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Title: Multiscale Monte Carlo equilibration: Two-color QCD with two fermion flavors

In this study, we demonstrate the applicability of a recently proposed multiscale thermalization algorithm to two-color quantum chromodynamics (QCD) with two mass-degenerate fermion flavors. The algorithm involves refining an ensemble of gauge configurations that had been generated using a renormalization group (RG) matched coarse action, thereby producing a fine ensemble that is close to the thermalized distribution of a target fine action; the refined ensemble is subsequently rethermalized using conventional algorithms. Although the generalization of this algorithm from pure Yang-Mills theory to QCD with dynamical fermions is straightforward, we find that in the latter case, the method is susceptible to numerical instabilities during the initial stages of rethermalization when using the hybrid Monte Carlo algorithm. We find that these instabilities arise from large fermion forces in the evolution, which are attributed to an accumulation of spurious near-zero modes of the Dirac operator. We propose a simple strategy for curing this problem, and demonstrate that rapid thermalization--as probed by a variety of gluonic and fermionic operators--is possible with the use of this solution. Also, we study the sensitivity of rethermalization rates to the RG matching of the coarse and fine actions, and identify effective matching conditions based on a variety ofmore » measured scales.« less
Authors:
 [1] ;  [1]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Center for Theoretical Physics
Publication Date:
Grant/Contract Number:
SC0010495; SC0011090
Type:
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 94; Journal Issue: 11; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society (APS)
Research Org:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
OSTI Identifier:
1424917
Alternate Identifier(s):
OSTI ID: 1334216

Detmold, William, and Endres, Michael G. Multiscale Monte Carlo equilibration: Two-color QCD with two fermion flavors. United States: N. p., Web. doi:10.1103/PhysRevD.94.114502.
Detmold, William, & Endres, Michael G. Multiscale Monte Carlo equilibration: Two-color QCD with two fermion flavors. United States. doi:10.1103/PhysRevD.94.114502.
Detmold, William, and Endres, Michael G. 2016. "Multiscale Monte Carlo equilibration: Two-color QCD with two fermion flavors". United States. doi:10.1103/PhysRevD.94.114502. https://www.osti.gov/servlets/purl/1424917.
@article{osti_1424917,
title = {Multiscale Monte Carlo equilibration: Two-color QCD with two fermion flavors},
author = {Detmold, William and Endres, Michael G.},
abstractNote = {In this study, we demonstrate the applicability of a recently proposed multiscale thermalization algorithm to two-color quantum chromodynamics (QCD) with two mass-degenerate fermion flavors. The algorithm involves refining an ensemble of gauge configurations that had been generated using a renormalization group (RG) matched coarse action, thereby producing a fine ensemble that is close to the thermalized distribution of a target fine action; the refined ensemble is subsequently rethermalized using conventional algorithms. Although the generalization of this algorithm from pure Yang-Mills theory to QCD with dynamical fermions is straightforward, we find that in the latter case, the method is susceptible to numerical instabilities during the initial stages of rethermalization when using the hybrid Monte Carlo algorithm. We find that these instabilities arise from large fermion forces in the evolution, which are attributed to an accumulation of spurious near-zero modes of the Dirac operator. We propose a simple strategy for curing this problem, and demonstrate that rapid thermalization--as probed by a variety of gluonic and fermionic operators--is possible with the use of this solution. Also, we study the sensitivity of rethermalization rates to the RG matching of the coarse and fine actions, and identify effective matching conditions based on a variety of measured scales.},
doi = {10.1103/PhysRevD.94.114502},
journal = {Physical Review D},
number = 11,
volume = 94,
place = {United States},
year = {2016},
month = {12}
}