Photon propagation in slowly varying electromagnetic fields

TL;DR

This paper derives a new analytical expression for the photon polarization tensor in slowly varying electromagnetic fields, relevant for understanding quantum vacuum nonlinearities in high-intensity laser experiments.

Contribution

It provides a novel analytical formula for the photon polarization tensor in counter-propagating laser beams, bridging different field configurations in quantum electrodynamics.

Findings

Analytical expression for photon polarization tensor in specific laser configurations

Interpolates between single-beam and standing-wave scenarios

Applicable to high-intensity laser experiments studying quantum vacuum nonlinearities

Abstract

We study the effective theory of soft photons in slowly varying electromagnetic background fields at one-loop order in QED. This is of relevance for the study of all-optical signatures of quantum vacuum nonlinearity in realistic electromagnetic background fields as provided by high-intensity lasers. The central result derived in this article is a new analytical expression for the photon polarization tensor in two linearly polarized counter-propagating pulsed Gaussian laser beams. As we treat the peak field strengths of both laser beams as free parameters this field configuration can be considered as interpolating between the limiting cases of a purely right- or left-moving laser beam (if one of the peak field strengths is set to zero) and the standing-wave type scenario with two counter-propagating beams of equal strength.