BRST symmetry and fictitious parameters

TL;DR

This paper explores the variational method of fictitious parameters and its relation to BRST symmetry, applying it to QED and GQED at finite temperature to demonstrate gauge independence of physical results.

Contribution

It introduces the application of the variational method of fictitious parameters to gauge theories at finite temperature, linking it with BRST symmetry to ensure gauge invariance.

Findings

Validated the method in zero-temperature QED

Extended analysis to finite-temperature GQED

Confirmed gauge independence due to BRST symmetry

Abstract

Our goal in this work is to present the variational method of fictitious parameters and its connection with the BRST symmetry. Firstly we implement the method in QED at zero temperature and then we extend the analysis to GQED at finite temperature. As we will see the core of the study is the general statement in gauge theories at finite temperature, assigned by Tyutin work, that the physics does not depend on the gauge choices, covariant or not, due to BRST symmetry.