TY - JOUR

T1 - Non-equilibration of topological charge and its effects

AU - Bernard, Claude

AU - Toussaint, Doug

N1 - Funding Information:
This work was supported by US DOE contracts DE-FG02-91ER40628 and DE-FG02-13ER- 41976. Computations were done at centers supported by the US DOE and NSF, including ALCF, NCSA Bluewaters, NERSC, TACC, NCAR and USQCD facilities.
Publisher Copyright:
© Copyright owned by the author(s).

PY - 2016

Y1 - 2016

N2 - In QCD simulations at small lattice spacings, the topological charge Q evolves very slowly and, if this quantity is not properly equilibrated, we could get incorrect results for physical quantities, or incorrect estimates of their errors. We use the known relation between the dependence of masses and decay constants on the QCD vacuum angle q and the squared topological charge Q2 together with chiral perturbation theory results for the dependence of masses and decay constants on q to estimate the size of these effects and suggest strategies for dealing with them. For the partially quenched case, we sketch an alternative derivation of the known cPT results of Aoki and Fukaya, using the nonperturbatively correct chiral theory worked out by Golterman, Sharpe and Singleton, and by Sharpe and Shoresh. With the MILC collaboration's ensembles of lattices with four flavors of HISQ dynamical quarks, we measure the Q2 dependence of masses and decay constants and compare to the cPT forms. The observed agreement gives us confidence that we can reliably estimate the errors from slow topology change, and even correct for its leading effects.

AB - In QCD simulations at small lattice spacings, the topological charge Q evolves very slowly and, if this quantity is not properly equilibrated, we could get incorrect results for physical quantities, or incorrect estimates of their errors. We use the known relation between the dependence of masses and decay constants on the QCD vacuum angle q and the squared topological charge Q2 together with chiral perturbation theory results for the dependence of masses and decay constants on q to estimate the size of these effects and suggest strategies for dealing with them. For the partially quenched case, we sketch an alternative derivation of the known cPT results of Aoki and Fukaya, using the nonperturbatively correct chiral theory worked out by Golterman, Sharpe and Singleton, and by Sharpe and Shoresh. With the MILC collaboration's ensembles of lattices with four flavors of HISQ dynamical quarks, we measure the Q2 dependence of masses and decay constants and compare to the cPT forms. The observed agreement gives us confidence that we can reliably estimate the errors from slow topology change, and even correct for its leading effects.

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U2 - 10.22323/1.256.0189

DO - 10.22323/1.256.0189

M3 - Conference article

AN - SCOPUS:85025842873

VL - Part F128557

JO - Proceedings of Science

JF - Proceedings of Science

SN - 1824-8039

T2 - 34th Annual International Symposium on Lattice Field Theory, LATTICE 2016

Y2 - 24 July 2016 through 30 July 2016

ER -