Gauge Invariance of Resummation Schemes: The QCD Partition Function

TL;DR

This paper extends a diagrammatic method to verify gauge invariance in thermal QCD calculations, demonstrating its effectiveness by confirming the gauge independence of the QCD partition function up to order g^4.

Contribution

It generalizes a vacuum perturbation technique to thermal field theory, enabling diagrammatic checks of gauge invariance in resummation schemes.

Findings

Confirmed gauge invariance of the QCD partition function up to O(g^4).

Validated the resummation scheme's consistency across different gauges.

Abstract

We pick up a method originally developed by Cheng and Tsai for vacuum perturbation theory which allows to test the consistency of different sets of Feynman rules on a purely diagrammatic level, making explicit loop calculations superfluous. We generalize it to perturbative calculations in thermal field theory and we show that it can be adapted to check the gauge invariance of physical quantities calculated in improved perturbation schemes. Specifically, we extend this diagrammatic technique to a simple resummation scheme in imaginary time perturbation theory. As an application, we check up to O(g^4) in general covariant gauge the gauge invariance of the result for the QCD partition function which was recently obtained in Feynman gauge.