On the circular polarisation of light from axion-photon mixing

TL;DR

This paper proposes that the observed large-scale quasar polarisation alignments can be explained by axion-photon mixing in extragalactic magnetic fields, with new wave packet analysis highlighting implications for circular polarisation.

Contribution

It introduces a novel wave packet approach to axion-photon mixing and explores its effects on circular polarisation in quasar light.

Findings

Explains quasar polarisation alignments via axion-photon mixing.

Highlights potential circular polarisation signals from axion-like particles.

Provides a new theoretical framework for light-particle interactions in cosmic magnetic fields.

Abstract

From the analysis of measurements of the linear polarisation of visible light coming from quasars, the existence of large-scale coherent orientations of quasar polarisation vectors in some regions of the sky has been reported. Here, we show that this can be explained by the mixing of the incoming photons with nearly massless pseudoscalar (axion-like) particles in extragalactic magnetic fields. We present a new treatment in terms of wave packets and discuss its implications for the circular polarisation.