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We introduce the feedforward neural network to attack the sign problem via the path optimization method. The variables of integration is complexified and the integration path is optimized in the complexified space by minimizing the cost…

High Energy Physics - Lattice · Physics 2019-12-06 Yuto Mori , Kouji Kashiwa , Akira Ohnishi

The \emph{ab initio} path integral Monte Carlo (PIMC) method is one of the most successful methods in statistical physics, quantum chemistry and related fields, but its application to quantum degenerate Fermi systems is severely hampered by…

Computational Physics · Physics 2023-08-14 Tobias Dornheim , Panagiotis Tolias , Simon Groth , Zhandos Moldabekov , Jan Vorberger , Barak Hirshberg

The Worldvolume Hybrid Monte Carlo (WV-HMC) method [arXiv:2012.08468] is an efficient algorithm for addressing the numerical sign problem at moderate computational cost. It mitigates the sign problem while avoiding the ergodicity issues…

Strongly Correlated Electrons · Physics 2026-05-15 Masafumi Fukuma , Yusuke Namekawa

We give a brief discussion of the recently developed Constrained-Path Monte Carlo Method. This method is a quantum Monte Carlo technique that eliminates the fermion sign problem plaguing simulations of systems of interacting electrons. The…

Strongly Correlated Electrons · Physics 2009-10-31 J. E. Gubernatis , M. Guerrero

Quantum Monte Carlo simulations provide one of the more powerful and versatile numerical approaches to condensed matter systems. However, their application to frustrated quantum spin models, in all relevant temperature regimes, is hamstrung…

Strongly Correlated Electrons · Physics 2017-07-20 Stefan Wessel , B. Normand , Frédéric Mila , Andreas Honecker

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

The quantum Monte Carlo method on asymptotic Lefschetz thimbles is a numerical algorithm devised specifically for alleviation of the sign problem appearing in the simulations of quantum many-body systems. In this method, the sign problem is…

Strongly Correlated Electrons · Physics 2021-10-26 Petr A. Mishchenko , Yasuyuki Kato , Yukitoshi Motome

Recently, we have proposed a novel approach (arxiv:1205.3996) to deal with the sign problem that hinders Monte Carlo simulations of many quantum field theories (QFTs). The approach consists in formulating the QFT on a Lefschetz thimble. In…

High Energy Physics - Lattice · Physics 2015-06-11 Marco Cristoforetti , Francesco Di Renzo , Luigi Scorzato

We present a guiding principle for designing fermionic Hamiltonians and quantum Monte Carlo (QMC) methods that are free from the infamous sign problem by exploiting the Lie groups and Lie algebras that appear naturally in the Monte Carlo…

Strongly Correlated Electrons · Physics 2015-12-23 Lei Wang , Ye-Hua Liu , Mauro Iazzi , Matthias Troyer , Gergely Harcos

Lattice scalar field theories encounter a sign problem when the coupling constant is complex. This is a close cousin of the real-time sign problems that afflict the lattice Schwinger-Keldysh formalism, and a more distant relative of the…

High Energy Physics - Lattice · Physics 2022-12-28 Scott Lawrence , Hyunwoo Oh , Yukari Yamauchi

The study of lattice gauge theories with Monte Carlo simulations is hindered by the infamous sign problem that appears under certain circumstances, in particular at non-zero chemical potential. So far, there is no universal method to…

High Energy Physics - Lattice · Physics 2017-03-27 Mari Carmen Bañuls , Krzysztof Cichy , J. Ignacio Cirac , Karl Jansen , Stefan Kühn , Hana Saito

We use the Shadow Wave Function formalism as a convenient model to study the fermion sign problem affecting all projector Quantum Monte Carlo methods in continuum space. We demonstrate that the efficiency of imaginary time projection…

Computational Physics · Physics 2016-05-04 Francesco Calcavecchia , Markus Holzmann

The Monte Carlo evaluation of path integrals is one of a few general purpose methods to approach strongly coupled systems. It is used in all branches of Physics, from QCD/nuclear physics to the correlated electron systems. However, many…

High Energy Physics - Lattice · Physics 2020-07-13 Andrei Alexandru , Gokce Basar , Paulo F. Bedaque , Neill C. Warrington

Quantum Monte-Carlo (QMC) simulations involving fermions have the notorious sign problem. Some well-known exceptions of the auxiliary field QMC algorithm rely on the factorizibility of the fermion determinant. Recently, a fermionic QMC…

Strongly Correlated Electrons · Physics 2009-02-06 Congjun Wu , Shou-Cheng Zhang

Lattice Monte Carlo calculations of interacting systems on non-bipartite lattices exhibit an oscillatory imaginary phase known as the phase or sign problem, even at zero chemical potential. One method to alleviate the sign problem is to…

Strongly Correlated Electrons · Physics 2021-03-31 Jan-Lukas Wynen , Evan Berkowitz , Stefan Krieg , Thomas Luu , Johann Ostmeyer

The extreme computational costs of calculating the sign of the Wilson matrix within the overlap operator have so far prevented four dimensional dynamical overlap simulations on realistic lattice sizes, because the computational power…

High Energy Physics - Lattice · Physics 2008-12-18 N. Cundy , S. Krieg , G. Arnold , A. Frommer , Th. Lippert , K. Schilling

The fermion sign problem constitutes one of the most fundamental obstacles in quantum many-body theory. Recently, it has been suggested to circumvent the sign problem by carrying out path integral simulations with a fictitious quantum…

Quantum field theories with complex actions cannot be investigated using importance sampling due to the sign problem. One possible solution is to use the holomorphic gradient flow, a method we introduced related to the Lefschetz thimbles…

High Energy Physics - Lattice · Physics 2017-08-23 Andrei Alexandru , Gokce Basar , Paulo F. Bedaque , Neill C. Warrington

A method is presented to tackle the sign problem in the simulations of systems having indefinite or complex-valued measures. In general, this new approach is shown to yield statistical errors smaller than the crude Monte Carlo using…

High Energy Physics - Lattice · Physics 2008-11-26 T D Kieu , C J Griffin

Nowadays the term 'sign problem' is used to identify two different problems. The ideas to overcome the first type of the 'sign problem' of strongly oscillating complex valued imtegrand in the Feynman path integrals comes from…

Statistical Mechanics · Physics 2020-03-04 Vladimir Filinov , Alexander Larkin