Consistency of the string inspired electroweak axion with cosmic birefringence

TL;DR

This paper explores how an electroweak axion with a string-theory inspired decay constant can naturally explain the observed cosmic birefringence, addressing naturalness concerns in the model parameter space.

Contribution

It demonstrates that the electroweak axion with a decay constant around 10^{16} GeV can account for cosmic birefringence, considering naturalness of parameters often overlooked.

Findings

Electroweak axion explains cosmic birefringence

Decay constant around 10^{16} GeV is natural

Model addresses naturalness issues

Abstract

We revisit the constraint from the recently reported cosmic birefringence on axion-like particles with a general decay constant. A particular attention is paid to the naturalness of the model parameter space, which has been overlooked in the literature. We show that the observed cosmic birefringence is naturally explained by the electroweak axion with a string-theory inspired decay constant $F_A\simeq 10^{16}$ GeV.