Cosmological Birefringence: an Astrophysical test of Fundamental Physics

TL;DR

This paper reviews astrophysical methods for testing cosmological birefringence, which could indicate fundamental physics violations, by analyzing polarization data from radio sources and the cosmic microwave background.

Contribution

It provides a comprehensive overview of current techniques and results in testing cosmological birefringence using polarization measurements across different astrophysical sources.

Findings

No significant evidence for cosmological birefringence so far.

Different methods have varying sensitivities and limitations.

Future observations could improve constraints on fundamental physics.

Abstract

We review the methods used to test for the existence of cosmological birefringence, i.e. a rotation of the plane of linear polarization for electromagnetic radiation traveling over cosmological distances, which might arise in a number of important contexts involving the violation of fundamental physical principles. The main methods use: (1) the radio polarization of radio galaxies and quasars, (2) the ultraviolet polarization of radio galaxies, and (3) the cosmic microwave background polarization. We discuss the main results obtained so far, the advantages and disadvantages of each method, and future prospects.