when the conventional equations fail
Morgenstern Horing, Norman J
2017-01-01
This book provides an introduction to the methods of coupled quantum statistical field theory and Green's functions. The methods of coupled quantum field theory have played a major role in the extensive development of nonrelativistic quantum many-particle theory and condensed matter physics. This introduction to the subject is intended to facilitate delivery of the material in an easily digestible form to advanced undergraduate physics majors at a relatively early stage of their scientific development. The main mechanism to accomplish this is the early introduction of variational calculus and the Schwinger Action Principle, accompanied by Green's functions. Important achievements of the theory in condensed matter and quantum statistical physics are reviewed in detail to help develop research capability. These include the derivation of coupled field Green's function equations-of-motion for a model electron-hole-phonon system, extensive discussions of retarded, thermodynamic and nonequilibrium Green's functions...
Carrier transport in THz quantum cascade lasers: Are Green's functions necessary?
Energy Technology Data Exchange (ETDEWEB)
Matyas, A; Jirauschek, C [Emmy Noether Research Group ' Modeling of Quantum Cascade Devices' , TU Muenchen, D-80333 Muenchen (Germany); Kubis, T [Walter Schottky Institute, TU Muenchen, D-85748 Garching (Germany); Lugli, P, E-mail: alparmat@mytum.d [Institute of Nanoelectronics, TU Muenchen, D-80333 Muenchen (Germany)
2009-11-15
We have applied two different simulation models for the stationary carrier transport and optical gain analysis in resonant phonon depopulation THz Quantum Cascade Lasers (QCLs), based on the semiclassical ensemble Monte Carlo (EMC) and fully quantum mechanical non-equilibrium Green's functions (NEGF) method, respectively. We find in the incoherent regime near and above the threshold current a qualitative and quantitative agreement of both methods. Therefore, we show that THz-QCLs can be successfully optimized utilizing the numerically efficient EMC method.
Green's function approach to neutron flux discontinuities
International Nuclear Information System (INIS)
Saad, E.A.; El-Wakil, S.A.
1980-01-01
The present work is devoted to the presentation of analytical method for the calculation of elastically and inelastically slowed down neutrons in an infinite non-absorbing medium. On the basis of the central limit theory (CLT) and the integral transform technique the slowing down equation including inelastic scattering, in terms of the Green function of elastic scattering, is solved. The Green function is decomposed according to the number of collisions. Placzec discontinuity associated with elastic scattering in addition to two discontinuities due to inelastic scattering are investigated. Numerical calculations for Fe 56 show that the elastic discontinuity produces about 41.8% change in the collision density whilst the ratio of the inelastic collision density discontinuity at qsub(o)sup(+) to the Placzec discontinuity at usub(o) + 1n 1/oc gives 55.7 percent change. (author)
Temporal quadratic expansion nodal Green's function method
International Nuclear Information System (INIS)
Liu Cong; Jing Xingqing; Xu Xiaolin
2000-01-01
A new approach is presented to efficiently solve the three-dimensional space-time reactor dynamics equation which overcomes the disadvantages of current methods. In the Temporal Quadratic Expansion Nodal Green's Function Method (TQE/NGFM), the Quadratic Expansion Method (QEM) is used for the temporal solution with the Nodal Green's Function Method (NGFM) employed for the spatial solution. Test calculational results using TQE/NGFM show that its time step size can be 5-20 times larger than that of the Fully Implicit Method (FIM) for similar precision. Additionally, the spatial mesh size with NGFM can be nearly 20 times larger than that using the finite difference method. So, TQE/NGFM is proved to be an efficient reactor dynamics analysis method
Gluon Green functions free of quantum fluctuations
Directory of Open Access Journals (Sweden)
A. Athenodorou
2016-09-01
Full Text Available This letter reports on how the Wilson flow technique can efficaciously kill the short-distance quantum fluctuations of 2- and 3-gluon Green functions, remove the ΛQCD scale and destroy the transition from the confining non-perturbative to the asymptotically-free perturbative sector. After the Wilson flow, the behavior of the Green functions with momenta can be described in terms of the quasi-classical instanton background. The same behavior also occurs, before the Wilson flow, at low-momenta. This last result permits applications as, for instance, the detection of instanton phenomenological properties or a determination of the lattice spacing only from the gauge sector of the theory.
Discrete state perturbation theory via Green's functions
International Nuclear Information System (INIS)
Rubinson, W.
1975-01-01
The exposition of stationary-state perturbation theory via the Green's function method in Goldberger and Watson's Collision Theory is reworked in a way that makes explicit its mathematical basis. It is stressed that the theory consists of the construction of, and manipulations on, a mathematical identity. The perturbation series fall out of the identity almost immediately. The logical status of the method is commented on
convergent methods for calculating thermodynamic Green functions
Bowen, S. P.; Williams, C. D.; Mancini, J. D.
1984-01-01
A convergent method of approximating thermodynamic Green functions is outlined briefly. The method constructs a sequence of approximants which converges independently of the strength of the Hamiltonian's coupling constants. Two new concepts associated with the approximants are introduced: the resolving power of the approximation, and conditional creation (annihilation) operators. These ideas are illustrated on an exactly soluble model and a numerical example. A convergent expression for the s...
Electrical tensor Green functions for cylindrical waveguides
International Nuclear Information System (INIS)
Prijmenko, S.D.; Papkovich, V.G.; Khizhnyak, N.A.
1988-01-01
Formation of electrical tensor Green functions for cylindrical waveguides is considered. Behaviour of these functions in the source region is studied. Cases of electrical tensor Green functions for vector potential G E (r-vector, r'-vector) and electric field G e (r-vector, r'-vector) are analysed. When forming G E (r-vector, r'-vector), its dependence on lateral coordinates is taken into account by means of two-dimensional fundamental vector Hansen functions, several methods are used to take into account the dependence on transverse coordinate. When forming G e (r-vector, r'-vector) we use the fact that G E (r-vector, r'-vector) and G e (r-vector, r'-vector) are the generalized functions. It is shown that G e (r-vector, r'-vector) behaviour in the source region is defined by a singular term, which properties are described by the delta-function. Two variants of solving the problem of defining singular and regular sides of tensor function G E (r-vector, r'-vector) are presented. 23 refs
A Floquet-Green's function approach to mesoscopic transport under ac bias
International Nuclear Information System (INIS)
Wu, B H; Cao, J C
2008-01-01
The current response of a mesoscopic system under a periodic ac bias is investigated by combining the Floquet theorem and the nonequilibrium Green's function method. The band structure of the lead under ac bias is fully taken into account by using appropriate self-energies in an enlarged Floquet space. Both the retarded and lesser Green's functions are obtained in the Floquet basis to account for the interference and interaction effects. In addition to the external ac bias, the time-varying Coulomb interaction, which is treated at the self-consistent Hartree-Fock level, provides another internal ac field. The numerical results show that the time-varying Coulomb field yields decoherence and reduces the ringing behavior of the current response to a harmonic bias
Statistical mechanics of nonequilibrium liquids
Evans, Denis J; Craig, D P; McWeeny, R
1990-01-01
Statistical Mechanics of Nonequilibrium Liquids deals with theoretical rheology. The book discusses nonlinear response of systems and outlines the statistical mechanical theory. In discussing the framework of nonequilibrium statistical mechanics, the book explains the derivation of a nonequilibrium analogue of the Gibbsian basis for equilibrium statistical mechanics. The book reviews the linear irreversible thermodynamics, the Liouville equation, and the Irving-Kirkwood procedure. The text then explains the Green-Kubo relations used in linear transport coefficients, the linear response theory,
Single-particle properties from Kohn-Sham Green's functions
International Nuclear Information System (INIS)
Bhattacharyya, Anirban; Furnstahl, R.J.
2005-01-01
An effective action approach to Kohn-Sham density functional theory is used to illustrate how the exact Green's function can be calculated in terms of the Kohn-Sham Green's function. An example based on Skyrme energy functionals shows that single-particle Kohn-Sham spectra can be improved by adding sources used to construct the energy functional
Non-equilibrium coupling of protein structure and function to translation-elongation kinetics.
Sharma, Ajeet K; O'Brien, Edward P
2018-04-01
Protein folding research has been dominated by the assumption that thermodynamics determines protein structure and function. And that when the folding process is compromised in vivo the proteostasis machinery-chaperones, deaggregases, the proteasome-work to restore proteins to their soluble, functional form or degrade them to maintain the cellular pool of proteins in a quasi-equilibrium state. During the past decade, however, more and more proteins have been identified for which altering only their speed of synthesis alters their structure and function, the efficiency of the down-stream processes they take part in, and cellular phenotype. Indeed, evidence has emerged that evolutionary selection pressures have encoded translation-rate information into mRNA molecules to coordinate diverse co-translational processes. Thus, non-equilibrium physics can play a fundamental role in influencing nascent protein behavior, mRNA sequence evolution, and disease. Here, we discuss how our understanding of this phenomenon is being advanced by the application of theoretical tools from the physical sciences. Copyright © 2018 Elsevier Ltd. All rights reserved.
International Nuclear Information System (INIS)
Nguyen Bich Ha; Nguyen Van Hop
2009-01-01
The Kondo and Fano resonances in the two-point Green's function of the single-level quantum dot were found and investigated in many previous works by means of different numerical calculation methods. In this work we present the derivation of the analytical expressions of resonance terms in the expression of the two-point Green's function. For that purpose the system of Dyson equations for the two-point nonequilibrium Green's functions in the complex-time Keldysh formalism was established in the second order with respect to the tunneling coupling constants and the mean field approximation. This system of Dyson equations was solved exactly and the analytical expressions of the resonance terms are derived. The conditions for the existence of Kondo or Fano resonances are found.
Relativistic dynamics, Green function and pseudodifferential operators
Energy Technology Data Exchange (ETDEWEB)
Cirilo-Lombardo, Diego Julio [National Institute of Plasma Physics (INFIP), Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires 1428 (Argentina); Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation)
2016-06-15
The central role played by pseudodifferential operators in relativistic dynamics is known very well. In this work, operators like the Schrodinger one (e.g., square root) are treated from the point of view of the non-local pseudodifferential Green functions. Starting from the explicit construction of the Green (semigroup) theoretical kernel, a theorem linking the integrability conditions and their dependence on the spacetime dimensions is given. Relativistic wave equations with arbitrary spin and the causality problem are discussed with the algebraic interpretation of the radical operator and their relation with coherent and squeezed states. Also we perform by means of pure theoretical procedures (based in physical concepts and symmetry) the relativistic position operator which satisfies the conditions of integrability: it is a non-local, Lorentz invariant and does not have the same problems as the “local”position operator proposed by Newton and Wigner. Physical examples, as zitterbewegung and rogue waves, are presented and deeply analyzed in this theoretical framework.
Directory of Open Access Journals (Sweden)
Krzysztof Jόzwikowska
2015-06-01
Full Text Available The main goal of this work is to determine a statistical non-equilibrium distribution function for the electron and holes in semiconductor heterostructures in steady-state conditions. Based on the postulates of local equilibrium, as well as on the integral form of the weighted Gyarmati’s variational principle in the force representation, using an alternative method, we have derived general expressions, which have the form of the Fermi–Dirac distribution function with four additional components. The physical interpretation of these components has been carried out in this paper. Some numerical results of a non-equilibrium distribution function for an electron in HgCdTe structures are also presented.
International Nuclear Information System (INIS)
Hoover, W.G.; Evans, D.J.; Hickman, R.B.; Ladd, A.J.C.; Ashurst, W.T.; Moran, B.
1980-01-01
A new Hamiltonian method for deformation simulations is related to the Green-Kubo fluctuation theory through perturbation theory and linear-response theory. Numerical results for the bulk and shear viscosity coefficients are compared to corresponding Green-Kubo calculations. Both viscosity coefficients depend similarly on frequency, in a way consistent with enhanced ''long-time tails.''
Green functions of graphene: An analytic approach
Energy Technology Data Exchange (ETDEWEB)
Lawlor, James A., E-mail: jalawlor@tcd.ie [School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Ferreira, Mauro S. [School of Physics, Trinity College Dublin, Dublin 2 (Ireland); CRANN, Trinity College Dublin, Dublin 2 (Ireland)
2015-04-15
In this article we derive the lattice Green Functions (GFs) of graphene using a Tight Binding Hamiltonian incorporating both first and second nearest neighbour hoppings and allowing for a non-orthogonal electron wavefunction overlap. It is shown how the resulting GFs can be simplified from a double to a single integral form to aid computation, and that when considering off-diagonal GFs in the high symmetry directions of the lattice this single integral can be approximated very accurately by an algebraic expression. By comparing our results to the conventional first nearest neighbour model commonly found in the literature, it is apparent that the extended model leads to a sizeable change in the electronic structure away from the linear regime. As such, this article serves as a blueprint for researchers who wish to examine quantities where these considerations are important.
Fermionic green function and functional determinant in QCD2
International Nuclear Information System (INIS)
Nielsen, N.K.; Rothe, K.D.; Schroer, B.
1979-01-01
We obtain a closed representation for the QCD 2 fermion determinant, euclidean Green functions and induced current in generic external fields. In the absence of zero modes the results are representable as sums over tree diagrams which as we show, can also be obtained from the original Feynman perturbation series via resummation and integration over loop variables. We also investigate the modifications due to the presence of zero modes. (orig.)
International Nuclear Information System (INIS)
Wu, C.-H.; Lee, D.-S.
2005-01-01
We employ the Schwinger-Keldysh formalism to study the nonequilibrium dynamics of the mirror with perfect reflection moving in a quantum field. In the case where the mirror undergoes the small displacement, the coarse-grained effective action is obtained by integrating out the quantum field with the method of influence functional. The semiclassical Langevin equation is derived, and is found to involve two levels of backreaction effects on the dynamics of mirrors: radiation reaction induced by the motion of the mirror and backreaction dissipation arising from fluctuations in quantum field via a fluctuation-dissipation relation. Although the corresponding theorem of fluctuation and dissipation for the case with the small mirror's displacement is of model independence, the study from the first principles derivation shows that the theorem is also independent of the regulators introduced to deal with short-distance divergences from the quantum field. Thus, when the method of regularization is introduced to compute the dissipation and fluctuation effects, this theorem must be fulfilled as the results are obtained by taking the short-distance limit in the end of calculations. The backreaction effects from vacuum fluctuations on moving mirrors are found to be hardly detected while those effects from thermal fluctuations may be detectable
Green's function matching method for adjoining regions having different masses
International Nuclear Information System (INIS)
Morgenstern Horing, Norman J
2006-01-01
We present a primer on the method of Green's function matching for the determination of the global Schroedinger Green's function for all space subject to joining conditions at an interface between two (or more) separate parts of the region having different masses. The object of this technique is to determine the full space Schroedinger Green's function in terms of the individual Green's functions of the constituent parts taken as if they were themselves extended to all space. This analytical method has had successful applications in the theory of surface states, and remains of interest for nanostructures
The green's functions of superconductivity- A review | Imo | Global ...
African Journals Online (AJOL)
We present some basic Green's functions of superconductivity, making emphasis on their geneology and analytic properties. From calculations, we note that the temperature dependence of the Green's functions for fermionic (and bosonic) systems limits and defines the extent of their applications and results. Furthermore ...
Study of Ion Acoustic Wave Damping through Green's Functions
DEFF Research Database (Denmark)
Hsuan, H.C.S.; Jensen, Vagn Orla
1973-01-01
Green's function analyses of ion acoustic waves in streaming plasmas show that, in general, the waves damp algebraically rather than exponentially with distance from exciter.......Green's function analyses of ion acoustic waves in streaming plasmas show that, in general, the waves damp algebraically rather than exponentially with distance from exciter....
Non-equilibrium dynamics of open systems and fluctuation-dissipation theorems
Czech Academy of Sciences Publication Activity Database
Špička, Václav; Velický, B.; Kalvová, Anděla
2017-01-01
Roč. 65, 6-8 (2017), s. 1-23, č. článku 1700032. ISSN 0015-8208 Institutional support: RVO:68378271 Keywords : non-equilibrium * fluctuation-dissipation theorems * non-equilibrium Greens function * transient and steady state magnetic current * molecular bridge Subject RIV: BE - Theoretical Physics OBOR OECD: Atomic, molecular and chemical physics ( physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 2.434, year: 2016
Nonequilibrium quantum field theories
International Nuclear Information System (INIS)
Niemi, A.J.
1988-01-01
Combining the Feynman-Vernon influence functional formalism with the real-time formulation of finite-temperature quantum field theories we present a general approach to relativistic quantum field theories out of thermal equilibrium. We clarify the physical meaning of the additional fields encountered in the real-time formulation of quantum statistics and outline diagrammatic rules for perturbative nonequilibrium computations. We derive a generalization of Boltzmann's equation which gives a complete characterization of relativistic nonequilibrium phenomena. (orig.)
``Green's function'' approach & low-mode asymmetries
Masse, Laurent; Clark, Dan; Salmonson, Jay; MacLaren, Steve; Ma, Tammy; Khan, Shahab; Pino, Jesse; Ralph, Jo; Czajka, C.; Tipton, Robert; Landen, Otto; Kyrala, Georges; 2 Team; 1 Team
2017-10-01
Long wavelength, low mode asymmetries are believed to play a leading role in limiting the performance of current ICF implosions on NIF. These long wavelength modes are initiated and driven by asymmetries in the x-ray flux from the hohlraum; however, the underlying hydrodynamics of the implosion also act to amplify these asymmetries. The work presented here aim to deepen our understanding of the interplay of the drive asymmetries and the underlying implosion hydrodynamics in determining the final imploded configuration. This is accomplished through a synthesis of numerical modeling, analytic theory, and experimental data. In detail, we use a Green's function approach to connect the drive asymmetry seen by the capsule to the measured inflight and hot spot symmetries. The approach has been validated against a suite of numerical simulations. Ultimately, we hope this work will identify additional measurements to further constrain the asymmetries and increase hohlraum illumination design flexibility on the NIF. The technique and derivation of associated error bars will be presented. LLC, (LLNS) Contract No. DE-AC52-07NA27344.
International Nuclear Information System (INIS)
Li Rui; Zhang Jiaxing; Hou Shimin; Qian Zekan; Shen Ziyong; Zhao Xingyu; Xue Zengquan
2007-01-01
We discuss two problems in the conventional approach for studying charge transport in molecular electronic devices that is based on the non-equilibrium Green's function formalism and density functional theory, i.e., the bound states and the numerical integration of the non-equilibrium density matrix. A scheme of filling the bound states in the bias window and a method of patching the non-equilibrium integration are proposed, both of which are referred to as the non-equilibrium correction. The discussion is illustrated by means of calculations on a model system consisting of a 4,4 bipyridine molecule connected to two semi-infinite gold monatomic chains
Functionalized dicationic ionic liquids: Green and efficient ...
Indian Academy of Sciences (India)
have the advantages of liquid and solid phase together.11. Task-specific ionic liquids ... more attention as alternative reaction media in green chemistry than conventional ..... The reaction mixture was divided into two. Figure 3. Reusability of ...
Zeng, Lang; He, Yu; Povolotskyi, Michael; Liu, XiaoYan; Klimeck, Gerhard; Kubis, Tillmann
2013-06-01
In this work, the low rank approximation concept is extended to the non-equilibrium Green's function (NEGF) method to achieve a very efficient approximated algorithm for coherent and incoherent electron transport. This new method is applied to inelastic transport in various semiconductor nanodevices. Detailed benchmarks with exact NEGF solutions show (1) a very good agreement between approximated and exact NEGF results, (2) a significant reduction of the required memory, and (3) a large reduction of the computational time (a factor of speed up as high as 150 times is observed). A non-recursive solution of the inelastic NEGF transport equations of a 1000 nm long resistor on standard hardware illustrates nicely the capability of this new method.
Sourcewise represented green's function of the circular waveguide
International Nuclear Information System (INIS)
Prijmenko, S.D.; Bondarenko, L.A.
2007-01-01
Singular part of the Green's function of unbounded space is singled out in explicit form and contains all singularities, including a delta-shaped singularity. The problem of construction of Green's function for a field is solved, as a problem for diffraction of potential and rotational components electric field intensity of a point current source on the circular waveguide walls. The singling out of the electric field intensity singularity in an explicit form about a source enables to develop an effective algorithm of Green's function calculation at any distance between the source point and observation point in a circular waveguide
The method of images and Green's function for spherical domains
International Nuclear Information System (INIS)
Gutkin, Eugene; Newton, Paul K
2004-01-01
Motivated by problems in electrostatics and vortex dynamics, we develop two general methods for constructing Green's function for simply connected domains on the surface of the unit sphere. We prove a Riemann mapping theorem showing that such domains can be conformally mapped to the upper hemisphere. We then categorize all domains on the sphere for which Green's function can be constructed by an extension of the classical method of images. We illustrate our methods by several examples, such as the upper hemisphere, geodesic triangles, and latitudinal rectangles. We describe the point vortex motion in these domains, which is governed by a Hamiltonian determined by the Dirichlet Green's function
Green's function for anti--de Sitter space gravity
International Nuclear Information System (INIS)
Kleppe, G.
1994-01-01
We solve for the retarded Green's function for linearized gravity in a background with a negative cosmological constant, anti--de Sitter space. In this background, it is possible for a signal to reach spatial infinity in a finite time. Therefore the form of the Green's function depends on a choice of boundary condition at spatial infinity. We take as our condition that a signal which reaches infinity should be lost, not reflected back. We calculate the Green's function associated with this condition, and show that it reproduces the correct classical solution for a point mass at the origin, the anti--de Sitter--Schwarzschild solution
Boundary conditions for quasiclassical Green's function for superfluid Fermi systems
International Nuclear Information System (INIS)
Nagai, K.; Hara, J.
1988-01-01
The authors show that the quasiclassical Green's Function for Fermi liquids can be constructed from the solutions of the Bogoliubov-de Gennes equation within the Andreev approximation and derive self-consistent relations to be satisfied by the quasiclassical Green's function at the surfaces. The so-called normalization condition for the quasiclassical Green's function is obtained from this self-consistent relation. They consider a specularly reflecting wall, a randomly rippled wall, and a proximity boundary as model surfaces. Their boundary condition for the randomly rippled wall is different from that derived by Buchholtz and Rainer and Buchholtz
Green's function and boundary elements of multifield materials
Qin, Qing-Hua
2007-01-01
Green's Function and Boundary Elements of Multifield Materials contains a comprehensive treatment of multifield materials under coupled thermal, magnetic, electric, and mechanical loads. Its easy-to-understand text clarifies some of the most advanced techniques for deriving Green's function and the related boundary element formulation of magnetoelectroelastic materials: Radon transform, potential function approach, Fourier transform. Our hope in preparing this book is to attract interested readers and researchers to a new field that continues to provide fascinating and technologically important challenges. You will benefit from the authors' thorough coverage of general principles for each topic, followed by detailed mathematical derivation and worked examples as well as tables and figures where appropriate. In-depth explanations of the concept of Green's function Coupled thermo-magneto-electro-elastic analysis Detailed mathematical derivation for Green's functions.
Green-Tao theorem in function fields
Le, Thai Hoang
2009-01-01
We adapt the proof of the Green-Tao theorem on arithmetic progressions in primes to the setting of polynomials over a finite field, to show that for every $k$, the irreducible polynomials in $\\mathbf{F}_q[t]$ contain configurations of the form $\\{f+ Pg : \\d(P)
Non-perturbative Green functions in quantum gauge theories
International Nuclear Information System (INIS)
Shabanov, S.V.
1991-01-01
Non-perturbative Green functions for gauge invariant variables are considered. The Green functions are found to be modified as compared with the usual ones in a definite gauge because of a physical configuration space (PCS) reduction. In the Yang-Mills theory with fermions this phenomenon follows from the Singer theorem about the absence of a global gauge condition for the fields tensing to zero at spatial infinity. 20 refs
Green's functions for spin half field theory in Rindler space
International Nuclear Information System (INIS)
Iyer, B.R.; Kumar, Arvind
1977-01-01
The solutions of Dirac equation in different regions of the complete extension of Rindler space are obtained near the event horizons and in the asymptotic limits. Continuity of these solutions across the event horizons is established. The Green's functions are written down in the two casually disconnected regions, continued in the future (F) and past (P) regions using the techniques a la Boulware and a consistent scheme of Green's functions in all regions is exhibited. (author)
Green's functions for spin half field theory in Rindler space
Energy Technology Data Exchange (ETDEWEB)
Iyer, B R; Kumar, Arvind [Birla Inst. of Tech., Ranchi (India). Dept. of Physics
1977-11-01
The solutions of Dirac equation in different regions of the complete extension of Rindler space are obtained near the event horizons and in the asymptotic limits. Continuity of these solutions across the event horizons is established. The Green's functions are written down in the two casually disconnected regions, continued in the future (F) and past (P) regions using the techniques a la Boulware and a consistent scheme of Green's functions in all regions is exhibited.
Directory of Open Access Journals (Sweden)
Hirokazu Takaki
2014-01-01
Full Text Available We present an efficient computation technique for ab-initio electron transport calculations based on density functional theory and the nonequilibrium Green’s function formalism for application to heterostructures with two-dimensional (2D interfaces. The computational load for constructing the Green’s functions, which depends not only on the energy but also on the 2D Bloch wave vector along the interfaces and is thus catastrophically heavy, is circumvented by parallel computational techniques with the message passing interface, which divides the calculations of the Green’s functions with respect to energy and wave vectors. To demonstrate the computational efficiency of the present code, we perform ab-initio electron transport calculations of Al(100-Si(100-Al(100 heterostructures, one of the most typical metal-semiconductor-metal systems, and show their transmission spectra, density of states (DOSs, and dependence on the thickness of the Si layers.
Modeling the NPE with finite sources and empirical Green`s functions
Energy Technology Data Exchange (ETDEWEB)
Hutchings, L.; Kasameyer, P.; Goldstein, P. [Lawrence Livermore National Lab., CA (United States)] [and others
1994-12-31
In order to better understand the source characteristics of both nuclear and chemical explosions for purposes of discrimination, we have modeled the NPE chemical explosion as a finite source and with empirical Green`s functions. Seismograms are synthesized at four sties to test the validity of source models. We use a smaller chemical explosion detonated in the vicinity of the working point to obtain empirical Green`s functions. Empirical Green`s functions contain all the linear information of the geology along the propagation path and recording site, which are identical for chemical or nuclear explosions, and therefore reduce the variability in modeling the source of the larger event. We further constrain the solution to have the overall source duration obtained from point-source deconvolution results. In modeling the source, we consider both an elastic source on a spherical surface and an inelastic expanding spherical volume source. We found that the spherical volume solution provides better fits to observed seismograms. The potential to identify secondary sources was examined, but the resolution is too poor to be definitive.
Acoustic Green's function extraction in the ocean
Zang, Xiaoqin
The acoustic Green's function (GF) is the key to understanding the acoustic properties of ocean environments. With knowledge of the acoustic GF, the physics of sound propagation, such as dispersion, can be analyzed; underwater communication over thousands of miles can be understood; physical properties of the ocean, including ocean temperature, ocean current speed, as well as seafloor bathymetry, can be investigated. Experimental methods of acoustic GF extraction can be categorized as active methods and passive methods. Active methods are based on employment of man-made sound sources. These active methods require less computational complexity and time, but may cause harm to marine mammals. Passive methods cost much less and do not harm marine mammals, but require more theoretical and computational work. Both methods have advantages and disadvantages that should be carefully tailored to fit the need of each specific environment and application. In this dissertation, we study one passive method, the noise interferometry method, and one active method, the inverse filter processing method, to achieve acoustic GF extraction in the ocean. The passive method of noise interferometry makes use of ambient noise to extract an approximation to the acoustic GF. In an environment with a diffusive distribution of sound sources, sound waves that pass through two hydrophones at two locations carry the information of the acoustic GF between these two locations; by listening to the long-term ambient noise signals and cross-correlating the noise data recorded at two locations, the acoustic GF emerges from the noise cross-correlation function (NCF); a coherent stack of many realizations of NCFs yields a good approximation to the acoustic GF between these two locations, with all the deterministic structures clearly exhibited in the waveform. To test the performance of noise interferometry in different types of ocean environments, two field experiments were performed and ambient noise
Adiabatic Hamiltonian deformation, linear response theory, and nonequilibrium molecular dynamics
International Nuclear Information System (INIS)
Hoover, W.G.
1980-01-01
Although Hamiltonians of various kinds have previously been used to derive Green-Kubo relations for the transport coefficients, the particular choice described is uniquely related to thermodynamics. This nonequilibrium Hamiltonian formulation of fluid flow provides pedagogically simple routes to nonequilibrium fluxes and distribution functions, to theoretical understanding of long-time effects, and to new numerical methods for simulating systems far from equilibrium. The same methods are now being applied to solid-phase problems. At the relatively high frequencies used in the viscous fluid calculations described, solids typically behave elastically. Lower frequencies lead to the formation of dislocations and other defects, making it possible to study plastic flow. A property of the nonequilibrium equations of motion which might be profitably explored is their effective irreversibility. Because only a few particles are necessary to generate irreversible behavior, simulations using adiabatic deformations of the kind described here could perhaps elucidate the instability in the equations of motion responsible for irreversibility
Green's function for a generalized two-dimensional fluid.
Iwayama, Takahiro; Watanabe, Takeshi
2010-09-01
A Green's function for a generalized two-dimensional (2D) fluid in an unbounded domain (the so-called α turbulence system) is discussed. The generalized 2D fluid is characterized by a relationship between an advected quantity q and the stream function ψ : namely, q=-(-Δ){α/2}ψ . Here, α is a real number and q is referred to as the vorticity. In this study, the Green's function refers to the stream function produced by a delta-functional distribution of q , i.e., a point vortex with unit strength. The Green's function has the form G{(α)}(r)∝r{α-2} , except when α is an even number, where r is the distance from the point vortex. This functional form is known as the Riesz potential. When α is a positive even number, the logarithmic correction to the Riesz potential has the form G(r){(α)}∝r{α-2} ln r . In contrast, when α is a negative even number, G{(α)} is given by the higher-order Laplacian of the delta function. The transition of the small-scale behavior of q at α=2 , a well-known property of forced and dissipative α turbulence, is explained in terms of the Green's function. Moreover, the azimuthal velocity around the point vortex is derived from the Green's function. The functional form of the azimuthal velocity indicates that physically realizable systems for the generalized 2D fluid exist only when α≤3 . The Green's function and physically realizable systems for an anisotropic generalized 2D fluid are presented as an application of the present study.
Introduction to nonequilibrium statistical mechanics with quantum field theory
International Nuclear Information System (INIS)
Kita, Takafumi
2010-01-01
In this article, we present a concise and self-contained introduction to nonequilibrium statistical mechanics with quantum field theory by considering an ensemble of interacting identical bosons or fermions as an example. Readers are assumed to be familiar with the Matsubara formalism of equilibrium statistical mechanics such as Feynman diagrams, the proper self-energy, and Dyson's equation. The aims are threefold: (1) to explain the fundamentals of nonequilibrium quantum field theory as simple as possible on the basis of the knowledge of the equilibrium counterpart; (2) to elucidate the hierarchy in describing nonequilibrium systems from Dyson's equation on the Keldysh contour to the Navier-Stokes equation in fluid mechanics via quantum transport equations and the Boltzmann equation; (3) to derive an expression of nonequilibrium entropy that evolves with time. In stage (1), we introduce nonequilibrium Green's function and the self-energy uniquely on the round-trip Keldysh contour, thereby avoiding possible confusions that may arise from defining multiple Green's functions at the very beginning. We try to present the Feynman rules for the perturbation expansion as simple as possible. In particular, we focus on the self-consistent perturbation expansion with the Luttinger-Ward thermodynamic functional, i.e., Baym's Φ-derivable approximation, which has a crucial property for nonequilibrium systems of obeying various conservation laws automatically. We also show how the two-particle correlations can be calculated within the Φ-derivable approximation, i.e., an issue of how to handle the 'Bogoliubov-Born-Green-Kirkwood-Yvons (BBGKY) hierarchy'. Aim (2) is performed through successive reductions of relevant variables with the Wigner transformation, the gradient expansion based on the Groenewold-Moyal product, and Enskog's expansion from local equilibrium. This part may be helpful for convincing readers that nonequilibrium systems can be handled microscopically with
Unified double- and single-sided homogeneous Green's function representations
Wapenaar, Kees; van der Neut, Joost; Slob, Evert
2016-06-01
In wave theory, the homogeneous Green's function consists of the impulse response to a point source, minus its time-reversal. It can be represented by a closed boundary integral. In many practical situations, the closed boundary integral needs to be approximated by an open boundary integral because the medium of interest is often accessible from one side only. The inherent approximations are acceptable as long as the effects of multiple scattering are negligible. However, in case of strongly inhomogeneous media, the effects of multiple scattering can be severe. We derive double- and single-sided homogeneous Green's function representations. The single-sided representation applies to situations where the medium can be accessed from one side only. It correctly handles multiple scattering. It employs a focusing function instead of the backward propagating Green's function in the classical (double-sided) representation. When reflection measurements are available at the accessible boundary of the medium, the focusing function can be retrieved from these measurements. Throughout the paper, we use a unified notation which applies to acoustic, quantum-mechanical, electromagnetic and elastodynamic waves. We foresee many interesting applications of the unified single-sided homogeneous Green's function representation in holographic imaging and inverse scattering, time-reversed wave field propagation and interferometric Green's function retrieval.
Yost, Dillon C.; Yao, Yi; Kanai, Yosuke
2017-09-01
In ion irradiation processes, electronic stopping power describes the energy transfer rate from the irradiating ion to the target material's electrons. Due to the scarcity and significant uncertainties in experimental electronic stopping power data for materials beyond simple solids, there has been growing interest in the use of first-principles theory for calculating electronic stopping power. In recent years, advances in high-performance computing have opened the door to fully first-principles nonequilibrium simulations based on real-time time-dependent density functional theory (RT-TDDFT). While it has been demonstrated that the RT-TDDFT approach is capable of predicting electronic stopping power for a wide range of condensed matter systems, there has yet to be an exhaustive examination of the physical and numerical approximations involved and their effects on the calculated stopping power. We discuss the results of such a study for crystalline silicon with protons as irradiating ions. We examine the influences of key approximations in RT-TDDFT nonequilibrium simulations on the calculated electronic stopping power, including approximations related to basis sets, finite size effects, exchange-correlation approximation, pseudopotentials, and more. Finally, we propose a simple and efficient correction scheme to account for the contribution from core-electron excitations to the stopping power, as it was found to be significant for large proton velocities.
First-principles modelling of scanning tunneling microscopy using non-equilibrium Green's functions
DEFF Research Database (Denmark)
Lin, H.P.; Rauba, J.M.C.; Thygesen, Kristian Sommer
2010-01-01
The investigation of electron transport processes in nano-scale architectures plays a crucial role in the development of surface chemistry and nano-technology. Experimentally, an important driving force within this research area has been the concurrent refinements of scanning tunneling microscopy...... into account. As an illustrating example we apply the NEGF-STM method to the Si(001)(2x1):H surface with sub-surface P doping and discuss the results in comparison to the Bardeen and Tersoff-Hamann methods....
DEFF Research Database (Denmark)
Papior, Nick Rübner; Lorente, Nicolás; Frederiksen, Thomas
2017-01-01
“post-processing” code (TBTRANS/PHTRANS) for electron and phonon transport is presented with several novelties such as Hamiltonian interpolations, Ne≥1 electrode capability, bond-currents, generalized interface for user-defined tight-binding transport, transmission projection using eigenstates...
Green's function approach to calculate spin injection in quantum dot
International Nuclear Information System (INIS)
Tan, S.G.; Jalil, M.B.A.; Liew, Thomas; Teo, K.L.
2006-01-01
We present a theoretical model to study spin injection (η) through a quantum dot system sandwiched by two ferromagnetic contacts. The effect of contact magnetization on η was studied using Green's function descriptions of the density of states. Green's function models have the advantages that coherent effects of temperature, electron occupation in the QD, and lead perturbation on the state wave function and hence the current can be formally included in the calculations. In addition, self-consistent treatment of current with applied electrochemical potential or lead conductivity, a necessary step which has not been considered in previous works, has also been implemented in our model
Floquet-Green function formalism for harmonically driven Hamiltonians
International Nuclear Information System (INIS)
Martinez, D F
2003-01-01
A method is proposed for the calculation of the Floquet-Green function of a general Hamiltonian with harmonic time dependence. We use matrix continued fractions to derive an expression for the 'dynamical effective potential' that can be used to calculate the Floquet-Green function of the system. We demonstrate the formalism for the simple case of a space-periodic (in the tight-binding approximation) Hamiltonian with a defect whose on-site energy changes harmonically with time. We study the local density of states for this system and the behaviour of the localized states as a function of the different parameters that characterize the system
The Green's function method for critical heterogeneous slabs
International Nuclear Information System (INIS)
Kornreich, D.E.
1996-01-01
Recently, the Green's Function Method (GFM) has been employed to obtain benchmark-quality results for nuclear engineering and radiative transfer calculations. This was possible because of fast and accurate calculations of the Green's function and the associated Fourier and Laplace transform inversions. Calculations have been provided in one-dimensional slab geometries for both homogeneous and heterogeneous media. A heterogeneous medium is analyzed as a series of homogeneous slabs, and Placzek's lemma is used to extend each slab to infinity. This allows use of the infinite medium Green's function (the anisotropic plane source in an infinite homogeneous medium) in the solution. To this point, a drawback of the GFM has been the limitation to media with c 1; however, mathematical solutions exist which result in oscillating Green's functions. Such calculations are briefly discussing. The limitation to media with c < 1 has been relaxed so that the Green's function may also be calculated for media with c ≥ 1. Thus, materials that contain fissionable isotopes may be modeled
Green function for three-wave coupling problems
International Nuclear Information System (INIS)
Molevich, N E
2001-01-01
The Green function is found for three-wave coupling problems. The function was used for analysis of parametric amplification in dissipative and active media. It is shown that the parametric increment in active media can become exponential. As an example, the nonstationary stimulated scattering of electromagnetic waves by sound and temperatures waves is considered. (nonlinear optical phenomena)
The P(phi)2 Green's functions; asymptotic perturbation expansion
International Nuclear Information System (INIS)
Dimock, J.
1976-01-01
The real time Green's functions in the P(phi) 2 quantum field theory are infinitely differentiable functions of the coupling constant lambda up to and including lamba=0. It follows that the perturbation series are asymptotic as lambda→0 + . (Auth.)
Green close-quote s function method with energy-independent vertex functions
International Nuclear Information System (INIS)
Tsay Tzeng, S.Y.; Kuo, T.T.; Tzeng, Y.; Geyer, H.B.; Navratil, P.
1996-01-01
In conventional Green close-quote s function methods the vertex function Γ is generally energy dependent. However, a model-space Green close-quote s function method where the vertex function is manifestly energy independent can be formulated using energy-independent effective interaction theories based on folded diagrams and/or similarity transformations. This is discussed in general and then illustrated for a 1p1h model-space Green close-quote s function applied to a solvable Lipkin many-fermion model. The poles of the conventional Green close-quote s function are obtained by solving a self-consistent Dyson equation and model space calculations may lead to unphysical poles. For the energy-independent model-space Green close-quote s function only the physical poles of the model problem are reproduced and are in satisfactory agreement with the exact excitation energies. copyright 1996 The American Physical Society
Nonlocal surface plasmons by Poisson Green's function matching
International Nuclear Information System (INIS)
Morgenstern Horing, Norman J
2006-01-01
The Poisson Green's function for all space is derived for the case in which an interface divides space into two separate semi-infinite media, using the Green's function matching method. Each of the separate semi-infinite constituent parts has its own dynamic, nonlocal polarizability, which is taken to be unaffected by the presence of the interface and is represented by the corresponding bulk response property. While this eliminates Friedel oscillatory phenomenology near the interface with p ∼ 2p F , it is nevertheless quite reasonable and useful for a broad range of lower (nonvanishing) wavenumbers, p F . The resulting full-space Poisson Green's function is dynamic, nonlocal and spatially inhomogeneous, and its frequency pole yields the surface plasmon dispersion relation, replete with dynamic and nonlocal features. It also accommodates an ambient magnetic field
Green's function in the color field of a large nucleus
International Nuclear Information System (INIS)
McLerran, L.; Venugopalan, R.
1994-01-01
We compute the Green's function for scalars, fermions, and vectors in the color field associated with the infinite momentum frame wave function of a large nucleus. Expectation values of this wave function can be computed by integrating over random orientations of the valence quark charge density. This relates the Green's functions to correlation functions of a two-dimensional, ultraviolet finite, field theory. We show how one can compute the sea quark distribution functions and explicitly compute them in the kinematic range of transverse momenta, α s 2 μ 2 much-lt k t 2 much-lt μ 2 , where μ 2 is the average color charge squared per unit area. When m quark 2 much-lt μ 2 ∼A 1/3 , the sea quark contribution to the infinite momentum frame wave function saturates at a value that is the same as that for massless sea quarks
Craven, Galen T.; Nitzan, Abraham
2018-01-01
Statistical properties of Brownian motion that arise by analyzing, separately, trajectories over which the system energy increases (upside) or decreases (downside) with respect to a threshold energy level are derived. This selective analysis is applied to examine transport properties of a nonequilibrium Brownian process that is coupled to multiple thermal sources characterized by different temperatures. Distributions, moments, and correlation functions of a free particle that occur during upside and downside events are investigated for energy activation and energy relaxation processes and also for positive and negative energy fluctuations from the average energy. The presented results are sufficiently general and can be applied without modification to the standard Brownian motion. This article focuses on the mathematical basis of this selective analysis. In subsequent articles in this series, we apply this general formalism to processes in which heat transfer between thermal reservoirs is mediated by activated rate processes that take place in a system bridging them.
Quantum-mechanical Green's functions and nonlinear superposition law
International Nuclear Information System (INIS)
Nassar, A.B.; Bassalo, J.M.F.; Antunes Neto, H.S.; Alencar, P. de T.S.
1986-01-01
The quantum-mechanical Green's function is derived for the problem of a time-dependent variable mass particle subject to a time-dependent forced harmonic oscillator potential by taking direct recourse of the corresponding Schroedinger equation. Through the usage of the nonlinear superposition law of Ray and Reid, it is shown that such a Green's function can be obtained from that for the problem of a particle with unit (constant) mass subject to either a forced harmonic potential with constant frequency or only to a time-dependent linear field. (Author) [pt
Quantum-mechanical Green's function and nonlinear superposition law
International Nuclear Information System (INIS)
Nassar, A.B.; Bassalo, J.M.F.; Antunes Neto, H.S.; Alencar, P.T.S.
1986-01-01
It is derived the quantum-mechanical Green's function for the problem of a time-dependent variable mass particle subject to a time-dependent forced harmonic-oscillator potential by taking direct recourse of the corresponding Schroedinger equation. Through the usage of the nonlinear superposition law of Ray and Reid, it is shown that such a Green's function can be obtained from that for the problem of a particle with unit (constant) mass subject to either a forced harmonic potential with constant frequency or only to a time-dependent linear field
A passive inverse filter for Green's function retrieval.
Gallot, Thomas; Catheline, Stefan; Roux, Philippe; Campillo, Michel
2012-01-01
Passive methods for the recovery of Green's functions from ambient noise require strong hypotheses, including isotropic distribution of the noise sources. Very often, this distribution is nonisotropic, which introduces bias in the Green's function reconstruction. To minimize this bias, a spatiotemporal inverse filter is proposed. The method is tested on a directive noise field computed from an experimental active seismic data set. The results indicate that the passive inverse filter allows the manipulation of the spatiotemporal degrees of freedom of a complex wave field, and it can efficiently compensate for the noise wavefield directivity. © 2012 Acoustical Society of America.
Construction of Green's functions for the Black-Scholes equation
Directory of Open Access Journals (Sweden)
Yuri A. Melnikov
2007-11-01
Full Text Available A technique is proposed for the construction of Green's functions for terminal-boundary value problems of the Black-Scholes equation. The technique permits an application to a variety of problems that vary by boundary conditions imposed. This is possible by extension of an approach that was earlier developed for partial differential equations in applied mechanics. The technique is based on the method of integral Laplace transform and the method of variation of parameters. It provides closed form analytic representations for the constructed Green's functions.
Multiloop world-line Green functions from string theory
International Nuclear Information System (INIS)
Roland, K.; Sato, H.T.
1996-01-01
We show how the multiloop bosonic Green function of closed string theory reduces to the world-line Green function as defined by Schmidt and Schubert in the limit where the string world-sheet degenerates into a Φ 3 particle diagram. To obtain this correspondence we have to make an appropriate choice of the local coordinates defined on the degenerate string world sheet. We also present a set of simple rules that specify, in the explicit setting of the Schottky parametrization, which is the corner of moduli space corresponding to a given multiloop Φ 3 diagram. (orig.)
Integral transform techniques for Green's function
Watanabe, Kazumi
2015-01-01
This book describes mathematical techniques for integral transforms in a detailed but concise manner. The techniques are subsequently applied to the standard partial differential equations, such as the Laplace equation, the wave equation and elasticity equations. Green’s functions for beams, plates and acoustic media are also shown, along with their mathematical derivations. The Cagniard-de Hoop method for double inversion is described in detail, and 2D and 3D elastodynamic problems are treated in full. This new edition explains in detail how to introduce the branch cut for the multi-valued square root function. Further, an exact closed form Green’s function for torsional waves is presented, as well as an application technique of the complex integral, which includes the square root function and an application technique of the complex integral.
International Nuclear Information System (INIS)
Maes, Christian
2012-01-01
In contrast to the quite unique entropy concept useful for systems in (local) thermodynamic equilibrium, there is a variety of quite distinct nonequilibrium entropies, reflecting different physical points. We disentangle these entropies as they relate to heat, fluctuations, response, time asymmetry, variational principles, monotonicity, volume contraction or statistical forces. However, not all of those extensions yield state quantities as understood thermodynamically. At the end we sketch how aspects of dynamical activity can take over for obtaining an extended Clausius relation.
Plant functional traits predict green roof ecosystem services.
Lundholm, Jeremy; Tran, Stephanie; Gebert, Luke
2015-02-17
Plants make important contributions to the services provided by engineered ecosystems such as green roofs. Ecologists use plant species traits as generic predictors of geographical distribution, interactions with other species, and ecosystem functioning, but this approach has been little used to optimize engineered ecosystems. Four plant species traits (height, individual leaf area, specific leaf area, and leaf dry matter content) were evaluated as predictors of ecosystem properties and services in a modular green roof system planted with 21 species. Six indicators of ecosystem services, incorporating thermal, hydrological, water quality, and carbon sequestration functions, were predicted by the four plant traits directly or indirectly via their effects on aggregate ecosystem properties, including canopy density and albedo. Species average height and specific leaf area were the most useful traits, predicting several services via effects on canopy density or growth rate. This study demonstrates that easily measured plant traits can be used to select species to optimize green roof performance across multiple key services.
On toroidal Green close-quote s functions
International Nuclear Information System (INIS)
Bates, J.W.
1997-01-01
Green close-quote s functions are valuable analytical tools for solving a myriad of boundary-value problems in mathematical physics. Here, Green close-quote s functions of the Laplacian and biharmonic operators are derived for a three-dimensional toroidal domain. In some sense, the former result may be regarded as open-quotes standard,close quotes but the latter is most certainly not. It is shown that both functions can be constructed to have zero value on a specified toroidal surface with a circular cross section. Additionally, the Green close-quote s function of the biharmonic operator may be chosen to have the property that its normal derivative also vanishes there. A open-quotes torsionalclose quotes Green close-quote s function is derived for each operator which is useful in solving some boundary-value problems involving axisymmetric vector equations. Using this approach, the magnetic vector potential of a wire loop is computed as a simple example. copyright 1997 American Institute of Physics
Green's functions for off-shell electromagnetism and spacelike correlations
International Nuclear Information System (INIS)
Land, M.C.; Horwitz, L.P.
1991-01-01
The requirement of gauge invariance for the Schwinger-DeWitt equations, interpreted as a manifestly covariant quantum theory for the evolution of a system in spacetime, implies the existence of a five-dimensional pre-Maxwell field on the manifold of spacetime and proper time τ. The Maxwell theory is contained in this theory; integration of the field equations over τ restores the Maxwell equations with the usual interpretation of the sources. Following Schwinger's techniques, the authors study the Green's functions for the five dimensional hyperbolic field equations for both signatures ± [corresponding to O(4, 1) or O(3, 2) symmetry of the field equations] of the proper time derivative. The classification of the Green's functions follows that of the four-dimensional theory for massive fields, for which the mass squared may be positive or negative, respectively. The Green's function for the five-dimensional field are then given by the Fourier transform over the mass parameter. They derive the Green's functions corresponding to the principal part Δ P and the homogeneous function Δ t ; all of the Green's functions can be expressed in terms of these, as for the usual field equations with definite mass. In the O(3, 2) case, the principal part function has support for x 2 ≥ τ 2 , corresponding to spacelike propagation, as well as along the light cone X 2 = 0 (for τ = 0). There can be no transmission of information in spacelike directions, with this propagator, since the Maxwell field, obtained by integration over τ, does not contain this component of the support. Measurements are characterized by such an integration. The spacelike field therefore can dynamically establish spacelike correlations
Nonlinear and Nonequilibrium Spin Injection in Magnetic Tunneling Junctions
Guo, Hong
2007-03-01
Quantitative analysis of charge and spin quantum transport in spintronic devices requires an atomistic first principles approach that can handle nonlinear and nonequilibrium transport conditions. We have developed an approach for this purpose based on real space density functional theory (DFT) carried out within the Keldysh nonequilibrium Green's function formalism (NEGF). We report theoretical analysis of nonlinear and nonequilibrium spin injection and quantum transport in Fe/MgO/Fe trilayer structures as a function of external bias voltage. Devices with well relaxed atomic structures and with FeO oxidization layers are investigated as a function of external bias voltage. We also report calculations of nonequilibrium spin injection into molecular layers and graphene. Comparisons to experimental data will be presented. Work in collaborations with: Derek Waldron, Vladimir Timochevski (McGill University); Ke Xia (Institute of Physics, Chinese Academy of Science, Beijing, China); Eric Zhu, Jian Wang (University of Hong Kong); Paul Haney, and Allan MacDonald (University of Texas at Austin).
Green-function description of dense polymeric systems
Schoot, van der P.P.A.M.
2000-01-01
A self-consistent Green-function description of concentrated polymer solutions and dense polymeric melts is presented. The method, which applies to both uniform and nonuniform systems, is used in this work to calculate the static structure factor of a homogeneous fluid of Gaussian model chains.
Mass corrections to Green functions in instanton vacuum model
International Nuclear Information System (INIS)
Esaibegyan, S.V.; Tamaryan, S.N.
1987-01-01
The first nonvanishing mass corrections to the effective Green functions are calculated in the model of instanton-based vacuum consisting of a superposition of instanton-antiinstanton fluctuations. The meson current correlators are calculated with account of these corrections; the mass spectrum of pseudoscalar octet as well as the value of the kaon axial constant are found. 7 refs
Existence of Green's functions in perturbative Q.E.D
International Nuclear Information System (INIS)
Seneor, R.
1976-01-01
A report is made on some work done in collaboration with P. Blanchard which shows how, in the framework developped by H.Epstein and V.Glaser, one can prove the existence of Green's functions in quantum electrodynamics (Q.E.D.). The proof can be extended, in principle, to any theory involving massive and non massive particles. (Auth.)
Green function of a three-dimensional Wick problem
International Nuclear Information System (INIS)
Matveev, V.A.
1988-01-01
An exact solution of a three-dimensional Coulomb Wick-Cutkovsky problem has been obtained which possesses the hidden 0(4)-symmetry. Here we shell give the derivation of the corresponding Green function and consider its connection with the asymptoric behaviour of the scattering amplitude. 9 refs
On the infrared behaviour of Yang-Mills Greens functions
International Nuclear Information System (INIS)
Olesen, P.
1976-01-01
Making certain assumptions (valid to any finite order of perturbation theory), it is shown that non-perturbatively pure Yang-Mills Greens functions are power behaved in the momenta in a limit related to the infrared limit. It is also shown that the fundamental vertices have a more singular behaviour than indicated by perturbation theory. (Auth.)
Asymptotic Green's function in homogeneous anisotropic viscoelastic media
Czech Academy of Sciences Publication Activity Database
Vavryčuk, Václav
2007-01-01
Roč. 463, č. 2086 (2007), s. 2689-2707 ISSN 1364-5021 Institutional research plan: CEZ:AV0Z30120515 Keywords : anisotropy * attenuation * Green's function * viscoelasticity Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.523, year: 2007
Relativistic Green function for atomic and molecular systems
Energy Technology Data Exchange (ETDEWEB)
Gruzdev, P.F.; Sherstyuk, A.I.
1981-12-01
The problem on Green function construction of Dirac equation is solved for a wide class of single electron potentials in the atom and molecule theory. The solution is obtained in the form of a spectrum analysis according to the total system of eigenfuctions of the generalized Dirac problem for eigenvalues. The problem possesses a purely discrete spectrum.
Patched Green's function techniques for two-dimensional systems
DEFF Research Database (Denmark)
Settnes, Mikkel; Power, Stephen; Lin, Jun
2015-01-01
We present a numerically efficient technique to evaluate the Green's function for extended two-dimensional systems without relying on periodic boundary conditions. Different regions of interest, or “patches,” are connected using self-energy terms which encode the information of the extended parts...
Green function and scattering amplitudes in many dimensional space
International Nuclear Information System (INIS)
Fabre de la Ripelle, M.
1991-06-01
Methods for solving scattering are studied in many dimensional space. Green function and scattering amplitudes are given in terms of the requested asymptotic behaviour of the wave function. The Born approximation and the optical theorem are derived in many dimensional space. Phase-shift analysis are developed for hypercentral potentials and for non-hypercentral potentials with the hyperspherical adiabatic approximation. (author) 16 refs., 3 figs
Applications of Green's functions in science and engineering
Greenberg, Michael D
2015-01-01
Concise and highly regarded, this treatment of Green's functions and their applications in science and engineering is geared toward undergraduate and graduate students with only a moderate background in ordinary differential equations and partial differential equations. The text also includes a wealth of information of a more general nature on boundary value problems, generalized functions, eigenfunction expansions, partial differential equations, and acoustics. The two-part treatment begins with an overview of applications to ordinary differential equations. Topics include the adjoint operato
Green functions and scattering amplitudes in many-dimensional space
International Nuclear Information System (INIS)
Fabre de la Ripelle, M.
1993-01-01
Methods for solving scattering are studied in many-dimensional space. Green function and scattering amplitudes are given in terms of the required asymptotic behaviour of the wave function. The Born approximation and the optical theorem are derived in many-dimensional space. Phase-shift analyses are performed for hypercentral potentials and for non-hypercentral potentials by use of the hyperspherical adiabatic approximation. (author)
DEFF Research Database (Denmark)
Chen, Jingzhe; Thygesen, Kristian S.; Jacobsen, Karsten W.
2012-01-01
We present an efficient implementation of a nonequilibrium Green's function method for self-consistent calculations of electron transport and forces in nanostructured materials. The electronic structure is described at the level of density functional theory using the projector augmented wave method...... over k points and real space makes the code highly efficient and applicable to systems containing several hundreds of atoms. The method is applied to a number of different systems, demonstrating the effects of bias and gate voltages, multiterminal setups, nonequilibrium forces, and spin transport....
Green's theorem and Green's functions for the steady-state cosmic-ray equation of transport
International Nuclear Information System (INIS)
Webb, G.M.; Gleeson, L.J.
1977-01-01
Green's Theorem is developed for the spherically-symmetric steady-state cosmic-ray equation of transport in interplanetary space. By means of it the momentum distribution function F 0 (r,p), (r=heliocentric distance, p=momentum) can be determined in a region rsub(a) 0 . Examples of Green's functions are given for the case rsub(a)=0, rsub(b)=infinity and derived for the cases of finite rsub(a) and rsub(b). The diffusion coefficient kappa is assumed of the form kappa=kappa 0 (p)rsup(b). The treatment systematizes the development of all analytic solutions for steady-state solar and galactic cosmic-ray propagation and previous solutions form a subset of the present solutions. (Auth.)
Paraxial Green's functions in synchrotron radiation theory
International Nuclear Information System (INIS)
Geloni, G.; Saldin, E.; Scheidmiller, E.; Yurkov, M.
2005-02-01
This work contains a systematic treatment of single particle synchrotron radiation and some application to realistic beams with given cross section area, divergence and energy spread. Standard theory relies on several approximations whose applicability limits and accuracy are often forgotten. We begin remarking that on the one hand, a paraxial approximation can always be applied without loss of generality and with ultra relativistic accuracy. On the other hand, dominance of the acceleration field over the velocity part in the Lienard-Wiechert expressions is not always guaranteed and constitutes a separate assumption, whose applicability is discussed. Treating synchrotron radiation in paraxial approximation we derive the equation for the slow varying envelope function of the Fourier components of the electric field vector. Calculations of Synchrotron Radiation properties performed by others showed that the phase of the Fourier components of the electric field vector differs from the phase of a virtual point source. In this paper we present a systematic, analytical description of this phase shift, calculating amplitude and phase of electric field from bending magnets, short magnets, two bending magnet system separated by a straight section (edge radiation) and undulator devices. We pay particular attention to region of applicability and accuracy of approximations used. Finally, taking advantage of results of analytical calculation presented in reduced form we analyze various features of radiation from a complex insertion device (set of two undulators with a focusing triplet in between) accounting for the influence of energy spread and electron beam emittance. (orig.)
Zhou, Chenyi; Guo, Hong
2017-01-01
We report a diagrammatic method to solve the general problem of calculating configurationally averaged Green's function correlators that appear in quantum transport theory for nanostructures containing disorder. The theory treats both equilibrium and nonequilibrium quantum statistics on an equal footing. Since random impurity scattering is a problem that cannot be solved exactly in a perturbative approach, we combine our diagrammatic method with the coherent potential approximation (CPA) so that a reliable closed-form solution can be obtained. Our theory not only ensures the internal consistency of the diagrams derived at different levels of the correlators but also satisfies a set of Ward-like identities that corroborate the conserving consistency of transport calculations within the formalism. The theory is applied to calculate the quantum transport properties such as average ac conductance and transmission moments of a disordered tight-binding model, and results are numerically verified to high precision by comparing to the exact solutions obtained from enumerating all possible disorder configurations. Our formalism can be employed to predict transport properties of a wide variety of physical systems where disorder scattering is important.
Green`s function of Maxwell`s equations and corresponding implications for iterative methods
Energy Technology Data Exchange (ETDEWEB)
Singer, B.S. [Macquarie Univ., Sydney (Australia); Fainberg, E.B. [Inst. of Physics of the Earth, Moscow (Russian Federation)
1996-12-31
Energy conservation law imposes constraints on the norm and direction of the Hilbert space vector representing a solution of Maxwell`s equations. In this paper, we derive these constrains and discuss the corresponding implications for the Green`s function of Maxwell`s equations in a dissipative medium. It is shown that Maxwell`s equations can be reduced to an integral equation with a contracting kernel. The equation can be solved using simple iterations. Software based on this algorithm have successfully been applied to a wide range of problems dealing with high contrast models. The matrix corresponding to the integral equation has a well defined spectrum. The equation can be symmetrized and solved using different approaches, for instance one of the conjugate gradient methods.
Water hammer prediction and control: the Green's function method
Xuan, Li-Jun; Mao, Feng; Wu, Jie-Zhi
2012-04-01
By Green's function method we show that the water hammer (WH) can be analytically predicted for both laminar and turbulent flows (for the latter, with an eddy viscosity depending solely on the space coordinates), and thus its hazardous effect can be rationally controlled and minimized. To this end, we generalize a laminar water hammer equation of Wang et al. (J. Hydrodynamics, B2, 51, 1995) to include arbitrary initial condition and variable viscosity, and obtain its solution by Green's function method. The predicted characteristic WH behaviors by the solutions are in excellent agreement with both direct numerical simulation of the original governing equations and, by adjusting the eddy viscosity coefficient, experimentally measured turbulent flow data. Optimal WH control principle is thereby constructed and demonstrated.
Green's function method for perturbed Korteweg-de Vries equation
International Nuclear Information System (INIS)
Cai Hao; Huang Nianning
2003-01-01
The x-derivatives of squared Jost solution are the eigenfunctions with the zero eigenvalue of the linearized equation derived from the perturbed Korteweg-de Vries equation. A method similar to Green's function formalism is introduced to show the completeness of the squared Jost solutions in multi-soliton cases. It is not related to Lax equations directly, and thus it is beneficial to deal with the nonlinear equations with complicated Lax pair
Green function formalism for nonlinear acoustic waves in layered media
International Nuclear Information System (INIS)
Lobo, A.; Tsoy, E.; De Sterke, C.M.
2000-01-01
Full text: The applications of acoustic waves in identifying defects in adhesive bonds between metallic plates have received little attention at high intensities where the media respond nonlinearly. However, the effects of reduced bond strength are more distinct in the nonlinear response of the structure. Here we assume a weak nonlinearity acting as a small perturbation, thereby reducing the problem to a linear one. This enables us to develop a specialized Green function formalism for calculating acoustic fields in layered media
Green's function for the scalar field in the early Universe
International Nuclear Information System (INIS)
Chowdhury, A.; Mallik, S.
1987-01-01
We derive the thermal Green's function for the scalar field in a de Sitter space-time and apply it to the problem of the early Universe. Field fluctuations relevant for inflation arise predominantly from wavelengths of the order of the inverse Hubble constant. Sufficient inflation is obtained in a Coleman-Weinberg model, provided the coupling constant is small enough. The results are insensitive to the choice of the vacuum of the field theory
International Nuclear Information System (INIS)
Caetano Neto, E.S.
1976-01-01
A stationary Green function is calculated for the Schroedinger Hamiltonian of the multidimensional isotropic harmonic oscillator and for physical systems, which may, somehow, have their Hamiltonian reduced to one in the form of a harmonic oscillator, for any dimension [pt
Preequilibrium decay models and the quantum Green function method
International Nuclear Information System (INIS)
Zhivopistsev, F.A.; Rzhevskij, E.S.; Gosudarstvennyj Komitet po Ispol'zovaniyu Atomnoj Ehnergii SSSR, Moscow. Inst. Teoreticheskoj i Ehksperimental'noj Fiziki)
1977-01-01
The nuclear process mechanism and preequilibrium decay involving complex particles are expounded on the basis of the Green function formalism without the weak interaction assumptions. The Green function method is generalized to a general nuclear reaction: A+α → B+β+γ+...rho, where A is the target nucleus, α is a complex particle in the initial state, B is the final nucleus, and β, γ, ... rho are nuclear fragments in the final state. The relationship between the generalized Green function and Ssub(fi)-matrix is established. The resultant equations account for: 1) direct and quasi-direct processes responsible for the angular distribution asymmetry of the preequilibrium component; 2) the appearance of addends corresponding to the excitation of complex states of final nucleus; and 3) the relationship between the preequilibrium decay model and the general models of nuclear reaction theories (Lippman-Schwinger formalism). The formulation of preequilibrium emission via the S(T) matrix allows to account for all the differential terms in succession important to an investigation of the angular distribution assymetry of emitted particles
Thermodynamical and Green function many-body Wick theorems
International Nuclear Information System (INIS)
Westwanski, B.
1987-01-01
The thermodynamical and Green function many-body reduction theorems of Wick type are proved for the arbitrary mixtures of the fermion, boson and spin systems. ''Many-body'' means that the operators used are the products of the arbitrary number of one-body standard basis operators [of the fermion or (and) spin types] with different site (wave vector) indices, but having the same ''time'' (in the interaction representation). The method of proving is based on'' 1) the first-order differential equation of Schwinger type for: 1a) anti T-product of operators; 1b) its average value; 2) KMS boundary conditions for this average. It is shown that the fermion, boson and spin systems can be unified in the many-body formulation (bosonification of the fermion systems). It is impossible in the one-body approach. Both of the many-body versions of the Wick theorem have the recurrent feature: nth order moment diagrams for the free energy or Green functions can be expressed by the (n-1)th order ones. This property corresponds to the automatic realization of: (i) summations over Bose-Einstein or (and) Fermi-Dirac frequencies; (ii) elimination of Bose-Einstein or (and) Fermi-Dirac distributions. The procedures (i) and (ii), being the results of using the Green function one-body reduction theorem, have constituted the significant difficulty up to now in the treatment of quantum systems. (orig.)
How to use retarded Green's functions in de Sitter spacetime
International Nuclear Information System (INIS)
Higuchi, Atsushi; Cheong, Lee Yen
2008-01-01
We demonstrate in examples that the covariant retarded Green's functions in electromagnetism and linearized gravity work as expected in de Sitter spacetime. We first clarify how retarded Green's functions should be used in spacetimes with spacelike past infinity such as de Sitter spacetime. In particular, we remind the reader of a general formula which gives the field for given initial data on a Cauchy surface and a given source (a charge or stress-energy tensor distribution) in its future. We then apply this formula to three examples: (i) electromagnetism in the future of a Cauchy surface in Minkowski spacetime, (ii) electromagnetism in de Sitter spacetime, and (iii) linearized gravity in de Sitter spacetime. In each example the field is reproduced correctly as predicted by the general argument. In the third example we construct a linearized gravitational field from two equal point masses located at the 'North and South Poles' which is nonsingular on the cosmological horizon and satisfies a covariant gauge condition and show that this field is reproduced by the retarded Green's function with corresponding gauge parameters.
Kinetic equations within the formalism of non-equilibrium thermo field dynamics
International Nuclear Information System (INIS)
Arimitsu, Toshihico
1988-01-01
After reviewing the real-time formalism of dissipative quantum field theory, i.e. non-equilibrium thermo field dynamics (NETFD), a kinetic equation, a self-consistent equation for the dissipation coefficient and a ''mass'' or ''chemical potential'' renormalization equation for non-equilibrium transient situations are extracted out of the two-point Green's function of the Heisenberg field, in their most general forms upon the basic requirements of NETFD. The formulation is applied to the electron-phonon system, as an example, where the gradient expansion and the quasi-particle approximation are performed. The formalism of NETFD is reinvestigated in connection with the kinetic equations. (orig.)
QCD Green's Functions and Phases of Strongly-Interacting Matter
Directory of Open Access Journals (Sweden)
Schaefer B.J.
2011-04-01
Full Text Available After presenting a brief summary of functional approaches to QCD at vanishing temperatures and densities the application of QCD Green's functions at non-vanishing temperature and vanishing density is discussed. It is pointed out in which way the infrared behavior of the gluon propagator reflects the (de-confinement transition. Numerical results for the quark propagator are given thereby verifying the relation between (de--confinement and dynamical chiral symmetry breaking (restoration. Last but not least some results of Dyson-Schwinger equations for the color-superconducting phase at large densities are shown.
Green function simulation of Hamiltonian lattice models with stochastic reconfiguration
International Nuclear Information System (INIS)
Beccaria, M.
2000-01-01
We apply a recently proposed Green function Monte Carlo procedure to the study of Hamiltonian lattice gauge theories. This class of algorithms computes quantum vacuum expectation values by averaging over a set of suitable weighted random walkers. By means of a procedure called stochastic reconfiguration the long standing problem of keeping fixed the walker population without a priori knowledge of the ground state is completely solved. In the U(1) 2 model, which we choose as our theoretical laboratory, we evaluate the mean plaquette and the vacuum energy per plaquette. We find good agreement with previous works using model-dependent guiding functions for the random walkers. (orig.)
Green polymer chemistry: enzyme catalysis for polymer functionalization.
Sen, Sanghamitra; Puskas, Judit E
2015-05-21
Enzyme catalyzed reactions are green alternative approaches to functionalize polymers compared to conventional methods. This technique is especially advantageous due to the high selectivity, high efficiency, milder reaction conditions, and recyclability of enzymes. Selected reactions can be conducted under solventless conditions without the application of metal catalysts. Hence this process is becoming more recognized in the arena of biomedical applications, as the toxicity created by solvents and metal catalyst residues can be completely avoided. In this review we will discuss fundamental aspects of chemical reactions biocatalyzed by Candida antarctica lipase B, and their application to create new functionalized polymers, including the regio- and chemoselectivity of the reactions.
Green Polymer Chemistry: Enzyme Catalysis for Polymer Functionalization
Directory of Open Access Journals (Sweden)
Sanghamitra Sen
2015-05-01
Full Text Available Enzyme catalyzed reactions are green alternative approaches to functionalize polymers compared to conventional methods. This technique is especially advantageous due to the high selectivity, high efficiency, milder reaction conditions, and recyclability of enzymes. Selected reactions can be conducted under solventless conditions without the application of metal catalysts. Hence this process is becoming more recognized in the arena of biomedical applications, as the toxicity created by solvents and metal catalyst residues can be completely avoided. In this review we will discuss fundamental aspects of chemical reactions biocatalyzed by Candida antarctica lipase B, and their application to create new functionalized polymers, including the regio- and chemoselectivity of the reactions.
A hybrid method for the parallel computation of Green's functions
DEFF Research Database (Denmark)
Petersen, Dan Erik; Li, Song; Stokbro, Kurt
2009-01-01
of the large number of times this calculation needs to be performed, this is computationally very expensive even on supercomputers. The classical approach is based on recurrence formulas which cannot be efficiently parallelized. This practically prevents the solution of large problems with hundreds...... of thousands of atoms. We propose new recurrences for a general class of sparse matrices to calculate Green's and lesser Green's function matrices which extend formulas derived by Takahashi and others. We show that these recurrences may lead to a dramatically reduced computational cost because they only...... require computing a small number of entries of the inverse matrix. Then. we propose a parallelization strategy for block tridiagonal matrices which involves a combination of Schur complement calculations and cyclic reduction. It achieves good scalability even on problems of modest size....
The statistical error of Green's function Monte Carlo
International Nuclear Information System (INIS)
Ceperley, D.M.
1986-01-01
The statistical error in the ground state energy as calculated by Green's Function Monte Carlo (GFMC) is analyzed and a simple approximate formula is derived which relates the error to the number of steps of the random walk, the variational energy of the trial function, and the time step of the random walk. Using this formula it is argued that as the thermodynamic limit is approached with N identical molecules, the computer time needed to reach a given error per molecule increases as N/sup n/ where 0.5 < b < 1.5 and as the nuclear charge Z of a system is increased the computer time necessary to reach a given error grows as Z/sup 5.5/. Thus GFMC simulations will be most useful for calculating the properties of low Z elements. The implications for choosing the optimal trial function from a series of trial functions is also discussed
Non-equilibrium scalar two point functions in AdS/CFT
International Nuclear Information System (INIS)
Keränen, Ville; Kleinert, Philipp
2015-01-01
In the first part of the paper, we discuss different versions of the AdS/CFT dictionary out of equilibrium. We show that the Skenderis-van Rees prescription and the “extrapolate” dictionary are equivalent at the level of “in-in” two point functions of free scalar fields in arbitrary asymptotically AdS spacetimes. In the second part of the paper, we calculate two point correlation functions in dynamical spacetimes using the “extrapolate” dictionary. These calculations are performed for conformally coupled scalar fields in examples of spacetimes undergoing gravitational collapse, the AdS 2 -Vaidya spacetime and the AdS 3 -Vaidya spacetime, which allow us to address the problem of thermalization following a quench in the boundary field theory. The computation of the correlators is formulated as an initial value problem in the bulk spacetime. Finally, we compare our results for AdS 3 -Vaidya to results in the previous literature obtained using the geodesic approximation and we find qualitative agreement.
Non-equilibrium scalar two point functions in AdS/CFT
Energy Technology Data Exchange (ETDEWEB)
Keränen, Ville [Rudolf Peierls Centre for Theoretical Physics, University of Oxford,1 Keble Road, Oxford OX1 3NP (United Kingdom); Kleinert, Philipp [Rudolf Peierls Centre for Theoretical Physics, University of Oxford,1 Keble Road, Oxford OX1 3NP (United Kingdom); Merton College, University of Oxford,Merton Street, Oxford OX1 4JD (United Kingdom)
2015-04-22
In the first part of the paper, we discuss different versions of the AdS/CFT dictionary out of equilibrium. We show that the Skenderis-van Rees prescription and the “extrapolate” dictionary are equivalent at the level of “in-in” two point functions of free scalar fields in arbitrary asymptotically AdS spacetimes. In the second part of the paper, we calculate two point correlation functions in dynamical spacetimes using the “extrapolate” dictionary. These calculations are performed for conformally coupled scalar fields in examples of spacetimes undergoing gravitational collapse, the AdS{sub 2}-Vaidya spacetime and the AdS{sub 3}-Vaidya spacetime, which allow us to address the problem of thermalization following a quench in the boundary field theory. The computation of the correlators is formulated as an initial value problem in the bulk spacetime. Finally, we compare our results for AdS{sub 3}-Vaidya to results in the previous literature obtained using the geodesic approximation and we find qualitative agreement.
Supersymmetric electroweak baryogenesis, nonequilibrium field theory and quantum Boltzmann equations
Riotto, Antonio
1998-01-01
The closed time-path (CPT) formalism is a powerful Green's function formulation to describe nonequilibrium phenomena in field theory and it leads to a complete nonequilibrium quantum kinetic theory. In this paper we make use of the CPT formalism to write down a set of quantum Boltzmann equations describing the local number density asymmetries of the particles involved in supersymmetric electroweak baryogenesis. These diffusion equations automatically and self-consistently incorporate the CP-violating sources which fuel baryogenesis when transport properties allow the CP-violating charges to diffuse in front of the bubble wall separating the broken from the unbroken phase at the electroweak phase transition. This is a significant improvement with respect to recent approaches where the CP-violating sources are inserted by hand into the diffusion equations. Furthermore, the CP-violating sources and the particle number changing interactions manifest ``memory'' effects which are typical of the quantum transp ort t...
Green function of the model two-centre quantum-mechanical problem
International Nuclear Information System (INIS)
Khoma, M.V.; Lazur, V.Yu.
2002-01-01
The expansions of a Green function for the Simmons molecular potential (SMP) in terms of spheroidal function are built. The solutions of degenerate hypergeometric equation are used as basis function system while expanding regular and irregular model spheroidal functions into series. Rather simple three-terms recurrence relations are obtained for the coefficients of these expansions. Much attentions is given to different asymptotic representation as well as Sturmian expansions of the Green function of the two-centre SMP wave functions. In all cases considered the Green function is reduced to the form similar to the Hostler's representation of the Coulomb Green function
Linking Equilibrium and Nonequilibrium Dynamics in Glass-Forming Systems
DEFF Research Database (Denmark)
Mauro, John C.; Guo, Xiaoju; Smedskjær, Morten Mattrup
, we show that the nonequilibrium glassy dynamics are intimately connected with the equilibrium liquid dynamics. This is accomplished by deriving a new functional form for the thermal history dependence of nonequilibrium viscosity, which is validated against experimental measurements of industrial...
Green's functions in quantum chemistry - I. The Σ perturbation method
International Nuclear Information System (INIS)
Sebastian, K.L.
1978-01-01
As an improvement over the Hartree-Fock approximation, a Green's Function method - the Σ perturbation method - is investigated for molecular calculations. The method is applied to the hydrogen molecule and to the π-electron system of ethylene under PPP approximation. It is found that when the algebraic approximation is used, the energy obtained is better than that of the HF approach, but is not as good as that of the configuration-interaction method. The main advantage of this procedure is that it is devoid of the most serious defect of HF method, viz. incorrect dissociation limits. (K.B.)
Inverse electronic scattering by Green's functions and singular values decomposition
International Nuclear Information System (INIS)
Mayer, A.; Vigneron, J.-P.
2000-01-01
An inverse scattering technique is developed to enable a sample reconstruction from the diffraction figures obtained by electronic projection microscopy. In its Green's functions formulation, this technique takes account of all orders of diffraction by performing an iterative reconstruction of the wave function on the observation screen. This scattered wave function is then backpropagated to the sample to determine the potential-energy distribution, which is assumed real valued. The method relies on the use of singular values decomposition techniques, thus providing the best least-squares solutions and enabling a reduction of noise. The technique is applied to the analysis of a two-dimensional nanometric sample that is observed in Fresnel conditions with an electronic energy of 25 eV. The algorithm turns out to provide results with a mean relative error of the order of 5% and to be very stable against random noise
Green functions for an electron in an external electromagnetic field
International Nuclear Information System (INIS)
Khokhlov, I.A.
1982-01-01
New representations permitting to considerably simplify their calculation have been obtained for the Green functions of electron. These representations are based on an idea, used in the quantum electrodynamics formulation in variables of a zero plane, of writing down the Dirac field operator psi through its part psisub((-)). It is shown that T product of psi and psi + operators can be expressed through T product of their parts psisub((-)) and psisub((-))sup(+). At that, if the anticommutator of the operators psisub((-)) and psisub((-))sup(+) satisfies the initial condition, the operations of the chronological ordering of the operator product psi(-) and psisub((-))sup(+) with respect to variable x 0 and variable u 0 playing a part of time in the formulation of the zero plane (Pu 0 product) coincide. In correspondence with this fact all the Green functions of electron can be expressed depending on the convenience of concrete calculations through vacuum averages of either from T product or from Pu 0 product of psisub((-)) and psisub((-))sup(+) operators only [ru
Functional-derivative study of the Hubbard model. III. Fully renormalized Green's function
International Nuclear Information System (INIS)
Arai, T.; Cohen, M.H.
1980-01-01
The functional-derivative method of calculating the Green's function developed earlier for the Hubbard model is generalized and used to obtain a fully renormalized solution. Higher-order functional derivatives operating on the basic Green's functions, G and GAMMA, are all evaluated explicitly, thus making the solution applicable to the narrow-band region as well as the wide-band region. Correction terms Phi generated from functional derivatives of equal-time Green's functions of the type delta/sup n/ /deltaepsilon/sup n/, etc., with n > or = 2. It is found that the Phi's are, in fact, renormalization factors involved in the self-energy Σ and that the structure of the Phi's resembles that of Σ and contains the same renormalization factors Phi. The renormalization factors Phi are shown to satisfy a set of equations and can be evaluated self-consistently. In the presence of the Phi's, all difficulties found in the previous results (papers I and II) are removed, and the energy spectrum ω can now be evaluated for all occupations n. The Schwinger relation is the only basic relation used in generating this fully self-consistent Green's function, and the Baym-Kadanoff continuity condition is automatically satisfied
Electromagnetic fields and Green functions in elliptical vacuum chambers
AUTHOR|(CDS)2084216; Biancacci, Nicolo; Migliorati, Mauro; Palumbo, Luigi; Vaccaro, Vittorio; CERN. Geneva. ATS Department
2017-01-01
In this paper, we discuss the electromagnetic interaction between a point charge travelling inside a waveguide of elliptical cross section, and the waveguide itself. By using a convenient expansion of the Mathieu functions, useful in particular for treating a variety of problems in applied mathematics and physics with elliptic geometry, we first obtain the longitudinal electromagnetic field of a point charge (Green function) in free space in terms of elliptical coordinates. This expression allows, then, to calculate the scattered field due to the boundary conditions in our geometry. By summing the contribution of the direct or primary field and the indirect field scattered by the boundary, after a careful choice of some expansion expressions, we derive a novel formula of the longitudinal electric field, in any transverse position of the elliptical cross section, generated by the charge moving along the longitudinal axis of the waveguide. The obtained expression is represented in a closed form, it can be diffe...
Improved quasi-static nodal green's function method
International Nuclear Information System (INIS)
Li Junli; Jing Xingqing; Hu Dapu
1997-01-01
Improved Quasi-Static Green's Function Method (IQS/NGFM) is presented, as an new kinetic method. To solve the three-dimensional transient problem, improved Quasi-Static Method is adopted to deal with the temporal problem, which will increase the time step as long as possible so as to decrease the number of times of space calculation. The time step of IQS/NGFM can be increased to 5∼10 times longer than that of Full Implicit Differential Method. In spatial calculation, the NGFM is used to get the distribution of shape function, and it's spatial mesh can be nearly 20 times larger than that of Definite Differential Method. So the IQS/NGFM is considered as an efficient kinetic method
Electronic diffraction tomography by Green's functions and singular values decompositions
International Nuclear Information System (INIS)
Mayer, A.
2001-01-01
An inverse scattering technique is developed to enable a three-dimensional sample reconstruction from the diffraction figures obtained for different sample orientations by electronic projection microscopy, thus performing a diffraction tomography. In its Green's-functions formulation, this technique takes account of all orders of diffraction by performing an iterative reconstruction of the wave function on the observation screen and in the sample. In a final step, these quantities enable a reconstruction of the potential-energy distribution, which is assumed real valued. The method relies on the use of singular values decomposition techniques, thus providing the best least-squares solutions and enabling a reduction of noise. The technique is applied to the analysis of a three-dimensional nanometric sample that is observed in Fresnel conditions with an electron energy of 40 eV. The algorithm turns out to provide results with a mean relative error around 3% and to be stable against random noise
Nonequilibrium molecular dynamics: The first 25 years
International Nuclear Information System (INIS)
Hoover, W.G.
1992-08-01
Equilibrium Molecular Dynamics has been generalized to simulate Nonequilibrium systems by adding sources of thermodynamic heat and work. This generalization incorporates microscopic mechanical definitions of macroscopic thermodynamic and hydrodynamic variables, such as temperature and stress, and augments atomistic forces with special boundary, constraint, and driving forces capable of doing work on, and exchanging heat with, an otherwise Newtonian system. The underlying Lyapunov instability of these nonequilibrium equations of motion links microscopic time-reversible deterministic trajectories to macroscopic time-irreversible hydrodynamic behavior as described by the Second Law of Thermodynamics. Green-Kubo linear-response theory has been checked. Nonlinear plastic deformation, intense heat conduction, shockwave propagation, and nonequilibrium phase transformation have all been simulated. The nonequilibrium techniques, coupled with qualitative improvements in parallel computer hardware, are enabling simulations to approximate real-world microscale and nanoscale experiments
Shear Viscosity of Benzene, Toluene, and p-Xylene by Non-equilibrium Molecular Dynamics Simulations
International Nuclear Information System (INIS)
Lee, Song Hi
2004-01-01
Green and Kubo showed that the phenomenological coefficients describing many transport processes and time dependent phenomena in general could be written as integrals over a certain type of function called a time correlation function. The Green-Kubo formulas are the formal expressions for hydrodynamic field variables and some of the thermodynamic properties in terms of the microscopic variables of an N-particle system. The identification of microscopic expressions for macroscopic variables is made by a process of comparison of the conservation equations of hydrodynamics with the microscopic equations of change for conserved densities. The importance of these formulas is three-fold: they provide an obvious method for calculating transport coefficients using computer simulation, a convenient starting point for constructing analytic theories for non-equilibrium processes, and an essential information for designing non-equilibrium molecular dynamics (NEMD) algorithm.
Multiquark masses and wave functions through modified Green's function Monte Carlo method
International Nuclear Information System (INIS)
Kerbikov, B.O.; Polikarpov, M.I.; Shevchenko, L.V.
1987-01-01
The Modified Green's function Monte Carlo method (MGFMC) is used to calculate the masses and ground-state wave functions of multiquark systems in the potential model. The previously developed MGFMC is generalized in order to treat systems containing quarks with inequal masses. The obtained results are presented with the Cornell potential for the masses and the wave functions of light and heavy flavoured baryons and multiquark states (N=6, 9, 12) made of light quarks
Green's function approach to the anisotropic Kondo-necklace lattice
International Nuclear Information System (INIS)
Rezania, H.; Langari, A.; Thalmeier, P.
2007-01-01
Full text: We have studied the effect of anisotropy on the quantum phase transition of the 2D anisotropic Kondo necklace lattice [1] within a Green's function approach [2]. In the disordered phase the ground state is the product of all singlet bonds between itinerant and localized spins. It is separated by a finite energy gap from the triplet excited states. The quantum phase transition to the antiferromagnetically ordered phase takes place where the gap vanishes. In this approach we use the bond operator formalism introduced in Ref.[3] where each bond is represented by the singlet and triplet operators. The Kondo necklace Hamiltonian in the bond operator representation is composed of the kinetic energy and pairing part (H2), the two particle interaction (H4) of the boson gas and a term which includes three boson operators (H3). In order to ensure that the physical states are either singlets or triplets we impose the hard-core condition by introducing an infinite on-site repulsion between triplet bosons (H U ). The scattering vertex in the ladder approximation satisfies the Bethe-Salpeter equation [4]. By calculating the scattering vertex function we obtain the self energy contribution of the Hamiltonian H U . We have added the second order contribution of the self energy of H3 to the self energy of H U . It should be noted that the non conservation of triplet boson numbers requires the inclusion of the anomalous Green's functions. We treat H 4 in mean-field theory, by splitting the quartic operator into all possible pairs. Finally we obtain the renormalization of coefficients in the H 2 Hamiltonian and calculate the energy gap. Indeed at the critical point a condensation of triplet bosons occurs. We have numerically found the critical point of this model and compared our results with the corresponding mean field values [5]. Moreover, the critical exponent of the energy gap can be obtained more accurately than the mean field results. (authors)
Modeling photonic crystal waveguides with noncircular geometry using green function method
International Nuclear Information System (INIS)
Uvarovaa, I.; Tsyganok, B.; Bashkatov, Y.; Khomenko, V.
2012-01-01
Currently in the field of photonics is an acute problem fast and accurate simulation photonic crystal waveguides with complex geometry. This paper describes an improved method of Green's functions for non-circular geometries. Based on comparison of selected efficient numerical method for finding the eigenvalues for the Green's function method for non-circular holes chosen effective method for our purposes. Simulation is realized in Maple environment. The simulation results confirmed experimentally. Key words: photonic crystal, waveguide, modeling, Green function, complex geometry
Dyadic Green's function of a cluster of spheres.
Moneda, Angela P; Chrissoulidis, Dimitrios P
2007-11-01
The electric dyadic Green's function (dGf) of a cluster of spheres is obtained by application of the superposition principle, dyadic algebra, and the indirect mode-matching method. The analysis results in a set of linear equations for the unknown, vector, wave amplitudes of the dGf; that set is solved by truncation and matrix inversion. The theory is exact in the sense that no simplifying assumptions are made in the analytical steps leading to the dGf, and it is general in the sense that any number, position, size and electrical properties can be considered for the spheres that cluster together. The point source can be anywhere, even within one of the spheres. Energy conservation, reciprocity, and other tests prove that this solution is correct. Numerical results are presented for an electric Hertz dipole radiating in the presence of an array of rexolite spheres, which manifests lensing and beam-forming capabilities.
Model of coupling with core in the Green function method
International Nuclear Information System (INIS)
Kamerdzhiev, S.P.; Tselyaev, V.I.
1983-01-01
Models of coupling with core in the method of the Green functions, presenting generalization of conventional method of chaotic phases, i.e. account of configurations of more complex than monoparticle-monohole (1p1h) configurations, have been considered. Odd nuclei are studied only to the extent when the task of odd nucleus is solved for even-even nucleus. Microscopic model of the account of delay effects in mass operator M=M(epsilon), which corresponds to the account of the effects influence only on the change of quasiparticle behaviour in magic nucleus as compared with their behaviour, described by pure model of cores, has been considered. The change results in fragmentation of monoparticle levels, which is the main effect, and in the necessity to use new basis as compared with the shell one, corresponding to inoculative quasiparticles. When formulas have been devived concrete type of mass operator M(epsilon) is not used
Green's function calculation of the satellite spectrum of neon
International Nuclear Information System (INIS)
Kheifets, A.S.
1995-01-01
The single-hole Green's function with the lowest-order self-energy part has been used to calculate energies and spectroscopic factors of the neon ion ground and excited states which originated from the removal of the 2s and 2p valence electrons. The simplest two-hole-one-electron ion sates were included explicitly to the self-energy. More complex (m+l)-hole-m-electron states were treated implicitly by using the experimental energy of the two holes in the simplest ion states. The results of the calculation are found to be consistent with experimental satellite line positions and intensities obtained from recent photoionization and electron impact ionization measurements. 20 refs., 5 tabs
The Green-function transform and wave propagation
Directory of Open Access Journals (Sweden)
Colin eSheppard
2014-11-01
Full Text Available Fourier methods well known in signal processing are applied to three-dimensional wave propagation problems. The Fourier transform of the Green function, when written explicitly in terms of a real-valued spatial frequency, consists of homogeneous and inhomogeneous components. Both parts are necessary to result in a pure out-going wave that satisfies causality. The homogeneous component consists only of propagating waves, but the inhomogeneous component contains both evanescent and propagating terms. Thus we make a distinction between inhomogeneous waves and evanescent waves. The evanescent component is completely contained in the region of the inhomogeneous component outside the k-space sphere. Further, propagating waves in the Weyl expansion contain both homogeneous and inhomogeneous components. The connection between the Whittaker and Weyl expansions is discussed. A list of relevant spherically symmetric Fourier transforms is given.
Quasiaverages, symmetry breaking and irreducible Green functions method
Directory of Open Access Journals (Sweden)
A.L.Kuzemsky
2010-01-01
Full Text Available The development and applications of the method of quasiaverages to quantum statistical physics and to quantum solid state theory and, in particular, to quantum theory of magnetism, were considered. It was shown that the role of symmetry (and the breaking of symmetries in combination with the degeneracy of the system was reanalyzed and essentially clarified within the framework of the method of quasiaverages. The problem of finding the ferromagnetic, antiferromagnetic and superconducting "symmetry broken" solutions of the correlated lattice fermion models was discussed within the irreducible Green functions method. A unified scheme for the construction of generalized mean fields (elastic scattering corrections and self-energy (inelastic scattering in terms of the equations of motion and Dyson equation was generalized in order to include the "source fields". This approach complements previous studies of microscopic theory of antiferromagnetism and clarifies the concepts of Neel sublattices for localized and itinerant antiferromagnetism and "spin-aligning fields" of correlated lattice fermions.
Allometric scaling of kidney function in green iguanas.
Maxwell, Lara K; Jacobson, Elliott R
2004-07-01
Numerous physiological parameters, such as metabolic rate and glomerular filtration rate (GFR), are allometrically related to body mass. Whereas the interspecific relationships between metabolic rate and body mass have been extensively studied in vertebrates, intraspecific studies of renal function have been limited. Therefore, kidney function was studied in 16 green iguanas, (Iguana iguana; 322-4764 g), by using nuclear scintigraphy to measure the renal uptake of 99mTc-diethylenetriamine pentaacetic acid (99mTc-DTPA), following either intravenous or intraosseous administration. Route of 99mTc-DTPA administration did not affect the percentage of the dose that accumulated in the kidney (P > 0.05). Renal uptake of 99mTc-DTPA was related to body mass (W, g) as: %Dose Kidney (min-1) = 11.09W(-0.235). Although not directly measured, the apparent renal clearance of 99mTc-DTPA could be described as: Renal CL 99mTc-DTPA (ml.min-1) = 0.005W(0.759), and the mass exponent did not differ from either the 2/3 or 3/4 values (P > 0.05). The similarity of the mass exponents relating both renal function and metabolic rate to body mass suggests a common mechanism underlying these allometric relationships. As this study also demonstrated that renal scintigraphy can be used to quantify kidney function in iguanas, this technique may be a useful research and diagnostic tool.
Green's Function and Stress Fields in Stochastic Heterogeneous Continua
Negi, Vineet
Many engineering materials used today are heterogenous in composition e.g. Composites - Polymer Matrix Composites, Metal Matrix Composites. Even, conventional engineering materials - metals, plastics, alloys etc. - may develop heterogeneities, like inclusions and residual stresses, during the manufacturing process. Moreover, these materials may also have intrinsic heterogeneities at a nanoscale in the form of grain boundaries in metals, crystallinity in amorphous polymers etc. While, the homogenized constitutive models for these materials may be satisfactory at a macroscale, recent studies of phenomena like fatigue failure, void nucleation, size-dependent brittle-ductile transition in polymeric nanofibers reveal a major play of micro/nanoscale physics in these phenomena. At this scale, heterogeneities in a material may no longer be ignored. Thus, this demands a study into the effects of various material heterogeneities. In this work, spatial heterogeneities in two material properties - elastic modulus and yield stress - have been investigated separately. The heterogeneity in the elastic modulus is studied in the context of Green's function. The Stochastic Finite Element method is adopted to get the mean statistics of the Green's function defined on a stochastic heterogeneous 2D infinite space. A study of the elastic-plastic transition in a domain having stochastic heterogenous yield stress was done using Mont-Carlo methods. The statistics for various stress and strain fields during the transition were obtained. Further, the effects of size of the domain and the strain-hardening rate on the stress fields during the heterogeneous elastic-plastic transition were investigated. Finally, a case is made for the role of the heterogenous elastic-plastic transition in damage nucleation and growth.
Integrals of the motion, Green functions, and coherent states of dynamical systems
International Nuclear Information System (INIS)
Dodonov, V.V.; Malkin, I.A.; Man'ko, V.I.
1975-01-01
The connection between the integrals of the motion of a quantum system and its Green function is established. The Green function is shown to be the eigenfunction of the integrals of the motion which describe initial points of the system trajectory in the phase space of average coordinates and moments. The explicit expressions for the Green functions of the N-dimensional system with the Hamiltonians which is the most general quadratic form of coordinates and momenta with time-dependent coefficients is obtained in coordinate, momentum, and coherent states representations. The Green functions of the nonstationary singular oscillator and of the stationary Schroedinger equation are also obtained. (author)
Plant species and functional group combinations affect green roof ecosystem functions.
Lundholm, Jeremy; Macivor, J Scott; Macdougall, Zachary; Ranalli, Melissa
2010-03-12
Green roofs perform ecosystem services such as summer roof temperature reduction and stormwater capture that directly contribute to lower building energy use and potential economic savings. These services are in turn related to ecosystem functions performed by the vegetation layer such as radiation reflection and transpiration, but little work has examined the role of plant species composition and diversity in improving these functions. We used a replicated modular extensive (shallow growing- medium) green roof system planted with monocultures or mixtures containing one, three or five life-forms, to quantify two ecosystem services: summer roof cooling and water capture. We also measured the related ecosystem properties/processes of albedo, evapotranspiration, and the mean and temporal variability of aboveground biomass over four months. Mixtures containing three or five life-form groups, simultaneously optimized several green roof ecosystem functions, outperforming monocultures and single life-form groups, but there was much variation in performance depending on which life-forms were present in the three life-form mixtures. Some mixtures outperformed the best monocultures for water capture, evapotranspiration, and an index combining both water capture and temperature reductions. Combinations of tall forbs, grasses and succulents simultaneously optimized a range of ecosystem performance measures, thus the main benefit of including all three groups was not to maximize any single process but to perform a variety of functions well. Ecosystem services from green roofs can be improved by planting certain life-form groups in combination, directly contributing to climate change mitigation and adaptation strategies. The strong performance by certain mixtures of life-forms, especially tall forbs, grasses and succulents, warrants further investigation into niche complementarity or facilitation as mechanisms governing biodiversity-ecosystem functioning relationships in green
Nonequilibrium excitations and transport of Dirac electrons in electric-field-driven graphene
Li, Jiajun; Han, Jong E.
2018-05-01
We investigate nonequilibrium excitations and charge transport in charge-neutral graphene driven with dc electric field by using the nonequilibrium Green's-function technique. Due to the vanishing Fermi surface, electrons are subject to nontrivial nonequilibrium excitations such as highly anisotropic momentum distribution of electron-hole pairs, an analog of the Schwinger effect. We show that the electron-hole excitations, initiated by the Landau-Zener tunneling with a superlinear I V relation I ∝E3 /2 , reaches a steady state dominated by the dissipation due to optical phonons, resulting in a marginally sublinear I V with I ∝E , in agreement with recent experiments. The linear I V starts to show the sign of current saturation as the graphene is doped away from the Dirac point, and recovers the semiclassical relation for the saturated velocity. We give a detailed discussion on the nonequilibrium charge creation and the relation between the electron-phonon scattering rate and the electric field in the steady-state limit. We explain how the apparent Ohmic I V is recovered near the Dirac point. We propose a mechanism where the peculiar nonequilibrium electron-hole creation can be utilized in a infrared device.
Dirac Coulomb Green's function and its application to relativistic Rayleigh scattering
International Nuclear Information System (INIS)
Wong, M.K.F.; Yeh, E.H.Y.
1985-01-01
The Dirac Coulomb Green's function is obtained in both coordinate and momentum space. The Green's function in coordinate space is obtained by the eigenfunction expansion method in terms of the wave functions obtained by Wong and Yeh. The result is simpler than those obtained previously by other authors, in that the radial part for each component contains one term only instead of four terms. Our Green's function reduces to the Schroedinger Green's function upon some simple conditions, chiefly by neglecting the spin and replacing lambda by l. The Green's function in momentum space is obtained as the Fourier transform of the coordinate space Green's function, and is expressed in terms of basically three types of functions: (1) F/sub A/ (α; β 1 β 2 β 3 ; γ 1 γ 2 γ 3 ; z 1 z 2 z 3 ), (2) the hypergeometric function, and (3) spherical harmonics. The matrix element for Rayleigh scattering, or elastic Compton scattering, from relativistically bound electrons is then obtained in analytically closed form. The matrix element is written basically in terms of the coordinate space Dirac Coulomb Green's function. The technique used in the evaluation of the matrix element is based on the calculation of the momentum space Dirac Coulomb Green's function. Finally the relativistic result is compared with the nonrelativistic result
Calculation of the mutual diffusion coefficient by equilibrium and nonequilibrium molecular dynamics
International Nuclear Information System (INIS)
Erpenbeck, J.J.; Kincaid, J.M.
1985-01-01
A nonequilibrium molecular dynamics method for the calculation of the mutual diffusion coefficient for a mixture of hard spheres is described. The method is applied to a 50-50 mixture of equidiameter particles having a mass ratio of 0.1 for the two species, at a volume of three times close-packing. By extrapolating the results to the limit of vanishing concentration gradient and infinite system size, we obtain a value in statistical agreement with the result obtained using a Green-Kubo molecular dynamics procedure which is also described. The nonequilibrium calculation yields a mutual diffusion coefficient which decreases slightly with increasing concentration gradient. The Green-Kubo time correlation function for mutual diffusion displays a slow decay with time, qualitatively similar to the long-time tail which has been predicted by the hydrodynamic theory of Pomeau
Calculation of the mutual diffusion coefficient by equilibrium and nonequilibrium molecular dynamics
International Nuclear Information System (INIS)
Erpenbeck, J.J.; Kincaid, J.M.
1986-01-01
A nonequilibrium molecular dynamics method for the calculation of the mutual diffusion coefficient for a mixture of hard spheres is described. The method is applied to a 50-50 mixture of equidiameter particles having a mass ratio of 0.1 for the two species, at a volume of three times close-packing. By extrapolating the results to the limit of vanishing concentration gradient and infinite system size, we obtain a value in statistical agreement with the result obtained using a Green-Kubo molecular dynamics procedure, which is also described. The nonequilibrium calculation yields a mutual diffusion coefficient which decreases slightly with increasing concentration gradient. The Green-Kubo timecorrelation function for mutual diffusion displays a slow decay with time, qualitatively similar to the long-time tail which has been predicted by the hydrodynamic theory of Pomeau
Energy Technology Data Exchange (ETDEWEB)
Guasp, J
1972-07-01
The Green Function of the thermalization problem is studied in the secondary model case through the spatial Fourier transform. A relation between singularities and eigenvalues allows the determination of the analyticity dominion. The eigenvalue spectrum has a purely discrete part, laying on an interval of the imaginary axis of the K complex plane (the Fourier parameter), and another part, purely continuous, laying in the reminder of the imaginary axis. A correspondence between discrete eigenvalues and exponential modes of the Green Function, extemal properties for the eigenvalues and some remarkable properties of the eigenfunctions are established. (Author) 32 refs.
Recursive evaluation of space-time lattice Green's functions
International Nuclear Information System (INIS)
De Hon, Bastiaan P; Arnold, John M
2012-01-01
Up to a multiplicative constant, the lattice Green's function (LGF) as defined in condensed matter physics and lattice statistical mechanics is equivalent to the Z-domain counterpart of the finite-difference time-domain Green's function (GF) on a lattice. Expansion of a well-known integral representation for the LGF on a ν-dimensional hyper-cubic lattice in powers of Z −1 and application of the Chu–Vandermonde identity results in ν − 1 nested finite-sum representations for discrete space-time GFs. Due to severe numerical cancellations, these nested finite sums are of little practical use. For ν = 2, the finite sum may be evaluated in closed form in terms of a generalized hypergeometric function. For special lattice points, that representation simplifies considerably, while on the other hand the finite-difference stencil may be used to derive single-lattice-point second-order recurrence schemes for generating 2D discrete space-time GF time sequences on the fly. For arbitrary symbolic lattice points, Zeilberger's algorithm produces a third-order recurrence operator with polynomial coefficients of the sixth degree. The corresponding recurrence scheme constitutes the most efficient numerical method for the majority of lattice points, in spite of the fact that for explicit numeric lattice points the associated third-order recurrence operator is not the minimum recurrence operator. As regards the asymptotic bounds for the possible solutions to the recurrence scheme, Perron's theorem precludes factorial or exponential growth. Along horizontal lattices directions, rapid initial growth does occur, but poses no problems in augmented dynamic-range fixed precision arithmetic. By analysing long-distance wave propagation along a horizontal lattice direction, we have concluded that the chirp-up oscillations of the discrete space-time GF are the root cause of grid dispersion anisotropy. With each factor of ten increase in the lattice distance, one would have to roughly
Green's function of compressible Petschek-type magnetic reconnection
International Nuclear Information System (INIS)
Penz, Thomas; Semenov, V.S.; Ivanova, V.V.; Heyn, M.F.; Ivanov, I.B.; Biernat, H.K.
2006-01-01
We present a method to analyze the wave and shock structures arising from Petschek-type magnetic reconnection. Based on a time-dependent analytical approach developed by Heyn and Semenov [Phys. Plasmas 3, 2725 (1996)] and Semenov et al. [Phys. Plasmas 11, 62 (2004)], we calculate the perturbations caused by a delta function-shaped reconnection electric field, which allows us to achieve a representation of the plasma variables in the form of Green's functions. Different configurations for the initial conditions are considered. In the case of symmetric, antiparallel magnetic fields and symmetric plasma density, the well-known structure of an Alfven discontinuity, a fast body wave, a slow shock, a slow wave, and a tube wave occurs. In the case of asymmetric, antiparallel magnetic fields, additionally surface waves are found. We also discuss the case of symmetric, antiparallel magnetic fields and asymmetric densities, which leads to a faster propagation in the lower half plane, causing side waves forming a Mach cone in the upper half plane. Complex effects like anisotropic propagation characteristics, intrinsic wave coupling, and the generation of different nonlinear and linear wave modes in a finite β plasma are retained. The temporal evolution of these wave and shock structures is shown
Functional Use Change in Green Spaces: A Case Study of Kirklareli Province
Sat Gungor, Beyza; Culha Ozanguc, Kadiriye
2017-10-01
Green spaces which are one of the most important public spaces in urban design have an important role on qualified daily urban life. People escape from intense work pressure and traffic jam of metropoles to those urban green areas to take a breath even they cover a small size. In time, people’s expectations from green spaces as functional and quantitative needs are changing. This change occurs due to increasing population and as the character of the urban life. This study examines the functional use and quantitative change of urban green spaces of Kırklareli Province from past to present. Kırklareli is a border city to Bulgaria which is located in north-west part of Turkey and this gives a transitional and a multicultural character to the city. The population is about 67360. In the course of time; green space needs have increased by the increasing population. In addition to this, green spaces’ functional use change has been identified. According to the results of the study; from the aspect of the green space standards, Kırklareli found above standards with 17.5 m2 per capita, but on the other hand, sport and playground areas found insufficient. The Oldest and the newest city plans of Kırklareli (1940s and 2012s cadastral plans) have been compared and site surveys implemented as the methodology. In site survey, current green spaces’ functional uses as sport or playground are observed and determined and also current quantitative measure of the green spaces are verified. Urban green spaces in Kırklareli Province evaluated through considering world’s most populated urban green space standards and Turkey’s standards. This study utilizes to compose a substructure of the urban green space. Determined deficiencies and inadequacies of green spaces and functional needs in this study, can guide to further studies and implementations of Kırklareli Municipality.
Non-equilibrium magnetic interactions in strongly correlated systems
Energy Technology Data Exchange (ETDEWEB)
Secchi, A., E-mail: a.secchi@science.ru.nl [Institute for Molecules and Materials, Radboud University Nijmegen, 6525 AJ Nijmegen (Netherlands); Brener, S.; Lichtenstein, A.I. [Institut für Theoretische Physik, Universitat Hamburg, Jungiusstraße 9, D-20355 Hamburg (Germany); Katsnelson, M.I. [Institute for Molecules and Materials, Radboud University Nijmegen, 6525 AJ Nijmegen (Netherlands)
2013-06-15
We formulate a low-energy theory for the magnetic interactions between electrons in the multi-band Hubbard model under non-equilibrium conditions determined by an external time-dependent electric field which simulates laser-induced spin dynamics. We derive expressions for dynamical exchange parameters in terms of non-equilibrium electronic Green functions and self-energies, which can be computed, e.g., with the methods of time-dependent dynamical mean-field theory. Moreover, we find that a correct description of the system requires, in addition to exchange, a new kind of magnetic interaction, that we name twist exchange, which formally resembles Dzyaloshinskii–Moriya coupling, but is not due to spin–orbit, and is actually due to an effective three-spin interaction. Our theory allows the evaluation of the related time-dependent parameters as well. -- Highlights: •We develop a theory for magnetism of strongly correlated systems out of equilibrium. •Our theory is suitable for laser-induced ultrafast magnetization dynamics. •We write time-dependent exchange parameters in terms of electronic Green functions. •We find a new magnetic interaction, a “twist exchange”. •We give general expressions for magnetic noise in itinerant-electron systems.
Proof of the relativistic covariance of the fermion Green function in QED
International Nuclear Information System (INIS)
Nguyen Suan Han.
1995-02-01
This paper is devoted to the calculation of the fermion Green function in QED in the framework of the Minimal Quantization Method, based on an explicit solution of the constraint equations and the gauge-invariance principle. The relativistic invariant expression for the fermion Green function which has the right analytical properties is obtained. (author). 24 refs
Green's function for a neutral particle of spin 1/2 in a magnetic field
International Nuclear Information System (INIS)
Rodrigues, Rafael de Lima; Vaidya, Arvind Narayan
2001-12-01
Using the spectral theorema in context of Green's function in momentum space of neutrons in the magnetic field of a linear conductor with current the bound state energy spectrum and eigenfunctions are deduced. It's also pointed out that this problem present a new scenary of Green's function in non-relativistic quantum mechanics. (author)
Maci, S.; Neto, A.
2004-01-01
This second part of a two-paper sequence deals with the uniform asymptotic description of the Green's function of an infinite slot printed between two different homogeneous dielectric media. Starting from the magnetic current derived in Part I, the dyadic green's function is first formulated in
Wapenaar, Kees; Thorbecke, Jan; van der Neut, Joost
2016-04-01
Green's theorem plays a fundamental role in a diverse range of wavefield imaging applications, such as holographic imaging, inverse scattering, time-reversal acoustics and interferometric Green's function retrieval. In many of those applications, the homogeneous Green's function (i.e. the Green's function of the wave equation without a singularity on the right-hand side) is represented by a closed boundary integral. In practical applications, sources and/or receivers are usually present only on an open surface, which implies that a significant part of the closed boundary integral is by necessity ignored. Here we derive a homogeneous Green's function representation for the common situation that sources and/or receivers are present on an open surface only. We modify the integrand in such a way that it vanishes on the part of the boundary where no sources and receivers are present. As a consequence, the remaining integral along the open surface is an accurate single-sided representation of the homogeneous Green's function. This single-sided representation accounts for all orders of multiple scattering. The new representation significantly improves the aforementioned wavefield imaging applications, particularly in situations where the first-order scattering approximation breaks down.
Green's function method and its application to verification of diffusion models of GASFLOW code
International Nuclear Information System (INIS)
Xu, Z.; Travis, J.R.; Breitung, W.
2007-07-01
To validate the diffusion model and the aerosol particle model of the GASFLOW computer code, theoretical solutions of advection diffusion problems are developed by using the Green's function method. The work consists of a theory part and an application part. In the first part, the Green's functions of one-dimensional advection diffusion problems are solved in infinite, semi-infinite and finite domains with the Dirichlet, the Neumann and/or the Robin boundary conditions. Novel and effective image systems especially for the advection diffusion problems are made to find the Green's functions in a semi-infinite domain. Eigenfunction method is utilized to find the Green's functions in a bounded domain. In the case, key steps of a coordinate transform based on a concept of reversed time scale, a Laplace transform and an exponential transform are proposed to solve the Green's functions. Then the product rule of the multi-dimensional Green's functions is discussed in a Cartesian coordinate system. Based on the building blocks of one-dimensional Green's functions, the multi-dimensional Green's function solution can be constructed by applying the product rule. Green's function tables are summarized to facilitate the application of the Green's function. In the second part, the obtained Green's function solutions benchmark a series of validations to the diffusion model of gas species in continuous phase and the diffusion model of discrete aerosol particles in the GASFLOW code. Perfect agreements are obtained between the GASFLOW simulations and the Green's function solutions in case of the gas diffusion. Very good consistencies are found between the theoretical solutions of the advection diffusion equations and the numerical particle distributions in advective flows, when the drag force between the micron-sized particles and the conveying gas flow meets the Stokes' law about resistance. This situation is corresponding to a very small Reynolds number based on the particle
Euclidean scalar Green's functions near the black hole and black brane horizons
International Nuclear Information System (INIS)
Haba, Z
2009-01-01
We discuss approximations of the Riemannian geometry near the horizon. If a (D + 1)-dimensional manifold N has a bifurcate Killing horizon then we approximate N by a product of the two-dimensional Rindler space R 2 and a (D - 1)-dimensional Riemannian manifold M. We obtain approximate formulae for scalar Green's functions. We study the behavior of the Green's functions near the horizon and their dimensional reduction. We show that if M is compact then the Green's function near the horizon can be approximated by the Green's function of the two-dimensional quantum field theory. The correction term is exponentially small away from the horizon. We extend the results to black brane solutions of supergravity in 10 and 11 dimensions. The near-horizon geometry can be approximated by N=AdS p xS q . We discuss the Euclidean Green's functions on N and their behavior near the horizon.
Soil-structure interaction analysis by Green function
International Nuclear Information System (INIS)
Muto, Kiyoshi; Kobayashi, Toshio; Nakahara, Mitsuharu.
1985-01-01
Using the method of discretized Green function which had been suggested by the authors, the parametric study of the effects of base mat foundation thickness and soil stiffness were conducted. There was no upper structure effects from the response and reaction stress of the soil by employing different base mat foundation thicknesses. However, the response stress of base mat itself had considerable effect on the base mat foundation stress. The harder the soil, became larger accelerations, and smaller displacements on the upper structure. The upper structure lines of force were directed onto the soil. In the case of soft soil, the reaction soil stress were distributed evenly over the entire reactor building area. Common characteristics of all cases, in-plane shear deformation of the upper floor occured and in-plane acceleration and displacement at the center of the structure become larger. Also, the soil stresses around the shield wall of the base mat foundation became large cecause of the effect of the shield wall bending. (Kubozono, M.)
Dyadic Green's function of an eccentrically stratified sphere.
Moneda, Angela P; Chrissoulidis, Dimitrios P
2014-03-01
The electric dyadic Green's function (dGf) of an eccentrically stratified sphere is built by use of the superposition principle, dyadic algebra, and the addition theorem of vector spherical harmonics. The end result of the analytical formulation is a set of linear equations for the unknown vector wave amplitudes of the dGf. The unknowns are calculated by truncation of the infinite sums and matrix inversion. The theory is exact, as no simplifying assumptions are required in any one of the analytical steps leading to the dGf, and it is general in the sense that any number, position, size, and electrical properties can be considered for the layers of the sphere. The point source can be placed outside of or in any lossless part of the sphere. Energy conservation, reciprocity, and other checks verify that the dGf is correct. A numerical application is made to a stratified sphere made of gold and glass, which operates as a lens.
Estimation of Cumulative Absolute Velocity using Empirical Green's Function Method
International Nuclear Information System (INIS)
Park, Dong Hee; Yun, Kwan Hee; Chang, Chun Joong; Park, Se Moon
2009-01-01
In recognition of the needs to develop a new criterion for determining when the OBE (Operating Basis Earthquake) has been exceeded at nuclear power plants, Cumulative Absolute Velocity (CAV) was introduced by EPRI. The concept of CAV is the area accumulation with the values more than 0.025g occurred during every one second. The equation of the CAV is as follows. CAV = ∫ 0 max |a(t)|dt (1) t max = duration of record, a(t) = acceleration (>0.025g) Currently, the OBE exceedance criteria in Korea is Peak Ground Acceleration (PGA, PGA>0.1g). When Odesan earthquake (M L =4.8, January 20th, 2007) and Gyeongju earthquake (M L =3.4, June 2nd, 1999) were occurred, we have had already experiences of PGA greater than 0.1g that did not even cause any damage to the poorly-designed structures nearby. This moderate earthquake has motivated Korea to begin the use of the CAV for OBE exceedance criteria for NPPs. Because the present OBE level has proved itself to be a poor indicator for small-to-moderate earthquakes, for which the low OBE level can cause an inappropriate shut down the plant. A more serious possibility is that this scenario will become a reality at a very high level. Empirical Green's Function method was a simulation technique which can estimate the CAV value and it is hereby introduced
A Green function approach to superconductivity in nanofilms
Energy Technology Data Exchange (ETDEWEB)
Saniz, Rolando; Partoens, Bart; Peeters, Francois [Universiteit Antwerpen, Antwerpen (Belgium)
2012-07-01
We reformulate the BCS theory of superconductivity in the Green function framework in such a way that it is readily applied to inhomogeneous systems. We study here nanofilms and go beyond previous models in that we take into account the effects of confinement on electron-phonon coupling, as well as on the electron and phonon fields. We show that, contrary to what has been advanced in recent years, the increases of the density of states as the film thickness increases will tend to suppress the critical temperature, and not enhance it. Instead, it is the increase of the phonon modes with increasing film thickness that can lead to increases of the critical temperature above the bulk value. Further, we show that the multigap character of superconductivity in nanofilms will result in general in a condensate composed of subcondensates with different coherence lengths. This is in analogy with the very recent suggestion that different coherence lengths exist in two-gap superconductors such as MgB{sub 2}.
Green function theory of random ferromagnets with large exchange anisotropy
International Nuclear Information System (INIS)
Patterson, J.D.
1977-01-01
Spin 1/2 systems which are coupled with an Ising-like Hamiltonian with fluctuating exchange are discussed by the use of thermodynamic Green functions in four different approximations. The first is equivalent to a local mean field approximation and the second is an approximation to the first in which the local mean field is assumed to be proportional to the overall magnetization and to the sum of the neighboring exchange 'bonds'. The third is also a special case of the first, but the local mean field is approximated in such a way as to be appropriate for the discussion of spin glasses. The fourth is a coherent potential-like approximation (CPA). The second approximation can be shown to imply no reduction of the Curie temperature (T sub(c)) due to exchange fluctuations, while the CPA does result in a lowering of T sub(c) (assuming small fluctuations about an average positive exchange in both cases). However, the CPA that was used is also an approximation to the second method. Hence, even though the CPA does result in a lowering of T sub(c) (which is generally conceded to be correct for the original model), this fact cannot be used as an argument for the validity of the CPA. This calculation thus emphasizes the necessity of critically examining any CPA-like calculation before accepting its predictions as valid [pt
Directory of Open Access Journals (Sweden)
Elena Grigoryeva
2011-02-01
Full Text Available The “green” topic follows the “youngsters”, which is quite natural for the Russian language.Traditionally these words put together sound slightly derogatory. However, “green” also means fresh, new and healthy.For Russia, and for Siberia in particular, “green” architecture does sound new and fresh. Forced by the anxious reality, we are addressing this topic intentionally. The ecological crisis, growing energy prices, water, air and food deficits… Alexander Rappaport, our regular author, writes: “ It has been tolerable until a certain time, but under transition to the global civilization, as the nature is destroyed, and swellings of megapolises expand incredibly fast, the size and the significance of all these problems may grow a hundredfold”.However, for this very severe Siberian reality the newness of “green” architecture may turn out to be well-forgotten old. A traditional Siberian house used to be built on principles of saving and environmental friendliness– one could not survive in Siberia otherwise.Probably, in our turbulent times, it is high time to fasten “green belts”. But we should keep from enthusiastic sticking of popular green labels or repainting of signboards into green color. We should avoid being drowned in paper formalities under “green” slogans. And we should prevent the Earth from turning into the planet “Kin-dza-dza”.
On Green's function for 3-D wave-body interaction in a channel
DEFF Research Database (Denmark)
Xia, Jinzhu
1997-01-01
series of images is evaluated accurately based on an asmptotic analysis. It is demonstrated that the Green's function has a square-root singular behaviour due to the side walls when the wave frequency approaches one of the resonant frequencies. The numerical results for the Green's function has a square......An analytical and numerical study is presented for efficient evaluation of the Green's function that satisfies the linear free surface condition and the non-penetration condition on the channel bottomand the side walls. the formulation is based on the open-sea green's function and the complete......-root singular behaviour due to the side walls when the wave frequency approaches one of the resonant frequencies. The numerical results for the Green's funciton presented in the present paper are believed to have an absolute accuracy of 10-5....
DEFF Research Database (Denmark)
Leitherer, Susanne; Jager, C. M.; Krause, A.
2017-01-01
In weakly interacting organic semiconductors, static disorder and dynamic disorder often have an important impact on transport properties. Describing charge transport in these systems requires an approach that correctly takes structural and electronic fluctuations into account. Here, we present...... are used in organic field-effect transistors....
Green function iterative solution of ground state wave function for Yukawa potential
International Nuclear Information System (INIS)
Zhang Zhao
2003-01-01
The newly developed single trajectory quadrature method is applied to solve central potentials. First, based on the series expansion method an exact analytic solution of the ground state for Hulthen potential and an approximate solution for Yukawa potential are obtained respectively. Second, the newly developed iterative method based on Green function defined by quadratures along the single trajectory is applied to solve Yukawa potential using the Coulomb solution and Hulthen solution as the trial functions respectively. The results show that a more proper choice of the trial function will give a better convergence. To further improve the convergence the iterative method is combined with the variational method to solve the ground state wave function for Yukawa potential, using variational solutions of the Coulomb and Hulthen potentials as the trial functions. The results give much better convergence. Finally, the obtained critical screen coefficient is applied to discuss the dissociate temperature of J/ψ in high temperature QGP
Empirical Green's function analysis: Taking the next step
Hough, S.E.
1997-01-01
An extension of the empirical Green's function (EGF) method is presented that involves determination of source parameters using standard EGF deconvolution, followed by inversion for a common attenuation parameter for a set of colocated events. Recordings of three or more colocated events can thus be used to constrain a single path attenuation estimate. I apply this method to recordings from the 1995-1996 Ridgecrest, California, earthquake sequence; I analyze four clusters consisting of 13 total events with magnitudes between 2.6 and 4.9. I first obtain corner frequencies, which are used to infer Brune stress drop estimates. I obtain stress drop values of 0.3-53 MPa (with all but one between 0.3 and 11 MPa), with no resolved increase of stress drop with moment. With the corner frequencies constrained, the inferred attenuation parameters are very consistent; they imply an average shear wave quality factor of approximately 20-25 for alluvial sediments within the Indian Wells Valley. Although the resultant spectral fitting (using corner frequency and ??) is good, the residuals are consistent among the clusters analyzed. Their spectral shape is similar to the the theoretical one-dimensional response of a layered low-velocity structure in the valley (an absolute site response cannot be determined by this method, because of an ambiguity between absolute response and source spectral amplitudes). I show that even this subtle site response can significantly bias estimates of corner frequency and ??, if it is ignored in an inversion for only source and path effects. The multiple-EGF method presented in this paper is analogous to a joint inversion for source, path, and site effects; the use of colocated sets of earthquakes appears to offer significant advantages in improving resolution of all three estimates, especially if data are from a single site or sites with similar site response.
Dual number algebra method for Green's function derivatives in 3D magneto-electro-elasticity
Dziatkiewicz, Grzegorz
2018-01-01
The Green functions are the basic elements of the boundary element method. To obtain the boundary integral formulation the Green function and its derivative should be known for the considered differential operator. Today the interesting group of materials are electronic composites. The special case of the electronic composite is the magnetoelectroelastic continuum. The mentioned continuum is a model of the piezoelectric-piezomagnetic composites. The anisotropy of their physical properties makes the problem of Green's function determination very difficult. For that reason Green's functions for the magnetoelectroelastic continuum are not known in the closed form and numerical methods should be applied to determine such Green's functions. These means that the problem of the accurate and simply determination of Green's function derivatives is even harder. Therefore in the present work the dual number algebra method is applied to calculate numerically the derivatives of 3D Green's functions for the magnetoelectroelastic materials. The introduced method is independent on the step size and it can be treated as a special case of the automatic differentiation method. Therefore, the dual number algebra method can be applied as a tool for checking the accuracy of the well-known finite difference schemes.
Current experience concerning Romanian green certificates market functioning
International Nuclear Information System (INIS)
Vladescu, Gherghina; Lupului, Luminita; Vasilevschi, Constantin; Ghinea, Smaranda
2006-01-01
The renewable energy sources are promoted by their beneficial use, namely: - diversification of energy sources for producing electric power; - reduction of pollution produced by fossil fuel burning; - reduction of gas releases producing the greenhouse effects, etc. Currently, most of the renewable energy sources cannot concur on electric power free market because of the high costs of implied investments. To ensure an efficient use of renewable energy sources in electricity production and to maintain the installations implied on the electric power market, it is necessary to implement a system able to produce an output greater than that obtained from electric energy selling. The Romanian Government chose to promote the electric energy production by renewable energy sources by using the green certificate trading system. This system ensures the progress in developing the technologies employed in electric energy production from renewable energy sources and, at the same time the costs implied by their promotion can be adjusted by market mechanisms what will reduce the effects upon the electric energy consumers. The paper presents the legislation frame existing in Romania for promoting the electric energy produced from renewable energy sources, the green certificate trading system applied in Romania, as well as, the role shared by the entities implied in operation and development of the system. In November 2005, a first transaction with green certificates on controlled green certificate market in Romania took place. Analyzed is the evolution of the green certificate market registered so far from its inception, as well as, the lessons learned so far from the experience acquired
Accurate calculation of Green functions on the d-dimensional hypercubic lattice
International Nuclear Information System (INIS)
Loh, Yen Lee
2011-01-01
We write the Green function of the d-dimensional hypercubic lattice in a piecewise form covering the entire real frequency axis. Each piece is a single integral involving modified Bessel functions of the first and second kinds. The smoothness of the integrand allows both real and imaginary parts of the Green function to be computed quickly and accurately for any dimension d and any real frequency, and the computational time scales only linearly with d.
Use of Green's functions in the numerical solution of two-point boundary value problems
Gallaher, L. J.; Perlin, I. E.
1974-01-01
This study investigates the use of Green's functions in the numerical solution of the two-point boundary value problem. The first part deals with the role of the Green's function in solving both linear and nonlinear second order ordinary differential equations with boundary conditions and systems of such equations. The second part describes procedures for numerical construction of Green's functions and considers briefly the conditions for their existence. Finally, there is a description of some numerical experiments using nonlinear problems for which the known existence, uniqueness or convergence theorems do not apply. Examples here include some problems in finding rendezvous orbits of the restricted three body system.
Study on application of green's function method in thermal stress rapid calculation
International Nuclear Information System (INIS)
Zhang Guihe; Duan Yuangang; Xu Xiao; Chen Rong
2013-01-01
This paper presents a quick and accuracy thermal stress calculation method, the Green's Function Method, which is a combination of finite element method and numerical algorithm method. Thermal stress calculation of Safe Injection Nozzle of Reactor Coolant Line of PWR plant is performed with Green's function method for heatup and cooldown thermal transients as a demonstration example, and the result is compared with finite element method to verify the rationality and accuracy of this method. The advantage and disadvantage of the Green's function method and the finite element method are also compared. (authors)
Green's functions in Bianchi type-I spaces. Relation between Minkowski and Euclidean approaches
International Nuclear Information System (INIS)
Bukhbinder, I.L.; Kirillova, E.N.
1988-01-01
A theory is considered for a free scalar field with a conformal connection in a curved space-time with a Bianchi type-I metric. A representation is obtained for the Green's function G∼ in in in the form of an integral of a Schwinger-DeWitt kernel along a contour in a plane of complex-valued proper time. It is shown how as transition may be accomplished from Green's functions in space with the Euclidean signature to Green's functions in space with Minkowski signature and vice versa
Scalar Green's functions in an Euclidean space with a conical-type line singularity
International Nuclear Information System (INIS)
Guimaraes, M.E.X.; Linet, B.
1994-01-01
In an Euclidean space with a conical-type line singularity, we determine the Green's function for a charged massive scalar field interacting with a magnetic flux running through the line singularity. We give an integral expression of the Green's function and a local form in the neighbourhood of the point source, where it is the sum of the usual Green's function in Euclidean space and a regular term. As an application, we derive the vacuum energy-momentum tensor in the massless case for an arbitrary magnetic flux. (orig.)
International Nuclear Information System (INIS)
Rinaldi, Massimiliano
2007-01-01
We consider Green's functions associated to a scalar field propagating on a curved, ultrastatic background, in the presence of modified dispersion relations. The usual proper-time DeWitt-Schwinger procedure to obtain a series representation of Green's functions is doomed to failure because of higher order spatial derivatives in the Klein-Gordon operator. We show how to overcome this difficulty by considering a preferred frame, associated to a unit timelike vector. With respect to this frame, we can express Green's functions as an integral over all frequencies of a space-dependent function. The latter can be expanded in momentum space, as a series with geometric coefficients similar to the DeWitt-Schwinger ones. By integrating over all frequencies, we finally find the expansion of Green's function up to four derivatives of the metric tensor. The relation with the proper-time formalism is also discussed
Braaker, Sonja; Obrist, Martin Karl; Ghazoul, Jaboury; Moretti, Marco
2017-05-01
Increasing development of urban environments creates high pressure on green spaces with potential negative impacts on biodiversity and ecosystem services. There is growing evidence that green roofs - rooftops covered with vegetation - can contribute mitigate the loss of urban green spaces by providing new habitats for numerous arthropod species. Whether green roofs can contribute to enhance taxonomic and functional diversity and increase connectivity across urbanized areas remains, however, largely unknown. Furthermore, only limited information is available on how environmental conditions shape green roof arthropod communities. We investigated the community composition of arthropods (Apidae, Curculionidae, Araneae and Carabidae) on 40 green roofs and 40 green sites at ground level in the city of Zurich, Switzerland. We assessed how the site's environmental variables (such as area, height, vegetation, substrate and connectivity among sites) affect species richness and functional diversity using generalized linear models. We used an extension of co-inertia analysis (RLQ) and fourth-corner analysis to highlight the mechanism underlying community assemblages across taxonomic groups on green roof and ground communities. Species richness was higher at ground-level sites, while no difference in functional diversity was found between green roofs and ground sites. Green roof arthropod diversity increased with higher connectivity and plant species richness, irrespective of substrate depth, height and area of green roofs. The species trait analysis reviewed the mechanisms related to the environmental predictors that shape the species assemblages of the different taxa at ground and roof sites. Our study shows the important contribution of green roofs in maintaining high functional diversity of arthropod communities across different taxonomic groups, despite their lower species richness compared with ground sites. Species communities on green roofs revealed to be characterized
Röpke, G.
2018-01-01
One of the fundamental problems in physics that are not yet rigorously solved is the statistical mechanics of nonequilibrium processes. An important contribution to describing irreversible behavior starting from reversible Hamiltonian dynamics was given by D. N. Zubarev, who invented the method of the nonequilibrium statistical operator. We discuss this approach, in particular, the extended von Neumann equation, and as an example consider the electrical conductivity of a system of charged particles. We consider the selection of the set of relevant observables. We show the relation between kinetic theory and linear response theory. Using thermodynamic Green's functions, we present a systematic treatment of correlation functions, but the convergence needs investigation. We compare different expressions for the conductivity and list open questions.
Development of multi-functional streetscape green infrastructure using a performance index approach
Czech Academy of Sciences Publication Activity Database
Tiwary, A.; Williams, L. D.; Heidrich, O.; Namdeo, A.; Bandaru, V.; Calfapietra, Carlo
2016-01-01
Roč. 208, jan (2016), s. 209-220 ISSN 0269-7491 Institutional support: RVO:67179843 Keywords : Green infrastructure * Multi-functional * Pollution * Performance index * Streetscape Subject RIV: EH - Ecology, Behaviour Impact factor: 5.099, year: 2016
International Nuclear Information System (INIS)
Dorning, J.
1981-01-01
The research and development over the past eight years on local Green's function methods for the high-accuracy, high-efficiency numerical solution of nuclear engineering problems is reviewed. The basic concepts and key ideas are presented by starting with an expository review of the original fully two-dimensional local Green's function methods developed for neutron diffusion and heat conduction, and continuing through the progressively more complicated and more efficient nodal Green's function methods for neutron diffusion, heat conduction and neutron transport to establish the background for the recent development of Green's function methods in computational fluid mechanics. Some of the impressive numerical results obtained via these classes of methods for nuclear engineering problems are briefly summarized. Finally, speculations are proffered on future directions in which the development of these types of methods in fluid mechanics and other areas might lead. (orig.) [de
Sum-over-histories representation for the causal Green function of free scalar field theory
International Nuclear Information System (INIS)
Rudolph, O.
1993-10-01
A set of Green functions G α (x-y), α element of [0, 2π], for free scalar field theory is introduced, varying between the Hadamard Green function Δ 1 (x-y) triple bond 0vertical stroke {φ(x), φ(y)}vertical stroke 0> and the causal Green function G π (x-y)=iΔ(x-y) triple bond [φ(x), φ(y)]. For every α element of [0, 2π] a path-integral representation for G α is obtained both in the configuration space and in the phase space of the classical relativistic particle. Especially setting α=π a sum-over-histories representation for the causal Green function is obtained. Furthermore using BRST theory an alternative path-integral representation for G α is presented. From these path integral representations the composition laws for the G α 's are derived using a modified path decomposition expansion. (orig.)
Vector Green's function algorithm for radiative transfer in plane-parallel atmosphere
Energy Technology Data Exchange (ETDEWEB)
Qin Yi [School of Physics, University of New South Wales (Australia)]. E-mail: yi.qin@csiro.au; Box, Michael A. [School of Physics, University of New South Wales (Australia)
2006-01-15
Green's function is a widely used approach for boundary value problems. In problems related to radiative transfer, Green's function has been found to be useful in land, ocean and atmosphere remote sensing. It is also a key element in higher order perturbation theory. This paper presents an explicit expression of the Green's function, in terms of the source and radiation field variables, for a plane-parallel atmosphere with either vacuum boundaries or a reflecting (BRDF) surface. Full polarization state is considered but the algorithm has been developed in such way that it can be easily reduced to solve scalar radiative transfer problems, which makes it possible to implement a single set of code for computing both the scalar and the vector Green's function.
Vector Green's function algorithm for radiative transfer in plane-parallel atmosphere
International Nuclear Information System (INIS)
Qin Yi; Box, Michael A.
2006-01-01
Green's function is a widely used approach for boundary value problems. In problems related to radiative transfer, Green's function has been found to be useful in land, ocean and atmosphere remote sensing. It is also a key element in higher order perturbation theory. This paper presents an explicit expression of the Green's function, in terms of the source and radiation field variables, for a plane-parallel atmosphere with either vacuum boundaries or a reflecting (BRDF) surface. Full polarization state is considered but the algorithm has been developed in such way that it can be easily reduced to solve scalar radiative transfer problems, which makes it possible to implement a single set of code for computing both the scalar and the vector Green's function
Exact solutions for fermionic Green's functions in the Bloch-Nordsieck approximation of QED
International Nuclear Information System (INIS)
Kernemann, A.; Stefanis, N.G.
1989-01-01
A set of new closed-form solutions for fermionic Green's functions in the Bloch-Nordsieck approximation of QED is presented. A manifestly covariant phase-space path-integral method is applied for calculating the n-fermion Green's function in a classical external field. In the case of one and two fermions, explicit expressions for the full Green's functions are analytically obtained, with renormalization carried out in the modified minimal subtraction scheme. The renormalization constants and the corresponding anomalous dimensions are determined. The mass-shell behavior of the two-fermion Green's function is investigated in detail. No assumptions are made concerning the structure of asymptotic states and no IR cutoff is used in the calculations
A relationship between scalar Green functions on hyperbolic and Euclidean Rindler spaces
International Nuclear Information System (INIS)
Haba, Z
2007-01-01
We derive a formula connecting in any dimension the Green function on the (D + 1)-dimensional Euclidean Rindler space and the one for a minimally coupled scalar field with a mass m in the D-dimensional hyperbolic space. The relation takes a simple form in the momentum space where the Green functions are equal at the momenta (p 0 , p) for Rindler and (m,p-hat) for hyperbolic space with a simple additive relation between the squares of the mass and the momenta. The formula has applications to finite temperature Green functions, Green functions on the cone and on the (compactified) Milne spacetime. Analytic continuations and interacting quantum fields are briefly discussed
Green functions in a super self-dual Yang-Mills background
International Nuclear Information System (INIS)
McArthur, I.N.
1984-01-01
In euclidean supersymmetric theories of chiral superfields and vector superfields coupled to a super-self-dual Yang-Mills background, we define Green functions for the Laplace-type differential operators which are obtained from the quadratic parot the action. These Green functions are expressed in terms of the Green function on the space of right chiral superfields, and an explicit expression for the right chiral Green function in the fundamental representation of an SU(n) gauge group is presented using the supersymmetric version of the ADHM formalism. The superfield kernels associated with the Laplace-type operators are used to obtain the one-loop quantum corrections to the super-self-dual Yang-Mills action, and also to provide a superfield version of the super-index theorems for the components of chiral superfields in a self-dual background. (orig.)
Discontinuities of Green functions in field theory at finite temperature and density
International Nuclear Information System (INIS)
Kobes, R.L.; Semenoff, G.W.
1985-01-01
We derive systematic rules for calculating the imaginary parts of Minkowski space Green functions in quantum field theory at finite temperature and density. Self-energy corrections are used as an example of the application of these rules. (orig.)
Nonequilibrium Phenomena in Plasmas
Sharma, A Surjalal
2005-01-01
The complexity of plasmas arises mainly from their inherent nonlinearity and far from equilibrium nature. The nonequilibrium behavior of plasmas is evident in the natural settings, for example, in the Earth's magnetosphere. Similarly, laboratory plasmas such as fusion bottles also have their fair share of complex behavior. Nonequilibrium phenomena are intimately connected with statistical dynamics and form one of the growing research areas in modern nonlinear physics. These studies encompass the ideas of self-organization, phase transition, critical phenomena, self-organized criticality and turbulence. This book presents studies of complexity in the context of nonequilibrium phenomena using theory, modeling, simulations, and experiments, both in the laboratory and in nature.
On nonequilibrium many-body systems. 1: The nonequilibrium statistical operator method
International Nuclear Information System (INIS)
Algarte, A.C.S.; Vasconcellos, A.R.; Luzzi, R.; Sampaio, A.J.C.
1985-01-01
The theoretical aspects involved in the treatment of many-body systems strongly departed from equilibrium are discussed. The nonequilibrium statistical operator (NSO) method is considered in detail. Using Jaynes' maximum entropy formalism complemented with an ad hoc hypothesis a nonequilibrium statistical operator is obtained. This approach introduces irreversibility from the outset and we recover statistical operators like those of Green-Mori and Zubarev as particular cases. The connection with Generalized Thermodynamics and the construction of nonlinear transport equations are briefly described. (Author) [pt
International Nuclear Information System (INIS)
Schulze-Halberg, Axel
2010-01-01
We study Green's functions of the generalized Sturm-Liouville problems that are related to each other by Darboux -equivalently, supersymmetrical - transformations. We establish an explicit relation between the corresponding Green's functions and derive a simple formula for their trace. The class of equations considered here includes the conventional Schroedinger equation and generalizations, such as for position-dependent mass and with linearly energy-dependent potential, as well as the stationary Fokker-Planck equation.
Directory of Open Access Journals (Sweden)
Roman Urban
2004-12-01
Full Text Available We consider the Green functions for second-order left-invariant differential operators on homogeneous manifolds of negative curvature, being a semi-direct product of a nilpotent Lie group $N$ and $A=mathbb{R}^+$. We obtain estimates for mixed derivatives of the Green functions both in the coercive and non-coercive case. The current paper completes the previous results obtained by the author in a series of papers [14,15,16,19].
Green's functions for a graphene sheet and quantum dot in a normal magnetic field
International Nuclear Information System (INIS)
Horing, Norman J Morgenstern; Liu, S Y
2009-01-01
This paper is concerned with the derivation of the retarded Green's function for a two-dimensional graphene layer in a perpendicular magnetic field in two explicit, analytic forms, which we employ in obtaining a closed-form solution for the Green's function of a tightly confined magnetized graphene quantum dot. The dot is represented by a δ (2) (r)-potential well and the system is subject to Landau quantization in the normal magnetic field
Computing the real-time Green's Functions of large Hamiltonian matrices
Iitaka, Toshiaki
1998-01-01
A numerical method is developed for calculating the real time Green's functions of very large sparse Hamiltonian matrices, which exploits the numerical solution of the inhomogeneous time-dependent Schroedinger equation. The method has a clear-cut structure reflecting the most naive definition of the Green's functions, and is very suitable to parallel and vector supercomputers. The effectiveness of the method is illustrated by applying it to simple lattice models. An application of this method...
Calculation of the Green functions by the coupling constant dispersion relations
International Nuclear Information System (INIS)
Bogomalny, E.B.
1977-01-01
The discontinuities of the Green functions on the cut in the complex plane of the coupling constant are calculated by the steepest descent method. The saddle points are given by the solutions of the classical field equations at those values of the coupling constant for which the classical theory has no ground state. The Green functions at the physical values of the coupling constant are determined by dispersion relations. (Auth.)
Thermal properties of Green's functions in Rindler, de Sitter, and Schwarzschild spaces
International Nuclear Information System (INIS)
Dowker, J.S.
1978-01-01
The conventional massless scalar Green's functions in the Minkowski, de Sitter, and two-dimensional Schwarzschild spaces are reinterpreted as finite-temperature Green's functions and the corresponding averages of the stress-energy operator are calculated. The renormalization adopted consists of subtracting the zero-temperature quantities. In all cases the averages give the stress tensor of a purely Planck-type perfect gas
The one-loop Green's functions of dimensionally reduced gauge theories
International Nuclear Information System (INIS)
Ketov, S.V.; Prager, Y.S.
1988-01-01
The dimensional regularization technique as well as that by dimensional reduction is applied to the calculation of the regularized one-loop Green's functions in dsub(o)-dimensional Yang-Mills theory with real massless scalars and spinors in arbitrary (real) representations of a gauge group G. As a particular example, the super-symmetrically regularized one-loop Green's functions of the N=4 supersymmetric Yang-Mills model are derived. (author). 17 refs
Development of thermal stress screening method. Application of green function method
International Nuclear Information System (INIS)
Furuhashi, Ichiro; Shibamoto, Hiroshi; Kasahara, Naoto
2004-01-01
This work was achieved for the development of the screening method of thermal transient stresses in FBR components. We proposed an approximation method for evaluations of thermal stress under variable heat transfer coefficients (non-linear problems) using the Green functions of thermal stresses with constant heat transfer coefficients (linear problems). Detailed thermal stress analyses provided Green functions for a skirt structure and a tube-sheet of Intermediate Heat Exchanger. The upper bound Green functions were obtained by the analyses using those upper bound heat transfer coefficients. The medium and the lower bound Green functions were got by the analyses of those under medium and the lower bound heat transfer coefficients. Conventional evaluations utilized the upper bound Green functions. On the other hand, we proposed a new evaluation method by using the upper bound, medium and the lower bound Green functions. The comparison of above results gave the results as follows. The conventional evaluations were conservative and appropriate for the cases under one fluid thermal transient structure such as the skirt. The conventional evaluations were generally conservative for the complicated structures under two or more fluids thermal transients such as the tube-sheet. But the danger locations could exists for the complicated structures under two or more fluids transients, namely the conventional evaluations were non-conservative. The proposed evaluations gave good estimations for these complicated structures. Though above results, we have made the basic documents of the screening method of thermal transient stresses using the conventional method and the new method. (author)
Phonon conductivity and relaxation rate in solids with disturbances by the Green function method
International Nuclear Information System (INIS)
Singh, M.
1980-09-01
In this present article we have established an expression for the temperature dependence of the lattice thermal conductivity of solids with harmonic disturbances. The relaxation rate for scattering of phonons with point defect is also derived. We will apply the Kubo-correlation function formalism for the thermal conductivity, and the double time temperature dependent Green function technique for the evaluation of correlation functions
Bi-conformal symmetry and static Green functions in the Schwarzschild-Tangherlini spacetimes
International Nuclear Information System (INIS)
Frolov, Valeri P.; Zelnikov, Andrei
2015-01-01
We study a static massless minimally coupled scalar field created by a source in a static D-dimensional spacetime. We demonstrate that the corresponding equation for this field is invariant under a special transformation of the background metric. This transformation consists of the static conformal transformation of the spatial part of the metric accompanied by a properly chosen transformation of the red-shift factor. Both transformations are determined by one function Ω of the spatial coordinates. We show that in a case of higher dimensional spherically symmetric black holes one can find such a bi-conformal transformation that the symmetry of the D-dimensional metric is enhanced after its application. Namely, the metric becomes a direct sum of the metric on a unit sphere and the metric of 2D anti-de Sitter space. The method of the heat kernels is used to find the Green function in this new space, which allows one, after dimensional reduction, to obtain a static Green function in the original space of the static black hole. The general useful representation of static Green functions is obtained in the Schwarzschild-Tangherlini spacetimes of arbitrary dimension. The exact explicit expressions for the static Green functions are obtained in such metrics for D<6. It is shown that in the four dimensional case the corresponding Green function coincides with the Copson solution.
Leser, William P.; Yuan, Fuh-Gwo; Leser, William P.
2013-01-01
A method of numerically estimating dynamic Green's functions using the finite element method is proposed. These Green's functions are accurate in a limited frequency range dependent on the mesh size used to generate them. This range can often match or exceed the frequency sensitivity of the traditional acoustic emission sensors. An algorithm is also developed to characterize an acoustic emission source by obtaining information about its strength and temporal dependence. This information can then be used to reproduce the source in a finite element model for further analysis. Numerical examples are presented that demonstrate the ability of the band-limited Green's functions approach to determine the moment tensor coefficients of several reference signals to within seven percent, as well as accurately reproduce the source-time function.
Euclidean scalar Green function in a higher dimensional global monopole space-time
International Nuclear Information System (INIS)
Bezerra de Mello, E.R.
2002-01-01
We construct the explicit Euclidean scalar Green function associated with a massless field in a higher dimensional global monopole space-time, i.e., a (1+d)-space-time with d≥3 which presents a solid angle deficit. Our result is expressed in terms of an infinite sum of products of Legendre functions with Gegenbauer polynomials. Although this Green function cannot be expressed in a closed form, for the specific case where the solid angle deficit is very small, it is possible to develop the sum and obtain the Green function in a more workable expression. Having this expression it is possible to calculate the vacuum expectation value of some relevant operators. As an application of this formalism, we calculate the renormalized vacuum expectation value of the square of the scalar field, 2 (x)> Ren , and the energy-momentum tensor, μν (x)> Ren , for the global monopole space-time with spatial dimensions d=4 and d=5
Nonequilibrium Transport through a Spinful Quantum Dot with Superconducting Leads
DEFF Research Database (Denmark)
Andersen, Brian Møller; Flensberg, Karsten; Koerting, Verena
2011-01-01
We study the nonlinear cotunneling current through a spinful quantum dot contacted by two superconducting leads. Applying a general nonequilibrium Green function formalism to an effective Kondo model, we study the rich variation in the IV characteristics with varying asymmetry in the tunnel...... coupling to source and drain electrodes. The current is found to be carried, respectively, by multiple Andreev reflections in the symmetric limit, and by spin-induced Yu-Shiba-Rusinov bound states in the strongly asymmetric limit. The interplay between these two mechanisms leads to qualitatively different...... IV characteristics in the crossover regime of intermediate symmetry, consistent with recent experimental observations of negative differential conductance and repositioned conductance peaks in subgap cotunneling spectroscopy....
Correlations in Many-Body systems from two-time Greens functions
International Nuclear Information System (INIS)
Morawetz, K.; Kohler, H.S.
2000-01-01
The Kadanoff-Baym (KB) equations are solved numerically for infinite nuclear matter. In particular we calculate correlation energies and correlation times. Approximating the Green's functions in the KB collision kernel by the free Green's functions the Levinson equation is obtained. This approximation is valid for weak interactions and/or low densities. It relates to the extended quasi-particle approximation for the spectral function. The Levinson correlation energy reduces for large times to a second order Born approximation for the energy. Comparing the Levinson, Born and KB calculations allows for an estimate of higher order spectral corrections to the correlations. (authors)
Green tea effects on cognition, mood and human brain function: A systematic review.
Mancini, Edele; Beglinger, Christoph; Drewe, Jürgen; Zanchi, Davide; Lang, Undine E; Borgwardt, Stefan
2017-10-15
Green tea (Camellia sinensis) is a beverage consumed for thousands of years. Numerous claims about the benefits of its consumption were stated and investigated. As green tea is experiencing a surge in popularity in Western culture and as millions of people all over the world drink it every day, it is relevant to understand its effects on the human brain. To assess the current state of knowledge in the literature regarding the effects of green tea or green tea extracts, l-theanine and epigallocatechin gallate both components of green tea-on general neuropsychology, on the sub-category cognition and on brain functions in humans. We systematically searched on PubMed database and selected studies by predefined eligibility criteria. We then assessed their quality and extracted data. We structured our effort according to the PRISMA statement. We reviewed and assessed 21 studies, 4 of which were randomised controlled trials, 12 cross-over studies (both assessed with an adapted version of the DELPHI-list), 4 were cross-sectional studies and one was a cohort study (both assessed with an adapted version of the Newcastle-Ottawa assessment scale). The average study quality as appraised by means of the DELPHI-list was good (8.06/9); the studies evaluated with the Newcastle-Ottawa-scale were also good (6.7/9). The reviewed studies presented evidence that green tea influences psychopathological symptoms (e.g. reduction of anxiety), cognition (e.g. benefits in memory and attention) and brain function (e.g. activation of working memory seen in functional MRI). The effects of green tea cannot be attributed to a single constituent of the beverage. This is exemplified in the finding that beneficial green tea effects on cognition are observed under the combined influence of both caffeine and l-theanine, whereas separate administration of either substance was found to have a lesser impact. Copyright © 2017. Published by Elsevier GmbH.
Wapenaar, Kees
2017-06-01
A unified scalar wave equation is formulated, which covers three-dimensional (3D) acoustic waves, 2D horizontally-polarised shear waves, 2D transverse-electric EM waves, 2D transverse-magnetic EM waves, 3D quantum-mechanical waves and 2D flexural waves. The homogeneous Green's function of this wave equation is a combination of the causal Green's function and its time-reversal, such that their singularities at the source position cancel each other. A classical representation expresses this homogeneous Green's function as a closed boundary integral. This representation finds applications in holographic imaging, time-reversed wave propagation and Green's function retrieval by cross correlation. The main drawback of the classical representation in those applications is that it requires access to a closed boundary around the medium of interest, whereas in many practical situations the medium can be accessed from one side only. Therefore, a single-sided representation is derived for the homogeneous Green's function of the unified scalar wave equation. Like the classical representation, this single-sided representation fully accounts for multiple scattering. The single-sided representation has the same applications as the classical representation, but unlike the classical representation it is applicable in situations where the medium of interest is accessible from one side only.
Green's functions on spheres and on closed Robertson--Walker spacetimes
International Nuclear Information System (INIS)
Hahne, G.E.
1975-01-01
The objective of this investigation was to carry the theory and calculations of certain Green functions as far as seemed possible toward applications, in particular toward the calculation of the rate of spontaneous creation of scalar particles by strong gravitational fields. The latter calculation has not yet been carried out in full on account of its apparent mathematical intractability. As an introduction to Green functions concern is with the Green function for the Laplacian operator Δ (or NABLA 2 ) and the Helmholtz operator DELTA + omega 2 on n-spheres, with a few examples worked out. Subsequently, Green's functions for massless particles on Einstein spacetimes of two (S 1 x T) and four (S 3 x T) dimensions are obtained. By a fortuitous circumstance the conformally invariant equation in the case of the 4-dimensional Einstein space could be worked out in detail. The conformally invariant case predicts no spontaneous creation of particles, however. In the final calculation a special kind of Green function associated with the Klein-Gordon equation was related to the particle creation amplitude for an Einstein universe. (Diss. Abstr. Int., B)
On the Reliability of Source Time Functions Estimated Using Empirical Green's Function Methods
Gallegos, A. C.; Xie, J.; Suarez Salas, L.
2017-12-01
The Empirical Green's Function (EGF) method (Hartzell, 1978) has been widely used to extract source time functions (STFs). In this method, seismograms generated by collocated events with different magnitudes are deconvolved. Under a fundamental assumption that the STF of the small event is a delta function, the deconvolved Relative Source Time Function (RSTF) yields the large event's STF. While this assumption can be empirically justified by examination of differences in event size and frequency content of the seismograms, there can be a lack of rigorous justification of the assumption. In practice, a small event might have a finite duration when the RSTF is retrieved and interpreted as the large event STF with a bias. In this study, we rigorously analyze this bias using synthetic waveforms generated by convolving a realistic Green's function waveform with pairs of finite-duration triangular or parabolic STFs. The RSTFs are found using a time-domain based matrix deconvolution. We find when the STFs of smaller events are finite, the RSTFs are a series of narrow non-physical spikes. Interpreting these RSTFs as a series of high-frequency source radiations would be very misleading. The only reliable and unambiguous information we can retrieve from these RSTFs is the difference in durations and the moment ratio of the two STFs. We can apply a Tikhonov smoothing to obtain a single-pulse RSTF, but its duration is dependent on the choice of weighting, which may be subjective. We then test the Multi-Channel Deconvolution (MCD) method (Plourde & Bostock, 2017) which assumes that both STFs have finite durations to be solved for. A concern about the MCD method is that the number of unknown parameters is larger, which would tend to make the problem rank-deficient. Because the kernel matrix is dependent on the STFs to be solved for under a positivity constraint, we can only estimate the rank-deficiency with a semi-empirical approach. Based on the results so far, we find that the
Discrete Green's Theorem, Green's Functions and Stable Radiative FDTD Boundary Conditions
Arnold, J.M.; Hon, de B.P.
2007-01-01
We propose a radiative boundary condition for the discrete-grid formulation of Helmholtz’ equation, based on rational approximation in the frequency domain of a Green’s function for the discretised system. This boundary condition is free from instabilities.
An integral transform of Green's function, off-shell Jost solution and T ...
Indian Academy of Sciences (India)
integral transform of the Green's function for motion in Coulomb–Yamaguchi potential is derived via the r-space ... use in the calculation of the corresponding off-shell quantities without the explicit use of two-potential theorem and ..... (x), spherical Bessel function and gli(βli,r)s, the form factors of the sep- arable potential the ...
Genus one super-Green function revisited and superstring amplitudes with non-maximal supersymmetry
International Nuclear Information System (INIS)
Itoyama, H.; Yano, Kohei
2016-01-01
We reexamine genus one super-Green functions with general boundary conditions twisted by (α,β) for (σ,τ) directions in the eigenmode expansion and derive expressions as infinite series of hypergeometric functions. Using these, we compute one-loop superstring amplitudes with non-maximal supersymmetry, taking the example of massless vector emissions of open string type I Z 2 orbifold
Nonequilibrium thermodynamics of restricted Boltzmann machines
Salazar, Domingos S. P.
2017-08-01
In this work, we analyze the nonequilibrium thermodynamics of a class of neural networks known as restricted Boltzmann machines (RBMs) in the context of unsupervised learning. We show how the network is described as a discrete Markov process and how the detailed balance condition and the Maxwell-Boltzmann equilibrium distribution are sufficient conditions for a complete thermodynamics description, including nonequilibrium fluctuation theorems. Numerical simulations in a fully trained RBM are performed and the heat exchange fluctuation theorem is verified with excellent agreement to the theory. We observe how the contrastive divergence functional, mostly used in unsupervised learning of RBMs, is closely related to nonequilibrium thermodynamic quantities. We also use the framework to interpret the estimation of the partition function of RBMs with the annealed importance sampling method from a thermodynamics standpoint. Finally, we argue that unsupervised learning of RBMs is equivalent to a work protocol in a system driven by the laws of thermodynamics in the absence of labeled data.
Nonequilibrium thermodynamics of restricted Boltzmann machines.
Salazar, Domingos S P
2017-08-01
In this work, we analyze the nonequilibrium thermodynamics of a class of neural networks known as restricted Boltzmann machines (RBMs) in the context of unsupervised learning. We show how the network is described as a discrete Markov process and how the detailed balance condition and the Maxwell-Boltzmann equilibrium distribution are sufficient conditions for a complete thermodynamics description, including nonequilibrium fluctuation theorems. Numerical simulations in a fully trained RBM are performed and the heat exchange fluctuation theorem is verified with excellent agreement to the theory. We observe how the contrastive divergence functional, mostly used in unsupervised learning of RBMs, is closely related to nonequilibrium thermodynamic quantities. We also use the framework to interpret the estimation of the partition function of RBMs with the annealed importance sampling method from a thermodynamics standpoint. Finally, we argue that unsupervised learning of RBMs is equivalent to a work protocol in a system driven by the laws of thermodynamics in the absence of labeled data.
Finite medium Green's function solutions to nuclide transport in porous media
International Nuclear Information System (INIS)
Oston, S.G.
1979-01-01
Current analytical techniques for predicting the transport of nuclides in porous materials center on the Green's function approach - i.e., determining the response characteristics of a geologic pathway to an impulse function input. To data, the analyses all have set the boundary conditions needed to solve the 1-D transport equation as though each pathway were infinite in length. The purpose of this work is to critically examine the effect that this infinite pathway assumption has on Green's function models of nuclide transport in porous media. The work described herein has directly attacked the more difficult problem of obtaining suitable Green's functions for finite pathways whose dimensions, in fact, may not be much greater than the diffusion length. Two different finite media Green's functions describing the nuclide mass flux have been determined, depending on whether the pathway is terminated by a high or a low flow resistance at the outlet end. Pulse shapes and peak amplitudes have been computed for each Green's function over a wide range of geohydrologic parameters. These results have been compared to both infinite and semi-infinite medium solutions. It was found that predicted pulse shapes are quite sensitive to selection of a Green's function model for short pathways only. For long pathways all models tend toward a symmetric Gaussian flux-time history at the outlet. Thus, the results of our previous waste transport studies using the infinite pathway assumption are still generally valid because they always included at least one long pathway. It was also found that finite medium models offer some unique computational advantages for evaluating nuclide transport in a series of connecting pathways
Nonequilibrium statistical physics
Röpke, Gerd
2013-01-01
Authored by one of the top theoretical physicists in Germany, and a well-known authority in the field, this is the only coherent presentation of the subject suitable for masters and PhD students, as well as postdocs in physics and related disciplines.Starting from a general discussion of the nonequilibrium state, different standard approaches such as master equations, and kinetic and linear response theory, are derived after special assumptions. This allows for an insight into the problems of nonequilibrium physics, a discussion of the limits, and suggestions for improvements. Applications
Jia, Shouqing; La, Dongsheng; Ma, Xuelian
2018-04-01
The finite difference time domain (FDTD) algorithm and Green function algorithm are implemented into the numerical simulation of electromagnetic waves in Schwarzschild space-time. FDTD method in curved space-time is developed by filling the flat space-time with an equivalent medium. Green function in curved space-time is obtained by solving transport equations. Simulation results validate both the FDTD code and Green function code. The methods developed in this paper offer a tool to solve electromagnetic scattering problems.
Recursive evaluation of space-time lattice Green's functions
Hon, de B.P.; Arnold, J.M.
2012-01-01
Up to a multiplicative constant, the lattice Green’s function (LGF) as defined in condensed matter physics and lattice statistical mechanics is equivalent to the Z- domain counterpart of the finite-difference time-domain Green’s function (GF) on a lattice. Expansion of a well-known integral
Xie, J.; Schaff, D. P.; Chen, Y.; Schult, F.
2013-12-01
Reliably estimated source time functions (STFs) from high-frequency regional waveforms, such as Lg, Pn and Pg, provide important input for seismic source studies, explosion detection and discrimination, and minimization of parameter trade-off in attenuation studies. We have searched for candidate pairs of larger and small earthquakes in and around China that share the same focal mechanism but significantly differ in magnitudes, so that the empirical Green's function (EGF) method can be applied to study the STFs of the larger events. We conducted about a million deconvolutions using waveforms from 925 earthquakes, and screened the deconvolved traces to exclude those that are from event pairs that involved different mechanisms. Only 2,700 traces passed this screening and could be further analyzed using the EGF method. We have developed a series of codes for speeding up the final EGF analysis by implementing automations and user-graphic interface procedures. The codes have been fully tested with a subset of screened data and we are currently applying them to all the screened data. We will present a large number of deconvolved STFs retrieved using various phases (Lg, Pn, Sn and Pg and coda) with information on any directivities, any possible dependence of pulse durations on the wave types, on scaling relations for the pulse durations and event sizes, and on the estimated source static stress drops.
Simulations of Coulomb systems confined by polarizable surfaces using periodic Green functions.
Dos Santos, Alexandre P; Girotto, Matheus; Levin, Yan
2017-11-14
We present an efficient approach for simulating Coulomb systems confined by planar polarizable surfaces. The method is based on the solution of the Poisson equation using periodic Green functions. It is shown that the electrostatic energy arising from the surface polarization can be decoupled from the energy due to the direct Coulomb interaction between the ions. This allows us to combine an efficient Ewald summation method, or any other fast method for summing over the replicas, with the polarization contribution calculated using Green function techniques. We apply the method to calculate density profiles of ions confined between the charged dielectric and metal surfaces.
Time-domain Green's Function Method for three-dimensional nonlinear subsonic flows
Tseng, K.; Morino, L.
1978-01-01
The Green's Function Method for linearized 3D unsteady potential flow (embedded in the computer code SOUSSA P) is extended to include the time-domain analysis as well as the nonlinear term retained in the transonic small disturbance equation. The differential-delay equations in time, as obtained by applying the Green's Function Method (in a generalized sense) and the finite-element technique to the transonic equation, are solved directly in the time domain. Comparisons are made with both linearized frequency-domain calculations and existing nonlinear results.
International Nuclear Information System (INIS)
Iagolnitzer, D.
1983-11-01
Recent axiomatic results on the (non holonomic) analytic structure of the multiparticle S matrix and Green functions are reviewed and related general conjectures are described: (i) formal expansions of Green functions in terms of (holonomic) Feynman-type integrals in which each vertex represents an irreducible kernel, and (ii) ''graph by graph unitarity'' and other discontinuity formulae of the latter. These conjectures are closely linked with unitarity or asymptotic completeness equations, which they yield in a formal sense. In constructive field theory, a direct proof of the first conjecture (together with an independent proof of the second) would thus imply, as a first step, asymptotic completeness in that sense
Green's functions of the induction equation on regions with boundary. 1
International Nuclear Information System (INIS)
Braeuer, H.J.; Raedler, K.H.
1986-01-01
The evolution of a magnetic field is considered which pervades an electrically conducting fluid and its non-conducting surroundings under the influence of electromotive forces due to internal motion and other causes. The governing equations - among which the induction equation of magnetohydrodynamics is the most prominent - pose an initial value problem for the magnetic flux density. Properties of this initial value problem and of the solving Green's function are reviewed and a general construction principle for the Green's function is given. Detailed treatment of cases where the fluid occupies a sphere or an evenly bounded half-space are presented in two subsequent papers. (author)
The function of green belt Jatibarang as quality control for the environment of Semarang city
Murtini, Titien Woro; Harani, Arnis Rochma; Ernadia, Loretta
2017-06-01
The quality of the healthy environment in a neighborhood city is decreasing in number. According to the government regulation, Act No. 26 of 2007, a city should have 20% of green areas from the total area of the city. Now, Semarang only has 7.5% of green areas from the total city area. One of the efforts made by the Government of Semarang is the establishment of a greenbelt in Jatibarang area. It consists of several parts, namely, the reservoirs in the green belt area and also the plant zone in other sectors. The reservoir has a function as the controller of water resources sustainability where the crops serve as the balance for the combination. Thus, it is interesting to study how the interplay of these two functions in a green belt area. The primary data used in this study was obtained from the locus of research by direct observation, interview, and physical data collection. Based on the data collection, data was then processed and analyzed in accordance with the indicators that had been compiled based on theories of reservoirs, green belts, and the quality of the urban environment. Government regulations regarding with the greenbelt and tanks were also used as references in the discussion. The research found out that the presence of the reservoir and the plants in the green belt of Jatibarang can improve the function of the green belt optimally which is a real influence for the improvement of the environment quality, especially water. The Greenbelt was divided into four zones, namely the Arboretum, Argo - Forestry, Ecotourism, Buffer - Zone also made the region became a beautiful greenbelt that brought a positive influence to environmental quality.
Maximum entropy formalism for the analytic continuation of matrix-valued Green's functions
Kraberger, Gernot J.; Triebl, Robert; Zingl, Manuel; Aichhorn, Markus
2017-10-01
We present a generalization of the maximum entropy method to the analytic continuation of matrix-valued Green's functions. To treat off-diagonal elements correctly based on Bayesian probability theory, the entropy term has to be extended for spectral functions that are possibly negative in some frequency ranges. In that way, all matrix elements of the Green's function matrix can be analytically continued; we introduce a computationally cheap element-wise method for this purpose. However, this method cannot ensure important constraints on the mathematical properties of the resulting spectral functions, namely positive semidefiniteness and Hermiticity. To improve on this, we present a full matrix formalism, where all matrix elements are treated simultaneously. We show the capabilities of these methods using insulating and metallic dynamical mean-field theory (DMFT) Green's functions as test cases. Finally, we apply the methods to realistic material calculations for LaTiO3, where off-diagonal matrix elements in the Green's function appear due to the distorted crystal structure.
Energy Technology Data Exchange (ETDEWEB)
Kowalski, K., E-mail: karol.kowalski@pnnl.gov; Bhaskaran-Nair, K.; Shelton, W. A. [William R. Wiley Environmental Molecular Sciences Laboratory, Battelle, Pacific Northwest National Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352 (United States)
2014-09-07
In this paper we discuss a new formalism for producing an analytic coupled-cluster (CC) Green's function for an N-electron system by shifting the poles of similarity transformed Hamiltonians represented in N − 1 and N + 1 electron Hilbert spaces. Simple criteria are derived for the states in N − 1 and N + 1 electron spaces that are then corrected in the spectral resolution of the corresponding matrix representations of the similarity transformed Hamiltonian. The accurate description of excited state processes within a Green's function formalism would be of significant importance to a number of scientific communities ranging from physics and chemistry to engineering and the biological sciences. This is because the Green's function methodology provides a direct path for not only calculating properties whose underlying origins come from coupled many-body interactions but also provides a straightforward path for calculating electron transport, response, and correlation functions that allows for a direct link with experiment. As a special case of this general formulation, we discuss the application of this technique for Green's function defined by the CC with singles and doubles representation of the ground-state wave function.
Energy Technology Data Exchange (ETDEWEB)
Kowalski, K. [William R. Wiley Environmental Molecular Sciences Laboratory, Battelle, Pacific Northwest National Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352, USA; Bhaskaran-Nair, K. [William R. Wiley Environmental Molecular Sciences Laboratory, Battelle, Pacific Northwest National Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352, USA; Shelton, W. A. [William R. Wiley Environmental Molecular Sciences Laboratory, Battelle, Pacific Northwest National Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352, USA
2014-09-07
In this paper we discuss a new formalism for producing an analytic coupled-cluster (CC) Green's function for an N-electron system by shifting the poles of similarity transformed Hamiltonians represented in N - 1 and N + 1 electron Hilbert spaces. Simple criteria are derived for the states in N - 1 and N + 1 electron spaces that are then corrected in the spectral resolution of the corresponding matrix representations of the similarity transformed Hamiltonian. The accurate description of excited state processes within a Green's function formalism would be of significant importance to a number of scientific communities ranging from physics and chemistry to engineering and the biological sciences. This is because the Green's function methodology provides a direct path for not only calculating properties whose underlying origins come from coupled many-body interactions but also provides a straightforward path for calculating electron transport, response, and correlation functions that allows for a direct link with experiment. Finally, as a special case of this general formulation, we discuss the application of this technique for Green's function defined by the CC with singles and doubles representation of the ground-state wave function.
International Nuclear Information System (INIS)
Kowalski, K.; Bhaskaran-Nair, K.; Shelton, W. A.
2014-01-01
In this paper we discuss a new formalism for producing an analytic coupled-cluster (CC) Green's function for an N-electron system by shifting the poles of similarity transformed Hamiltonians represented in N − 1 and N + 1 electron Hilbert spaces. Simple criteria are derived for the states in N − 1 and N + 1 electron spaces that are then corrected in the spectral resolution of the corresponding matrix representations of the similarity transformed Hamiltonian. The accurate description of excited state processes within a Green's function formalism would be of significant importance to a number of scientific communities ranging from physics and chemistry to engineering and the biological sciences. This is because the Green's function methodology provides a direct path for not only calculating properties whose underlying origins come from coupled many-body interactions but also provides a straightforward path for calculating electron transport, response, and correlation functions that allows for a direct link with experiment. As a special case of this general formulation, we discuss the application of this technique for Green's function defined by the CC with singles and doubles representation of the ground-state wave function
Pinho, Pedro; Correia, Otília; Lecoq, Miguel; Munzi, Silvana; Vasconcelos, Sasha; Gonçalves, Paula; Rebelo, Rui; Antunes, Cristina; Silva, Patrícia; Freitas, Catarina; Lopes, Nuno; Santos-Reis, Margarida; Branquinho, Cristina
2016-05-01
Forested areas within cities host a large number of species, responsible for many ecosystem services in urban areas. The biodiversity in these areas is influenced by human disturbances such as atmospheric pollution and urban heat island effect. To ameliorate the effects of these factors, an increase in urban green areas is often considered sufficient. However, this approach assumes that all types of green cover have the same importance for species. Our aim was to show that not all forested green areas are equal in importance for species, but that based on a multi-taxa and functional diversity approach it is possible to value green infrastructure in urban environments. After evaluating the diversity of lichens, butterflies and other-arthropods, birds and mammals in 31 Mediterranean urban forests in south-west Europe (Almada, Portugal), bird and lichen functional groups responsive to urbanization were found. A community shift (tolerant species replacing sensitive ones) along the urbanization gradient was found, and this must be considered when using these groups as indicators of the effect of urbanization. Bird and lichen functional groups were then analyzed together with the characteristics of the forests and their surroundings. Our results showed that, contrary to previous assumptions, vegetation density and more importantly the amount of urban areas around the forest (matrix), are more important for biodiversity than forest quantity alone. This indicated that not all types of forested green areas have the same importance for biodiversity. An index of forest functional diversity was then calculated for all sampled forests of the area. This could help decision-makers to improve the management of urban green infrastructures with the goal of increasing functionality and ultimately ecosystem services in urban areas. Copyright © 2016 Elsevier Inc. All rights reserved.
Nonequilibrium thermodynamics of nucleation
Schweizer, M.; Sagis, L.M.C.
2014-01-01
We present a novel approach to nucleation processes based on the GENERIC framework (general equation for the nonequilibrium reversible-irreversible coupling). Solely based on the GENERIC structure of time-evolution equations and thermodynamic consistency arguments of exchange processes between a
Magnetic field effects on the quantum wire energy spectrum and Green's function
International Nuclear Information System (INIS)
Morgenstern Horing, Norman J.
2010-01-01
We analyze the energy spectrum and propagation of electrons in a quantum wire on a 2D host medium in a normal magnetic field, representing the wire by a 1D Dirac delta function potential which would support just a single subband state in the absence of the magnetic field. The associated Schroedinger Green's function for the quantum wire is derived in closed form in terms of known functions and the Landau quantized subband energy spectrum is examined.
Leading effect of visual plant characteristics for functional uses of green spaces
Directory of Open Access Journals (Sweden)
Beyza Şat Güngör
2016-07-01
Full Text Available Plant materials have the ability to lead the people’s functional use purposes with their visual characteristics. In this study, we examined whether the functional use follows the plant materials’ visual characteristics like a big size tree’s shade use. As visual characteristics of the plants; size, texture, color, and planting design basics are considered. Six urban green spaces determined for this experimental field study in the center of Kırklareli Province, and then a site survey implemented to determine apparent visual characteristics of the plants and matched functional uses with their visual characteristics. Five functional use types determined according to the visual plant characteristics (sitting and resting, pedestrian transition, meeting point, walking and recreational uses. Best representing four photos of each green space’s plant materials are used in photo questionnaires. 89 photo questionnaires were conducted. Five functional use type options indicated in the questionnaire for each green space and one of the options were coinciding with the visual plant characteristics of that green space according to the site survey results. For the analyses of questionnaires; SPSS 17 statistical packages were used. As result; the hypothesis was confirmed by coinciding statistical analyses results with the site survey results.
Frequency-domain Green's functions for radar waves in heterogeneous 2.5D media
Ellefsen, K.J.; Croize, D.; Mazzella, A.T.; McKenna, J.R.
2009-01-01
Green's functions for radar waves propagating in heterogeneous 2.5D media might be calculated in the frequency domain using a hybrid method. The model is defined in the Cartesian coordinate system, and its electromagnetic properties might vary in the x- and z-directions, but not in the y-direction. Wave propagation in the x- and z-directions is simulated with the finite-difference method, and wave propagation in the y-direction is simulated with an analytic function. The absorbing boundaries on the finite-difference grid are perfectly matched layers that have been modified to make them compatible with the hybrid method. The accuracy of these numerical Greens functions is assessed by comparing them with independently calculated Green's functions. For a homogeneous model, the magnitude errors range from -4.16% through 0.44%, and the phase errors range from -0.06% through 4.86%. For a layered model, the magnitude errors range from -2.60% through 2.06%, and the phase errors range from -0.49% through 2.73%. These numerical Green's functions might be used for forward modeling and full waveform inversion. ?? 2009 Society of Exploration Geophysicists. All rights reserved.
Bruni, S.; Llombart, N.; Neto, A.; Gerini, G.; Maci, S.
2004-01-01
A method is proposed for the analysis of arrays of linear printed antennas. After the formulation of pertinent set of integral equations, the appropriate equivalent currents of the Method of Moments are represented in terms of two sets of entire domain basis functions. These functions synthesize on
Brazilian Green Propolis Improves Antioxidant Function in Patients with Type 2 Diabetes Mellitus
Directory of Open Access Journals (Sweden)
Liting Zhao
2016-05-01
Full Text Available Propolis contains a variety of bioactive components and possesses many biological properties. This study was designed to evaluate potential effects of Brazilian green propolis on glucose metabolism and antioxidant function in patients with type 2 diabetes mellitus (T2DM. In the 18-week randomized controlled study, enrolled patients with T2DM were randomly assigned to Brazilian green propolis group (900 mg/day (n = 32 and control group (n = 33. At the end of the study, no significant difference was found in serum glucose, glycosylated hemoglobin, insulin, aldose reductase or adiponectin between the two groups. However, serum GSH and total polyphenols were significantly increased, and serum carbonyls and lactate dehydrogenase activity were significantly reduced in the Brazilian green propolis group. Serum TNF-α was significantly decreased, whereas serum IL-1β and IL-6 were significantly increased in the Brazilian green propolis group. It is concluded that Brazilian green propolis is effective in improving antioxidant function in T2DM patients.
Biçer, M.; Kaşkaş, A.
2018-03-01
The infinite medium Green's function is used to solve the half-space albedo, slab albedo and Milne problems for the unpolarized Rayleigh scattering case; these problems are the most classical problems of radiative transfer theory. The numerical results are obtained and are compared with previous ones.
Numerical solution of the potential problem by integral equations without Green's functions
International Nuclear Information System (INIS)
De Mey, G.
1977-01-01
An integral equation technique will be presented to solve Laplace's equation in a two-dimensional area S. The Green's function has been replaced by a particular solution of Laplace equation in order to establish the integral equation. It is shown that accurate results can be obtained provided the pivotal elimination method is used to solve the linear algebraic set
Green nesting material has a function in mate attraction in the European starling
Komdeur, J
The function of fresh green nest material has long been debated. It has been suggested that it reduces the number of ectoparasites in nests and on nestlings (nest protection hypothesis), or is used by males to signal condition and paternal quality (male quality hypothesis) or is used as a sexually
Plante, Ianik; Cucinotta, Francis A.
2011-01-01
Radiolytic species are formed approximately 1 ps after the passage of ionizing radiation through matter. After their formation, they diffuse and chemically react with other radiolytic species and neighboring biological molecules, leading to various oxidative damage. Therefore, the simulation of radiation chemistry is of considerable importance to understand how radiolytic species damage biological molecules [1]. The step-by-step simulation of chemical reactions is difficult, because the radiolytic species are distributed non-homogeneously in the medium. Consequently, computational approaches based on Green functions for diffusion-influenced reactions should be used [2]. Recently, Green functions for more complex type of reactions have been published [3-4]. We have developed exact random variate generators of these Green functions [5], which will allow us to use them in radiation chemistry codes. Moreover, simulating chemistry using the Green functions is which is computationally very demanding, because the probabilities of reactions between each pair of particles should be evaluated at each timestep [2]. This kind of problem is well adapted for General Purpose Graphic Processing Units (GPGPU), which can handle a large number of similar calculations simultaneously. These new developments will allow us to include more complex reactions in chemistry codes, and to improve the calculation time. This code should be of importance to link radiation track structure simulations and DNA damage models.
A time-dependent Green's function-based model for stream ...
African Journals Online (AJOL)
DRINIE
2003-07-03
Jul 3, 2003 ... applications, this Green's function has found use primarily in linear heat transfer and flow ... based on the mathematical description of the flow with the nonlinear .... i∂/∂x + j∂/∂y is the two-dimensional gradient operator,.
Energy Technology Data Exchange (ETDEWEB)
Blanchard, P [European Organization for Nuclear Research, Geneva (Switzerland); Seneor, R [European Organization for Nuclear Research, Geneva (Switzerland); Ecole Polytechnique, 75 - Paris (France). Centre de Physique Theorique)
1975-01-01
With the method of perturbative renormalization developed by Epstein and Glaser it is shown that Green's functions exist for theories with massless particles such as Q.E.D. and lambda:PHI/sup 2n/ theories. Growth properties are given in momentum space. In the case of Q.E.D., it is also shown that one can perform the physical mass renormalization.
Green's functions for a scalar fields in a class of Robertson-Walker space-times
International Nuclear Information System (INIS)
Mankin, Romi; Ainsaar, Ain
1997-01-01
The retarded and advanced Green's functions for a massless non conformally-coupled scalar field in a class of Robertson-Walker space-times are calculated analytically. The results are applied to the calculation of the Hadamard fundamental solutions in some special cases. (author)
Use of Green functions in line shape problems in nuclear Magnetic resonance
International Nuclear Information System (INIS)
Martin, M.; Moreno, J.A.
1982-01-01
A method based on the two times Green function formalism is presented. It permits the straightforward determination of the line shape in Magnetic Resonance experiments together with its temperature behavior. Model calculations are made on a two-spin system attached to a one-dimensional rotor obtaining the temperature dependence of its Magnetic Resonance line shape and second moment
The behaviour of the Green function for the BFKL pomeron with running coupling
International Nuclear Information System (INIS)
Kowalski, H.; Lipatov, L.N.; Ross, D.A.
2015-08-01
We analyse here in LO the physical properties of the Green function solution for the BFKL equation. We show that the solution obeys the orthonormality conditions in the physical region and fulfills the completeness requirements. The unintegrated gluon density is shown to consists of a set of few poles with parameters which could be determined by comparison with the DIS data of high precision.
International Nuclear Information System (INIS)
Zaytsev, S A
2010-01-01
The possibility of using straight-line paths of integration in computing the integral representation of the three-body Coulomb Green's function is discussed. In our numerical examples two different kinds of integration contours in the complex energy planes are considered. It is demonstrated that straight-line paths, which cross the positive real axis, are suitable for numerical computation.
Borel summability in the disorder parameter of the averaged Green's function for Gaussian disorder
International Nuclear Information System (INIS)
Constantinescu, F.; Kloeckner, K.; Scharffenberger, U.
1985-01-01
In this note we prove Borel summability in the disorder parameter of the averaged Green's function of tight binding models Hsub(v)=-Δ+V with Gaussian disorder. Using this, we can reconstruct the density of states rho(E)sub(γ) from the Borel sums. (orig./WL)
Vijaykumar, A.; Ouldridge, T.E.; ten Wolde, P.R.; Bolhuis, P.G.
2017-01-01
The modeling of complex reaction-diffusion processes in, for instance, cellular biochemical networks or self-assembling soft matter can be tremendously sped up by employing a multiscale algorithm which combines the mesoscopic Green's Function Reaction Dynamics (GFRD) method with explicit stochastic
Order- N Green's Function Technique for Local Environment Effects in Alloys
DEFF Research Database (Denmark)
Abrikosov, I. A.; Niklasson, A. M. N.; Simak, S. I.
1996-01-01
We have developed a new approach to the calculations of ground state properties of large crystalline systems with arbitrary atomic configurations based on a Green's function technique in conjunction with a self-consistent effective medium for the underlying randomly occupied lattice. The locally...
Relation between Euclidean and real time calculations of Green functions at finite temperature
International Nuclear Information System (INIS)
Bochkarev, A.
1993-01-01
We find a relation between the semiclassical approximation of the temperature (Matsubara) two-point correlator and the corresponding classical Green function in real time at finite temperature. The anharmonic oscillator at finite temperature is used to illustrate our statement, which is however of rather general origin
An algebraic construction of the Green functions for P(φ)2 theory with source
International Nuclear Information System (INIS)
Houard, J.C.; Irac-Astaud, M.
1987-01-01
The retarded solutions of nonlinear forced wave equations in two-dimensional space-time are diagrammatically expanded in a new way, different from the Feynman method. The Green functions associated with these diagrams are obtained in an explicit form. (author). 4 refs
Sum-over-histories representation for the causal Green function of free scalar field theory
International Nuclear Information System (INIS)
Rudolph, O.
1995-01-01
A set of Green functions scrG α (x-y), α element-of[0,2π] for free scalar field theory is introduced, varying between the Hadamard Green function Δ 1 (x-y)==left-angle 0|{cphi(x),cphi(y)}|0 right-angle and the causal Green function scrG π (x-y)=iΔ(x-y)==[cphi(x),cphi(y)]. For every α element-of[0,2π] a path integral representation for scrG α is obtained both in configuration space and in the phase space of the classical relativistic particle. Setting α=π a sum-over-histories representation for the causal Green function is obtained. Furthermore, a reduced phase space integral representation for the scrG α 's is stated and an alternative BRST path integral representation for scrG α is presented. From these path integral representations the composition laws for the scrG α 's are derived using a modified path decomposition expansion
Kuchment, Peter
2012-06-21
Precise asymptotics known for the Green\\'s function of the Laplace operator have found their analogs for periodic elliptic operators of the second order at and below the bottom of the spectrum. Due to the band-gap structure of the spectra of such operators, the question arises whether similar results can be obtained near or at the edges of spectral gaps. As the result of this work shows, this is possible at a spectral edge when the dimension d ≥ 3. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Application of the Green's function method for 2- and 3-dimensional steady transonic flows
Tseng, K.
1984-01-01
A Time-Domain Green's function method for the nonlinear time-dependent three-dimensional aerodynamic potential equation is presented. The Green's theorem is being used to transform the partial differential equation into an integro-differential-delay equation. Finite-element and finite-difference methods are employed for the spatial and time discretizations to approximate the integral equation by a system of differential-delay equations. Solution may be obtained by solving for this nonlinear simultaneous system of equations in time. This paper discusses the application of the method to the Transonic Small Disturbance Equation and numerical results for lifting and nonlifting airfoils and wings in steady flows are presented.
Infra-red ghost contribution to the gluon Green's functions
International Nuclear Information System (INIS)
Paccanoni, F.
1985-01-01
The Schwinger-Dyson equations for the ghost propagator and the ghost-ghost-gluon vertex function are studied in the Landau gauge. A confining infra-red singularity is assumed for the gluon propagator and a suitable approximation is devised for the solution of the integral equations. It is found that the bare values of the ghost propagator and coupling cannot be a consistent solution of either equation. It is determined a possible behaviour of the correction factor for the ghost propagator in the small-momentum limit and discussed the consistency of the approximation schemes for the gluon propagator that neglet Faddeev-Popov ghost
International Nuclear Information System (INIS)
Khromov, V.V.
1978-01-01
The notion of neutron importance when applied to nuclear reactor statics problems described by time-independent homogeneous equations of neutron transport with provision for normalization of neutron distribution is considered. An equation has been obtained for the function of neutron importance in a conditionally critical reactor with respect to an arbitrary nons linear functional determined for the normalized neutron distribution. Relation between this function and the generalized Green function of the selfconjugated operator of the reactor equation is determined and the formula of small perturbations for the functionals of a conditionally critical reactor is deduced
Generalized relations among N-dimensional Coulomb Green's functions using fractional derivatives
International Nuclear Information System (INIS)
Blinder, S.M.; Pollock, E.L.
1989-01-01
Hostler [J. Math. Phys. 11, 2966 (1970)] has shown that Coulomb Green's functions of different dimensionality N are related by G (N+2) =OG (N) , where O is a first-order derivative operator in the variables x and y. Thus all the even-dimensional functions are connected, as are analogously the odd-dimensional functions. It is shown that the operations of functional differentiation and integration can further connect the even- to the odd-dimensional functions, so that Hostler's relation can be extended to give G (N+1) =O 1/2 G (N)
Recent Advances in the Korringa-Kohn-Rostoker Green Function Method
Directory of Open Access Journals (Sweden)
Zeller Rudolf
2014-01-01
Full Text Available The Korringa-Kohn-Rostoker (KKR Green function (GF method is a technique for all-electron full-potential density-functional calculations. Similar to the historical Wigner-Seitz cellular method, the KKR-GF method uses a partitioning of space into atomic Wigner-Seitz cells. However, the numerically demanding wave-function matching at the cell boundaries is avoided by use of an integral equation formalism based on the concept of reference Green functions. The advantage of this formalism will be illustrated by the recent progress made for very large systems with thousands of inequivalent atoms and for very accurate calculations of atomic forces and total energies.
Electromagnetically induced nuclear beta decay calculated by a Green's function method
International Nuclear Information System (INIS)
Reiss, H.R.
1984-01-01
The transition probability for enhancement of forbidden nuclear beta decay by an applied plane-wave electromagnetic field is calculated in a nonrelativistic spinless approximation by a Green's function method. The calculation involves a stationary-phase approximation. The stationary phase points in the presence of an intense field are located in very different positions than they are in the field-free case. In order-of-magnitude terms, the results are completely consistent with an earlier, much more complete wave-function calculation which includes spin and relativistic effects. Both the present Green's function calculation and the earlier wave function calculation give electromagnetic contributions in first-forbidden nuclear beta decay matrix elements which are of order (R 0 /lambda-dash-bar/sub C/) 2 with respect to allowed decays, where R 0 is the nuclear radius and lambda-dash-bar/sub C/ is the electron Compton wavelength
De Hon, B. P.; Arnold, J. M.
2016-01-01
Time-domain 3-D lattice Green's function (LGF) sequences can be evaluated using a single-lattice point recurrence scheme, and play an important role in finite-difference Green's function diakoptics. Asymptotically, at large distances, the LGFs in three dimensions can be described in terms of six
de Hon, B.P.; Arnold, J.M.
2015-01-01
The robust and speedy evaluation of lattice Green's functions LGFs) is crucial to the effectiveness of finite-difference Green's function diakoptics schemes. We have recently determined a generic recurrence scheme for the construction of scalar LGF sequences at arbitrary points on a 3-D cubic
Infra-red asymptotic behaviour of the one-fermion Green's function in a scalar model with isospin
International Nuclear Information System (INIS)
Popov, V.N.; Wu, T.T.
1979-01-01
In a theory where massive fermions interact with a massless scalar field of isospin 1, the behaviour of the one-fermion Green's function is found to differ from the free Green's function by a factor (1 - (2g 2 /π 2 )ln mmod(x-y))sup(-3/8), in the limit of large separation mod(x-y). (Auth.)
International Nuclear Information System (INIS)
Lobanov, Yu.Yu.; Shahbagian, R.R.; Zhidkov, E.P.
1991-01-01
A new method for numerical solution of the boundary problem for Schroedinger-like partial differential equations in R n is elaborated. The method is based on representation of multidimensional Green function in the form of multiple functional integral and on the use of approximation formulas which are constructed for such integrals. The convergence of approximations to the exact value is proved, the remainder of the formulas is estimated. Method reduces the initial differential problem to quadratures. 16 refs.; 7 tabs
Adaptation of light-harvesting functions of unicellular green algae to different light qualities.
Ueno, Yoshifumi; Aikawa, Shimpei; Kondo, Akihiko; Akimoto, Seiji
2018-05-28
Oxygenic photosynthetic organisms perform photosynthesis efficiently by distributing captured light energy to photosystems (PSs) at an appropriate balance. Maintaining photosynthetic efficiency under changing light conditions requires modification of light-harvesting and energy-transfer processes. In the current study, we examined how green algae regulate their light-harvesting functions in response to different light qualities. We measured low-temperature time-resolved fluorescence spectra of unicellular green algae Chlamydomonas reinhardtii and Chlorella variabilis cells grown under different light qualities. By observing the delayed fluorescence spectra, we demonstrated that both types of green algae primarily modified the associations between light-harvesting chlorophyll protein complexes (LHCs) and PSs (PSII and PSI). Under blue light, Chlamydomonas transferred more energy from LHC to chlorophyll (Chl) located far from the PSII reaction center, while energy was transferred from LHC to PSI via different energy-transfer pathways in Chlorella. Under green light, both green algae exhibited enhanced energy transfer from LHCs to both PSs. Red light induced fluorescence quenching within PSs in Chlamydomonas and LHCs in Chlorella. In Chlorella, energy transfer from PSII to PSI appears to play an important role in balancing excitation between PSII and PSI.
Coulomb Green's function and image potential near a cylindrical diffuse interface
Xue, Changfeng; Huang, Qiongwei; Deng, Shaozhong
2015-12-01
In a preceding paper [Comput. Phys. Commun. 184 (1): 51-59, 2013], we revisited the problem of calculating Coulomb Green's function and image potential near a planar diffuse interface within which the dielectric permittivity of the inhomogeneous medium changes continuously along one Cartesian direction in a transition layer between two dissimilar dielectric materials. In the present paper, we consider a cylindrical diffuse interface within which the dielectric permittivity changes continuously along the radial direction instead. First we propose a specific cylindrical diffuse interface model, termed the quasi-harmonic diffuse interface model, that can admit analytical solution for the Green's function in terms of the modified Bessel functions. Then and more importantly we develop a robust numerical method for building Green's functions for any cylindrical diffuse interface models. The main idea of the numerical method is, after dividing a diffuse interface into multiple sublayers, to approximate the dielectric permittivity profile in each one of the sublayers by one of the quasi-harmonic functional form rather than simply by a constant value as one would normally do. Next we describe how to efficiently compute well-behaved ratios, products, and logarithmic derivatives of the modified Bessel functions so as to avoid direct evaluations of individual modified Bessel functions in our formulations. Finally we conduct numerical experiments to show the effectiveness of the quasi-harmonic diffuse interface model in overcoming the divergence of the image potential, to validate the numerical method in terms of its accuracy and convergence, and to demonstrate its capability for computing Green's functions for any cylindrical diffuse interface models.
Green's function Monte Carlo calculations of /sup 4/He
Energy Technology Data Exchange (ETDEWEB)
Carlson, J.A.
1988-01-01
Green's Function Monte Carlo methods have been developed to study the ground state properties of light nuclei. These methods are shown to reproduce results of Faddeev calculations for A = 3, and are then used to calculate ground state energies, one- and two-body distribution functions, and the D-state probability for the alpha particle. Results are compared to variational Monte Carlo calculations for several nuclear interaction models. 31 refs.
Three-point Green's function of massless QED in position space to lowest order
International Nuclear Information System (INIS)
Mitra, Indrajit
2009-01-01
The transverse part of the three-point Green's function of massless QED is determined to the lowest order in position space. Taken together with the evaluation of the longitudinal part in Mitra (2008) (J. Phys. A: Math. Theor. 41 315401), this gives a relation for QED which is analogous to the star-triangle relation. We relate our result to conformal-invariant three-point functions
Exciton correlations and input–output relations in non-equilibrium exciton superfluids
International Nuclear Information System (INIS)
Ye, Jinwu; Sun, Fadi; Yu, Yi-Xiang; Liu, Wuming
2013-01-01
The photoluminescence (PL) measurements on photons and the transport measurements on excitons are the two types of independent and complementary detection tools to search for possible exciton superfluids in electron–hole semi-conductor bilayer systems. In fact, it was believed that the transport measurements can provide more direct evidences on superfluids than the spectroscopic measurements. It is important to establish the relations between the two kinds of measurements. In this paper, using quantum Heisenberg–Langevin equations, we establish such a connection by calculating various exciton correlation functions in the putative exciton superfluids. These correlation functions include both normal and anomalous greater, lesser, advanced, retarded, and time-ordered exciton Green functions and also various two exciton correlation functions. We also evaluate the corresponding normal and anomalous spectral weights and the Keldysh distribution functions. We stress the violations of the fluctuation and dissipation theorem among these various exciton correlation functions in the non-equilibrium exciton superfluids. We also explore the input–output relations between various exciton correlation functions and those of emitted photons such as the angle resolved photon power spectrum, phase sensitive two mode squeezing spectrum and two photon correlations. Applications to possible superfluids in the exciton–polariton systems are also mentioned. For a comparison, using conventional imaginary time formalism, we also calculate all the exciton correlation functions in an equilibrium dissipative exciton superfluid in the electron–electron coupled semi-conductor bilayers at the quantum Hall regime at the total filling factor ν T =1. We stress the analogies and also important differences between the correlations functions in the two exciton superfluid systems. - Highlights: ► Establish the relations between photoluminescence and transport measurements. ► Stress the
Green's functions through so(2,1) lie algebra in nonrelativistic quantum mechanics
International Nuclear Information System (INIS)
Boschi-Filho, H.; Vaidya, A.N.
1991-01-01
The authors discuss an algebraic technique to construct the Green's function for systems described by the noncompact so(2,1) Lie algebra. They show that this technique solves the one-dimensional linear oscillator and Coulomb potentials and also generates particular solutions for other one-dimensional potentials. Then they construct explicitly the Green's function for the three-dimensional oscillator and the three-dimensional Coulomb potential, which are generalizations of the one-dimensional cases, and the Coulomb plus an Aharanov-Bohm, potential. They discuss the dynamical algebra involved in each case and also find their wave functions and bound state spectra. Finally they introduce in each case and also find their wave functions and bound state spectra. Finally they introduce a point canonical transformation in the generators of so(2,10) Lie algebra, show that this procedure permits us to solve the one-dimensional Morse potential in addition to the previous cases, and construct its Green's function and find its energy spectrum and wave functions
Mechanical, Thermal and Functional Properties of Green Lightweight Foamcrete
Directory of Open Access Journals (Sweden)
Md Azree Othuman Mydin
2012-09-01
Full Text Available In recent times, the construction industry has revealed noteworthy attention in the use of lightweight foamcrete as a building material due to its many favourable characteristics such as lighter weight, easy to fabricate, durable and cost effective. Foamcrete is a material consisting of Portland cement paste or cement filler matrix (mortar with a homogeneous pore structure created by introducing air in the form of small bubbles. With a proper control in dosage of foam and methods of production, a wide range of densities (400 – 1600 kg/m 3 of foamcrete can be produced thus providing flexibility for application such as structural elements, partition, insulating materials and filling grades. Foamcrete has so far been applied primarily as a filler material in civil engineering works. However, its good thermal and acoustic performance indicates its strong potential as a material in building construction. The focus of this paper is to classify literature on foamcrete in terms of its mechanical, thermal and functional properties.
Finite-Source Inversion for the 2004 Parkfield Earthquake using 3D Velocity Model Green's Functions
Kim, A.; Dreger, D.; Larsen, S.
2008-12-01
We determine finite fault models of the 2004 Parkfield earthquake using 3D Green's functions. Because of the dense station coverage and detailed 3D velocity structure model in this region, this earthquake provides an excellent opportunity to examine how the 3D velocity structure affects the finite fault inverse solutions. Various studies (e.g. Michaels and Eberhart-Phillips, 1991; Thurber et al., 2006) indicate that there is a pronounced velocity contrast across the San Andreas Fault along the Parkfield segment. Also the fault zone at Parkfield is wide as evidenced by mapped surface faults and where surface slip and creep occurred in the 1966 and the 2004 Parkfield earthquakes. For high resolution images of the rupture process"Ait is necessary to include the accurate 3D velocity structure for the finite source inversion. Liu and Aurchuleta (2004) performed finite fault inversions using both 1D and 3D Green's functions for 1989 Loma Prieta earthquake using the same source paramerization and data but different Green's functions and found that the models were quite different. This indicates that the choice of the velocity model significantly affects the waveform modeling at near-fault stations. In this study, we used the P-wave velocity model developed by Thurber et al (2006) to construct the 3D Green's functions. P-wave speeds are converted to S-wave speeds and density using by the empirical relationships of Brocher (2005). Using a finite difference method, E3D (Larsen and Schultz, 1995), we computed the 3D Green's functions numerically by inserting body forces at each station. Using reciprocity, these Green's functions are recombined to represent the ground motion at each station due to the slip on the fault plane. First we modeled the waveforms of small earthquakes to validate the 3D velocity model and the reciprocity of the Green"fs function. In the numerical tests we found that the 3D velocity model predicted the individual phases well at frequencies lower than 0
Green Imidazolium Ionics-From Truly Sustainable Reagents to Highly Functional Ionic Liquids.
Tröger-Müller, Steffen; Brandt, Jessica; Antonietti, Markus; Liedel, Clemens
2017-09-04
We report the synthesis of task-specific imidazolium ionic compounds and ionic liquids with key functionalities of organic molecules from electro-, polymer-, and coordination chemistry. Such products are highly functional and potentially suitable for technology applications even though they are formed without elaborate reactions and from cheap and potentially green reagents. We further demonstrate the versatility of the used synthetic approach by introducing different functional and green counterions to the formed ionic liquids directly during the synthesis or after metathesis reactions. The influence of different cation structures and different anions on the thermal and electrochemical properties of the resulting ionic liquids is discussed. Our goal is to make progress towards economically competitive and sustainable task-specific ionic liquids. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Optimum Design of Multi-Function Robot Arm Gripper for Varying Shape Green Product
Directory of Open Access Journals (Sweden)
Razali Zol Bahri
2016-01-01
Full Text Available The project focuses on thorough experimentally studies of the optimum design of Multi-function Robot Arm Gripper for varying shape green product. The purpose of this project is to design a few of robot arm gripper for multi-functionally grip a green product with varying shape. The main character of the gripper is that it can automated adjust its finger to suit with the shape of the product. An optimum design of multi-function robot arm gripper is verified through experimental study. The expected result is a series of analytical results on the proposal of gripper design and material that will be selected for the gripper. The analysis of the gripper design proposal by using ANSYS and CATIA software is described in detail in this paper.
Connected Green function approach to symmetry breaking in Φ1+14-theory
International Nuclear Information System (INIS)
Haeuser, J.M.; Cassing, W.; Peter, A.; Thoma, M.H.
1995-01-01
Using the cluster expansions for n-point Green functions we derive a closed set of dynamical equations of motion for connected equal-time Green functions by neglecting all connected functions higher than 4 th order for the λΦ 4 -theory in 1+1 dimensions. We apply the equations to the investigation of spontaneous symmetry breaking, i.e. to the evaluation of the effective potential at temperature T=0. Within our momentum space discretization we obtain a second order phase transition (in agreement with the Simon-Griffith theorem) and a critical coupling of λ crit /4m 2 =2.446 ascompared to a first order phase transition and λ crit /4m 2 =2.568 from the Gaussian effective potential approach. (orig.)
International Nuclear Information System (INIS)
Chen, Kuo-Chin; Su, Yu-Hsin; Chang, Ching-Ray; Chen, Son-Hsien
2014-01-01
We study the electron spin transport in two dimensional electron gas (2DEG) system with both Rashba and Dresselhaus (001) spin-orbital coupling (SOC). We assume spatial behavior of spin precession in the non-equilibrium transport regime, and study also quantum interference induced by non-Abelian spin-orbit gauge field. The method we adopt in this article is the non-equilibrium Green's function within a tight binding framework. We consider one ferromagnetic lead which injects spin polarized electron to a system with equal strength of Rashba and Dresselhaus (001) SOC, and we observe the persistent spin helix property. We also consider two ferromagnetic leads injecting spin polarized electrons into a pure Dresselhaus SOC system, and we observe the resultant spin wave interference pattern
International Nuclear Information System (INIS)
Van Leeuwen, Robert; Stefanucci, Gianluca
2013-01-01
We present a unified framework for equilibrium and nonequilibrium many-body perturbation theory. The most general nonequilibrium many-body theory valid for general initial states is based on a time-contour originally introduced by Konstantinov and Perel'. The various other well-known formalisms of Keldysh, Matsubara and the zero-temperature formalism are then derived as special cases that arise under different assumptions. We further present a single simple proof of Wick's theorem that is at the same time valid in all these flavors of many-body theory. It arises simply as a solution of the equations of the Martin-Schwinger hierarchy for the noninteracting many-particle Green's function with appropriate boundary conditions. We further discuss a generalized Wick theorem for general initial states on the Keldysh contour and derive how the formalisms based on the Keldysh and Konstantinov-Perel'-contours are related for the case of general initial states.
Nonequilibrium electron transport through quantum dots in the Kondo regime
DEFF Research Database (Denmark)
Wölfle, Peter; Paaske, Jens; Rosch, Achim
2005-01-01
Electron transport at large bias voltage through quantum dots in the Kondo regime is described within the perturbative renormalization group extended to nonequilibrium. The conductance, local magnetization, dynamical spin susceptibility and local spectral function are calculated. We show how...
Phytochrome from Green Plants: Properties and biological Function
Energy Technology Data Exchange (ETDEWEB)
Quail, Peter H.
2014-07-25
Pfr conformer reverses this activity upon initial light exposure, inducing the switch to photomorphogenic development. This reversal involves light-triggered translocation of the photoactivated phy molecule into the nucleus where it interacts with PIF-family members, inducing rapid phosphorylation and degradation of the PIFs via the ubiquitin-proteasome system. This degradation in turn elicits rapid alterations in gene expression that drive the deetiolation transition. This project has made considerable progress in defining phy-PIF signaling activity in controlling the SAR. The biological functions of the multiple PIF-family members in controlling the SAR, including dissection of the relative contributions of the individual PIFs to this process, as well as to diurnal growth-control oscillations, have been investigated using higher-order pif-mutant combinations. Using microarray analysis of a quadruple pif mutant we have defined the shade-induced, PIF-regulated transcriptional network genome-wide. This has revealed that a dynamic antagonism between the phys and PIFs generates selective reciprocal responses during deetiolation and the SAR in a rapidly light-responsive transcriptional network. Using integrated RNA-seq and ChIP-seq analysis of higher order pif-mutant combinations, we have defined the direct gene-targets of PIF transcriptional regulation, and have obtained evidence that this regulation involves differential direct targeting of rapidly light-responsive genes by the individual PIF-family members. This project has provided significant advances in our understanding of the molecular mechanisms by which the phy-PIF photosensory signaling pathway regulates an important bioenergy-related plant response to the light environment. The identification of molecular targets in the primary transcriptional-regulatory circuitry of this pathway has the potential to enable genetic or reverse-genetic manipulation of the partitioning of carbon between reproductive and
On Green's function retrieval by iterative substitution of the coupled Marchenko equations
van der Neut, Joost; Vasconcelos, Ivan; Wapenaar, Kees
2015-11-01
Iterative substitution of the coupled Marchenko equations is a novel methodology to retrieve the Green's functions from a source or receiver array at an acquisition surface to an arbitrary location in an acoustic medium. The methodology requires as input the single-sided reflection response at the acquisition surface and an initial focusing function, being the time-reversed direct wavefield from the acquisition surface to a specified location in the subsurface. We express the iterative scheme that is applied by this methodology explicitly as the successive actions of various linear operators, acting on an initial focusing function. These operators involve multidimensional crosscorrelations with the reflection data and truncations in time. We offer physical interpretations of the multidimensional crosscorrelations by subtracting traveltimes along common ray paths at the stationary points of the underlying integrals. This provides a clear understanding of how individual events are retrieved by the scheme. Our interpretation also exposes some of the scheme's limitations in terms of what can be retrieved in case of a finite recording aperture. Green's function retrieval is only successful if the relevant stationary points are sampled. As a consequence, internal multiples can only be retrieved at a subsurface location with a particular ray parameter if this location is illuminated by the direct wavefield with this specific ray parameter. Several assumptions are required to solve the Marchenko equations. We show that these assumptions are not always satisfied in arbitrary heterogeneous media, which can result in incomplete Green's function retrieval and the emergence of artefacts. Despite these limitations, accurate Green's functions can often be retrieved by the iterative scheme, which is highly relevant for seismic imaging and inversion of internal multiple reflections.
The Impact of Working in a Green Certified Building on Cognitive Function and Health.
MacNaughton, Piers; Satish, Usha; Laurent, Jose Guillermo Cedeno; Flanigan, Skye; Vallarino, Jose; Coull, Brent; Spengler, John D; Allen, Joseph G
2017-03-01
Thirty years of public health research have demonstrated that improved indoor environmental quality is associated with better health outcomes. Recent research has demonstrated an impact of the indoor environment on cognitive function. We recruited 109 participants from 10 high-performing buildings (i.e. buildings surpassing the ASHRAE Standard 62.1-2010 ventilation requirement and with low total volatile organic compound concentrations) in five U.S. cities. In each city, buildings were matched by week of assessment, tenant, type of worker and work functions. A key distinction between the matched buildings was whether they had achieved green certification. Workers were administered a cognitive function test of higher order decision-making performance twice during the same week while indoor environmental quality parameters were monitored. Workers in green certified buildings scored 26.4% (95% CI: [12.8%, 39.7%]) higher on cognitive function tests, controlling for annual earnings, job category and level of schooling, and had 30% fewer sick building symptoms than those in non-certified buildings. These outcomes may be partially explained by IEQ factors, including thermal conditions and lighting, but the findings suggest that the benefits of green certification standards go beyond measureable IEQ factors. We describe a holistic "buildingomics" approach for examining the complexity of factors in a building that influence human health.
METHOD OF GREEN FUNCTIONS IN MATHEMATICAL MODELLING FOR TWO-POINT BOUNDARY-VALUE PROBLEMS
Directory of Open Access Journals (Sweden)
E. V. Dikareva
2015-01-01
Full Text Available Summary. In many applied problems of control, optimization, system theory, theoretical and construction mechanics, for problems with strings and nods structures, oscillation theory, theory of elasticity and plasticity, mechanical problems connected with fracture dynamics and shock waves, the main instrument for study these problems is a theory of high order ordinary differential equations. This methodology is also applied for studying mathematical models in graph theory with different partitioning based on differential equations. Such equations are used for theoretical foundation of mathematical models but also for constructing numerical methods and computer algorithms. These models are studied with use of Green function method. In the paper first necessary theoretical information is included on Green function method for multi point boundary-value problems. The main equation is discussed, notions of multi-point boundary conditions, boundary functionals, degenerate and non-degenerate problems, fundamental matrix of solutions are introduced. In the main part the problem to study is formulated in terms of shocks and deformations in boundary conditions. After that the main results are formulated. In theorem 1 conditions for existence and uniqueness of solutions are proved. In theorem 2 conditions are proved for strict positivity and equal measureness for a pair of solutions. In theorem 3 existence and estimates are proved for the least eigenvalue, spectral properties and positivity of eigenfunctions. In theorem 4 the weighted positivity is proved for the Green function. Some possible applications are considered for a signal theory and transmutation operators.
Quantum field theory in the presence of a medium: Green's function expansions
Energy Technology Data Exchange (ETDEWEB)
Kheirandish, Fardin [Department of Physics, Islamic Azad University, Shahreza-Branch, Shahreza (Iran, Islamic Republic of); Salimi, Shahriar [Department of Physics, University of Kurdistan, Sanandaj (Iran, Islamic Republic of)
2011-12-15
Starting from a Lagrangian and using functional-integration techniques, series expansions of Green's function of a real scalar field and electromagnetic field, in the presence of a medium, are obtained. The parameter of expansion in these series is the susceptibility function of the medium. Relativistic and nonrelativistic Langevin-type equations are derived. Series expansions for Lifshitz energy in finite temperature and for an arbitrary matter distribution are derived. Covariant formulations for both scalar and electromagnetic fields are introduced. Two illustrative examples are given.
Baumeister, K. J.
1983-01-01
A time-dependent finite difference formulation to the inhomogeneous wave equation is derived for plane wave propagation with harmonic noise sources. The difference equation and boundary conditions are developed along with the techniques to simulate the Dirac delta function associated with a concentrated noise source. Example calculations are presented for the Green's function and distributed noise sources. For the example considered, the desired Fourier transformed acoustic pressures are determined from the transient pressures by use of a ramping function and an integration technique, both of which eliminates the nonharmonic pressure associated with the initial transient.
Baumeiste, K. J.
1983-01-01
A time-dependent finite difference formulation to the inhomogeneous wave equation is derived for plane wave propagation with harmonic noise sources. The difference equation and boundary conditions are developed along with the techniques to simulate the Dirac delta function associated with a concentrated noise source. Example calculations are presented for the Green's function and distributed noise sources. For the example considered, the desired Fourier transformed acoustic pressures are determined from the transient pressures by use of a ramping function and an integration technique, both of which eliminates the nonharmonic pressure associated with the initial transient.
Green's functions of one-dimensional quasicrystal bi-material with piezoelectric effect
Energy Technology Data Exchange (ETDEWEB)
Zhang, Liangliang [College of Engineering, China Agricultural University, Beijing 100083 (China); Sinomatech Wind Power Blade Co., Ltd, Beijing 100092 (China); Wu, Di [College of Engineering, China Agricultural University, Beijing 100083 (China); Xu, Wenshuai [College of Science, China Agricultural University, Beijing 100083 (China); Yang, Lianzhi [Civil and Environmental Engineering School, University of Science and Technology Beijing, Beijing 100083 (China); Ricoeur, Andreas; Wang, Zhibin [Institute of Mechanics, University of Kassel, 34125 Kassel (Germany); Gao, Yang, E-mail: gaoyangg@gmail.com [College of Science, China Agricultural University, Beijing 100083 (China)
2016-09-16
Based on the Stroh formalism of one-dimensional quasicrystals with piezoelectric effect, the problems of an infinite plane composed of two different quasicrystal half-planes are taken into account. The solutions of the internal and interfacial Green's functions of quasicrystal bi-material are obtained. Moreover, numerical examples are analyzed for a quasicrystal bi-material subjected to line forces or line dislocations, showing the contour maps of the coupled fields. The impacts of changing material constants on the coupled field components are investigated. - Highlights: • Green's functions of 1D piezoelectric quasicrystal bi-material are studied. • The coupled fields subjected to line forces or line dislocations are obtained. • Mechanical behavior under the effect of different material constants is researched.
International Nuclear Information System (INIS)
Kramer, T; Heller, E J; Parrott, R E
2008-01-01
Time-dependent quantum mechanics provides an intuitive picture of particle propagation in external fields. Semiclassical methods link the classical trajectories of particles with their quantum mechanical propagation. Many analytical results and a variety of numerical methods have been developed to solve the time-dependent Schroedinger equation. The time-dependent methods work for nearly arbitrarily shaped potentials, including sources and sinks via complex-valued potentials. Many quantities are measured at fixed energy, which is seemingly not well suited for a time-dependent formulation. Very few methods exist to obtain the energy-dependent Green function for complicated potentials without resorting to ensemble averages or using certain lead-in arrangements. Here, we demonstrate in detail a time-dependent approach, which can accurately and effectively construct the energy-dependent Green function for very general potentials. The applications of the method are numerous, including chemical, mesoscopic, and atomic physics
Nonequilibrium fluctuations in a resistor.
Garnier, N; Ciliberto, S
2005-06-01
In small systems where relevant energies are comparable to thermal agitation, fluctuations are of the order of average values. In systems in thermodynamical equilibrium, the variance of these fluctuations can be related to the dissipation constant in the system, exploiting the fluctuation-dissipation theorem. In nonequilibrium steady systems, fluctuations theorems (FT) additionally describe symmetry properties of the probability density functions (PDFs) of the fluctuations of injected and dissipated energies. We experimentally probe a model system: an electrical dipole driven out of equilibrium by a small constant current I, and show that FT are experimentally accessible and valid. Furthermore, we stress that FT can be used to measure the dissipated power P = R I2 in the system by just studying the PDFs' symmetries.
Rapid finite-fault inversions in Southern California using Cybershake Green's functions
Thio, H. K.; Polet, J.
2017-12-01
We have developed a system for rapid finite fault inversion for intermediate and large Southern California earthquakes using local, regional and teleseismic seismic waveforms as well as geodetic data. For modeling the local seismic data, we use 3D Green's functions from the Cybershake project, which were made available to us courtesy of the Southern California Earthquake Center (SCEC). The use of 3D Green's functions allows us to extend the inversion to higher frequency waveform data and smaller magnitude earthquakes, in addition to achieving improved solutions in general. The ultimate aim of this work is to develop the ability to provide high quality finite fault models within a few hours after any damaging earthquake in Southern California, so that they may be used as input to various post-earthquake assessment tools such as ShakeMap, as well as by the scientific community and other interested parties. Additionally, a systematic determination of finite fault models has value as a resource for scientific studies on detailed earthquake processes, such as rupture dynamics and scaling relations. We are using an established least-squares finite fault inversion method that has been applied extensively both on large as well as smaller regional earthquakes, in conjunction with the 3D Green's functions, where available, as well as 1D Green's functions for areas for which the Cybershake library has not yet been developed. We are carrying out validation and calibration of this system using significant earthquakes that have occurred in the region over the last two decades, spanning a range of locations and magnitudes (5.4 and higher).
Green's function for electrons in a narrow quantum well in a parallel magnetic field
International Nuclear Information System (INIS)
Horing, Norman J. Morgenstern; Glasser, M. Lawrence; Dong Bing
2005-01-01
Electron dynamics in a narrow quantum well in a parallel magnetic field of arbitrary strength are examined here. We derive an explicit analytical closed-form solution for the Green's function of Landau-quantized electrons in skipping states of motion between the narrow well walls coupled with in-plane translational motion and hybridized with the zero-field lowest subband energy eigenstate. Such Landau-quantized modes are not uniformly spaced
An Application of Green Quality Function Deployment to Designing an Air Conditioner
Peetam Kumar Dehariya; Dr. Devendra Singh Verma
2015-01-01
The paper tackles a systematic and operational approach to Green Quality Function Deployment (GQFD), a customer oriented survey based quality management system with regular improvement in product development. GQFD shows balance between product development and environmental protection. GQFD is not used to determine their attributes and their levels. GQFD captures what product developers “think” would best satisfy customer needs considering Environmental factor. This research used A...
Infrared divergences of Green functions and renormalization in massless theories. 2
International Nuclear Information System (INIS)
Anikin, S.A.; Zav'yalova, O.I.; Karchev, N.I.
1981-01-01
General theorems are proved concerning the infrared finiteness of Green functions in theories including massless particles. Considerations are based on α-representation of Feynman diagrams. Necessory conditions are considered for proving theorems in the case of diagrams with massive lines. Under certain conditions the contribution of the considered sections into the Feynman amplitude is shown to be free from infrared divergences, but only for those subgraphs which involve all the massive lines and contain all the outer vertexes in one affinity component
The gluon Green's function in the BFKL approach at next-to-leading logarithmic accuracy
International Nuclear Information System (INIS)
Andersen, Jeppe R.; Sabio Vera, Agustin
2004-01-01
We investigate the gluon Green's function in the high energy limit of QCD using a recently proposed iterative solution of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) equation at next-to-leading logarithmic (NLL) accuracy. To establish the applicability of this method in the NLL approximation we solve the BFKL equation as originally written by Fadin and Lipatov, and compare the results with previous studies in the leading logarithmic (LL) approximation
Quantum field theory in non-stationary coordinate systems and Green functions
International Nuclear Information System (INIS)
Svaiter, B.F.; Svaiter, N.F.
1988-01-01
In this paper we studied a neutral massive scalar field in a bi-dimensional Milne space time. The quantization is made on hyperboles which are Lorentz invariant surfaces. The expansion for the field operator was carried on using a complete set of orthonormal modes which have definite positive and negative dilatation frequence. We have calculated the advanced and retarded Green function and proved that the Feynman propagator diverges in the usual sense. (author) [pt
Laplace transforms of the Hulthén Green's function and their application to potential scattering
Laha, U.; Ray, S.; Panda, S.; Bhoi, J.
2017-10-01
We derive closed-form representations for the single and double Laplace transforms of the Hulthén Green's function of the outgoing wave multiplied by the Yamaguchi potential and write them in the maximally reduced form. We use the expression for the double transform to compute the low-energy phase shifts for the elastic scattering in the systems α-nucleon, α-He3, and α-H3. The calculation results agree well with the experimental data.
Wave resistance calculation method combining Green functions based on Rankine and Kelvin source
Directory of Open Access Journals (Sweden)
LI Jingyu
2017-12-01
Full Text Available [Ojectives] At present, the Boundary Element Method(BEM of wave-making resistance mostly uses a model in which the velocity distribution near the hull is solved first, and the pressure integral is then calculated using the Bernoulli equation. However,the process of this model of wave-making resistance is complex and has low accuracy.[Methods] To address this problem, the present paper deduces a compound method for the quick calculation of ship wave resistance using the Rankine source Green function to solve the hull surface's source density, and combining the Lagally theorem concerning source point force calculation based on the Kelvin source Green function so as to solve the wave resistance. A case for the Wigley model is given.[Results] The results show that in contrast to the thin ship method of the linear wave resistance theorem, this method has higher precision, and in contrast to the method which completely uses the Kelvin source Green function, this method has better computational efficiency.[Conclusions] In general, the algorithm in this paper provides a compromise between precision and efficiency in wave-making resistance calculation.
Chan, Eugene; Rose, L R Francis; Wang, Chun H
2015-05-01
Existing damage imaging algorithms for detecting and quantifying structural defects, particularly those based on diffraction tomography, assume far-field conditions for the scattered field data. This paper presents a major extension of diffraction tomography that can overcome this limitation and utilises a near-field multi-static data matrix as the input data. This new algorithm, which employs numerical solutions of the dynamic Green's functions, makes it possible to quantitatively image laminar damage even in complex structures for which the dynamic Green's functions are not available analytically. To validate this new method, the numerical Green's functions and the multi-static data matrix for laminar damage in flat and stiffened isotropic plates are first determined using finite element models. Next, these results are time-gated to remove boundary reflections, followed by discrete Fourier transform to obtain the amplitude and phase information for both the baseline (damage-free) and the scattered wave fields. Using these computationally generated results and experimental verification, it is shown that the new imaging algorithm is capable of accurately determining the damage geometry, size and severity for a variety of damage sizes and shapes, including multi-site damage. Some aspects of minimal sensors requirement pertinent to image quality and practical implementation are also briefly discussed. Copyright © 2015 Elsevier B.V. All rights reserved.
The infinite medium Green's function for neutron transport in plane geometry 40 years later
International Nuclear Information System (INIS)
Ganapol, B.D.
1993-01-01
In 1953, the first of what was supposed to be two volumes on neutron transport theory was published. The monograph, entitled open-quotes Introduction to the Theory of Neutron Diffusionclose quotes by Case et al., appeared as a Los Alamos National Laboratory report and was to be followed by a second volume, which never appeared as intended because of the death of Placzek. Instead, Case and Zweifel collaborated on the now classic work entitled Linear Transport Theory 2 in which the underlying mathematical theory of linear transport was presented. The initial monograph, however, represented the coming of age of neutron transport theory, which had its roots in radiative transfer and kinetic theory. In addition, it provided the first benchmark results along with the mathematical development for several fundamental neutron transport problems. In particular, one-dimensional infinite medium Green's functions for the monoenergetic transport equation in plane and spherical geometries were considered complete with numerical results to be used as standards to guide code development for applications. Unfortunately, because of the limited computational resources of the day, some numerical results were incorrect. Also, only conventional mathematics and numerical methods were used because the transport theorists of the day were just becoming acquainted with more modern mathematical approaches. In this paper, Green's function solution is revisited in light of modern numerical benchmarking methods with an emphasis on evaluation rather than theoretical results. The primary motivation for considering the Green's function at this time is its emerging use in solving finite and heterogeneous media transport problems
Summable chains of instantons: Green's functions and the Prasad-Sommerfield limit
International Nuclear Information System (INIS)
Boutaleb-Joutei, H.; Chakrabarti, A.; Comtet, A.
1981-01-01
We construct, for each homotopy class, a type of instanton configuration which exhibits many special, simple properties. The basic reason behind such properties is indicated by deriving our configuration in the 't Hooft gauge, starting from a class of particularly simple, static, and self-dual solutions in de Sitter space. Apart from this we consider, in this paper, mostly results for flat Euclidean space. We show that the static solutions are equivalent to multiply charged instantons at the origin in Witten's sense. Green's functions for this class of instanton background are studied. The known flat-space results of Brown et al. are shown to be reducible, for our case, to totally explicit and relatively compact forms. The sums over different indices arising in their formalism are performed. The inversion of a matrix, necessary for the isospin-1 massless scalar field, is carried out explicitly, for our configuration, for arbitrary index of the background instanton field. Green's functions for the Prasad-Sommerfield case are obtained as limits of our results directly in summed-up forms. Green's functions are studied also in de Sitter space. Special features due to periodic time are pointed out
Nonequilibrium effects in Isoscaling
International Nuclear Information System (INIS)
Dorso, C. O.; Lopez, J. A.
2007-01-01
In this work we study within a simple model different properties of the system that allow us to understand the properties of the isoscaling observable. We first show that isoscaling is a general property of fragmenting systems. We show this by using a simple generalized percolation model. We show that the usual isoscaling property can be obtained in the case of bond percolation in bichromatic lattices with any regular topology. In this case the probabilities of each color (isospin) are independent. We then explore the effect of introducing 'non-equilibrium' effects
Non-equilibrium thermodynamics
De Groot, Sybren Ruurds
1984-01-01
The study of thermodynamics is especially timely today, as its concepts are being applied to problems in biology, biochemistry, electrochemistry, and engineering. This book treats irreversible processes and phenomena - non-equilibrium thermodynamics.S. R. de Groot and P. Mazur, Professors of Theoretical Physics, present a comprehensive and insightful survey of the foundations of the field, providing the only complete discussion of the fluctuating linear theory of irreversible thermodynamics. The application covers a wide range of topics: the theory of diffusion and heat conduction, fluid dyn
The nonequilibrium molecular dynamics
International Nuclear Information System (INIS)
Hoover, W.G.
1992-03-01
MOLECULAR DYNAMICS has been generalized in order to simulate a variety of NONEQUILIBRIUM systems. This generalization has been achieved by adopting microscopic mechanical definitions of macroscopic thermodynamic and hydrodynamic variables, such as temperature and stress. Some of the problems already treated include rapid plastic deformation, intense heat conduction, strong shockwaves simulation, and far-from-equilibrium phase transformations. Continuing advances in technique and in the modeling of interatomic forces, coupled with qualitative improvements in computer hardware, are enabling such simulations to approximate real-world microscale and nanoscale experiments
Instabilities and nonequilibrium structures
International Nuclear Information System (INIS)
Tirapegui, E.; Villarroel, D.
1987-01-01
Physical systems can be studied both near to and far from equilibrium where instabilities appear. The behaviour in these two regions is reviewed in this book, from both the theoretical and application points of view. The influence of noise in these situations is an essential feature which cannot be ignored. It is therefore discussed using phenomenological and theoretical approaches for the numerous problems which still remain in the field. This volume should appeal to mathematicians and physicists interested in the areas of instability, bifurcation theory, dynamical systems, pattern formation, nonequilibrium structures and statistical mechanics. (Auth.)
Analytic properties for the honeycomb lattice Green function at the origin
Joyce, G. S.
2018-05-01
The analytic properties of the honeycomb lattice Green function are investigated, where is a complex variable which lies in a plane. This double integral defines a single-valued analytic function provided that a cut is made along the real axis from w = ‑3 to . In order to analyse the behaviour of along the edges of the cut it is convenient to define the limit function where . It is shown that and can be evaluated exactly for all in terms of various hypergeometric functions, where the argument function is always real-valued and rational. The second-order linear Fuchsian differential equation satisfied by is also used to derive series expansions for and which are valid in the neighbourhood of the regular singular points and . Integral representations are established for and , where with . In particular, it is proved that where J 0(z) and Y 0(z) denote Bessel functions of the first and second kind, respectively. The results derived in the paper are utilized to evaluate the associated logarithmic integral where w lies in the cut plane. A new set of orthogonal polynomials which are connected with the honeycomb lattice Green function are also briefly discussed. Finally, a link between and the theory of Pearson random walks in a plane is established.
Yoon, Ju Young; Brown, Roger L; Bowers, Barbara J; Sharkey, Siobhan S; Horn, Susan D
2016-01-01
Growing attention in the past few decades has focused on improving care quality and quality of life for nursing home residents. Many traditional nursing homes have attempted to transform themselves to become more homelike emphasizing individualized care. This trend is referred to as nursing home culture change in the U.S. A promising culture change nursing home model, the Green House nursing home model, has shown positive psychological outcomes. However, little is known about whether the Green House nursing home model has positive effects on physical function compared to traditional nursing homes. To examine the longitudinal effects of the Green House nursing home model by comparing change patterns of activities of daily living function over time between Green House home residents and traditional nursing home residents. A retrospective longitudinal study. Four Green House organizations (nine Green House units and four traditional units). A total of 242 residents (93 Green House residents and 149 traditional home residents) who had stayed in the nursing home at least 6 months from admission. The outcome was activities of daily living function, and the main independent variable was the facility type in which the resident stayed: a Green House or traditional unit. Age, gender, comorbidity score, cognitive function, and depressive symptoms at baseline were controlled. All of these measures were from a minimum dataset. Growth curve modeling and growth mixture modeling were employed in this study for longitudinal analyses. The mean activities of daily living function showed deterioration over time, and the rates of deterioration between Green House and traditional home residents were not different over time. Four different activities of daily living function trajectories were identified for 18 months, but there was no statistical difference in the likelihood of being in one of the four trajectory classes between the two groups. Although Green House nursing homes are
International Nuclear Information System (INIS)
Davis, A.B.; Marshak, A.; Cahalan, R.F.
2001-01-01
We survey radiative Green function theory (1) in linear transport theory where numerical procedures are required to obtain specific results and (2) in the photon diffusion limit (large optical depths) where it is analytically tractable, at least for homogeneous plane-parallel media. We then describe two recent applications of Green function theory to passive cloud remote sensing in the presence of strong three-dimensional transport effects. Finally, we describe recent instrumental breakthroughs in 'off-beam' cloud lidar which is based on direct measurements of radiative Green functions with special attention to the data collected during the Shuttle-based Lidar In-space Technology Experiment (LITE) mission.
The Application of Neutron Transport Green's Functions to Threat Scenario Simulation
Thoreson, Gregory G.; Schneider, Erich A.; Armstrong, Hirotatsu; van der Hoeven, Christopher A.
2015-02-01
Radiation detectors provide deterrence and defense against nuclear smuggling attempts by scanning vehicles, ships, and pedestrians for radioactive material. Understanding detector performance is crucial to developing novel technologies, architectures, and alarm algorithms. Detection can be modeled through radiation transport simulations; however, modeling a spanning set of threat scenarios over the full transport phase-space is computationally challenging. Previous research has demonstrated Green's functions can simulate photon detector signals by decomposing the scenario space into independently simulated submodels. This paper presents decomposition methods for neutron and time-dependent transport. As a result, neutron detector signals produced from full forward transport simulations can be efficiently reconstructed by sequential application of submodel response functions.
Analysis of Green's functions and stability problem in models of quantum field theory with solitons
International Nuclear Information System (INIS)
Raczka, R.; Roszkowski, L.
1983-10-01
A class of models of quantum field theory for a multiplet phi-vector=(phi 1 ,...,phisub(N)) of real scalar fields, possessing a particle-like classical solution phi-vector 0 , is considered. A new formula for generating functional for time-ordered Green's functions in terms of effective propagators is derived. The problem of classical and quantum stability is analyzed in detail. It is shown by partly non-perturbative analysis that in the considered models the excited states of mesons do exist and form the trajectories in the plane mass 2 -spin. These trajectories are linear or approximately linear like experimental trajectories. (author)
INTRODUCTION: Nonequilibrium Processes in Plasmas
Petrović, Zoran; Marić, Dragana; Malović, Gordana
2009-07-01
lead to new fundamental understanding is illustrated well in the paper by Uwe Czarnetzki which describes a new method for separate control of flux and energy of ions reaching the surface of electrodes. Deborah O'Connell from Belfast has shown space and phase resolved mode transitions in rf inductively coupled plasmas obtained by optical emission measurements. At the same time an application of a similar rf discharge for the treatment of paper was presented by Irina Filatova from Belarus. Many applications of non-equilibrium plasmas depend on the development of plasma sources operating at atmospheric pressure and one such source that promises to be prominent in medicine is described by Timo Gans. In a similar way, practical considerations require studies of the injection of liquids into plasmas and progress on the development of one such source is described by Mathew Goeckner and his colleagues from Dallas. From the Institute Jožef Štefan in Slovenia and the group of Miran Mozetič we have a detailed review of their work on functionalization of organic materials by oxygen plasmas. Even higher density plasmas, where the collective phenomena dominate, show different degrees of non-equilibrium and one example presented here by Zoltan Donko deals with two dimensional plasma dust crystals and liquids, while the lecture by Jovo Vranješ from Belgium deals with the treatment of collisions in multicomponent plasmas. Finally we have papers on the transport of pollutants. The association of the two fields started initially through joint interest in some of the methods for removal of NOx and SOx, from electrostatic precipitation of industrial dust to dielectric barrier discharges. The joint work continued on the application of flowing afterglow plasma combined with a hollow cathode discharge in order to achieve a proton transfer mass analysis of organic volatile compounds and also on the possibilities of applying similar methods for solving transport equations. In this volume we
International Nuclear Information System (INIS)
Bros, J.
1980-01-01
In this lecture, we present some of the ideas of a global consistent approach to the analytic and monodromic structure of Green's functions and scattering amplitudes of elementary particles on the basis of general quantum field theory. (orig.)
Miyake, Kazumasa; Tsuruta, Atsushi
2015-01-01
On the basis of the Luttinger-Ward formalism for the thermodynamic potential, the specific heat of single-component interacting fermion systems with fixed chemical potential is compactly expressed in terms of the fully renormalized Matsubara Green function.
International Nuclear Information System (INIS)
Bezerra de Mello, E.R.
2006-01-01
In this paper we present, in a integral form, the Euclidean Green function associated with a massless scalar field in the five-dimensional Kaluza-Klein magnetic monopole superposed to a global monopole, admitting a nontrivial coupling between the field with the geometry. This Green function is expressed as the sum of two contributions: the first one related with uncharged component of the field, is similar to the Green function associated with a scalar field in a four-dimensional global monopole space-time. The second contains the information of all the other components. Using this Green function it is possible to study the vacuum polarization effects on this space-time. Explicitly we calculate the renormalized vacuum expectation value * (x)Φ(x)> Ren , which by its turn is also expressed as the sum of two contributions
Non-equilibrium dynamics from RPMD and CMD.
Welsch, Ralph; Song, Kai; Shi, Qiang; Althorpe, Stuart C; Miller, Thomas F
2016-11-28
We investigate the calculation of approximate non-equilibrium quantum time correlation functions (TCFs) using two popular path-integral-based molecular dynamics methods, ring-polymer molecular dynamics (RPMD) and centroid molecular dynamics (CMD). It is shown that for the cases of a sudden vertical excitation and an initial momentum impulse, both RPMD and CMD yield non-equilibrium TCFs for linear operators that are exact for high temperatures, in the t = 0 limit, and for harmonic potentials; the subset of these conditions that are preserved for non-equilibrium TCFs of non-linear operators is also discussed. Furthermore, it is shown that for these non-equilibrium initial conditions, both methods retain the connection to Matsubara dynamics that has previously been established for equilibrium initial conditions. Comparison of non-equilibrium TCFs from RPMD and CMD to Matsubara dynamics at short times reveals the orders in time to which the methods agree. Specifically, for the position-autocorrelation function associated with sudden vertical excitation, RPMD and CMD agree with Matsubara dynamics up to O(t 4 ) and O(t 1 ), respectively; for the position-autocorrelation function associated with an initial momentum impulse, RPMD and CMD agree with Matsubara dynamics up to O(t 5 ) and O(t 2 ), respectively. Numerical tests using model potentials for a wide range of non-equilibrium initial conditions show that RPMD and CMD yield non-equilibrium TCFs with an accuracy that is comparable to that for equilibrium TCFs. RPMD is also used to investigate excited-state proton transfer in a system-bath model, and it is compared to numerically exact calculations performed using a recently developed version of the Liouville space hierarchical equation of motion approach; again, similar accuracy is observed for non-equilibrium and equilibrium initial conditions.
Self-consistent green function calculations for isospin asymmetric nuclear matter
International Nuclear Information System (INIS)
Mansour, Hesham; Gad, Khalaf; Hassaneen, Khaled S.A.
2010-01-01
The one-body potentials for protons and neutrons are obtained from the self-consistent Green-function calculations of asymmetric nuclear matter, in particular their dependence on the degree of proton/neutron asymmetry. Results of the binding energy per nucleon as a function of the density and asymmetry parameter are presented for the self-consistent Green function approach using the CD-Bonn potential. For the sake of comparison, the same calculations are performed using the Brueckner-Hartree-Fock approximation. The contribution of the hole-hole terms leads to a repulsive contribution to the energy per nucleon which increases with the nuclear density. The incompressibility for asymmetric nuclear matter has been also investigated in the framework of the self-consistent Green-function approach using the CD-Bonn potential. The behavior of the incompressibility is studied for different values of the nuclear density and the neutron excess parameter. The nuclear symmetry potential at fixed nuclear density is also calculated and its value decreases with increasing the nucleon energy. In particular, the nuclear symmetry potential at saturation density changes from positive to negative values at nucleon kinetic energy of about 200 MeV. For the sake of comparison, the same calculations are performed using the Brueckner-Hartree-Fock approximation. The proton/neutron effective mass splitting in neutron-rich matter has been studied. The predicted isospin splitting of the proton/neutron effective mass splitting in neutron-rich matter is such that m n * ≥ m p * . (author)
Casimir energies in M4≥/sup N/ for even N. Green's-function and zeta-function techniques
International Nuclear Information System (INIS)
Kantowski, R.; Milton, K.A.
1987-01-01
The Green's-function technique developed in the first paper in this series is generalized to apply to massive scalar, vector, second-order tensor, and Dirac spinor fields, as a preliminary to a full graviton calculation. The Casimir energies are of the form u/sub Casimir/ = (1/a 4 )[α/sub N/lna/b)+β/sub N/], where N (even) is the dimension of the internal sphere, a is its radius, and b/sup -1/ is an ultraviolet cutoff (presumably at the Planck scale). The coefficient of the divergent logarithm, α/sub N/, is unambiguously obtained for each field considered. The Green's-function technique gives rise to no difficulties in the evaluation of imaginary-mass-mode contributions to the Casimir energy. In addition, a new, simplified zeta-function technique is presented which is very easily implemented by symbolic programs, and which, of course, gives the same results. An error in a previous zeta-function calculation of the Casimir energy for even N is pointed out
Nucleon polarizabilities from deuteron Compton scattering within a Green's function hybrid approach
Energy Technology Data Exchange (ETDEWEB)
Hildebrandt, R.P.; Hemmert, T.R. [Technische Universitaet Muenchen, Institut fuer Theoretische Physik (T39), Physik-Department, Garching (Germany); Griesshammer, H.W. [Technische Universitaet Muenchen, Institut fuer Theoretische Physik (T39), Physik-Department, Garching (Germany); Universitaet Erlangen-Nuernberg, Institut fuer Theoretische Physik III, Naturwissenschaftliche Fakultaet I, Erlangen (Germany); The George Washington University, Center for Nuclear Studies, Department of Physics, Washington DC (United States)
2010-10-15
We examine elastic Compton scattering from the deuteron for photon energies ranging from zero to 100MeV, using state-of-the-art deuteron wave functions and NN potentials. Nucleon-nucleon rescattering between emission and absorption of the two photons is treated by Green's functions in order to ensure gauge invariance and the correct Thomson limit. With this Green's function hybrid approach, we fulfill the low-energy theorem of deuteron Compton scattering and there is no significant dependence on the deuteron wave function used. Concerning the nucleon structure, we use the chiral effective field theory with explicit {delta} (1232) degrees of freedom within the small-scale expansion up to leading-one-loop order. Agreement with available data is good at all energies. Our 2-parameter fit to all elastic {gamma} d data leads to values for the static isoscalar dipole polarizabilities which are in excellent agreement with the isoscalar Baldin sum rule. Taking this value as additional input, we find {alpha}{sub E}{sup s} = (11.3{+-}0.7(stat){+-}0.6(Baldin){+-}1(theory)){sup .}10{sup -4} fm{sup 3} and {beta}{sub M}{sup s} = (3.2{+-}0.7(stat){+-}0.6(Baldin){+-}1(theory)){sup .}10{sup -4} fm{sup 3} and conclude by comparison to the proton numbers that neutron and proton polarizabilities are the same within rather small errors. (orig.)
Single-site Green function of the Dirac equation for full-potential electron scattering
Energy Technology Data Exchange (ETDEWEB)
Kordt, Pascal
2012-05-30
I present an elaborated analytical examination of the Green function of an electron scattered at a single-site potential, for both the Schroedinger and the Dirac equation, followed by an efficient numerical solution, in both cases for potentials of arbitrary shape without an atomic sphere approximation. A numerically stable way to calculate the corresponding regular and irregular wave functions and the Green function is via the angular Lippmann-Schwinger integral equations. These are solved based on an expansion in Chebyshev polynomials and their recursion relations, allowing to rewrite the Lippmann-Schwinger equations into a system of algebraic linear equations. Gonzales et al. developed this method for the Schroedinger equation, where it gives a much higher accuracy compared to previous perturbation methods, with only modest increase in computational effort. In order to apply it to the Dirac equation, I developed relativistic Lippmann-Schwinger equations, based on a decomposition of the potential matrix into spin spherical harmonics, exploiting certain properties of this matrix. The resulting method was embedded into a Korringa-Kohn-Rostoker code for density functional calculations. As an example, the method is applied by calculating phase shifts and the Mott scattering of a tungsten impurity. (orig.)
Single-site Green function of the Dirac equation for full-potential electron scattering
International Nuclear Information System (INIS)
Kordt, Pascal
2012-01-01
I present an elaborated analytical examination of the Green function of an electron scattered at a single-site potential, for both the Schroedinger and the Dirac equation, followed by an efficient numerical solution, in both cases for potentials of arbitrary shape without an atomic sphere approximation. A numerically stable way to calculate the corresponding regular and irregular wave functions and the Green function is via the angular Lippmann-Schwinger integral equations. These are solved based on an expansion in Chebyshev polynomials and their recursion relations, allowing to rewrite the Lippmann-Schwinger equations into a system of algebraic linear equations. Gonzales et al. developed this method for the Schroedinger equation, where it gives a much higher accuracy compared to previous perturbation methods, with only modest increase in computational effort. In order to apply it to the Dirac equation, I developed relativistic Lippmann-Schwinger equations, based on a decomposition of the potential matrix into spin spherical harmonics, exploiting certain properties of this matrix. The resulting method was embedded into a Korringa-Kohn-Rostoker code for density functional calculations. As an example, the method is applied by calculating phase shifts and the Mott scattering of a tungsten impurity. (orig.)
Directory of Open Access Journals (Sweden)
Katalin Martinás
2007-02-01
Full Text Available A microeconomic, agent based framework to dynamic economics is formulated in a materialist approach. An axiomatic foundation of a non-equilibrium microeconomics is outlined. Economic activity is modelled as transformation and transport of commodities (materials owned by the agents. Rate of transformations (production intensity, and the rate of transport (trade are defined by the agents. Economic decision rules are derived from the observed economic behaviour. The non-linear equations are solved numerically for a model economy. Numerical solutions for simple model economies suggest that the some of the results of general equilibrium economics are consequences only of the equilibrium hypothesis. We show that perfect competition of selfish agents does not guarantee the stability of economic equilibrium, but cooperativity is needed, too.
Cryptochrome photoreceptors in green algae: Unexpected versatility of mechanisms and functions.
Kottke, Tilman; Oldemeyer, Sabine; Wenzel, Sandra; Zou, Yong; Mittag, Maria
2017-10-01
Green algae have a highly complex and diverse set of cryptochrome photoreceptor candidates including members of the following subfamilies: plant, plant-like, animal-like, DASH and cryptochrome photolyase family 1 (CPF1). While some green algae encode most or all of them, others lack certain members. Here we present an overview about functional analyses of so far investigated cryptochrome photoreceptors from the green algae Chlamydomonas reinhardtii (plant and animal-like cryptochromes) and Ostreococcus tauri (CPF1) with regard to their biological significance and spectroscopic properties. Cryptochromes of both algae have been demonstrated recently to be involved to various extents in circadian clock regulation and in Chlamydomonas additionally in life cycle control. Moreover, CPF1 even performs light-driven DNA repair. The plant cryptochrome and CPF1 are UVA/blue light receptors, whereas the animal-like cryptochrome responds to almost the whole visible spectrum including red light. Accordingly, plant cryptochrome, animal-like cryptochrome and CPF1 differ fundamentally in their structural response to light as revealed by their visible and infrared spectroscopic signatures, and in the role of the flavin neutral radical acting as dark form or signaling state. Copyright © 2017 Elsevier GmbH. All rights reserved.
Rate of tunneling nonequilibrium quasiparticles in superconducting qubits
International Nuclear Information System (INIS)
Ansari, Mohammad H
2015-01-01
In superconducting qubits the lifetime of quantum states cannot be prolonged arbitrarily by decreasing temperature. At low temperature quasiparticles tunneling between the electromagnetic environment and superconducting islands takes the condensate state out of equilibrium due to charge imbalance. We obtain the tunneling rate from a phenomenological model of non-equilibrium, where nonequilibrium quasiparticle tunnelling stimulates a temperature-dependent chemical potential shift in the superconductor. As a result we obtain a non-monotonic behavior for relaxation rate as a function of temperature. Depending on the fabrication parameters for some qubits, the lowest tunneling rate of nonequilibrium quasiparticles can take place only near the onset temperature below which nonequilibrium quasiparticles dominate over equilibrium one. Our theory also indicates that such tunnelings can influence the probability of transitions in qubits through a coupling to the zero-point energy of phase fluctuations. (paper)
A Radiation Chemistry Code Based on the Greens Functions of the Diffusion Equation
Plante, Ianik; Wu, Honglu
2014-01-01
Ionizing radiation produces several radiolytic species such as.OH, e-aq, and H. when interacting with biological matter. Following their creation, radiolytic species diffuse and chemically react with biological molecules such as DNA. Despite years of research, many questions on the DNA damage by ionizing radiation remains, notably on the indirect effect, i.e. the damage resulting from the reactions of the radiolytic species with DNA. To simulate DNA damage by ionizing radiation, we are developing a step-by-step radiation chemistry code that is based on the Green's functions of the diffusion equation (GFDE), which is able to follow the trajectories of all particles and their reactions with time. In the recent years, simulations based on the GFDE have been used extensively in biochemistry, notably to simulate biochemical networks in time and space and are often used as the "gold standard" to validate diffusion-reaction theories. The exact GFDE for partially diffusion-controlled reactions is difficult to use because of its complex form. Therefore, the radial Green's function, which is much simpler, is often used. Hence, much effort has been devoted to the sampling of the radial Green's functions, for which we have developed a sampling algorithm This algorithm only yields the inter-particle distance vector length after a time step; the sampling of the deviation angle of the inter-particle vector is not taken into consideration. In this work, we show that the radial distribution is predicted by the exact radial Green's function. We also use a technique developed by Clifford et al. to generate the inter-particle vector deviation angles, knowing the inter-particle vector length before and after a time step. The results are compared with those predicted by the exact GFDE and by the analytical angular functions for free diffusion. This first step in the creation of the radiation chemistry code should help the understanding of the contribution of the indirect effect in the
Definition of Nonequilibrium Entropy of General Systems
Mei, Xiaochun
1999-01-01
The definition of nonequilibrium entropy is provided for the general nonequilibrium processes by connecting thermodynamics with statistical physics, and the principle of entropy increment in the nonequilibrium processes is also proved in the paper. The result shows that the definition of nonequilibrium entropy is not unique.
A monequillibrium mary-body systems IV: Respouse function theory
International Nuclear Information System (INIS)
Luzzi, R.; Vasconcellos, A.R.; Algarte, A.C.S.
1987-01-01
A response function theory for many-body systems arbitrarily away from equilibrium is presented. It is based on the nonequilibrium statistical operator method fully described in a previous article. A formal theory is presented evaluation of transition probabilties and the average values of dynamical quantities in far-from-equilibrium many-body systems under the action of external perturbations. A nonequilibrium thermodynamic Green's function algorithn appropriate for the calculation of response functions and scattering cross sections in terms of a generalized fluctuation-dissipation theorem for far-from-equilibrium systems is also derived. (author) [pt
Nonequilibrium recombination after a curved shock wave
Wen, Chihyung; Hornung, Hans
2010-02-01
The effect of nonequilibrium recombination after a curved two-dimensional shock wave in a hypervelocity dissociating flow of an inviscid Lighthill-Freeman gas is considered. An analytical solution is obtained with the effective shock values derived by Hornung (1976) [5] and the assumption that the flow is ‘quasi-frozen’ after a thin dissociating layer near the shock. The solution gives the expression of dissociation fraction as a function of temperature on a streamline. A rule of thumb can then be provided to check the validity of binary scaling for experimental conditions and a tool to determine the limiting streamline that delineates the validity zone of binary scaling. The effects on the nonequilibrium chemical reaction of the large difference in free stream temperature between free-piston shock tunnel and equivalent flight conditions are discussed. Numerical examples are presented and the results are compared with solutions obtained with two-dimensional Euler equations using the code of Candler (1988) [10].
Purkayastha, Archak; Dhar, Abhishek; Kulkarni, Manas
2017-11-01
We investigate and map out the nonequilibrium phase diagram of a generalization of the well known Aubry-André-Harper (AAH) model. This generalized AAH (GAAH) model is known to have a single-particle mobility edge which also has an additional self-dual property akin to that of the critical point of the AAH model. By calculating the population imbalance, we get hints of a rich phase diagram. We also find a fascinating connection between single particle wave functions near the mobility edge of the GAAH model and the wave functions of the critical AAH model. By placing this model far from equilibrium with the aid of two baths, we investigate the open system transport via system size scaling of nonequilibrium steady state (NESS) current, calculated by fully exact nonequilibrium Green's function (NEGF) formalism. The critical point of the AAH model now generalizes to a `critical' line separating regions of ballistic and localized transport. Like the critical point of the AAH model, current scales subdiffusively with system size on the `critical' line (I ˜N-2 ±0.1 ). However, remarkably, the scaling exponent on this line is distinctly different from that obtained for the critical AAH model (where I ˜N-1.4 ±0.05 ). All these results can be understood from the above-mentioned connection between states near the mobility edge of the GAAH model and those of the critical AAH model. A very interesting high temperature nonequilibrium phase diagram of the GAAH model emerges from our calculations.
Analysis of the phonon surface specific heat using Green function techniques
International Nuclear Information System (INIS)
Carrico, A.S.; Albuquerque, E.L.
1980-01-01
Green functions are derived for the displacement associated with acoustic vibrations in isotropic elastic media and used to evaluate the surface specific heat in the harmonic approximation. We consider only the low-temperature limit case since, provided K B 1/h is very samll, we can replace the dispersion relation for the three acoustic branches by its long-wavelenghts form. The contributions of surface elastic waves ot the Rayleigh and Love types are pointed out and their features discussed. The nature of the result and their relations to previous work in this field is also presented and discussed. (author) [pt
International Nuclear Information System (INIS)
Wapenaar, Kees
2004-01-01
A correlation-type reciprocity theorem is used to show that the elastodynamic Green's function of any inhomogeneous medium (random or deterministic) can be retrieved from the cross correlation of two recordings of a wave field at different receiver locations at the free surface. Unlike in other derivations, which apply to diffuse wave fields in random media or irregular finite bodies, no assumptions are made about the diffusivity of the wave field. In a second version, it is assumed that the wave field is diffuse due to many uncorrelated sources inside the medium
A Green's function solution for a rectangular heat source on an infinite plate
International Nuclear Information System (INIS)
Bainbridge, B.L.
1989-01-01
The applications associated with a rectangular heat source on an infinite plate range from integrated circuits to thin film heat flux sensors on thin substrates. The particular problem from which the solution is developed concerns the use of a resistive strip for monitoring currents generated in circuits exposed to electromagnetic fields. The Green's function formulation is solved by using early and late time approximations for which analytical solutions can be derived. In this paper expressions are developed for three sets of boundary conditions and compared to the experimental performance of a physical device
Analysis of the phonon surface specific heat using Green function techniques
International Nuclear Information System (INIS)
Silva Carrico, A. da; Albuquerque, E.L. de
1981-01-01
Green functions are derived for the displacement associated with acoustic vibrations in isotropic elastic media and used to evaluate the surface specific heat in the harmonic approximation. Only the low-temperature limit case is considered since, provided K sub(B) T/h is very small, the dispersion relation for the three acoustic branches can be replaced by its long-wavelenght form. The contributions of surface elastic waves of the Rayleigh and Love types are pointed out and their features discussed. The nature of the result and their relations to previous work in this field is also presented and discussed. (Author) [pt
Kuchment, Peter; Raich, Andrew
2012-01-01
Precise asymptotics known for the Green's function of the Laplace operator have found their analogs for periodic elliptic operators of the second order at and below the bottom of the spectrum. Due to the band-gap structure of the spectra of such operators, the question arises whether similar results can be obtained near or at the edges of spectral gaps. As the result of this work shows, this is possible at a spectral edge when the dimension d ≥ 3. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
International Nuclear Information System (INIS)
De la Incera, V.; Ferrer, E.; Shalad, A.Y.
1987-01-01
A homogeneous and isotropic plasma made up of electrons and positrons is examined. The coefficients of the covariant expansion of the three-photon vertex are calculated in the one-loop approximation of the Green's function technique, together with the probability amplitudes of various processes involving three photons that produce information on the probability of the polarization states of the incoming and outgoing photons in the splitting process. The calculation results are used to verify the consequences of all exact symmetries which must be done for the vertex tensor. The case of a charge-symmetric plasma is considered together with the special case of photon collinearity
A calculation method for finite depth free-surface green function
Directory of Open Access Journals (Sweden)
Yingyi Liu
2015-03-01
Full Text Available An improved boundary element method is presented for numerical analysis of hydrodynamic behavior of marine structures. A new algorithm for numerical solution of the finite depth free-surface Green function in three dimensions is developed based on multiple series representations. The whole range of the key parameter R/h is divided into four regions, within which different representation is used to achieve fast convergence. The well-known epsilon algorithm is also adopted to accelerate the convergence. The critical convergence criteria for each representation are investigated and provided. The proposed method is validated by several well-documented benchmark problems.
Significance of constraints associated with Green's functions in Hamiltonian perturbation theory
International Nuclear Information System (INIS)
Maharana, L.; Muller-Kirsten, H.J.W.; Wiedemann, A.
1987-01-01
In many formulations of Hamiltonian perturbation theory a Green's function becomes undefined when some parameter is allowed to vanish. Here various examples are discussed to illustrate this phenomenon, and it is shown that they are all realizations of a general theorem. The cases considered are examples in classical mechanics, quantum mechanics, electrodynamics and field theory. The prime object is to illustrate the unity of the examples and thus to make the application of the procedure to field theory models of current interest more transparent. One example that it is referred to is the skyrmion model
Conformal use of retarded Green's functions for the Maxwell field in de Sitter space
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Faci, S.; Huguet, E.; Renaud, J.
2011-01-01
We propose a new propagation formula for the Maxwell field in de Sitter space which exploits the conformal invariance of this field together with a conformal gauge condition. This formula allows to determine the classical electromagnetic field in the de Sitter space from given currents and initial data. It only uses the Green's function of the massless Minkowskian scalar field. This leads to drastic simplifications in practical calculations. We apply this formula to the classical problem of the two charges of opposite signs at rest at the North and South Poles of the de Sitter space.
Origin of the tail in Green's functions in odd-dimensional space-times
Dai, De-Chang; Stojkovic, Dejan
2013-10-01
It is well known that the scalar field Green's function in odd dimensions has a tail, i.e. a non-zero support inside the light cone, which in turn implies that the Huygens' principle is violated. However, the reason behind this behavior is still not quite clear. In this paper we shed more light on the physical origin of the tail by regularizing the term which is usually ignored in the literature since it vanishes due to the action of the delta function. With this extra term the Green's function does not satisfy the source-free wave equation (in the region outside of the source). We show that this term corresponds to a charge imprinted on the light-cone shell. Unlike the vector field charge, a moving scalar field charge is not Lorentz invariant and is contracted by a factor. If a scalar charge is moving at the speed of light, it appears to be zero in the static (with respect to the original physical charge) observer's frame. However, the field it sources is not entirely on the light cone. Thus, it is likely that this hidden charge sources the mysterious tail in odd dimensions.
International Nuclear Information System (INIS)
Stoltz, G; Lazzeri, M; Mauri, F
2009-01-01
We present a study of the phononic thermal conductivity of isotopically disordered carbon nanotubes. In particular, the behaviour of the thermal conductivity as a function of the system length is investigated, using Green's function techniques to compute the transmission across the system. The method is implemented using linear scaling algorithms, which allow us to reach systems of lengths up to L = 2.5 μm (with up to 200 000 atoms). As for 1D systems, it is observed that the conductivity diverges with the system size L. We also observe a dramatic decrease of the thermal conductance for systems of experimental sizes (roughly 80% at room temperature for L = 2.5 μm), when a large fraction of isotopic disorder is introduced. The results obtained with Green's function techniques are compared to results obtained with a Boltzmann description of thermal transport. There is a good agreement between both approaches for systems of experimental sizes, even in the presence of Anderson localization. This is particularly interesting since the computation of the transmission using Boltzmann's equation is much less computationally expensive, so that larger systems may be studied with this method.
Pavlov, V. M.
2017-07-01
The problem of calculating complete synthetic seismograms from a point dipole with an arbitrary seismic moment tensor in a plane parallel medium composed of homogeneous elastic isotropic layers is considered. It is established that the solutions of the system of ordinary differential equations for the motion-stress vector have a reciprocity property, which allows obtaining a compact formula for the derivative of the motion vector with respect to the source depth. The reciprocity theorem for Green's functions with respect to the interchange of the source and receiver is obtained for a medium with cylindrical boundary. The differentiation of Green's functions with respect to the coordinates of the source leads to the same calculation formulas as the algorithm developed in the previous work (Pavlov, 2013). A new algorithm appears when the derivatives with respect to the horizontal coordinates of the source is replaced by the derivatives with respect to the horizontal coordinates of the receiver (with the minus sign). This algorithm is more transparent, compact, and economic than the previous one. It requires calculating the wavenumbers associated with Bessel function's roots of order 0 and order 1, whereas the previous algorithm additionally requires the second order roots.
About sign-constancy of Green's functions for impulsive second order delay equations
Directory of Open Access Journals (Sweden)
Alexander Domoshnitsky
2014-01-01
Full Text Available We consider the following second order differential equation with delay \\[\\begin{cases} (Lx(t\\equiv{x''(t+\\sum_{j=1}^p {b_{j}(tx(t-\\theta_{j}(t}}=f(t, \\quad t\\in[0,\\omega],\\\\ x(t_j=\\gamma_{j}x(t_j-0, x'(t_j=\\delta_{j}x'(t_j-0, \\quad j=1,2,\\ldots,r. \\end{cases}\\] In this paper we find necessary and sufficient conditions of positivity of Green's functions for this impulsive equation coupled with one or two-point boundary conditions in the form of theorems about differential inequalities. By choosing the test function in these theorems, we obtain simple sufficient conditions. For example, the inequality \\(\\sum_{i=1}^p{b_i(t\\left(\\frac{1}{4}+r\\right}\\lt \\frac{2}{\\omega^2}\\ is a basic one, implying negativity of Green's function of two-point problem for this impulsive equation in the case \\(0\\lt \\gamma_i\\leq{1}\\, \\(0\\lt \\delta_i\\leq{1}\\ for \\(i=1,\\ldots ,p\\.
International Nuclear Information System (INIS)
Tang Jian; Peng Muzhang; Cao Dongxing
1989-01-01
A new numerical method-nodal green's function method is used for solving heat conduction function. A heat conduction problem in cylindrical geometry with axial conduction is solved in this paper. The Kirchhoff transformation is used to deal with the problem with temperature dependent conductivity. Therefor, the calculation for the function is simplified. On the basis of the formulas developed, the code named NGMEFC is programmed. A sample problem which has been calculated by the code COBRA-IV is chosen as checking. A good agreement between both codes is achieved. The calculation shows that the calculation efficiency of the nodel green's function method is much higher than that of finite difference method
Green's functions for stress-intensity-factors for through cracks emanating from holes
International Nuclear Information System (INIS)
Bhandari, S.; Dubeaux, P.
1981-01-01
We conducted a parametric study of cracks at various elliptical openings in plates. We used five values of ellipticity and ten values of crack lengths at the edge of these holes. The computer program used is based on the Boundary Integral Equation method which requires only the contour of the structure to be segmented. The results concerning the stress distribution in the uncracked structure were verified for the cases where analytical results were available. Moreover the values of the S.I.F. for certain cases were checked through the use of some of the methods available in the literature. The final aim of this parametric study is to come up with simple Green's functions for cracks at holes. This has been possible through: (a) The use of the stress distribution in the uncracked structure (b) The Green's function for a crack in an infinite medium and (c) The principles underlying the Schwarz alternating technique used in the potential theory to resolve problems of finite regions. Finally the procedure is applied to treat a practical case of cracks as fastner holes. (orig.)
Capriotti, Margherita; Sternini, Simone; Lanza di Scalea, Francesco; Mariani, Stefano
2016-04-01
In the field of non-destructive evaluation, defect detection and visualization can be performed exploiting different techniques relying either on an active or a passive approach. In the following paper the passive technique is investigated due to its numerous advantages and its application to thermography is explored. In previous works, it has been shown that it is possible to reconstruct the Green's function between any pair of points of a sensing grid by using noise originated from diffuse fields in acoustic environments. The extraction of the Green's function can be achieved by cross-correlating these random recorded waves. Averaging, filtering and length of the measured signals play an important role in this process. This concept is here applied in an NDE perspective utilizing thermal fluctuations present on structural materials. Temperature variations interacting with thermal properties of the specimen allow for the characterization of the material and its health condition. The exploitation of the thermographic image resolution as a dense grid of sensors constitutes the basic idea underlying passive thermography. Particular attention will be placed on the creation of a proper diffuse thermal field, studying the number, placement and excitation signal of heat sources. Results from numerical simulations will be presented to assess the capabilities and performances of the passive thermal technique devoted to defect detection and imaging of structural components.
Cancellation of spurious arrivals in Green's function extraction and the generalized optical theorem
Snieder, R.; Van Wijk, K.; Haney, M.; Calvert, R.
2008-01-01
The extraction of the Green's function by cross correlation of waves recorded at two receivers nowadays finds much application. We show that for an arbitrary small scatterer, the cross terms of scattered waves give an unphysical wave with an arrival time that is independent of the source position. This constitutes an apparent inconsistency because theory predicts that such spurious arrivals do not arise, after integration over a complete source aperture. This puzzling inconsistency can be resolved for an arbitrary scatterer by integrating the contribution of all sources in the stationary phase approximation to show that the stationary phase contributions to the source integral cancel the spurious arrival by virtue of the generalized optical theorem. This work constitutes an alternative derivation of this theorem. When the source aperture is incomplete, the spurious arrival is not canceled and could be misinterpreted to be part of the Green's function. We give an example of how spurious arrivals provide information about the medium complementary to that given by the direct and scattered waves; the spurious waves can thus potentially be used to better constrain the medium. ?? 2008 The American Physical Society.
Recombination yield of geminate radical pairs in low magnetic fields - A Green's function method
International Nuclear Information System (INIS)
Doktorov, A.B.; Hansen, M.J.; Pedersen, J. Boiden
2006-01-01
An analytic expression for the recombination yield of a geminate radical pair with a single spin one half nuclei is derived. The expression is valid for any field strength of the static magnetic field. It is assumed that the spin mixing is caused solely by the hyperfine interaction of the nuclear spin and the difference in Zeeman energies of the two radical partners, that the recombination occurs at the distance of closest approach, and that there is a locally strong dephasing at contact. This is a special result of a new general approach where a Green's function technique is used to recast the stochastic Liouville equation into a low dimensional matrix equation that is particularly convenient for locally strong dephasing systems. The equation is expressed in terms of special values (determined by the magnetic parameters) of the Green's function for the relative motion of the radicals and it is therefore valid for any motional model, e.g. diffusion, one and two site models. The applicability of the strong dephasing approximation is illustrated by comparison with numerical exact results
McCollom, Brittany A; Collis, Jon M
2014-09-01
A normal mode solution to the ocean acoustic problem of the Pekeris waveguide with an elastic bottom using a Green's function formulation for a compressional wave point source is considered. Analytic solutions to these types of waveguide propagation problems are strongly dependent on the eigenvalues of the problem; these eigenvalues represent horizontal wavenumbers, corresponding to propagating modes of energy. The eigenvalues arise as singularities in the inverse Hankel transform integral and are specified by roots to a characteristic equation. These roots manifest themselves as poles in the inverse transform integral and can be both subtle and difficult to determine. Following methods previously developed [S. Ivansson et al., J. Sound Vib. 161 (1993)], a root finding routine has been implemented using the argument principle. Using the roots to the characteristic equation in the Green's function formulation, full-field solutions are calculated for scenarios where an acoustic source lies in either the water column or elastic half space. Solutions are benchmarked against laboratory data and existing numerical solutions.
Source analysis using regional empirical Green's functions: The 2008 Wells, Nevada, earthquake
Mendoza, C.; Hartzell, S.
2009-01-01
We invert three-component, regional broadband waveforms recorded for the 21 February 2008 Wells, Nevada, earthquake using a finite-fault methodology that prescribes subfault responses using eight MW∼4 aftershocks as empirical Green's functions (EGFs) distributed within a 20-km by 21.6-km fault area. The inversion identifies a seismic moment of 6.2 x 1024 dyne-cm (5.8 MW) with slip concentrated in a compact 6.5-km by 4-km region updip from the hypocenter. The peak slip within this localized area is 88 cm and the stress drop is 72 bars, which is higher than expected for Basin and Range normal faults in the western United States. The EGF approach yields excellent fits to the complex regional waveforms, accounting for strong variations in wave propagation and site effects. This suggests that the procedure is useful for studying moderate-size earthquakes with limited teleseismic or strong-motion data and for examining uncertainties in slip models obtained using theoretical Green's functions.
Use of time space Green's functions in the computation of transient eddy current fields
International Nuclear Information System (INIS)
Davey, K.; Turner, L.
1988-01-01
The utility of integral equations to solve eddy current problems has been borne out by numerous computations in the past few years, principally in sinusoidal steady-state problems. This paper attempts to examine the applicability of the integral approaches in both time and space for the more generic transient problem. The basic formulation for the time space Green's function approach is laid out. A technique employing Gauss-Laguerre integration is employed to realize the temporal solution, while Gauss--Legendre integration is used to resolve the spatial field character. The technique is then applied to the fusion electromagnetic induction experiments (FELIX) cylinder experiments in both two and three dimensions. It is found that quite accurate solutions can be obtained using rather coarse time steps and very few unknowns; the three-dimensional field solution worked out in this context used basically only four unknowns. The solution appears to be somewhat sensitive to the choice of time step, a consequence of a numerical instability imbedded in the Green's function near the origin
Temperature-dependent striped antiferromagnetism of LaFeAsO in a Green's function approach
International Nuclear Information System (INIS)
Liu Guibin; Liu Banggui
2009-01-01
We use a Green's function method to study the temperature-dependent average moment and magnetic phase-transition temperature of the striped antiferromagnetism of LaFeAsO, and other similar compounds, as the parents of FeAs-based superconductors. We consider the nearest and the next-nearest couplings in the FeAs layer, and the nearest coupling for inter-layer spin interaction. The dependence of the transition temperature T N and the zero-temperature average spin on the interaction constants is investigated. We obtain an analytical expression for T N and determine our temperature-dependent average spin from zero temperature to T N in terms of unified self-consistent equations. For LaFeAsO, we obtain a reasonable estimation of the coupling interactions with the experimental transition temperature T N = 138 K. Our results also show that a non-zero antiferromagnetic (AFM) inter-layer coupling is essential for the existence of a non-zero T N , and the many-body AFM fluctuations reduce substantially the low-temperature magnetic moment per Fe towards the experimental value. Our Green's function approach can be used for other FeAs-based parent compounds and these results should be useful to understand the physical properties of FeAs-based superconductors.
Anisotropic nonequilibrium hydrodynamic attractor
Strickland, Michael; Noronha, Jorge; Denicol, Gabriel S.
2018-02-01
We determine the dynamical attractors associated with anisotropic hydrodynamics (aHydro) and the DNMR equations for a 0 +1 d conformal system using kinetic theory in the relaxation time approximation. We compare our results to the nonequilibrium attractor obtained from the exact solution of the 0 +1 d conformal Boltzmann equation, the Navier-Stokes theory, and the second-order Mueller-Israel-Stewart theory. We demonstrate that the aHydro attractor equation resums an infinite number of terms in the inverse Reynolds number. The resulting resummed aHydro attractor possesses a positive longitudinal-to-transverse pressure ratio and is virtually indistinguishable from the exact attractor. This suggests that an optimized hydrodynamic treatment of kinetic theory involves a resummation not only in gradients (Knudsen number) but also in the inverse Reynolds number. We also demonstrate that the DNMR result provides a better approximation of the exact kinetic theory attractor than the Mueller-Israel-Stewart theory. Finally, we introduce a new method for obtaining approximate aHydro equations which relies solely on an expansion in the inverse Reynolds number. We then carry this expansion out to the third order, and compare these third-order results to the exact kinetic theory solution.
Green's function enriched Poisson solver for electrostatics in many-particle systems
Sutmann, Godehard
2016-06-01
A highly accurate method is presented for the construction of the charge density for the solution of the Poisson equation in particle simulations. The method is based on an operator adjusted source term which can be shown to produce exact results up to numerical precision in the case of a large support of the charge distribution, therefore compensating the discretization error of finite difference schemes. This is achieved by balancing an exact representation of the known Green's function of regularized electrostatic problem with a discretized representation of the Laplace operator. It is shown that the exact calculation of the potential is possible independent of the order of the finite difference scheme but the computational efficiency for higher order methods is found to be superior due to a faster convergence to the exact result as a function of the charge support.
Off-Shell Green Functions: One-Loop with Growing Legs
International Nuclear Information System (INIS)
Bashir, A.; Concha-Sanchez, Y.; Delbourgo, R.; Tejeda-Yeomans, M. E.
2008-01-01
One loop calculations in gauge theories in arbitrary gauge and dimensions become exceedingly hard with growing number of external off-shell legs. Let alone higher point functions, such a calculation for even the three point one-loop vertices for quantum electrodynamics (QED) and quantum chromodynamics (QCD) has been made available only recently. In this article, we discuss how Ward-Fradkin-Green-Takahashi identities (WFGTI) may provide a helpful tool in these computations. After providing a glimpse of our suggestion for the case of the 3-point vertex, we present our preliminary findings towards our similar efforts for the 4-point function. We restrict ourselves to the example of scalar quantum electrodynamics (SQED)
Method of the reduced-added Green function in the calculation of atomic polarizabilities
International Nuclear Information System (INIS)
Chernov, V.E.; Dorofeev, D.L.; Kretinin, I.Yu.; Zon, B.A.
2005-01-01
The Green function in the quantum defect theory provides an exact account for high-excited and continuum electronic states. We modify it by taking into account the ground and low-excited states using their wave functions calculated ab initio. As an application, we present a simple and efficient semianalytical method for the calculation of atomic electric frequency-dependent scalar dipole polarizability, for both real and imaginary frequencies. The polarizabilities calculated for some atoms (Li, Na, K, Be, Mg, Ca, Si, P, S, O, Al, Ge, C, N, F, He, Ne, Ar, Kr, and Xe) are compared with existing methods of computational quantum chemistry and with experiments; good accuracy of the proposed method is demonstrated
Application of the Green's function method to some nonlinear problems of an electron storage ring
International Nuclear Information System (INIS)
Kheifets, S.
1984-01-01
One of the most important characteristics of an electron storage ring is the size of the beam. However analytical calculations of beam size are beset with problems and the computational methods and programs which are used to overcome these are inadequate for all problems in which stochastic noise is an essential part. Two examples are, for an electron storage ring, beam-size evaluation including beam-beam interactions, and finding the beam size for a nonlinear machine. The method described should overcome some of the problems. It uses the Green's function method applied to the Fokker-Planck equation governing the distribution function in the phase space of particle motion. The new step is to consider the particle motion in two degrees of freedom rather than in one dimension. The technique is described fully and is then applied to a strong-focusing machine. (U.K.)
Audebert, Chloe; Vignon-Clementel, Irene E
2018-03-30
The indocyanine green (ICG) clearance, presented as plasma disappearance rate is, presently, a reliable method to estimate the hepatic "function". However, this technique is not instantaneously available and thus cannot been used intra-operatively (during liver surgery). Near-infrared spectroscopy enables to assess hepatic ICG concentration over time in the liver tissue. This article proposes to extract more information from the liver intensity dynamics by interpreting it through a dedicated pharmacokinetics model. In order to account for the different exchanges between the liver tissues, the proposed model includes three compartments for the liver model (sinusoids, hepatocytes and bile canaliculi). The model output dependency to parameters is studied with sensitivity analysis and solving an inverse problem on synthetic data. The estimation of model parameters is then performed with in-vivo measurements in rabbits (El-Desoky et al. 1999). Parameters for different liver states are estimated, and their link with liver function is investigated. A non-linear (Michaelis-Menten type) excretion rate from the hepatocytes to the bile canaliculi was necessary to reproduce the measurements for different liver conditions. In case of bile duct ligation, the model suggests that this rate is reduced, and that the ICG is stored in the hepatocytes. Moreover, the level of ICG remains high in the blood following the ligation of the bile duct. The percentage of retention of indocyanine green in blood, which is a common test for hepatic function estimation, is also investigated with the model. The impact of bile duct ligation and reduced liver inflow on the percentage of ICG retention in blood is studied. The estimation of the pharmacokinetics model parameters may lead to an evaluation of different liver functions. Copyright © 2018 Elsevier B.V. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Rodrigues, Rafael de Lima [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Vaidya, Arvind Narayan [Universidade Federal, Rio de Janeiro, RJ (Brazil). Inst. de Fisica
2001-12-01
Using the spectral theorema in context of Green's function in momentum space of neutrons in the magnetic field of a linear conductor with current the bound state energy spectrum and eigenfunctions are deduced. It's also pointed out that this problem present a new scenary of Green's function in non-relativistic quantum mechanics. (author)
International Nuclear Information System (INIS)
Freericks, J. K.; Turkowski, V.
2009-01-01
Spectral moment sum rules are presented for the inhomogeneous many-body problem described by the fermionic Falicov-Kimball or Hubbard models. These local sum rules allow for arbitrary hoppings, site energies, and interactions. They can be employed to quantify the accuracy of numerical solutions to the inhomogeneous many-body problem such as strongly correlated multilayered devices, ultracold atoms in an optical lattice with a trap potential, strongly correlated systems that are disordered, or systems with nontrivial spatial ordering such as a charge-density wave or a spin-density wave. We also show how the spectral moment sum rules determine the asymptotic behavior of the Green function, self-energy, and dynamical mean field when applied to the dynamical mean-field theory solution of the many-body problem. In particular, we illustrate in detail how one can dramatically reduce the number of Matsubara frequencies needed to solve the Falicov-Kimball model while still retaining high precision, and we sketch how one can incorporate these results into Hirsch-Fye quantum Monte Carlo solvers for the Hubbard (or more complicated) models. Since the solution of inhomogeneous problems is significantly more time consuming than periodic systems, efficient use of these sum rules can provide a dramatic speed up in the computational time required to solve the many-body problem. We also discuss how these sum rules behave in nonequilibrium situations as well, where the Hamiltonian has explicit time dependence due to a driving field or due to the time-dependent change in a parameter such as the interaction strength or the origin of the trap potential.
International Nuclear Information System (INIS)
Zimmermann, Frank
1998-01-01
We compare different approximations to the point-charge Green function for the radial electric monopole field excited by an ultrarelativistic particle propagating through a resistive pipe, and study the applicability of these approximations for calculating the field of a bunch with finite length. It has been speculated that the exact form of the electric field could be important for simulations of the electron-cloud instability. In this paper, we show, however, that the usual approximation of the Green function by a delta function is adequate, except for extremely short bunch lengths
Enforcing conservation laws in nonequilibrium cluster perturbation theory
Gramsch, Christian; Potthoff, Michael
2017-05-01
Using the recently introduced time-local formulation of the nonequilibrium cluster perturbation theory (CPT), we construct a generalization of the approach such that macroscopic conservation laws are respected. This is achieved by exploiting the freedom for the choice of the starting point of the all-order perturbation theory in the intercluster hopping. The proposed conserving CPT is a self-consistent propagation scheme which respects the conservation of energy, particle number, and spin, which treats short-range correlations exactly up to the linear scale of the cluster, and which represents a mean-field-like approach on length scales beyond the cluster size. Using Green's functions, conservation laws are formulated as local constraints on the local spin-dependent particle and the doublon density. We consider them as conditional equations to self-consistently fix the time-dependent intracluster one-particle parameters. Thanks to the intrinsic causality of the CPT, this can be set up as a step-by-step time propagation scheme with a computational effort scaling linearly with the maximum propagation time and exponentially in the cluster size. As a proof of concept, we consider the dynamics of the two-dimensional, particle-hole-symmetric Hubbard model following a weak interaction quench by simply employing two-site clusters only. Conservation laws are satisfied by construction. We demonstrate that enforcing them has strong impact on the dynamics. While the doublon density is strongly oscillating within plain CPT, a monotonic relaxation is observed within the conserving CPT.
A Lagrangian formalism for nonequilibrium ensembles
International Nuclear Information System (INIS)
Sobouti, Y.
1989-08-01
It is suggested to formulate a nonequilibrium ensemble theory by maximizing a time-integrated entropy constrained by Liouville's equation. This leads to distribution functions of the form f = Z -1 exp(-g/kT), where g(p,q,t) is a solution of Liouville's equation. A further requirement that the entropy should be an additivie functional of the integrals of Liouville's equation, limits the choice of g to linear superpositions of the nonlinearly independent integrals of motion. Time-dependent and time-independent integrals may participate in this superposition. (author). 14 refs
International Nuclear Information System (INIS)
Cresti, Alessandro; Grosso, Giuseppe; Parravicini, Giuseppe Pastori
2006-01-01
We have derived closed analytic expressions for the Green's function of an electron in a two-dimensional electron gas threaded by a uniform perpendicular magnetic field, also in the presence of a uniform electric field and of a parabolic spatial confinement. A workable and powerful numerical procedure for the calculation of the Green's functions for a large infinitely extended quantum wire is considered exploiting a lattice model for the wire, the tight-binding representation for the corresponding matrix Green's function, and the Peierls phase factor in the Hamiltonian hopping matrix element to account for the magnetic field. The numerical evaluation of the Green's function has been performed by means of the decimation-renormalization method, and quite satisfactorily compared with the analytic results worked out in this paper. As an example of the versatility of the numerical and analytic tools here presented, the peculiar semilocal character of the magnetic Green's function is studied in detail because of its basic importance in determining magneto-transport properties in mesoscopic systems
International Nuclear Information System (INIS)
Mondaini, Leonardo; Marino, E.C.
2011-01-01
Full text: Despite the fact that quantum field theories are usually formulated in coordinate space, calculations, in both T = 0 and T ≠ 0 cases, are almost always performed in momentum space. However, when we are faced with the exact calculation of correlation functions we are naturally led to the problem of finding closed-form expressions for Green functions in coordinate space. In the present work, we derive an exact closed-form representation for the Euclidian thermal Green function of the two-dimensional (2D) free massless scalar field in coordinate space. This can be interpreted as the real part of a complex analytic function of a variable that conformally maps the infinite strip -∞ < x < ∞ (0 < τ < β of the z = x + iτ (τ: imaginary time) plane into the upper-half-plane. Use of the Cauchy-Riemann conditions, then allows us to identify the dual thermal Green function as the imaginary part of that function. Using both the thermal Green function and its dual, we obtain an explicit series expression for the fermionic correlation functions of the massive Thirring model (MTM) at a finite temperature. (author)
Green leaf volatiles: biosynthesis, biological functions and their applications in biotechnology.
ul Hassan, Muhammad Naeem; Zainal, Zamri; Ismail, Ismanizan
2015-08-01
Plants have evolved numerous constitutive and inducible defence mechanisms to cope with biotic and abiotic stresses. These stresses induce the expression of various genes to activate defence-related pathways that result in the release of defence chemicals. One of these defence mechanisms is the oxylipin pathway, which produces jasmonates, divinylethers and green leaf volatiles (GLVs) through the peroxidation of polyunsaturated fatty acids (PUFAs). GLVs have recently emerged as key players in plant defence, plant-plant interactions and plant-insect interactions. Some GLVs inhibit the growth and propagation of plant pathogens, including bacteria, viruses and fungi. In certain cases, GLVs released from plants under herbivore attack can serve as aerial messengers to neighbouring plants and to attract parasitic or parasitoid enemies of the herbivores. The plants that perceive these volatile signals are primed and can then adapt in preparation for the upcoming challenges. Due to their 'green note' odour, GLVs impart aromas and flavours to many natural foods, such as vegetables and fruits, and therefore, they can be exploited in industrial biotechnology. The aim of this study was to review the progress and recent developments in research on the oxylipin pathway, with a specific focus on the biosynthesis and biological functions of GLVs and their applications in industrial biotechnology. © 2015 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.
Surface Functionalization of “Rajshahi Silk” Using Green Silver Nanoparticles
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Sakil Mahmud
2017-09-01
Full Text Available In this study, a novel functionalization approach has been addressed by using sodium alginate (Na-Alg assisted green silver nanoparticles (AgNPs on traditional “Rajshahi silk” fabric via an exhaustive method. The synthesized nanoparticles and coated silk fabrics were characterized by different techniques, including ultraviolet–visible spectroscopy (UV–vis spectra, scanning electron microscopy (SEM, transmission electron microscopy (TEM, energy dispersive X-ray spectroscopy (EDS, X-ray diffraction (XRD, thermogravimetric analysis (TGA, and Fourier transform infrared spectroscopy (FT-IR, which demonstrated that AgNPs with an average size of 6–10 nm were consistently deposited in the fabric surface under optimized conditions (i.e., pH 4, temperature 40 °C, and time 40 min. The silk fabrics treated with AgNPs showed improved colorimetric values and color fastness properties. Moreover, the UV-protection ability and antibacterial activity, as well as other physical properties—including tensile properties, the crease recovery angle, bending behavior, the yellowness index, and wettability (surface contact angle of the AgNPs-coated silk were distinctly augmented. Therefore, green AgNPs-coated traditional silk with multifunctional properties has high potential in the textile industry.
Broggini, Filippo; Wapenaar, Kees; van der Neut, Joost; Snieder, Roel
2014-01-01
An iterative method is presented that allows one to retrieve the Green's function originating from a virtual source located inside a medium using reflection data measured only at the acquisition surface. In addition to the reflection response, an estimate of the travel times corresponding to the direct arrivals is required. However, no detailed information about the heterogeneities in the medium is needed. The iterative scheme generalizes the Marchenko equation for inverse scattering to the seismic reflection problem. To give insight in the mechanism of the iterative method, its steps for a simple layered medium are analyzed using physical arguments based on the stationary phase method. The retrieved Green's wavefield is shown to correctly contain the multiples due to the inhomogeneities present in the medium. Additionally, a variant of the iterative scheme enables decomposition of the retrieved wavefield into its downgoing and upgoing components. These wavefields then enable creation of a ghost-free image of the medium with either cross correlation or multidimensional deconvolution, presenting an advantage over standard prestack migration.
Development of multi-functional streetscape green infrastructure using a performance index approach
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Tiwary, A.; Williams, I.D.; Heidrich, O.; Namdeo, A.; Bandaru, V.; Calfapietra, C.
2016-01-01
This paper presents a performance evaluation framework for streetscape vegetation. A performance index (PI) is conceived using the following seven traits, specific to the street environments – Pollution Flux Potential (PFP), Carbon Sequestration Potential (CSP), Thermal Comfort Potential (TCP), Noise Attenuation Potential (NAP), Biomass Energy Potential (BEP), Environmental Stress Tolerance (EST) and Crown Projection Factor (CPF). Its application is demonstrated through a case study using fifteen street vegetation species from the UK, utilising a combination of direct field measurements and inventoried literature data. Our results indicate greater preference to small-to-medium size trees and evergreen shrubs over larger trees for streetscaping. The proposed PI approach can be potentially applied two-fold: one, for evaluation of the performance of the existing street vegetation, facilitating the prospects for further improving them through management strategies and better species selection; two, for planning new streetscapes and multi-functional biomass as part of extending the green urban infrastructure. - Highlights: • A performance evaluation framework for streetscape vegetation is presented. • Seven traits, relevant to street vegetation, are included in a performance index (PI). • The PI approach is applied to quantify and rank fifteen street vegetation species. • Medium size trees and evergreen shrubs are found more favourable for streetscapes. • The PI offers a metric for developing sustainable streetscape green infrastructure. - A performance index is developed and applied to fifteen vegetation species indicating greater preference to medium size trees and evergreen shrubs for streetscaping.
Braaker, Sonja; Obrist, Martin Karl; Ghazoul, Jaboury; Moretti, Marco
2017-01-01
Increasing development of urban environments creates high pressure on green spaces with potential negative impacts on biodiversity and ecosystem services. There is growing evidence that green roofs – rooftops covered with vegetation – can contribute mitigate the loss of urban green spaces by
Tsunami excitation by inland/coastal earthquakes: the Green function approach
Directory of Open Access Journals (Sweden)
T. B. Yanovskaya
2003-01-01
Full Text Available In the framework of the linear theory, the representation theorem is derived for an incompressible liquid layer with a boundary of arbitrary shape and in a homogeneous gravity field. In addition, the asymptotic representation for the Green function, in a layer of constant thickness is obtained. The validity of the approach for the calculation of the tsunami wavefield based on the Green function technique is verified comparing the results with those obtained from the modal theory, for a liquid layer of infinite horizontal dimensions. The Green function approach is preferable for the estimation of the excitation spectra, since in the case of an infinite liquid layer it leads to simple analytical expressions. From this analysis it is easy to describe the peculiarities of tsunami excitation by different sources. The method is extended to the excitation of tsunami in a semiinfinite layer with a sloping boundary. Numerical modelling of the tsunami wavefield, excited by point sources at different distances from the coastline, shows that when the source is located at a distance from the coastline equal or larger than the source depth, the shore presence does not affect the excitation of the tsunami. When the source is moved towards thecoastline, the low frequency content in the excitation spectrum ecreases, while the high frequencies content increases dramatically. The maximum of the excitation spectra from inland sources, located at a distance from the shore like the source depth, becomes less than 10% of that radiated if the same source is located in the open ocean. The effect of the finiteness of the source is also studied and the excitation spectrum is obtained by integration over the fault area. Numerical modelling of the excitation spectra for different source models shows that, for a given seismic moment, the spectral level, as well as the maximum value of the spectra, decreases with increasing fault size. When the sources are located in the
Stress-based fatigue assessment of major component in NPP using modified Green's function approach
International Nuclear Information System (INIS)
Ko, Han Ok; Jhung, Myung Jo; Choi, Jae Boong
2013-01-01
In this paper, the modified GFA which can consider temperature-dependent material properties is proposed by using a neural network (NN) and weight factor. To verify the modified GFA, thermal stresses by the proposed method are compared with those by FEM. Finally, pros and cons of the new method as well as technical findings from the assessment are discussed to show applicability of them. In this paper, the modified GFA considering temperature-dependent material properties is proposed by using NN and weight factor. To verify the proposed method, thermal stresses by the modified Green's function are compared with those by FEM and the results between two methods show a good agreement. Finally, it is anticipated that more precise fatigue evaluation is performed by using the proposed method. Recently, 434 nuclear reactors are being operated in the world. Among them, about 40% reactors are being operated beyond their design life or will be approaching their life. During the long term operation, various degradation mechanisms are occurred. Fatigue damage caused by alternating operational stresses in terms of temperature or pressure change is the one of important damage mechanisms in the nuclear power plants (NPPs). Although components important to safety were designed to withstand the fatigue damage, cumulative usage factor (CUF) at some locations can exceed the design limit beyond the design life. So, it is necessary to monitor the fatigue damage of major components during the long term operation. Researches on fatigue monitoring system (FMS) have been widely performed. In USA, the FatiguePro was developed by EPRI and was applied to the CE, WEC, B and W and GE type reactors. In Korea, the Kori unit 1 which started commercial operation in 1978 is being operated beyond its design life. At the stage of the license renewal, various plans for degradation mechanisms were established and reviewed. And, in case of fatigue damage, to monitor the fatigue damage of major components
Ambient Noise Green's Function Simulation of Long-Period Ground Motions for Reverse Faulting
Miyake, H.; Beroza, G. C.
2009-12-01
Long-time correlation of ambient seismic noise has been demonstrated as a useful tool for strong ground motion prediction [Prieto and Beroza, 2008]. An important advantage of ambient noise Green's functions is that they can be used for ground motion simulation without resorting to either complex 3-D velocity structure to develop theoretical Green’s functions, or aftershock records for empirical Green’s function analysis. The station-to-station approach inherent to ambient noise Green’s functions imposes some limits to its application, since they are band-limited, applied at the surface, and for a single force. We explore the applicability of this method to strong motion prediction using the 2007 Chuetsu-oki, Japan, earthquake (Mw 6.6, depth = 9 km), which excited long-period ground motions in and around the Kanto basin almost 200 km from the epicenter. We test the performance of ambient noise Green's function for long-period ground motion simulation. We use three components of F-net broadband data at KZK station, which is located near the source region, as a virtual source, and three components of six F-net stations in and around the Kanto basin to calculate the response. An advantage to applying this approach in Japan is that ambient-noise sources are active in diverse directions. The dominant period of the ambient noise for the F-net datasets is mostly 7 s over the year, and amplitudes are largest in winter. This period matches the dominant periods of the Kanto and Niigata basins. For the 9 components of the ambient noise Green’s functions, we have confirmed long-period components corresponding to Love wave and Rayleigh waves that can be used for simulation of the 2007 Chuetsu-oki earthquake. The relative amplitudes, phases, and durations of the ambient noise Green’s functions at the F-net stations in and around the Kanto basin respect to F-net KZK station are fairly well matched with those of the observed ground motions for the 2007 Chuetsu
Cassettari, Vanessa Mello Granado; Machado, Nilton Carlos; Lourenção, Pedro Luiz Toledo de Arruda; Carvalho, Marry Assis; Ortolan, Erika Veruska Paiva
2018-01-05
Evaluate the effect of combinations of green banana biomass and laxatives in children and adolescents with chronic constipation. This was a randomized study of 80 children and adolescents with functional constipation according to the Rome IV Criteria, who were divided into five groups: (1) green banana biomass alone; (2) green banana biomass plus PEG 3350 with electrolytes; (3) green banana biomass plus sodium picosulfate; (4) PEG 3350 with electrolytes alone; and (5) sodium picosulfate alone. Primary outcome measure was the reduction of the proportion of patients with Bristol Stool Form Scale ratings 1 or 2. Secondary outcome measures were: increase of the proportion of >3 bowel movements/week and reduction of the proportion of fecal incontinence, straining on defecation, painful defecation, blood in stool, abdominal pain, and decreased laxative doses. On consumption of green banana biomass alone, a statistically significant reduction was observed in the proportion of children with Bristol Stool Form Scale rating 1 or 2, straining on defecation, painful defecation, and abdominal pain. Conversely, no reduction was observed in fecal incontinence episodes/week, blood in stool, and no increase was observed in the proportion of children with >3 bowel movements/week. The percentage of children who required decreased laxative dose was high when green banana biomass was associated with sodium picosulfate (87%), and PEG 3350 with electrolytes (63%). Green banana biomass alone and associated with laxatives was well tolerated, and no adverse effects were reported. Green banana biomass is advantageous as an adjunct therapy on functional constipation, mainly for reducing doses of laxatives. Copyright © 2017 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.
International Nuclear Information System (INIS)
John, R.W.
1987-01-01
First, in connection with their construction due to Hadamard, the mathematical and physical meaning of covariant Green's functions in relativistic gravitational fields - according to Einstein: on curved space-time - is discussed. Then, in the case of a general static spherically symmetric space-time the construction equations for a scalar Green's function are cast into symmetry-adapted form providing a convenient starting point for an explicit calculation of the Hadamard building elements. In applying the obtained basic scheme to a special one-parameter family of model metrics one succeeds in advancing to the explicit exact calculation of tail-term coefficients of a massless Green's function which are simultaneously coefficients in the Schwinger-De Witt expansion of the Feynman propagator for the corresponding massive Klein-Gordon equation on curved space-time. (author)
International Nuclear Information System (INIS)
Flume, R.
1978-01-01
The unitary (U) gauge Green's functions of the U(1) and SU(2) Higgs-Kibble models are constructed applying a renormalized point transformation and a non-local gauge changing transformation to a manifestly renormalizable (R gauge) version of the respective theory. It is shown that the cancellation mechanism known as 'tree graph unitarity' rendering in tree graph approximation a smooth high energy behaviour of the U gauge Green's functions on mass shell can in a natural way be extended to all orders of perturbation theory. The conditions imposed by this 'generalized tree graph unitarity' on the renormalization programme are shown to be equivalent with the requirement of renormalized Slavnov identities for the R gauge Green's functions
Tanaka, Hiroshi
1998-01-01
A real-space scheme is developed to calculate matrix elements of the Green function from first principles for large disordered systems. The scheme is an extension of the particle source method, combined with the tight-binding linear muffin-tin orbitals and has the following advantages: (i) It is possible to evaluate both the diagonal and off-diagonal parts of the Green function and also their products with other quantum operators, (ii) it allows for an explicit control of the numerical accuracy and clear-cut physical interpretations of the results on the basis of the definition of the Green function, and (iii) the scheme is suitable for both vector and parallel processing and requires CPU time and memory size proportional only to the system size. The method is applied to the densities of states of bcc and amorphous Fe. The dc conductivity is also evaluated for the latter from the Kubo-Greenwood formula.
International Nuclear Information System (INIS)
Ishida, Hidenobu
2015-01-01
The dynamical diffraction theory of X-rays for a distorted crystal with the Green's function method is applied to the Bragg case. The transmitted and diffracted crystal waves are represented as the solutions of the integral equations using the Green's function. For a perfect crystal, the most exact form of the solution of the equations is given by the Green's function and its derivatives, and the waves are analytically expressed by using them. The results can be applied in a general case where the amplitude modulation of the incident wave is not negligibly small compared with the wave vector. If the amplitude modulation is small, those results are reduced essentially to the same as those given by Takagi's theory. (author)
Bruni, S.; Llombart Juan, N.; Neto, A.; Gerini, G.; Maci, S.
2004-01-01
A general algorithm for the analysis of microstrip coupled leaky wave slot antennas was discussed. The method was based on the construction of physically appealing entire domain Methods of Moments (MoM) basis function that allowed a consistent reduction of the number of unknowns and of total
International Nuclear Information System (INIS)
Poirier, M.
1997-01-01
Though one would expect that large-angular momentum doubly excited states exhibit weak electronic correlations, it is shown in this paper that a first-order perturbation theory ignoring such correlations may completely fail in predicting correct autoionization probabilities: quadrupolar transitions are poorly described by lowest-order perturbation theory, except for very large angular momenta. Inclusion of second-order dipole-dipole term considerably improves the accuracy of the method. This effect is computed using Coulomb Green's function in its analytical form, probably applied here for the first time to autoionization processes. Examples are given in barium for 5d j 5g [k[ states (j=3/2, 5/2) and for 5d 5/2 nl [k[ states with l > 4. (orig.)
Moon, H.; Donderici, B.; Teixeira, F. L.
2016-11-01
We present a robust algorithm for the computation of electromagnetic fields radiated by point sources (Hertzian dipoles) in cylindrically stratified media where each layer may exhibit material properties (permittivity, permeability, and conductivity) with uniaxial anisotropy. Analytical expressions are obtained based on the spectral representation of the tensor Green's function based on cylindrical Bessel and Hankel eigenfunctions, and extended for layered uniaxial media. Due to the poor scaling of these eigenfunctions for extreme arguments and/or orders, direct numerical evaluation of such expressions can produce numerical instability, i.e., underflow, overflow, and/or round-off errors under finite precision arithmetic. To circumvent these problems, we develop a numerically stable formulation through suitable rescaling of various expressions involved in the computational chain, to yield a robust algorithm for all parameter ranges. Numerical results are presented to illustrate the robustness of the formulation including cases of practical interest.
Energy Technology Data Exchange (ETDEWEB)
Moon, H., E-mail: haksu.moon@gmail.com [ElectroScience Laboratory, The Ohio State University, Columbus, OH 43212 (United States); Donderici, B., E-mail: burkay.donderici@halliburton.com [Sensor Physics & Technology, Halliburton Energy Services, Houston, TX 77032 (United States); Teixeira, F.L., E-mail: teixeira@ece.osu.edu [ElectroScience Laboratory, The Ohio State University, Columbus, OH 43212 (United States)
2016-11-15
We present a robust algorithm for the computation of electromagnetic fields radiated by point sources (Hertzian dipoles) in cylindrically stratified media where each layer may exhibit material properties (permittivity, permeability, and conductivity) with uniaxial anisotropy. Analytical expressions are obtained based on the spectral representation of the tensor Green's function based on cylindrical Bessel and Hankel eigenfunctions, and extended for layered uniaxial media. Due to the poor scaling of these eigenfunctions for extreme arguments and/or orders, direct numerical evaluation of such expressions can produce numerical instability, i.e., underflow, overflow, and/or round-off errors under finite precision arithmetic. To circumvent these problems, we develop a numerically stable formulation through suitable rescaling of various expressions involved in the computational chain, to yield a robust algorithm for all parameter ranges. Numerical results are presented to illustrate the robustness of the formulation including cases of practical interest.
Vijaykumar, Adithya; Ouldridge, Thomas E.; ten Wolde, Pieter Rein; Bolhuis, Peter G.
2017-03-01
The modeling of complex reaction-diffusion processes in, for instance, cellular biochemical networks or self-assembling soft matter can be tremendously sped up by employing a multiscale algorithm which combines the mesoscopic Green's Function Reaction Dynamics (GFRD) method with explicit stochastic Brownian, Langevin, or deterministic molecular dynamics to treat reactants at the microscopic scale [A. Vijaykumar, P. G. Bolhuis, and P. R. ten Wolde, J. Chem. Phys. 143, 214102 (2015)]. Here we extend this multiscale MD-GFRD approach to include the orientational dynamics that is crucial to describe the anisotropic interactions often prevalent in biomolecular systems. We present the novel algorithm focusing on Brownian dynamics only, although the methodology is generic. We illustrate the novel algorithm using a simple patchy particle model. After validation of the algorithm, we discuss its performance. The rotational Brownian dynamics MD-GFRD multiscale method will open up the possibility for large scale simulations of protein signalling networks.
Surface green function matching for a three-dimensional non-local continuum
International Nuclear Information System (INIS)
Idiodi, J.O.A.
1985-07-01
With a view toward helping to bridge the gap, from the continuum side, between discrete and continuum models of crystalline, elastic solids, explicit results are presented for non-local stress tensors that describe exactly some lattice dynamical models that have been widely used in the literature for cubic lattices. The Surface Green Function Matching (SGFM) method, which has been used successfully for a variety of surface problems, is then extended, within a continuum approach, to a non-local continuum that models a three-dimensional discrete lattice. The practical use of the method is demonstrated by performing a fairly complete analytical study of the vibrational surface modes of the SCC semi-infinite medium. Some results are presented for the [100] direction of the (001) surface of the SCC lattice. (author)
Identification of a functional nuclear export signal in the green fluorescent protein asFP499
International Nuclear Information System (INIS)
Mustafa, Huseyin; Strasser, Bernd; Rauth, Sabine; Irving, Robert A.; Wark, Kim L.
2006-01-01
The green fluorescent protein (GFP) asFP499 from Anemonia sulcata is a distant homologue of the GFP from Aequorea victoria. We cloned the asFP499 gene into a mammalian expression vector and showed that this protein was expressed in the human lymphoblast cell line Ramos RA1 and in the embryonic kidney 293T cell line (HEK 293T). In HEK 293T cells, asFP499 was localized mainly in the cytoplasm, suggesting that the protein was excluded from the nucleus. We identified 194 LRMEKLNI 201 as a candidate nuclear export signal in asFP499 and mutated the isoleucine at position 201 to an alanine. Unlike the wildtype form, the mutant protein was distributed throughout the cytoplasm and nucleus. This is First report of a GFP that contains a functional NES
Directory of Open Access Journals (Sweden)
Alexander Domoshnitsky
2014-01-01
Full Text Available The impulsive delay differential equation is considered (Lx(t=x′(t+∑i=1mpi(tx(t-τi(t=f(t, t∈[a,b], x(tj=βjx(tj-0, j=1,…,k, a=t0
Electronic Structure Calculation of Permanent Magnets using the KKR Green's Function Method
Doi, Shotaro; Akai, Hisazumi
2014-03-01
Electronic structure and magnetic properties of permanent magnetic materials, especially Nd2Fe14B, are investigated theoretically using the KKR Green's function method. Important physical quantities in magnetism, such as magnetic moment, Curie temperature, and anisotropy constant, which are obtained from electronics structure calculations in both cases of atomic-sphere-approximation and full-potential treatment, are compared with past band structure calculations and experiments. The site preference of heavy rare-earth impurities are also evaluated through the calculation of formation energy with the use of coherent potential approximations. Further, the development of electronic structure calculation code using the screened KKR for large super-cells, which is aimed at studying the electronic structure of realistic microstructures (e.g. grain boundary phase), is introduced with some test calculations.
International Nuclear Information System (INIS)
Censor, Dan
2010-01-01
Identifying invariance properties helps in simplifying calculations and consolidating concepts. Presently the Special Relativistic invariance of dispersion relations and their associated scalar wave operators is investigated for general dispersive homogeneous linear media. Invariance properties of the four-dimensional Fourier-transform integrals is demonstrated, from which the invariance of the scalar Green-function is inferred. Dispersion relations and the associated group velocities feature in Hamiltonian ray tracing theory. The derivation of group velocities for moving media from the dispersion relation for these media at rest is discussed. It is verified that the group velocity concept satisfies the relativistic velocity-addition formula. In this respect it is considered to be 'real', i.e., substantial, physically measurable, and not merely a mathematical artifact. Conversely, if we assume the group velocity to be substantial, it follows that the dispersion relation must be a relativistic invariant. (orig.)
High-temperature electronic structure with the Korringa-Kohn-Rostoker Green's function method
Starrett, C. E.
2018-05-01
Modeling high-temperature (tens or hundreds of eV), dense plasmas is challenging due to the multitude of non-negligible physical effects including significant partial ionization and multisite effects. These effects cause the breakdown or intractability of common methods and approximations used at low temperatures, such as pseudopotentials or plane-wave basis sets. Here we explore the Korringa-Kohn-Rostoker Green's function method at these high-temperature conditions. The method is all electron, does not rely on pseudopotentials, and uses a spherical harmonic basis set, and so avoids the aforementioned limitations. It is found to be accurate for solid density aluminum and iron plasmas when compared to a plane-wave method at low temperature, while being able to access high temperatures.
Green functions and dimensional reduction of quantum fields on product manifolds
International Nuclear Information System (INIS)
Haba, Z
2008-01-01
We discuss Euclidean Green functions on product manifolds P=N x M. We show that if M is compact and N is not compact then the Euclidean field on P can be approximated by its zero mode which is a Euclidean field on N. We estimate the remainder of this approximation. We show that for large distances on N the remainder is small. If P=R D-1 x S β , where S β is a circle of radius β, then the result reduces to the well-known approximation of the D-dimensional finite temperature quantum field theory by (D - 1)-dimensional one in the high-temperature limit. Analytic continuation of Euclidean fields is discussed briefly
Quantized Dirac field in curved Riemann--Cartan background. I. Symmetry properties, Green's function
International Nuclear Information System (INIS)
Nieh, H.T.; Yan, M.L.
1982-01-01
In the present series of papers, we study the properties of quantized Dirac field in curved Riemann--Cartan space, with particular attention on the role played by torsion. In this paper, we give, in the spirit of the original work of Weyl, a systematic presentation of Dirac's theory in curved Riemann--Cartan space. We discuss symmetry properties of the system, and derive conservation laws as direct consequences of these symmetries. Also discussed is conformal gauge symmetry, with torsion effectively playing the role of a conformal gauge field. To obtain short-distance behavior, we calculate the spinor Green's function, in curved Riemann--Cartan background, using the Schwinger--DeWitt method of proper-time expansion. The calculation corresponds to a generalization of DeWitt's calculation for a Riemannian background
Energy Technology Data Exchange (ETDEWEB)
Lee, Young-Chul [Department of Chemical and Biomolecular Engineering (BK21 Program), KAIST, 335 Gwahak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Kim, Eui Jin [Department of Chemical and Biochemical Engineering, Chosun University, Seosuk-dong, Dong-gu, Gwangju 501-759 (Korea, Republic of); Yang, Ji-Won [Department of Chemical and Biomolecular Engineering (BK21 Program), KAIST, 335 Gwahak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Shin, Hyun-Jae, E-mail: shinhj@chosun.ac.kr [Department of Chemical and Biochemical Engineering, Chosun University, Seosuk-dong, Dong-gu, Gwangju 501-759 (Korea, Republic of)
2011-08-15
Highlights: {yields} Preparation of aminopropyl functionalized magnesium phyllosilicate (AMP clay). {yields} Characterization of AMP clay and AMP clay-malachite green (MG) mixture. {yields} Novel precipitation mechanism including MG fading plus collapsed AMP clay. {yields} Adsorption kinetics and thermodynamics of MG using AMP clay. - Abstract: We report a method for the removal of malachite green (MG) by adsorption and precipitation using nano-sized aminopropyl functionalized magnesium phyllosilicate (AMP) clay. MG, which is used in aquaculture and fisheries, is a carcinogenic and mutagenic compound. In response to these health risks, many efforts have been focused on adsorption of MG onto various adsorbents, which is a versatile and widely used technique for removing MG from water. Herein, we describe the adsorption and precipitation of MG using AMP clay, as well as the alkaline fading phenomenon of MG. In this study, prepared AMP clay and the precipitate product after the reaction of MG-AMP clay mixture were characterized. In addition, adsorption isotherms and kinetics, as well as thermodynamic studies are presented. Based on the results, we suggest a macro- and microscopic removal mechanism for the adsorption and precipitation of MG using AMP clay. An AMP clay dosage of 0.1 mg mL{sup -1} exhibited a maximum removal capacity of 334.80 mg g{sup -1} and 81.72% MG removal efficiency. With further increases of the AMP clay dosage, removal capacity by AMP clay gradually decreased; at dosage above 0.2 mg mL{sup -1} of AMP clay, the removal efficiency reached 100%.
International Nuclear Information System (INIS)
Lee, Young-Chul; Kim, Eui Jin; Yang, Ji-Won; Shin, Hyun-Jae
2011-01-01
Highlights: → Preparation of aminopropyl functionalized magnesium phyllosilicate (AMP clay). → Characterization of AMP clay and AMP clay-malachite green (MG) mixture. → Novel precipitation mechanism including MG fading plus collapsed AMP clay. → Adsorption kinetics and thermodynamics of MG using AMP clay. - Abstract: We report a method for the removal of malachite green (MG) by adsorption and precipitation using nano-sized aminopropyl functionalized magnesium phyllosilicate (AMP) clay. MG, which is used in aquaculture and fisheries, is a carcinogenic and mutagenic compound. In response to these health risks, many efforts have been focused on adsorption of MG onto various adsorbents, which is a versatile and widely used technique for removing MG from water. Herein, we describe the adsorption and precipitation of MG using AMP clay, as well as the alkaline fading phenomenon of MG. In this study, prepared AMP clay and the precipitate product after the reaction of MG-AMP clay mixture were characterized. In addition, adsorption isotherms and kinetics, as well as thermodynamic studies are presented. Based on the results, we suggest a macro- and microscopic removal mechanism for the adsorption and precipitation of MG using AMP clay. An AMP clay dosage of 0.1 mg mL -1 exhibited a maximum removal capacity of 334.80 mg g -1 and 81.72% MG removal efficiency. With further increases of the AMP clay dosage, removal capacity by AMP clay gradually decreased; at dosage above 0.2 mg mL -1 of AMP clay, the removal efficiency reached 100%.
Energy Technology Data Exchange (ETDEWEB)
Ren, Xiaoying; Hu, Zhongai, E-mail: zhongai@nwnu.edu.cn; Hu, Haixiong; Qiang, Ruibin; Li, Li; Li, Zhimin; Yang, Yuying; Zhang, Ziyu; Wu, Hongying
2015-10-15
Graphical abstract: Electroactive methyl green (MG) is selected to functionalize reduced graphene oxide (RGO) through non-covalent modification and the composite achieves high specific capacitance, good rate capability and excellent long life cycle. - Highlights: • MG–RGO composites were firstly prepared through non-covalent modification. • The mass ratio in composites is a key for achieving high specific capacitance. • MG–RGO 5:4 exhibits the highest specific capacitance of 341 F g{sup −1}. • MG–RGO 5:4 shows excellent rate capability and long life cycle. - Abstract: In the present work, water-soluble electroactive methyl green (MG) has been used to non-covalently functionalize reduced graphene oxide (RGO) for enhancing supercapacitive performance. The microstructure, composition and morphology of MG–RGO composites are systematically characterized by UV–vis absorption, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrochemical performances are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). The fast redox reactions from MG could generate additional pseudocapacitance, which endows RGO higher capacitances. As a result, the MG–RGO composite (with the 5:4 mass ratio of MG:RGO) achieve a maximum value of 341 F g{sup −1} at 1 A g{sup −1} within the potential range from −0.25 to 0.75 V and provide a 180% enhancement in specific capacitance in comparison with pure RGO. Furthermore, excellent rate capability (72% capacitance retention from 1 A g{sup −1} to 20 A g{sup −1}) and long life cycle (12% capacitance decay after 5000 cycles) are achieved for the MG–RGO composite electrode.
Bolhuis, Peter
Important reaction-diffusion processes, such as biochemical networks in living cells, or self-assembling soft matter, span many orders in length and time scales. In these systems, the reactants' spatial dynamics at mesoscopic length and time scales of microns and seconds is coupled to the reactions between the molecules at microscopic length and time scales of nanometers and milliseconds. This wide range of length and time scales makes these systems notoriously difficult to simulate. While mean-field rate equations cannot describe such processes, the mesoscopic Green's Function Reaction Dynamics (GFRD) method enables efficient simulation at the particle level provided the microscopic dynamics can be integrated out. Yet, many processes exhibit non-trivial microscopic dynamics that can qualitatively change the macroscopic behavior, calling for an atomistic, microscopic description. The recently developed multiscale Molecular Dynamics Green's Function Reaction Dynamics (MD-GFRD) approach combines GFRD for simulating the system at the mesocopic scale where particles are far apart, with microscopic Molecular (or Brownian) Dynamics, for simulating the system at the microscopic scale where reactants are in close proximity. The association and dissociation of particles are treated with rare event path sampling techniques. I will illustrate the efficiency of this method for patchy particle systems. Replacing the microscopic regime with a Markov State Model avoids the microscopic regime completely. The MSM is then pre-computed using advanced path-sampling techniques such as multistate transition interface sampling. I illustrate this approach on patchy particle systems that show multiple modes of binding. MD-GFRD is generic, and can be used to efficiently simulate reaction-diffusion systems at the particle level, including the orientational dynamics, opening up the possibility for large-scale simulations of e.g. protein signaling networks.
Non-equilibrium phase transitions
Henkel, Malte; Lübeck, Sven
2009-01-01
This book describes two main classes of non-equilibrium phase-transitions: (a) static and dynamics of transitions into an absorbing state, and (b) dynamical scaling in far-from-equilibrium relaxation behaviour and ageing. The first volume begins with an introductory chapter which recalls the main concepts of phase-transitions, set for the convenience of the reader in an equilibrium context. The extension to non-equilibrium systems is made by using directed percolation as the main paradigm of absorbing phase transitions and in view of the richness of the known results an entire chapter is devoted to it, including a discussion of recent experimental results. Scaling theories and a large set of both numerical and analytical methods for the study of non-equilibrium phase transitions are thoroughly discussed. The techniques used for directed percolation are then extended to other universality classes and many important results on model parameters are provided for easy reference.
Brix, H.; Menemenlis, D.; Hill, C.; Dutkiewicz, S.; Jahn, O.; Wang, D.; Bowman, K.; Zhang, H.
2015-11-01
The NASA Carbon Monitoring System (CMS) Flux Project aims to attribute changes in the atmospheric accumulation of carbon dioxide to spatially resolved fluxes by utilizing the full suite of NASA data, models, and assimilation capabilities. For the oceanic part of this project, we introduce ECCO2-Darwin, a new ocean biogeochemistry general circulation model based on combining the following pre-existing components: (i) a full-depth, eddying, global-ocean configuration of the Massachusetts Institute of Technology general circulation model (MITgcm), (ii) an adjoint-method-based estimate of ocean circulation from the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project, (iii) the MIT ecosystem model "Darwin", and (iv) a marine carbon chemistry model. Air-sea gas exchange coefficients and initial conditions of dissolved inorganic carbon, alkalinity, and oxygen are adjusted using a Green's Functions approach in order to optimize modeled air-sea CO2 fluxes. Data constraints include observations of carbon dioxide partial pressure (pCO2) for 2009-2010, global air-sea CO2 flux estimates, and the seasonal cycle of the Takahashi et al. (2009) Atlas. The model sensitivity experiments (or Green's Functions) include simulations that start from different initial conditions as well as experiments that perturb air-sea gas exchange parameters and the ratio of particulate inorganic to organic carbon. The Green's Functions approach yields a linear combination of these sensitivity experiments that minimizes model-data differences. The resulting initial conditions and gas exchange coefficients are then used to integrate the ECCO2-Darwin model forward. Despite the small number (six) of control parameters, the adjusted simulation is significantly closer to the data constraints (37% cost function reduction, i.e., reduction in the model-data difference, relative to the baseline simulation) and to independent observations (e.g., alkalinity). The adjusted air-sea gas
Directory of Open Access Journals (Sweden)
Linhai Biao
2018-01-01
Full Text Available Green synthesis of gold nanoparticles using plant extracts is one of the more promising approaches for obtaining environmentally friendly nanomaterials for biological applications and environmental remediation. In this study, proanthocyanidins-functionalized gold nanoparticles were synthesized via a hydrothermal method. The obtained gold nanoparticles were characterized by ultraviolet and visible spectrophotometry (UV-Vis, Fourier transform infrared spectroscopy (FTIR, transmission electron microscopy (TEM and X-ray diffraction (XRD measurements. UV-Vis and FTIR results indicated that the obtained products were mainly spherical in shape, and that the phenolic hydroxyl of proanthocyanidins had strong interactions with the gold surface. TEM and XRD determination revealed that the synthesized gold nanoparticles had a highly crystalline structure and good monodispersity. The application of proanthocyanidins-functionalized gold nanoparticles for the removal of dyes and heavy metal ions Ni2+, Cu2+, Cd2+ and Pb2+ in an aqueous solution was investigated. The primary results indicate that proanthocyanidins-functionalized gold nanoparticles had high removal rates for the heavy metal ions and dye, which implies that they have potential applications as a new kind of adsorbent for the removal of contaminants in aqueous solution.
Derivation of Green's function of a spin Calogero-Sutherland model by Uglov's method
International Nuclear Information System (INIS)
Nakai, Ryota; Kato, Yusuke
2009-01-01
The hole propagator of a spin 1/2 Calogero-Sutherland model is derived using Uglov's method, which maps the exact eigenfunctions of the model, called the Yangian Gelfand-Zetlin basis, to a limit of Macdonald polynomials (gl 2 -Jack polynomials). To apply this mapping method to the calculation of 1-particle Green's function, we confirm that the sum of the field annihilation operator ψ u + ψ ↓ on a Yangian Gelfand-Zetlin basis is transformed to the field annihilation operator ψ on gl 2 -Jack polynomials by the mapping. The resultant expression for the hole propagator for a finite-size system is written in terms of renormalized momenta and spin of quasi-holes, and the expression in the thermodynamic limit coincides with the earlier result derived by another method. We also discuss the singularity of the spectral function for a specific coupling parameter where the hole propagator of the spin Calogero-Sutherland model becomes equivalent to the dynamical colour correlation function of an SU(3) Haldane-Shastry model
Function and dynamics of aptamers: A case study on the malachite green aptamer
Energy Technology Data Exchange (ETDEWEB)
Wang, Tianjiao [Iowa State Univ., Ames, IA (United States)
2008-01-01
Aptamers are short single-stranded nucleic acids that can bind to their targets with high specificity and high affinity. To study aptamer function and dynamics, the malachite green aptamer was chosen as a model. Malachite green (MG) bleaching, in which an OH- attacks the central carbon (C1) of MG, was inhibited in the presence of the malachite green aptamer (MGA). The inhibition of MG bleaching by MGA could be reversed by an antisense oligonucleotide (AS) complementary to the MGA binding pocket. Computational cavity analysis of the NMR structure of the MGA-MG complex predicted that the OH^{-} is sterically excluded from the C1 of MG. The prediction was confirmed experimentally using variants of the MGA with changes in the MG binding pocket. This work shows that molecular reactivity can be reversibly regulated by an aptamer-AS pair based on steric hindrance. In addition to demonstrate that aptamers could control molecular reactivity, aptamer dynamics was studied with a strategy combining molecular dynamics (MD) simulation and experimental verification. MD simulation predicted that the MG binding pocket of the MGA is largely pre-organized and that binding of MG involves reorganization of the pocket and a simultaneous twisting of the MGA terminal stems around the pocket. MD simulation also provided a 3D-structure model of unoccupied MGA that has not yet been obtained by biophysical measurements. These predictions were consistent with biochemical and biophysical measurements of the MGA-MG interaction including RNase I footprinting, melting curves, thermodynamic and kinetic constants measurement. This work shows that MD simulation can be used to extend our understanding of the dynamics of aptamer-target interaction which is not evident from static 3D-structures. To conclude, I have developed a novel concept to control molecular reactivity by an aptamer based on steric protection and a strategy to study the dynamics of aptamer-target interaction by combining MD
Demuzere, M; Orru, K; Heidrich, O; Olazabal, E; Geneletti, D; Orru, H; Bhave, A G; Mittal, N; Feliu, E; Faehnle, M
2014-12-15
In order to develop climate resilient urban areas and reduce emissions, several opportunities exist starting from conscious planning and design of green (and blue) spaces in these landscapes. Green urban infrastructure has been regarded as beneficial, e.g. by balancing water flows, providing thermal comfort. This article explores the existing evidence on the contribution of green spaces to climate change mitigation and adaptation services. We suggest a framework of ecosystem services for systematizing the evidence on the provision of bio-physical benefits (e.g. CO2 sequestration) as well as social and psychological benefits (e.g. improved health) that enable coping with (adaptation) or reducing the adverse effects (mitigation) of climate change. The multi-functional and multi-scale nature of green urban infrastructure complicates the categorization of services and benefits, since in reality the interactions between various benefits are manifold and appear on different scales. We will show the relevance of the benefits from green urban infrastructures on three spatial scales (i.e. city, neighborhood and site specific scales). We will further report on co-benefits and trade-offs between the various services indicating that a benefit could in turn be detrimental in relation to other functions. The manuscript identifies avenues for further research on the role of green urban infrastructure, in different types of cities, climates and social contexts. Our systematic understanding of the bio-physical and social processes defining various services allows targeting stressors that may hamper the provision of green urban infrastructure services in individual behavior as well as in wider planning and environmental management in urban areas. Copyright © 2014 Elsevier Ltd. All rights reserved.
Open problems in non-equilibrium physics
International Nuclear Information System (INIS)
Kusnezov, D.
1997-01-01
The report contains viewgraphs on the following: approaches to non-equilibrium statistical mechanics; classical and quantum processes in chaotic environments; classical fields in non-equilibrium situations: real time dynamics at finite temperature; and phase transitions in non-equilibrium conditions
Open problems in non-equilibrium physics
Energy Technology Data Exchange (ETDEWEB)
Kusnezov, D.
1997-09-22
The report contains viewgraphs on the following: approaches to non-equilibrium statistical mechanics; classical and quantum processes in chaotic environments; classical fields in non-equilibrium situations: real time dynamics at finite temperature; and phase transitions in non-equilibrium conditions.
International Nuclear Information System (INIS)
Kozhakhmetov, S.K.
1996-01-01
Possibility of Green formalism use for calculation of photoabsorption of high-energy x-ray radiation is shown. Analytical expression for photoabsorption cross section is carried out. It does not contains wave functions in explicit form responding to finite states of photoelectron. 5 refs
Czech Academy of Sciences Publication Activity Database
Červený, V.; Pšenčík, Ivan
2016-01-01
Roč. 26 (2016), s. 131-153 ISSN 2336-3827 R&D Projects: GA ČR(CZ) GA16-05237S Institutional support: RVO:67985530 Keywords : elastodynamic Green function * inhomogeneous anisotropic media * integral superposition of Gaussian beams Subject RIV: DC - Siesmology, Volcanology, Earth Structure
Energy Technology Data Exchange (ETDEWEB)
Nishijima, K; Sasaki, R [Tokyo Univ. (Japan). Dept. of Physics
1975-06-01
On the basis of the dispersion formulation of field theories the Schwinger term in spinor electrodynamics is shown to be a c-number. The essence of the proof consists in the dimensional argument and the characteristic features of the linear unitarity condition for a set of Green's functions involving the Schwinger term.
Yang, Yang; Xiao, Li; Qu, Wenzhong; Lu, Ye
2017-11-01
Recent theoretical and experimental studies have demonstrated that a local Green's function can be retrieved from the cross-correlation of ambient noise field. This technique can be used to detect fatigue cracking in metallic structures, owing to the fact that the presence of crack can lead to a change in Green's function. This paper presents a method of structural fatigue cracking characterization method by measuring Green's function reconstruction from noise excitation and verifies the feasibility of crack detection in poor noise source distribution. Fatigue cracks usually generate nonlinear effects, in which different wave amplitudes and frequency compositions can cause different nonlinear responses. This study also undertakes analysis of the capacity of the proposed approach to identify fatigue cracking under different noise amplitudes and frequency ranges. Experimental investigations of an aluminum plate are conducted to assess the cross-correlations of received noise between sensor pairs and finally to detect the introduced fatigue crack. A damage index is proposed according to the variation between cross-correlations obtained from the pristine crack closed state and the crack opening-closure state when sufficient noise amplitude is used to generate nonlinearity. A probability distribution map of damage is calculated based on damage indices. The fatigue crack introduced in the aluminum plate is successfully identified and oriented, verifying that a fatigue crack can be detected by reconstructing Green's functions from an imperfect diffuse field in which ambient noise sources exist locally. Copyright © 2017 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Wortis, R.; Song Yun; Atkinson, W.A.
2008-01-01
With the goal of measuring localization in disordered interacting systems, we examine the finite-size scaling of the geometrically averaged density of states calculated from the local Green's function with finite energy resolution. Our results show that, unlike in a simple energy binning procedure, there is no limit in which the finite energy resolution is irrelevant
No-neighbours recurrence schemes for space-time Green's functions on a 3D simple cubic lattice
De Hon, Bastiaan P.; Floris, Sander J.; Arnold, John M.
2018-01-01
Application of multivariate creative telescoping to a finite triple sum representation of the discrete space-time Green's function for an arbitrary numeric (non-symbolic) lattice point on a 3D simple cubic lattice produces a fast, no-neighbours, seventh-order, eighteenth-degree, discrete-time
Kleinert, H.; Zatloukal, V.
2013-11-01
The statistics of rare events, the so-called black-swan events, is governed by non-Gaussian distributions with heavy power-like tails. We calculate the Green functions of the associated Fokker-Planck equations and solve the related stochastic differential equations. We also discuss the subject in the framework of path integration.
International Nuclear Information System (INIS)
Kolesnichenko, A.V.
1980-01-01
An expression for the anomalous dimension of the single-particle Green function is derived in the scalar theory with the interaction Hamiltonian Hsub(int)=g(phisup(n)/n) in the limit n→infinity. It is simultaneously shown that in this model the range of essential distances is of order of nsup(-1/2)
International Nuclear Information System (INIS)
Chu, Yi-Zen
2014-01-01
Motivated by the desire to understand the causal structure of physical signals produced in curved spacetimes – particularly around black holes – we show how, for certain classes of geometries, one might obtain its retarded or advanced minimally coupled massless scalar Green's function by using the corresponding Green's functions in the higher dimensional Minkowski spacetime where it is embedded. Analogous statements hold for certain classes of curved Riemannian spaces, with positive definite metrics, which may be embedded in higher dimensional Euclidean spaces. The general formula is applied to (d ≥ 2)-dimensional de Sitter spacetime, and the scalar Green's function is demonstrated to be sourced by a line emanating infinitesimally close to the origin of the ambient (d + 1)-dimensional Minkowski spacetime and piercing orthogonally through the de Sitter hyperboloids of all finite sizes. This method does not require solving the de Sitter wave equation directly. Only the zero mode solution to an ordinary differential equation, the “wave equation” perpendicular to the hyperboloid – followed by a one-dimensional integral – needs to be evaluated. A topological obstruction to the general construction is also discussed by utilizing it to derive a generalized Green's function of the Laplacian on the (d ≥ 2)-dimensional sphere
A fixed point approach to the Green's functions of PHI42: Local exsistence of the Borel transforms
International Nuclear Information System (INIS)
Bros, J.; Iagolnitzer, D.
1981-01-01
We prove the existence at small μ of a unique solution of the system B = M(B) to be satisfied by the set of Borel transformed euclidean Green's functions of a PHI 4 2 theory, μ being the Borel conjugate variable of the coupling lambda. As a byproduct, a new proof of convergence of the Borel transformed perturbative series is obtained. (orig.)
Non-equilibrium supramolecular polymerization.
Sorrenti, Alessandro; Leira-Iglesias, Jorge; Markvoort, Albert J; de Greef, Tom F A; Hermans, Thomas M
2017-09-18
Supramolecular polymerization has been traditionally focused on the thermodynamic equilibrium state, where one-dimensional assemblies reside at the global minimum of the Gibbs free energy. The pathway and rate to reach the equilibrium state are irrelevant, and the resulting assemblies remain unchanged over time. In the past decade, the focus has shifted to kinetically trapped (non-dissipative non-equilibrium) structures that heavily depend on the method of preparation (i.e., pathway complexity), and where the assembly rates are of key importance. Kinetic models have greatly improved our understanding of competing pathways, and shown how to steer supramolecular polymerization in the desired direction (i.e., pathway selection). The most recent innovation in the field relies on energy or mass input that is dissipated to keep the system away from the thermodynamic equilibrium (or from other non-dissipative states). This tutorial review aims to provide the reader with a set of tools to identify different types of self-assembled states that have been explored so far. In particular, we aim to clarify the often unclear use of the term "non-equilibrium self-assembly" by subdividing systems into dissipative, and non-dissipative non-equilibrium states. Examples are given for each of the states, with a focus on non-dissipative non-equilibrium states found in one-dimensional supramolecular polymerization.
Rheology via nonequilibrium molecular dynamics
International Nuclear Information System (INIS)
Hoover, W.G.
1982-10-01
The equilibrium molecular dynamics formulated by Newton, Lagrange, and Hamilton has been modified in order to simulate rheologial molecular flows with fast computers. This modified Nonequilibrium Molecular Dynamics (NEMD) has been applied to fluid and solid deformations, under both homogeneous and shock conditions, as well as to the transport of heat. The irreversible heating associated with dissipation could be controlled by carrying out isothermal NEMD calculations. The new isothermal NEMD equations of motion are consistent with Gauss' 1829 Least-Constraint principle as well as certain microscopic equilibrium and nonequilibrium statistical formulations due to Gibbs and Boltzmann. Application of isothermal NEMD revealed high-frequency and high-strain-rate behavior for simple fluids which resembled the behavior of polymer solutions and melts at lower frequencies and strain rates. For solids NEMD produces plastic flows consistent with experimental observations at much lower strain rates. The new nonequilibrium methods also suggest novel formulations of thermodynamics in nonequilibrium systems and shed light on the failure of the Principle of Material Frame Indifference
Green's function approach to the Kondo effect in nanosized quantum corrals
Li, Q. L.; Wang, R.; Xie, K. X.; Li, X. X.; Zheng, C.; Cao, R. X.; Miao, B. F.; Sun, L.; Wang, B. G.; Ding, H. F.
2018-04-01
We present a theoretical study of the Kondo effect for a magnetic atom placed inside nanocorrals using Green's function calculations. Based on the standard mapping of the Anderson impurity model to a one-dimensional chain model, we formulate a weak-coupling theory to study the Anderson impurities in a hosting bath with a surface state. With further taking into account the multiple scattering effect of the surrounding atoms, our calculations show that the Kondo resonance width of the atom placed at the center of the nanocorral can be significantly tuned by the corral size, in good agreement with recent experiments [Q. L. Li et al., Phys. Rev. B 97, 035417 (2018), 10.1103/PhysRevB.97.035417]. The method can also be applied to the atom placed at an arbitrary position inside the corral where our calculation shows that the Kondo resonance width also oscillates as the function of its separation from the corral center. The prediction is further confirmed by the low-temperature scanning tunneling microscopy studies where a one-to-one correspondence is found. The good agreement with the experiments validates the generality of the method to the system where multiadatoms are involved.
Effects of self-consistency in a Green's function description of saturation in nuclear matter
International Nuclear Information System (INIS)
Dewulf, Y.; Neck, D. van; Waroquier, M.
2002-01-01
The binding energy in nuclear matter is evaluated within the framework of self-consistent Green's function theory, using a realistic nucleon-nucleon interaction. The two-body dynamics is solved at the level of summing particle-particle and hole-hole ladders. We go beyond the on-shell approximation and use intermediary propagators with a discrete-pole structure. A three-pole approximation is used, which provides a good representation of the quasiparticle excitations, as well as reproducing the zeroth- and first-order energy-weighted moments in both the nucleon removal and addition domains of the spectral function. Results for the binding energy are practically independent of the details of the discretization scheme. The main effect of the increased self-consistency is to introduce an additional density dependence, which causes a shift towards lower densities and smaller binding energies, as compared to a (continuous choice) Brueckner calculation with the same interaction. Particle number conservation and the Hugenholz-Van Hove theorem are satisfied with reasonable accuracy
Thermal one- and two-graviton Green's functions in the temporal gauge
International Nuclear Information System (INIS)
Brandt, F.T.; Cuadros-Melgar, B.; Machado, F.R.
2003-01-01
The thermal one- and two-graviton Green's functions are computed using a temporal gauge. In order to handle the extra poles which are present in the propagator, we employ an ambiguity-free technique in the imaginary-time formalism. For temperatures T high compared with the external momentum, we obtain the leading T 4 as well as the subleading T 2 and log(T) contributions to the graviton self-energy. The gauge fixing independence of the leading T 4 terms as well as the Ward identity relating the self-energy with the one-point function are explicitly verified. We also verify the 't Hooft identities for the subleading T 2 terms and show that the logarithmic part has the same structure as the residue of the ultraviolet pole of the zero temperature graviton self-energy. We explicitly compute the extra terms generated by the prescription poles and verify that they do not change the behavior of the leading and sub-leading contributions from the hard thermal loop region. We discuss the modification of the solutions of the dispersion relations in the graviton plasma induced by the subleading T 2 contributions
Williams, C. A.; Wallace, L. M.; Bartlow, N. M.
2017-12-01
Slow slip events (SSEs) have been observed throughout the world, and the existence of these events has fundamentally altered our understanding of the possible ranges of slip behavior at subduction plate boundaries. In New Zealand, SSEs occur along the Hikurangi Margin, with shallower events in the north and deeper events to the south. In a recent study, Williams and Wallace (2015) found that static SSE inversions that consider elastic property variations provided significantly different results than those based on an elastic half-space. For deeper events, the heterogeneous models predicted smaller amounts of slip, while for shallower events the heterogeneous model predicted larger amounts of slip. In this study, we extend our initial work to examine the temporal variations in slip. We generate Green's functions using the PyLith finite element code (Aagaard et al., 2013) to allow consideration of elastic property variations provided by the New Zealand-wide seismic velocity model (Eberhart-Phillips et al., 2010). These Green's functions are then integrated to provide Green's functions compatible with the Network Inversion Filter (NIF, Segall and Matthews,1997; McGuire and Segall, 2003; Miyazaki et al.,2006). We examine 12 SSEs occurring along the Hikurangi Margin during 2010 and 2011, and compare the results using heterogeneous Green's functions with those of Bartlow et al. (2014), who examined the same set of SSEs with the NIF using a uniform elastic half-space model. The use of heterogeneous Green's functions should provide a more accurate picture of the slip distribution and evolution of the SSEs. This will aid in understanding the correlations between SSEs and seismicity and/or tremor and the role of SSEs in the accommodation of plate motion budgets in New Zealand.
Greening in sunflower butter cookies as a function of egg replacers and baking temperature.
Rogers, Amanda; Hahn, Lan; Pham, Vu; Were, Lilian
2018-04-01
Chlorogenic acid (CGA) binding to proteins in alkaline conditions results in the production of green trihydroxy benzacradine (TBA) derivatives. The formation of TBA derivatives could decrease product quality due to the potential losses in soluble protein and antioxidants and the production of an undesirable green color. To determine how cookie formulation affected the formation of TBA derivatives in sunflower butter cookies, two egg replacers (chia and banana) and two baking temperatures (162.8 and 190.6 °C) were used. Moisture, greening intensity, CGA content and antioxidant capacity were measured. Cookies made with egg and baked at 162.8 °C had the highest moisture, internal greening intensity, and TBA derivative formation, in addition to lower CGA content and antioxidant capacity. Cookies made with banana baked at 190.6 °C produced the opposite outcome with 35, 4, and 23% less internal greening, moisture, and TBA derivatives, respectively, and 90 and 76% higher CGA and antioxidant capacity. Internal greening was positively correlated with moisture and adduct concentration, and negatively correlated with spread factor and CGA content. Moisture had a significant impact on greening, which indicates that baking temperature and cookie dough formulation can be modified to produce a less green cookie with more unreacted antioxidants and protein.
Green infrastructure represents a broad set of site- to landscape-scale practices that can be flexibly implemented to increase sewershed retention capacity, and can thereby improve on the management of water quantity and quality. Although much green infrastructure presents as for...
International Nuclear Information System (INIS)
Koo, Gyeong-Hoi; Kwon, Jong-Jooh; Kim, Wanjae
2009-01-01
In this paper, a method to consider temperature dependent material properties when using the Green's function method is proposed by using a numerical weight function approach. This is verified by using detailed finite element analyses for a pressurizer spray nozzle with various assumed thermal transient load cases. From the results, it is found that the temperature dependent material properties can significantly affect the maximum peak stresses and the proposed method can resolve this problem with the weight function approach. Finally, it is concluded that the temperature dependency of the material properties affects the maximum stress ranges for a fatigue evaluation. Therefore, it is necessary to consider this effect to monitor fatigue damage when using a Green's function method for the real operating conditions in a nuclear power plant
International Nuclear Information System (INIS)
Adam, G.; Adam, S.
2007-01-01
The Green function (GF) equation of motion technique for solving the effective two-band Hubbard model of high-T c superconductivity in cuprates rests on the Hubbard operator (HO) algebra. We show that, if we take into account the invariance to translations and spin reversal, the HO algebra results in invariance properties of several specific correlation functions. The use of these properties allows rigorous derivation and simplification of the expressions of the frequency matrix (FM) and of the generalized mean-field approximation (GMFA) Green functions (GFs) of the model. For the normal singlet hopping and anomalous exchange pairing correlation functions which enter the FM and GMFA-GFs, the use of spectral representations allows the identification and elimination of exponentially small quantities. This procedure secures the reduction of the correlation order to the GMFA-GF expressions
Giron, Maria D.; Salto, Rafael
2011-01-01
Structure-function relationship studies in proteins are essential in modern Cell Biology. Laboratory exercises that allow students to familiarize themselves with basic mutagenesis techniques are essential in all Genetic Engineering courses to teach the relevance of protein structure. We have implemented a laboratory course based on the…
International Nuclear Information System (INIS)
Tserkovnikov, Yu.A.
2001-01-01
The regular method for deriving the equations for the Green functions in the tasks on the molecular hydrodynamics and kinetics, making it possible to account consequently the contribution into the generalized kinetics coefficients, conditioned by interaction of two, three and more hydrodynamic modes. In contrast to the general theory of perturbations by the interaction constant the consequent approximations are accomplished by the degree of accounting for the higher correlations, described by the irreducible functions [ru
International Nuclear Information System (INIS)
Skachkov, N.B.; Solovtsov, I.L.; Shevchenko, O.Yu.
1985-01-01
The Dayson-Schwinger equations for the gauge-invariant (G.I.) spinor Green function are derived for an Abelian case. On the basis of these equations as well as the functional integration method the behaviour of the G.I. spinor propagator is studied in the infrared region. It is shown that the G.I. propagator has a singularity of a simple pole in this region
Measures of trajectory ensemble disparity in nonequilibrium statistical dynamics
International Nuclear Information System (INIS)
Crooks, Gavin E; Sivak, David A
2011-01-01
Many interesting divergence measures between conjugate ensembles of nonequilibrium trajectories can be experimentally determined from the work distribution of the process. Herein, we review the statistical and physical significance of several of these measures, in particular the relative entropy (dissipation), Jeffreys divergence (hysteresis), Jensen–Shannon divergence (time-asymmetry), Chernoff divergence (work cumulant generating function), and Rényi divergence
Two-point Green's functions in quantum electrodynamics at finite temperature and density
International Nuclear Information System (INIS)
Bechler, A.
1981-01-01
One-particle propagators of the relativistic electron--positron gas are systematically investigated. With the nonvanishing chemical potential the neutrality of the whole system is secured by a uniformly charged classical background described by a classical current J/sub μ/. Due to the translational invariance of this model it is natural to investigate the properties of the propagators in the momentum space. The Fourier-transforms of the Green's functions have been expressed in terms of the generalized spectral Lehmann representation and the second-order spectral functions of the photon and electron propagators have been found. The matter-dependent part of the propagator is finite and only the vacuum part has to be renormalized with the use of standard renormalization counterterms. The singularities of the gauge-independent photon propagator have been further investigated with the use of the spectral representation and nonperturbative expressions for the spectrum of collective excitations have been obtained. In the second order of perturbation they reproduce the asymptotic formulas at T→0 and T→infinity cited previously in the literature. In particular, the relativistic plasma frequency (photon effective mass) has been expressed in a simple form in terms of the integrals over the spectral functions. Our formulas for the relativistic plasmon mass squared Ω 2 exhibit an interesting property that at some temperature and density Ω 2 should become negative. However, simple estimates show that this phenomenon occurs at highly nonrealistic temperatures of the order of e 137 , i.e., in the region where the perturbation theory fails. The damping of the collective excitations is also considered
International Nuclear Information System (INIS)
Mukhopadhyay, N.K.; Dutta, B.K.; Kushwaha, H.S.
1994-01-01
Green's function technique is the heart of the on- line fatigue monitoring methodology. The plant transients are converted to stress and temperature response using this technique. To implement this methodology in a nuclear power plant, Green's functions are to be generated in advance. For structures of complex geometries, Green's functions are to be stored in a data base to convert on-line, the plant data to temperature/stress response, using a personal computer. End fitting, end shield, pressurizer, steam generator tube sheet are few such components of PHWR where fatigue monitoring is needed. In the present paper, Green's functions are generated for end fitting of a 235 MWe Indian PHWR using finite element method. End fitting has been analysed using both 3-D and 2-D (axisymmetric) finite element models. Temperature and stress Green's functions are generated at few critical locations using the code ABAQUS. (author). 10 refs., 11 figs
Nonequilibrium fermion production in quantum field theory
International Nuclear Information System (INIS)
Pruschke, Jens
2010-01-01
The creation of matter in the early universe or in relativistic heavy-ion collisions is inevitable connected to nonequilibrium physics. One of the key challenges is the explanation of the corresponding thermalization process following nonequilibrium instabilities. The role of fermionic quantum fields in such scenarios is discussed in the literature by using approximations of field theories which neglect important quantum corrections. This thesis goes beyond such approximations. A quantum field theory where scalar bosons interact with Dirac fermions via a Yukawa coupling is analyzed in the 2PI effective action formalism. The chosen approximation allows for a correct description of the dynamics including nonequilibrium instabilities. In particular, fermion-boson loop corrections allow to study the interaction of fermions with large boson fluctuations. The applied initial conditions generate nonequilibrium instabilities like parametric resonance or spinodal instabilities. The equations of motion for correlation functions are solved numerically and major characteristics of the fermion dynamics are described by analytical solutions. New mechanisms for the production of fermions are found. Simulations in the case of spinodal instability show that unstable boson fluctuations induce exponentially growing fermion modes with approximately the same growth rate. If the unstable regime lasts long enough a thermalization of the infrared part of the fermion occupation number occurs on time scales much shorter than the time scale on which bosonic quantum fields thermalize. Fermions acquire an excess of occupation in the ultraviolet regime compared to a Fermi-Dirac statistic characterized by a power-law with exponent two. The fermion production mechanism via parametric resonance is found to be most efficient after the instability ends. Quantum corrections then provide a very efficient particle creation mechanism which is interpreted as an amplification of decay processes. The ratio
Nonequilibrium fermion production in quantum field theory
Energy Technology Data Exchange (ETDEWEB)
Pruschke, Jens
2010-06-16
The creation of matter in the early universe or in relativistic heavy-ion collisions is inevitable connected to nonequilibrium physics. One of the key challenges is the explanation of the corresponding thermalization process following nonequilibrium instabilities. The role of fermionic quantum fields in such scenarios is discussed in the literature by using approximations of field theories which neglect important quantum corrections. This thesis goes beyond such approximations. A quantum field theory where scalar bosons interact with Dirac fermions via a Yukawa coupling is analyzed in the 2PI effective action formalism. The chosen approximation allows for a correct description of the dynamics including nonequilibrium instabilities. In particular, fermion-boson loop corrections allow to study the interaction of fermions with large boson fluctuations. The applied initial conditions generate nonequilibrium instabilities like parametric resonance or spinodal instabilities. The equations of motion for correlation functions are solved numerically and major characteristics of the fermion dynamics are described by analytical solutions. New mechanisms for the production of fermions are found. Simulations in the case of spinodal instability show that unstable boson fluctuations induce exponentially growing fermion modes with approximately the same growth rate. If the unstable regime lasts long enough a thermalization of the infrared part of the fermion occupation number occurs on time scales much shorter than the time scale on which bosonic quantum fields thermalize. Fermions acquire an excess of occupation in the ultraviolet regime compared to a Fermi-Dirac statistic characterized by a power-law with exponent two. The fermion production mechanism via parametric resonance is found to be most efficient after the instability ends. Quantum corrections then provide a very efficient particle creation mechanism which is interpreted as an amplification of decay processes. The ratio
Soltanmoradi, Elmira; Shokri, Babak
2017-05-01
In this article, the electromagnetic wave scattering from plasma columns with inhomogeneous electron density distribution is studied by the Green's function volume integral equation method. Due to the ready production of such plasmas in the laboratories and their practical application in various technological fields, this study tries to find the effects of plasma parameters such as the electron density, radius, and pressure on the scattering cross-section of a plasma column. Moreover, the incident wave frequency influence of the scattering pattern is demonstrated. Furthermore, the scattering cross-section of a plasma column with an inhomogeneous collision frequency profile is calculated and the effect of this inhomogeneity is discussed first in this article. These results are especially used to determine the appropriate conditions for radar cross-section reduction purposes. It is shown that the radar cross-section of a plasma column reduces more for a larger collision frequency, for a relatively lower plasma frequency, and also for a smaller radius. Furthermore, it is found that the effect of the electron density on the scattering cross-section is more obvious in comparison with the effect of other plasma parameters. Also, the plasma column with homogenous collision frequency can be used as a better shielding in contrast to its inhomogeneous counterpart.
A Monte Carlo Green's function method for three-dimensional neutron transport
International Nuclear Information System (INIS)
Gamino, R.G.; Brown, F.B.; Mendelson, M.R.
1992-01-01
This paper describes a Monte Carlo transport kernel capability, which has recently been incorporated into the RACER continuous-energy Monte Carlo code. The kernels represent a Green's function method for neutron transport from a fixed-source volume out to a particular volume of interest. This method is very powerful transport technique. Also, since kernels are evaluated numerically by Monte Carlo, the problem geometry can be arbitrarily complex, yet exact. This method is intended for problems where an ex-core neutron response must be determined for a variety of reactor conditions. Two examples are ex-core neutron detector response and vessel critical weld fast flux. The response is expressed in terms of neutron transport kernels weighted by a core fission source distribution. In these types of calculations, the response must be computed for hundreds of source distributions, but the kernels only need to be calculated once. The advance described in this paper is that the kernels are generated with a highly accurate three-dimensional Monte Carlo transport calculation instead of an approximate method such as line-of-sight attenuation theory or a synthesized three-dimensional discrete ordinates solution
A Green's Function Approach to Simulate DNA Damage by the Indirect Effect
Plante, Ianik; Cicinotta, Francis A.
2013-01-01
The DNA damage is of fundamental importance in the understanding of the effects of ionizing radiation. DNA is damaged by the direct effect of radiation (e.g. direct ionization) and by indirect effect (e.g. damage by.OH radicals created by the radiolysis of water). Despite years of research, many questions on the DNA damage by ionizing radiation remains. In the recent years, the Green's functions of the diffusion equation (GFDE) have been used extensively in biochemistry [1], notably to simulate biochemical networks in time and space [2]. In our future work on DNA damage, we wish to use an approach based on the GFDE to refine existing models on the indirect effect of ionizing radiation on DNA. To do so, we will use the code RITRACKS [3] developed at the NASA Johnson Space Center to simulate the radiation track structure and calculate the position of radiolytic species after irradiation. We have also recently developed an efficient Monte-Carlo sampling algorithm for the GFDE of reversible reactions with an intermediate state [4], which can be modified and adapted to simulate DNA damage by free radicals. To do so, we will use the known reaction rate constants between radicals (OH, eaq, H,...) and the DNA bases, sugars and phosphates and use the sampling algorithms to simulate the diffusion of free radicals and chemical reactions with DNA. These techniques should help the understanding of the contribution of the indirect effect in the formation of DNA damage and double-strand breaks.
International Nuclear Information System (INIS)
Choy, C.W.; Xiao, J.J.; Yu, K.W.
2007-01-01
The recent Green function formalism (GFF) has been used to study the local field distribution near a periodic interface separating two homogeneous media of different dielectric constants. In the GFF, the integral equations can be solved conveniently because of the existence of an analytic expression for the kernel (Greenian). However, due to a severe singularity in the Greenian, the formalism was formerly applied to compute the electric fields away from the interface region. In this work, we have succeeded in extending the GFF to compute the electric field inside the interface region by taking advantage of a sum rule. To our surprise, the strengths of the electric fields are quite similar in both media across the interface, despite of the large difference in dielectric constants. Moreover, we propose a simple effective medium approximation (EMA) to compute the electric field inside the interface region. We show that the EMA can indeed give an excellent description of the electric field, except near a surface plasmon resonance
Description of excitations in odd nonmagic nuclei by the Green's function method
International Nuclear Information System (INIS)
Avdeenkov, A.V.; Kamerdzhiev, S.P.
1999-01-01
General equations for single-particle Green's functions in nonmagic nuclei have been derived. A pairing mechanism similar to the Bardeen-Cooper-Schrieffer mechanism is singled out explicitly in these equations. A refining procedure for phenomenological single-particle energies and for the gap has been developed to avoid doubly taking into account mixing with phonons for the situation in which the input data for the problem in question are formulated in terms of these phenomenological quantities. The resulting general equations are written within the second-order approximation in the phonon-creation amplitude. This corresponds to taking into account quasiparticle(multiply-in-circle sign)phonon configuration and is shown to be a fairly good approximation for semimagic nuclei. A secular equation for calculating excitations in odd nuclei that takes fully into account ground-state correlations and which is invariant under the reversal of the sign of the energy variable has been derived in this approximation. Distributions of single-particle strengths have been computed for 119 Sn and 121 Sn. Reasonably good agreement with available experimental data has been obtained
Green's function method for the monoenergetic transport equation in heterogeneous plane geometry
International Nuclear Information System (INIS)
Ganapol, B.D.
1995-01-01
For the past several years, a series of papers by the transport group at the University of Arizona dealing with benchmark solutions of the monoenergetic transport equation has appeared. The approach has been to take advantage of highly successful numerical Laplace Fourier transform inversions to provide benchmark quality solutions in infinite media, half-space in one and two dimensions and in homogeneous slabs. This paper extends the set of solutions to include heterogeneous slab geometry by using the recently established Green's Function Method (GFM). Analytical benchmark solutions are an essential part of the quality control of computational algorithms developed for particle transport. In addition, benchmarking methods have applications in the classroom by providing examples of how computational mathematics is used to solve physical problems to obtain meaningful answers. In a structural context, monoenergetic solutions are directly applicable to the investigation of the microlight environment within a leaf. The leaf is considered to be a composition of alternating layers of highly absorbing pigments and water superimposed on a refractively scattering background
Green Extraction from Pomegranate Marcs for the Production of Functional Foods and Cosmetics
Directory of Open Access Journals (Sweden)
Raffaella Boggia
2016-10-01
Full Text Available The aim of this study was to investigate the potential of retrieving polyphenolic antioxidants directly from wet pomegranate marcs: the fresh by-products obtained after pomegranate juice processing. These by-products mainly consist of internal membranes (endocarp and aril residues. Even if they are still edible, they are usually discharged during juice production and, thus, they represent a great challenge in an eco-sustainable industrial context. Green technologies, such as ultrasound assisted extraction (UAE and microwave assisted extraction (MAE, have been employed to convert these organic residues into recycled products with high added value. UAE and MAE were used both in parallel and in series in order to make a comparison and to ensure exhaustive extractions, respectively. Water, as an environmentally friendly extraction solvent, has been employed. The results were compared with those ones coming from a conventional extraction. The most promising extract, in terms of total polyphenol yield and radical scavenging activity, has been tested both as a potential natural additive and as a functional ingredient after its incorporation in a real food model and in a real cosmetic matrix, respectively. This study represents a proposal to the agro-alimentary sector given the general need of environmental “responsible care”.
Irreducible Greens' Functions method in the theory of highly correlated systems
International Nuclear Information System (INIS)
Kuzemsky, A.L.
1994-09-01
The self-consistent theory of the correlation effects in Highly Correlated Systems (HCS) is presented. The novel Irreducible Green's Function (IGF) method is discussed in detail for the Hubbard model and random Hubbard model. The interpolation solution for the quasiparticle spectrum, which is valid for both the atomic and band limit is obtained. The (IGF) method permits to calculate the quasiparticle spectra of many-particle systems with the complicated spectra and strong interaction in a very natural and compact way. The essence of the method deeply related to the notion of the Generalized Mean Fields (GMF), which determine the elastic scattering corrections. The inelastic scattering corrections leads to the damping of the quasiparticles and are the main topic of the present consideration. The calculation of the damping has been done in a self-consistent way for both limits. For the random Hubbard model the weak coupling case has been considered and the self-energy operator has been calculated using the combination of the IGF method and Coherent Potential Approximation (CPA). The other applications of the method to the s-f model, Anderson model, Heisenberg antiferromagnet, electron-phonon interaction models and quasiparticle tunneling are discussed briefly. (author). 79 refs
Development of multi-functional streetscape green infrastructure using a performance index approach.
Tiwary, A; Williams, I D; Heidrich, O; Namdeo, A; Bandaru, V; Calfapietra, C
2016-01-01
This paper presents a performance evaluation framework for streetscape vegetation. A performance index (PI) is conceived using the following seven traits, specific to the street environments - Pollution Flux Potential (PFP), Carbon Sequestration Potential (CSP), Thermal Comfort Potential (TCP), Noise Attenuation Potential (NAP), Biomass Energy Potential (BEP), Environmental Stress Tolerance (EST) and Crown Projection Factor (CPF). Its application is demonstrated through a case study using fifteen street vegetation species from the UK, utilising a combination of direct field measurements and inventoried literature data. Our results indicate greater preference to small-to-medium size trees and evergreen shrubs over larger trees for streetscaping. The proposed PI approach can be potentially applied two-fold: one, for evaluation of the performance of the existing street vegetation, facilitating the prospects for further improving them through management strategies and better species selection; two, for planning new streetscapes and multi-functional biomass as part of extending the green urban infrastructure. Copyright © 2015 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Aruna Jyothi Kora
2012-01-01
Full Text Available A simple and ecofriendly procedure have been devised for the green synthesis of silver nanoparticles using the aqueous extract of gum tragacanth (Astragalus gummifer, a renewable, nontoxic natural phyto-exudate. The water soluble components in the gum act as reductants and stabilizers. The generated nanoparticles were analyzed using UV-visible spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy, and Raman spectroscopy. The role of gum concentration and reaction time on the synthesis of nanoparticles was studied. By regulating the reaction conditions, spherical nanoparticles of 13.1±1.0 nm size were produced. Also, the possible functional groups involved in reduction and capping of nanoparticles has been elucidated. The antibacterial activity of the fabricated nanoparticles was tested on model Gram-negative and Gram-positive bacterial strains with well-diffusion method. These nanoparticles exhibited considerable antibacterial activity on both the Gram classes of bacteria, implying their potential biomedical applications.
Saniz, R.; Partoens, B.; Peeters, F. M.
2013-02-01
The Green function approach to the Bardeen-Cooper-Schrieffer theory of superconductivity is used to study nanofilms. We go beyond previous models and include effects of confinement on the strength of the electron-phonon coupling as well as on the electronic spectrum and on the phonon modes. Within our approach, we find that in ultrathin films, confinement effects on the electronic screening become very important. Indeed, contrary to what has been advanced in recent years, the sudden increases of the density of states when new bands start to be occupied as the film thickness increases, tend to suppress the critical temperature rather than to enhance it. On the other hand, the increase of the number of phonon modes with increasing number of monolayers in the film leads to an increase in the critical temperature. As a consequence, the superconducting critical parameters in such nanofilms are determined by these two competing effects. Furthermore, in sufficiently thin films, the condensate consists of well-defined subcondensates associated with the occupied bands, each with a distinct coherence length. The subcondensates can interfere constructively or destructively giving rise to an interference pattern in the Cooper pair probability density.
International Nuclear Information System (INIS)
Snieder, Roel
2004-01-01
The Green's function of waves that propagate between two receivers can be found by cross-correlating multiply scattered waves recorded at these receivers. This technique obviates the need for a source at one of these locations, and is therefore called ''passive imaging.'' This principle has been explained by assuming that the normal modes of the system are uncorrelated and that all carry the same amount of energy (equipartitioning). Here I present an alternative derivation of passive imaging of the ballistic wave that is not based on normal modes. The derivation is valid for scalar waves in three dimensions, and for elastic surface waves. Passive imaging of the ballistic wave is based on the destructive interference of waves radiated from scatterers away from the receiver line, and the constructive interference of waves radiated from secondary sources near the receiver line. The derivation presented here shows that the global requirement of the equipartitioning of normal modes can be relaxed to the local requirement that the scattered waves propagate on average isotropically near the receivers
Origins of Singlet Fission in Solid Pentacene from an ab initio Green's Function Approach
Refaely-Abramson, Sivan; da Jornada, Felipe H.; Louie, Steven G.; Neaton, Jeffrey B.
2017-12-01
We develop a new first-principles approach to predict and understand rates of singlet fission with an ab initio Green's-function formalism based on many-body perturbation theory. Starting with singlet and triplet excitons computed from a G W plus Bethe-Salpeter equation approach, we calculate the exciton-biexciton coupling to lowest order in the Coulomb interaction, assuming a final state consisting of two noninteracting spin-correlated triplets with finite center-of-mass momentum. For crystalline pentacene, symmetries dictate that the only purely Coulombic fission decay process from a bright singlet state requires a final state consisting of two inequivalent nearly degenerate triplets of nonzero, equal and opposite, center-of-mass momenta. For such a process, we predict a singlet lifetime of 30-70 fs, in very good agreement with experimental data, indicating that this process can dominate singlet fission in crystalline pentacene. Our approach is general and provides a framework for predicting and understanding multiexciton interactions in solids.
International Nuclear Information System (INIS)
Li Jun; Wei Guozhu; Du An
2005-01-01
The compensation and critical behaviors of a mixed spin-2 and spin-12 Heisenberg ferrimagnetic system on a square lattice are investigated theoretically by the two-time Green's function technique, which takes into account the quantum nature of Heisenberg spins. The model can be relevant for understanding the magnetic behavior of the new class of organometallic ferromagnetic materials that exhibit spontaneous magnetic properties at room temperature. We carry out the calculation of the sublattice magnetizations and the spin-wave spectra of the ground state. In particular, we have studied the effects of the nearest, next-nearest-neighbor interactions, the crystal field and the external magnetic field on the compensation temperature and the critical temperature. When only the nearest-neighbor interactions and the crystal field are included, no compensation temperature exists; when the next-nearest-neighbor interaction between spin-12 is taken into account and exceeds a minimum value, a compensation point appears and it is basically unchanged for other parameters in Hamiltonian fixed. The next-nearest-neighbor interactions between spin-2 and the external magnetic field have the effects of changing the compensation temperature and there is a narrow range of parameters of the Hamiltonian for which the model has the compensation temperatures and compensation temperature exists only for a small value of them
A Radiation Chemistry Code Based on the Green's Function of the Diffusion Equation
Plante, Ianik; Wu, Honglu
2014-01-01
Stochastic radiation track structure codes are of great interest for space radiation studies and hadron therapy in medicine. These codes are used for a many purposes, notably for microdosimetry and DNA damage studies. In the last two decades, they were also used with the Independent Reaction Times (IRT) method in the simulation of chemical reactions, to calculate the yield of various radiolytic species produced during the radiolysis of water and in chemical dosimeters. Recently, we have developed a Green's function based code to simulate reversible chemical reactions with an intermediate state, which yielded results in excellent agreement with those obtained by using the IRT method. This code was also used to simulate and the interaction of particles with membrane receptors. We are in the process of including this program for use with the Monte-Carlo track structure code Relativistic Ion Tracks (RITRACKS). This recent addition should greatly expand the capabilities of RITRACKS, notably to simulate DNA damage by both the direct and indirect effect.
Zheng, Mingda; Wang, Chenge; Wang, Yingying; Wei, Wei; Ma, Shuang; Sun, Xiaohan; He, Jiang
2018-08-01
In this work, Lycii Fructus as raw materials for green synthesis of fluorescent carbon dots (CDs) reduce AgNO 3 . The CDs-AgNPs were synthesized by one-step method. CDs were applied to stabilize AgNPs due to abundant functional groups on the surface of CDs. In presence of phoxim, the dispersed CDs-AgNPs get aggregated and the absorption peak with red shift from 400 nm to 525 nm, resulting in the color changed from yellow to red. Under optimized conditions, the absorbance ratio at A 525 nm /A 400 nm was related linearly to the concentrations of phoxim in the range of 0.1-100 μM. The detection limit was calculated to 0.04 μM, which is lower than maximum residue limits of phoxim in samples in China. The colorimetric sensor was successfully utilized to monitoring phoxim in environmental and fruit samples with good recoveries ranges from 87% to 110.0%. These results showed the sensor had a promising application prospect in real samples. Copyright © 2018 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Ness, H; Dash, L K
2012-01-01
We consider the electron transport properties through fully interacting nanoscale junctions beyond the linear-response regime. We calculate the current flowing through an interacting region connected to two interacting leads, with interaction crossing at the left and right contacts, by using a non-equilibrium Green function technique. The total current at one interface (the left one for example) is made of several terms which can be regrouped into two sets. The first set corresponds to a very generalized Landauer-like current formula with physical quantities defined only in the interacting central region and with renormalized lead self-energies. The second set characterizes inelastic scattering events occurring in the left lead. We show how this term can be negligible or even vanish due to the pseudo-equilibrium statistical properties of the lead in the thermodynamic limit. The expressions for the different Green functions needed for practical calculations of the current are also provided. We determine the constraints imposed by the physical condition of current conservation. The corresponding equation imposed on the different self-energy quantities arising from the current conservation is derived. We discuss in detail its physical interpretation and its relation with previously derived expressions. Finally several important key features are discussed in relation to the implementation of our formalism for calculations of quantum transport in realistic systems. (paper)
Liska, Sebastian; Colonius, Tim
2017-02-01
A new parallel, computationally efficient immersed boundary method for solving three-dimensional, viscous, incompressible flows on unbounded domains is presented. Immersed surfaces with prescribed motions are generated using the interpolation and regularization operators obtained from the discrete delta function approach of the original (Peskin's) immersed boundary method. Unlike Peskin's method, boundary forces are regarded as Lagrange multipliers that are used to satisfy the no-slip condition. The incompressible Navier-Stokes equations are discretized on an unbounded staggered Cartesian grid and are solved in a finite number of operations using lattice Green's function techniques. These techniques are used to automatically enforce the natural free-space boundary conditions and to implement a novel block-wise adaptive grid that significantly reduces the run-time cost of solutions by limiting operations to grid cells in the immediate vicinity and near-wake region of the immersed surface. These techniques also enable the construction of practical discrete viscous integrating factors that are used in combination with specialized half-explicit Runge-Kutta schemes to accurately and efficiently solve the differential algebraic equations describing the discrete momentum equation, incompressibility constraint, and no-slip constraint. Linear systems of equations resulting from the time integration scheme are efficiently solved using an approximation-free nested projection technique. The algebraic properties of the discrete operators are used to reduce projection steps to simple discrete elliptic problems, e.g. discrete Poisson problems, that are compatible with recent parallel fast multipole methods for difference equations. Numerical experiments on low-aspect-ratio flat plates and spheres at Reynolds numbers up to 3700 are used to verify the accuracy and physical fidelity of the formulation.