Isotropic cosmic birefringence from an oscillating axion-like field

TL;DR

This paper introduces a novel mechanism where an oscillating axion-like field with an asymmetric potential causes observable isotropic cosmic birefringence, potentially linking it to dark matter and affecting CMB polarization spectra.

Contribution

It proposes a new model with an asymmetric potential for axion-like fields that produces detectable birefringence effects during recombination, overcoming previous cancellation issues.

Findings

A substantial EB spectrum can be generated by the proposed mechanism.

The model predicts a washout of the EE spectrum detectable in future observations.

The axion-like field could account for a significant fraction of dark matter.

Abstract

We propose a new mechanism for isotropic cosmic birefringence with an axion-like field that rapidly oscillates during the recombination epoch. In conventional models, the field oscillation during the recombination epoch leads to a cancellation of the birefringence effect and significantly suppresses the EB spectrum of the cosmic microwave background (CMB) polarization. By introducing an asymmetric potential to the axion, this cancellation becomes incomplete, and a substantial EB spectrum can be produced. This mechanism also results in a washout of the EE spectrum, which can be probed in future CMB observations. Our findings suggest the possibility that an axion-like field responsible for isotropic cosmic birefringence can also account for a significant fraction of dark matter.