The entropy of the QCD plasma

TL;DR

This paper develops a self-consistent approximation method to calculate the entropy of the QCD plasma, effectively matching lattice data for gluonic QCD at temperatures above twice the transition point.

Contribution

It introduces a novel approximation approach using fully dressed propagators to compute the entropy of the QCD plasma, validated against lattice results.

Findings

Accurately describes lattice data for gluonic QCD

Valid down to temperatures about twice the transition temperature

Provides a simple expression isolating elementary excitations

Abstract

Self-consistent approximations in terms of fully dressed propagators provide a simple expression for the entropy of an ultrarelativistic plasma, which isolates the contribution of the elementary excitations as a leading contribution. Further approximations, whose validity is checked on a soluble model involving a scalar field, allow us to calculate the entropy of the QCD plasma. We obtain an accurate description of lattice data for purely gluonic QCD, down to temperatures of about twice the transition temperature.