Non-Riemannian geometrical optics in QED

TL;DR

This paper investigates how torsion in spacetime, within a quantum electrodynamics framework, affects photon propagation, revealing effects absent in standard Riemannian geometries, especially in torsionic de Sitter backgrounds.

Contribution

It introduces a non-minimal photon-torsion coupling in QED and analyzes its impact on geometrical optics in Riemann-Cartan spacetime, focusing on torsion effects in flat and de Sitter backgrounds.

Findings

Torsion influences photon propagation in Minkowski spacetime with torsion.

Vacuum polarization modifies photon behavior in torsionic de Sitter space.

Effects of torsion are absent in purely Riemannian geometries.

Abstract

A non-minimal photon-torsion axial coupling in the quantum electrodynamics (QED) framework is considered. The geometrical optics in Riemannian-Cartan spacetime is considering and a plane wave expansion of the electromagnetic vector potential is considered leading to a set of the equations for the ray congruence. Since we are interested mainly on the torsion effects in this first report we just consider the Riemann-flat case composed of the Minkowskian spacetime with torsion. It is also shown that in torsionic de Sitter background the vacuum polarisation does alter the propagation of individual photons, an effect which is absent in Riemannian spaces.