The Pressure in 2, 2+1 and 3 Flavour QCD

TL;DR

This paper computes the pressure in 2, 2+1, and 3-flavor QCD on the lattice, analyzing the effects of quark masses and flavor content on thermodynamic properties with implications for continuum extrapolation.

Contribution

It provides the first lattice calculation of QCD pressure with different flavor compositions and quark masses, including systematic effects and continuum estimates.

Findings

Pressure dominated by Stefan-Boltzmann constant dependence on flavor

Finite lattice effects estimated below 15% for T > 2T_c

Adding a heavier quark reduces pressure more than ideal gas predictions

Abstract

We calculate the pressure in QCD with two and three light quarks on a lattice of size 16^3x4 using tree level improved gauge and fermion actions. We argue that for temperatures T > 2T_c systematic effects due to the finite lattice cut-off and non-vanishing quark masses are below 15% in this calculation and give an estimate for the continuum extrapolated pressure in QCD with massless quarks. We find that the flavour dependence of the pressure is dominated by that of the Stefan-Boltzmann constant. Furthermore we perform a calculation of the pressure using 2 light (m_u,d/T=0.4) and one heavier quark (m_s/T = 1). In this case the pressure is reduced relative to that of three flavour QCD. This effect is stronger than expected from the mass dependence of an ideal Fermi gas.