A birefringent universe could show itself through a rotation of the plane of polarisation of the cosmic microwave background photons. This is usually investigated using polarisation B modes, which is degenerate with miscalibration of the orientation of the polarimeters. Here we point out an independent method for extracting the birefringence angle using only temperature and E-mode signals. We forecast that, with an ideal cosmic-variance-limited experiment, we could constrain a birefringence angle of 0.3∘ with 3σ statistical significance, which is close to the current constraints using B modes. We explore how this method is affected by the systematic errors introduced by the polarisation efficiency. In the future, this could provide an additional way of checking any claimed B-mode derived birefringence signature.
@article{arxiv.2203.10733,
title = {Constraints on cosmic birefringence using $E$-mode polarisation},
author = {Arefe Abghari and Raelyn M. Sullivan and Lukas T. Hergt and Douglas Scott},
journal= {arXiv preprint arXiv:2203.10733},
year = {2022}
}