Stabilizing complex Langevin for real-time gauge theories with an anisotropic kernel

Abstract The complex Langevin (CL) method is a promising approach to overcome the sign problem that occurs in real-time formulations of quantum field theories. Using the Schwinger-Keldysh formalism, we study SU(N c ) gauge theories with CL. We observe that current stabilization techniques are insuff...

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Main Authors: Kirill Boguslavski, Paul Hotzy, David I. Müller
Format: Article
Language:English
Published: SpringerOpen 2023-06-01
Series:Journal of High Energy Physics
Subjects:
Online Access:https://doi.org/10.1007/JHEP06(2023)011
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author Kirill Boguslavski
Paul Hotzy
David I. Müller
author_facet Kirill Boguslavski
Paul Hotzy
David I. Müller
author_sort Kirill Boguslavski
collection DOAJ
description Abstract The complex Langevin (CL) method is a promising approach to overcome the sign problem that occurs in real-time formulations of quantum field theories. Using the Schwinger-Keldysh formalism, we study SU(N c ) gauge theories with CL. We observe that current stabilization techniques are insufficient to obtain correct results. Therefore, we revise the discretization of the CL equations on complex time contours, find a time reflection symmetric formulation and introduce a novel anisotropic kernel that enables CL simulations on discretized complex time paths. Applying it to SU(2) Yang-Mills theory in 3+1 dimensions, we obtain unprecedentedly stable results that we validate using additional observables and that can be systematically improved. For the first time, we are able to simulate non-Abelian gauge theory on time contours whose real-time extent exceeds its inverse temperature. Thus, our approach may pave the way towards an ab-initio real-time framework of QCD in and out of equilibrium with a potentially large impact on the phenomenology of heavy-ion collisions.
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spelling doaj.art-1b4eb2da4dc44e9a8b078733553a8cc22023-09-24T11:07:34ZengSpringerOpenJournal of High Energy Physics1029-84792023-06-012023614210.1007/JHEP06(2023)011Stabilizing complex Langevin for real-time gauge theories with an anisotropic kernelKirill Boguslavski0Paul Hotzy1David I. Müller2Institute for Theoretical Physics, TU WienInstitute for Theoretical Physics, TU WienInstitute for Theoretical Physics, TU WienAbstract The complex Langevin (CL) method is a promising approach to overcome the sign problem that occurs in real-time formulations of quantum field theories. Using the Schwinger-Keldysh formalism, we study SU(N c ) gauge theories with CL. We observe that current stabilization techniques are insufficient to obtain correct results. Therefore, we revise the discretization of the CL equations on complex time contours, find a time reflection symmetric formulation and introduce a novel anisotropic kernel that enables CL simulations on discretized complex time paths. Applying it to SU(2) Yang-Mills theory in 3+1 dimensions, we obtain unprecedentedly stable results that we validate using additional observables and that can be systematically improved. For the first time, we are able to simulate non-Abelian gauge theory on time contours whose real-time extent exceeds its inverse temperature. Thus, our approach may pave the way towards an ab-initio real-time framework of QCD in and out of equilibrium with a potentially large impact on the phenomenology of heavy-ion collisions.https://doi.org/10.1007/JHEP06(2023)011Algorithms and Theoretical DevelopmentsLattice QCDNon-Zero Temperature and DensityNon-Equilibrium Field Theory
spellingShingle Kirill Boguslavski
Paul Hotzy
David I. Müller
Stabilizing complex Langevin for real-time gauge theories with an anisotropic kernel
Journal of High Energy Physics
Algorithms and Theoretical Developments
Lattice QCD
Non-Zero Temperature and Density
Non-Equilibrium Field Theory
title Stabilizing complex Langevin for real-time gauge theories with an anisotropic kernel
title_full Stabilizing complex Langevin for real-time gauge theories with an anisotropic kernel
title_fullStr Stabilizing complex Langevin for real-time gauge theories with an anisotropic kernel
title_full_unstemmed Stabilizing complex Langevin for real-time gauge theories with an anisotropic kernel
title_short Stabilizing complex Langevin for real-time gauge theories with an anisotropic kernel
title_sort stabilizing complex langevin for real time gauge theories with an anisotropic kernel
topic Algorithms and Theoretical Developments
Lattice QCD
Non-Zero Temperature and Density
Non-Equilibrium Field Theory
url https://doi.org/10.1007/JHEP06(2023)011
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AT paulhotzy stabilizingcomplexlangevinforrealtimegaugetheorieswithananisotropickernel
AT davidimuller stabilizingcomplexlangevinforrealtimegaugetheorieswithananisotropickernel