Limits on Cosmological Birefringence from the Ultraviolet Polarization of Distant Radio Galaxies

TL;DR

This study constrains cosmological birefringence by analyzing UV polarization in distant radio galaxies, finding no significant rotation and thus limiting models involving pseudo-scalar fields or Chern-Simons terms.

Contribution

It provides updated constraints on cosmological birefringence using UV polarization data from high-redshift radio galaxies, improving previous limits.

Findings

No significant polarization rotation detected.

All-sky-average rotation constrained to -0.8 +/- 2.2 degrees.

Results limit models involving pseudo-scalar fields or Chern-Simons interactions.

Abstract

We report on an update of the test on the rotation of the plane of linear polarization for light traveling over cosmological distances, using a comparison between the measured direction of the UV polarization in 8 radio galaxies at z>2 and the direction predicted by the model of scattering of anisotropic nuclear radiation, which explains the polarization. No rotation is detected within a few degrees for each galaxy and, if the rotation does not depend on direction, then the all-sky-average rotation is constrained to be \theta = -0.8 +/- 2.2. We discuss the relevance of this result for constraining cosmological birefringence, when this is caused by the interaction with a cosmological pseudo-scalar field or by the presence of a Cherns-Simons term.