Constrained effective potential in hot QCD

TL;DR

This paper analyzes the constrained effective potential in hot QCD, highlighting the role of non-linear terms and gauge dependence, and calculates two-loop contributions for SU(N) gauge theories with and without quarks.

Contribution

It provides a detailed analysis of the gauge dependence and non-linear effects in the constrained effective potential in hot QCD, including explicit two-loop calculations.

Findings

Absolute minima at center group values of the Polyakov loop

Gauge dependence cancels through BRST identities

Two-loop contributions evaluated for SU(N) with and without quarks

Abstract

Constrained effective potentials in hot gauge theory give the probability that a configuration p of the order parameter (Polyakov loop) occurs. They are important in the analysis of surface effects and bubble formation in the plasma. The vector potential appears non-linearly in the loop; in weak coupling the linear term gives rise to the traditional free energy graphs. But the non-linear terms generate insertions of the constrained modes into the free energy graphs, through renormalisations of the Polyakov loop. These insertions are gauge dependent and are necessary to cancel the gauge dependence of the free energy graphs. The latter is shown, through the BRST identities, to have again the form of constrained mode insertions. It also follows, that absolute minima of the potential are at the centergroup values of the loop. We evaluate the two-loop contributions for SU(N) gauge theories, with and without quarks, for the full domain of the N-1 variables.