The QCD Equation of State

TL;DR

This paper presents lattice QCD calculations of the equation of state for 2+1 flavor QCD at zero baryon density, using the HISQ action across multiple lattice spacings, providing continuum results relevant for understanding QCD thermodynamics.

Contribution

The study provides the first continuum extrapolated results for the QCD equation of state using the HISQ action at physical quark masses.

Findings

Continuum extrapolated results for the QCD equation of state between 130 MeV and 400 MeV.

Small cutoff effects observed for lattices with N_t > 6.

Comparison with previous results shows consistency within errors.

Abstract

Results for the equation of state in 2+1 flavor QCD at zero net baryon density using the Highly Improved Staggered Quark (HISQ) action by the HotQCD collaboration are presented. The strange quark mass was tuned to its physical value and the light (up/down) quark masses fixed to $m_l = 0.05m_s$ corresponding to a pion mass of 160 MeV in the continuum limit. Lattices with temporal extent $N_t=6$, 8, 10 and 12 were used. Since the cutoff effects for $N_t>6$ were observed to be small, reliable continuum extrapolations of the lattice data for the phenomenologically interesting temperatures range $130 \mathord{\rm MeV} < T < 400 \mathord{\rm MeV}$ could be performed. We discuss statistical and systematic errors and compare our results with other published works.