Key points are not available for this paper at this time.
We provide an update to S. di Serego Alighieri, Int. J. Mod. Phys. D 24 (2015) 1530016, arXiv:1501.06460 astro-ph.CO, focusing on recent developments regarding constraints on Cosmic Polarization Rotation (CPR), also known as Cosmic Birefringence (CB), derived from Cosmic Microwave Background (CMB) polarization data.
Gruppuso et al. (Tue,) studied this question.