Power corrections and gradient expansion in QED transport theory

TL;DR

This paper demonstrates how power corrections to the HTL effective Lagrangian in QED can be derived from transport theory by including higher-order gradient terms, revealing IR finiteness and correct UV divergences.

Contribution

It extends the transport theory framework to include power corrections via higher-order gradient expansion, ensuring IR finiteness and proper UV divergence reproduction.

Findings

Power corrections are IR finite after regularization.

Higher-order gradient expansion reproduces correct UV divergences.

Transport theory accurately captures long-distance physics of QED plasma.

Abstract

The hard thermal loop (HTL) effective field theory of QED can be derived from the classical limit of transport theory, corresponding to the leading term in a gradient expansion of the quantum approach. In this paper, we show that power corrections to the HTL effective Lagrangian of QED can also be obtained from transport theory by including higher orders in such gradient expansion. The gradient expansion is increasingly infrared (IR) divergent, but the correction that we compute is IR finite. We employ dimensional regularization, and show that this result comes after a cancellation of divergencies between the vacuum and medium contributions. While the transport framework is an effective field theory of the long distance physics of the plasma, we show that it correctly reproduces the correct QED ultraviolet divergencies associated with the photon wave function renormalization.