Matteo Galaverni - Redshift evolution of isotropic cosmic birefringence

Abstract: Cosmic birefringence is a rotation of the polarization plane of photons coming from sources of astrophysical and cosmological origin. We discuss the imprints of a cosmological pseudoscalar field on Cosmic Microwave Background (CMB) propagation. Phenomenological and theoretically motivated redshift dependence of the pseudoscalar fields - such as axionlike early dark energy (EDE), quintessence (DE) or dark matter (DE) - are studied. We show how time evolution of the background pseudoscalar field imprints, in general, a nontrivial multipole dependence in the observed CMB angular power spectra which is not captured by the widely adopted approximation in which the redshift dependence of the rotation angle is neglected.