Photon-photon scattering and tests of gauge invariance

TL;DR

This paper investigates the effects of a gauge invariance-violating operator on photon interactions, constraining its magnitude through astrophysical observations and discussing potential Lorentz-violating extensions.

Contribution

It introduces a phenomenological analysis of a gauge-violating operator and derives constraints from cosmic microwave background interactions and high-energy scattering data.

Findings

Severe constraints on gauge-violating operator magnitude from CMB scattering

No induced photon mass observed in CMB propagation

High-energy scattering limits if a bare photon mass dominates

Abstract

We consider the phenomenology of a dimension-four operator that violates electromagnetic gauge invariance. Its magnitude is severely constrained by the lack of scattering of very low energy electromagnetic radiation off of the Cosmic Microwave Background (CMB) and by the lack of an induced mass when photons propagate in the CMB. We also discuss possible Lorentz-violating extensions of the operator basis. If a bare Proca mass exists and dominates over the induced mass, there is also a tight constraint from high energy scattering.