QCD thermodynamics with light quarks. Quantum corrections to the fermionic anisotropy parameter

Karsch F, Stamatescu IO. QCD thermodynamics with light quarks. Quantum corrections to the fermionic anisotropy parameter. Physics Letters, B. 1989;227(1):153-160.We determine the O(g 2) corrections to the anisotropy parameter in the fermionic action, which are required to guarantee a rotational invariant continuum limit on anisotropic lattices. We show the importance of these quantum corrections for QCD thermodynamics on isotropic lattices. Only after including these corrections do we find, on large lattices, agreement between lattice and continuum perturbation theory at finite temperature. The implied renormalization of the operators used in Monte Carlo simulations to measure the energy density leads to a 20% reduction of the fermionic part of the energy density which, to a large extent, compensates the previously found overshooting in the gluonic sector. We reanalyze existing Monte Carlo data for the thermodynamics of QCD with light quarks and extract the entropy density. We find that immediately above the chiral transition the entropy density is already close to the ideal gas value