Electromagnetic Fields in a Thermal Background

TL;DR

This paper calculates the one-loop effective action for electromagnetic fields in a thermal background, analyzing gauge invariance, Debye mass corrections, and the behavior of the effective coupling at high temperature and density.

Contribution

It provides a finite-temperature, finite-density calculation of the effective action for electromagnetic fields, including gauge invariance and the behavior of the coupling constant.

Findings

Debye mass corrections computed at high temperature and density.

Effective coupling behaves differently for electric fields at high temperature.

Discussion of pair production relevance in heavy-ion collisions.

Abstract

The one--loop effective action for a slowly varying electromagnetic field is computed at finite temperature and density using a real-time formalism. We discuss the gauge invariance of the result. Corrections to the Debye mass from an electric field are computed at high temperature and high density. The effective coupling constant, defined from a purely electric weak--field expansion, behaves at high temperature very differently from the case of a magnetic field, and does not satisfy the renormalization group equation. The issue of pair production in the real--time formalism is discussed and also its relevance for heavy--ion collisions.