Rotation of Linear Polarization Plane and Circular Polarization from Cosmological Pseudoscalar Fields

TL;DR

This paper investigates how cosmological pseudoscalar fields, as dark matter candidates, can rotate linear polarization and generate circular polarization, providing both analytical and numerical insights into their effects on the Stokes parameters.

Contribution

It offers a detailed analysis of polarization rotation and circular polarization production caused by pseudoscalar dark matter fields, comparing exact calculations with common approximations.

Findings

Rotation angle varies over time in realistic models

Exact results differ from constant-angle approximation

Numerical simulations confirm analytical predictions

Abstract

We discuss the rotation of the linear polarization plane and the production of circular polarization generated by a pseudoscalar field acting as dark matter. We compute analytically and numerically the propagation of the Stokes parameters from the last scattering surface for an oscillating and a monotonic decreasing pseudoscalar field. For the models studied in this paper, we show the comparison between the widely used approximation in which the rotation angle is constant in time and the exact result.