Generation of circular polarization of the CMB

TL;DR

This paper explores how primordial circular polarization of the CMB can be generated through magnetic fields or extensions of the standard model, offering a new way to probe fundamental physics.

Contribution

It demonstrates that CMB circular polarization can arise from magnetic fields or Lorentz-violating physics, which was previously considered negligible.

Findings

CMB circular polarization can be generated under certain new physics scenarios.

Future observations could detect this polarization as evidence of physics beyond the standard model.

Theoretical models predict measurable levels of circular polarization in the CMB.

Abstract

According to the standard cosmology, near the last scattering surface, the photons scattered via Compton scattering are just linearly polarized and then the primordial circular polarization of the CMB photons is zero. In this work we show that CMB polarization acquires a small degree of circular polarization when a background magnetic field is considered or the quantum electrodynamic sector of standard model is extended by Lorentz-noninvariant operators as well as noncommutativity. The existence of circular polarization for the CMB radiation may be verified during future observation programs and it represents a possible new channel for investigating new physics effects.