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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

We systematically generate the perturbative expansion for the two-particle spin susceptibility in the Feynman diagrammatic formalism and apply this expansion to a model system - the single-band Hubbard model on a square lattice. We make use…

Strongly Correlated Electrons · Physics 2020-07-15 Amir Taheridehkordi , S. H. Curnoe , J. P. F. LeBlanc

The past years have seen a revived interest in the diagrammatic Monte Carlo (DiagMC) methods for interacting fermions on a lattice. A promising recent development allows one to now circumvent the analytical continuation of dynamic…

Strongly Correlated Electrons · Physics 2021-05-05 J. Vucicevic , P. Stipsic , M. Ferrero

By merging algorithmic Matsubara integration with discrete pole representations we present a procedure to generate fully analytic closed form results for impurity problems at fixed perturbation order. To demonstrate the utility of this…

Strongly Correlated Electrons · Physics 2024-07-02 Daria Gazizova , Lei Zhang , Emanuel Gull , J. P. F. LeBlanc

We designed new algorithms for summing bold-line Feynman diagrams in arbitrary channels, where it can be readily modified for bare interaction series as well. When applied to magnetic channel bold-line series with on-site Hubbard…

Strongly Correlated Electrons · Physics 2025-04-09 Boyuan Shi

Perturbative calculations in field theory at finite temperature involve sums over the Matsubara frequencies. Besides the usual difficulties that appear in perturbative computations, these sums give rise to some new obstacles that are…

High Energy Physics - Phenomenology · Physics 2009-10-22 Agustin Nieto

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 method to accelerate the numerical evaluation of spatial integrals of Feynman diagrams when expressed on the real frequency axis. This can be realized through use of a renormalized perturbation expansion with a constant but…

Strongly Correlated Electrons · Physics 2023-04-05 M. D. Burke , Maxence Grandadam , J. P. F. LeBlanc

We present a general method to optimize the evaluation of Feynman diagrammatic expansions, which requires the automated symbolic assignment of momentum/energy conserving variables to each diagram. With this symbolic representation, we…

Strongly Correlated Electrons · Physics 2020-03-18 Amir Taheridehkordi , S. H. Curnoe , J. P. F. LeBlanc

We present a simple trick that allows to consider the sum of all connected Feynman diagrams at fixed position of interaction vertices for general fermionic models. With our approach one achieves superior performance compared to Diagrammatic…

Strongly Correlated Electrons · Physics 2017-08-02 Riccardo Rossi

In the context of the imaginary-time formalism for a scalar thermal field theory, it is shown that the result of performing the sums over Matsubara frequencies associated with loop Feynman diagrams can be written, for some classes of…

High Energy Physics - Phenomenology · Physics 2009-11-10 Olivier Espinosa , Edgardo Stockmeyer

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

We prove in full generality the thermal operator representation for Matsubara sums in a relativistic field theory of scalar and fermionic particles. It states that the full result of performing the Matsubara sum associated to any given…

High Energy Physics - Phenomenology · Physics 2011-07-19 Olivier Espinosa

In this work we introduce the Dual Boson Diagrammatic Monte Carlo technique for strongly interacting electronic systems. This method combines the strength of dynamical mean-filed theory for non-perturbative description of local correlations…

Strongly Correlated Electrons · Physics 2020-11-06 M. Vandelli , V. Harkov , E. A. Stepanov , J. Gukelberger , E. Kozik , A. Rubio , A. I. Lichtenstein

Feynman's diagrammatic series is a common language for a formally exact theoretical description of systems of infinitely-many interacting quantum particles, as well as a foundation for precision computational techniques. Here we introduce a…

Strongly Correlated Electrons · Physics 2024-09-12 Evgeny Kozik

A new algorithm for analytic continuation of noisy quantum Monte Carlo (QMC) data from the Matsubara domain to real frequencies is proposed. Unlike the widely used maximum-entropy (MaxEnt) procedure, our method is linear with respect to…

Strongly Correlated Electrons · Physics 2011-06-29 I. S. Krivenko , A. N. Rubtsov

We present a symbolic algorithm for treating perturbative expansions of Hamiltonians with general two-body interactions. The method, formally equivalent to determinant Monte Carlo methods, merges well-known analytics with the recently…

Strongly Correlated Electrons · Physics 2023-05-17 Ibsal Assi , J. P. F. LeBlanc

The ill-posed analytic continuation problem for Green's functions or self-energies can be done using the Pad\'e rational polynomial approximation. However, to extract accurate results from this approximation, high precision input data of…

Strongly Correlated Electrons · Physics 2017-06-28 Xing-Jie Han , Hai-Jun Liao , Hai-Dong Xie , Rui-Zhen Huang , Zi Yang Meng , Tao Xiang

The technique of decomposing Feynman diagrams at the one loop level into elementary integrals is generalized to the imaginary time Matsubara formalism. The three lowest integrals, containing one, two and three fermion lines, are provided in…

High Energy Physics - Phenomenology · Physics 2009-10-28 P. Rehberg , S. P. Klevansky

We present a massively parallel algorithm for calculating the self-energy in self-consistent finite temperature perturbation theory for lattice models. The algorithm uses analytic functions with appropriate asymptotic high frequency…

Condensed Matter · Physics 2007-05-23 J. J. Deisz , D. W. Hess , J. W. Serene
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