Equation of state in 2+1 flavor QCD with improved Wilson quarks by the fixed scale approach

TL;DR

This paper calculates the equation of state in 2+1 flavor QCD using improved Wilson quarks and a fixed-scale approach, enabling temperature variation without changing system size or renormalization constants.

Contribution

It introduces a fixed-scale method combined with the $T$-integration technique for more accurate equation of state calculations in lattice QCD.

Findings

Equation of state results are consistent with previous staggered quark studies.

The fixed-scale approach reduces scaling violations at low temperatures.

The study uses quark masses heavier than physical but still yields relevant insights.

Abstract

We study the equation of state in 2+1 flavor QCD with nonperturbatively improved Wilson quarks coupled with the RG-improved Iwasaki glue. We apply the $T$-integration method to nonperturbatively calculate the equation of state by the fixed-scale approach. With the fixed-scale approach, we can purely vary the temperature on a line of constant physics without changing the system size and renormalization constants. Unlike the conventional fixed-$N_t$ approach, it is easy to keep scaling violations small at low temperature in the fixed scale approach. We study 2+1 flavor QCD at light quark mass corresponding to $m_\pi/m_\rho \simeq 0.63$, while the strange quark mass is chosen around the physical point. Although the light quark masses are heavier than the physical values yet, our equation of state is roughly consistent with recent results with highly improved staggered quarks at large $N_t$.