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Diagrammatic expansions are a central tool for treating correlated electron systems. At thermal equilibrium, they are most naturally defined within the Matsubara formalism. However, extracting any dynamic response function from a Matsubara…

Strongly Correlated Electrons · Physics 2020-02-19 Jaksa Vucicevic , Michel Ferrero

The thermal one- and two-graviton Green's function 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…

High Energy Physics - Theory · Physics 2009-11-07 F. T. Brandt , B. Cuadros-Melgar , F. R. Machado

We develop a stochastic resolution of identity approach to the real-time second-order Green's function (real-time sRI-GF2) theory, extending our recent work for imaginary-time Matsubara Green's function {\em J. Chem. Phys.} {\bf 151},…

Chemical Physics · Physics 2019-09-17 Wenjie Dou , Tyler Y. Takeshita , Ming Chen , Roi Baer , Daniel Neuhauser , Eran Rabani

We critique a Pade analytic continuation method whereby a rational polynomial function is fit to a set of input points by means of a single matrix inversion. This procedure is accomplished to an extremely high accuracy using a novel…

Strongly Correlated Electrons · Physics 2009-10-31 K. S. D. Beach , R. J. Gooding , F. Marsiglio

Several recent works have introduced highly compact representations of single-particle Green's functions in the imaginary time and Matsubara frequency domains, as well as efficient interpolation grids used to recover the representations. In…

Strongly Correlated Electrons · Physics 2023-06-28 Nan Sheng , Alexander Hampel , Sophie Beck , Olivier Parcollet , Nils Wentzell , Jason Kaye , Kun Chen

We implement the GW space-time method at finite temperatures, in which the Green's function G and the screened Coulomb interaction W are represented in the real space on a suitable mesh and in imaginary time in terms of Chebyshev…

Materials Science · Physics 2025-11-11 Sam Azadi , Arkadiy Davydov , Evgeny Kozik

New model-independent compact representations of imaginary-time data are presented in terms of the intermediate representation (IR) of analytical continuation. This is motivated by a recent numerical finding by the authors [J. Otsuki et…

Strongly Correlated Electrons · Physics 2017-07-26 Hiroshi Shinaoka , Junya Otsuki , Masayuki Ohzeki , Kazuyoshi Yoshimi

Numerical results for ground state and excited state properties (energies, double occupancies, and Matsubara-axis self energies) of the single-orbital Hubbard model on a two-dimensional square lattice are presented, in order to provide an…

The high-temperature series expansion for quantum spin models is a well-established tool to compute thermodynamic quantities and equal-time spin correlations, in particular for frustrated interactions. We extend the scope of this expansion…

Strongly Correlated Electrons · Physics 2026-02-06 Ruben Burkard , Benedikt Schneider , Björn Sbierski

We implement the numerical method of summing Green function diagrams on the Matsubara frequency axis for the fluctuation exchange (FLEX) approximation. Our method has previously been applied to the attractive Hubbard model for low density.…

Condensed Matter · Physics 2016-08-15 J. J. Rodríguez-Núñez , S. Schafroth

We present a data-driven approach to mathematically model physical systems whose governing partial differential equations are unknown, by learning their associated Green's function. The subject systems are observed by collecting…

Numerical Analysis · Mathematics 2023-03-13 Harshwardhan Praveen , Nicolas Boulle , Christopher Earls

We generate the perturbative expansion of the single-particle Green's function and related self-energy for a half-filled single-band Hubbard model on a square lattice. We invoke algorithmic Matsubara integration to evaluate single-particle…

Strongly Correlated Electrons · Physics 2021-09-15 Bradley D. E. McNiven , G. Todd Andrews , James P. F. LeBlanc

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…

Mesoscale and Nanoscale Physics · Physics 2008-03-07 Tobias Kramer , Eric J. Heller , Robert E. Parrott

In this paper we compute the effective Lagrangian of static gravitational fields interacting with thermal fields of generalized electrodynamics at high temperature. We employ the usual Matsubara imaginary-time formalism to obtain a closed…

High Energy Physics - Theory · Physics 2014-12-09 R. Bufalo

Observed efficiencies of industrial power plants are often approximated by the square-root formula: $1-\sqrt{T_-/T_+}$, where $T_+ (T_-)$ is the highest (lowest) temperature achieved in the plant. This expression can be derived within…

Statistical Mechanics · Physics 2017-03-09 Ramandeep S. Johal

The discrete Fourier transform is approximated by summing over part of the terms with corresponding weights. The approximation reduces significantly the requirement for computer memory storage and enhances the numerical computation…

Strongly Correlated Electrons · Physics 2015-03-19 Xin-Zhong Yan

The Green-function technique, termed the irreducible Green functions (IGF) method, that is a certain reformulation of the equation-of motion method for double-time temperature dependent Green functions is presented. This method was…

Strongly Correlated Electrons · Physics 2007-05-23 A. L. Kuzemsky

In this paper, we review the set of rules specific to the calculation of the imaginary part of a Green's function at finite temperature in the real-time formalisms. Emphasis is put on the clarification of a recent controversy concerning…

High Energy Physics - Phenomenology · Physics 2009-10-30 Francois Gelis

Within the environmental context, numerical modeling is a promising approach to assessing the energy efficiency of buildings. Resilient buildings need to be designed, and capable of adapting to future extreme heat. Simulations are required…

Computational Engineering, Finance, and Science · Computer Science 2022-06-20 Julien Berger , Cyrille Allery , Anaïs Machard

In this paper we present a short survey on the concept of effective temperature, on its onset as a glass former vitrifies, on the various definitions in literature and their limits of applicability. An exactly solvable model glass is…

Disordered Systems and Neural Networks · Physics 2010-03-29 Luca Leuzzi