A common origin for parity-violating signatures in Cosmology?

Recent measurements of non-vanishing cross-spectra between the E and the B polarization modes of the Cosmic Microwave Background (CMB) have been interpreted as the rotation of the CMB linear polarization plane during propagation from the last-scattering surface up to us. Such effect — known as Cosmic Birefringence — can arise from parity-violating physics. In particular it can be modeled through a Chern-Simons interaction between photons and an axion-like pseudoscalar field which may play the role of dark matter or dark energy. On the other hand recent observations have suggested the possible detection of parity-violating signatures in the four-point correlation function of the galaxy distribution as well. In this Thesis we aim to show that the latter effect can emerge from the same underlying model used to explain Cosmic Birefringence by studying for the first time the coupling between CMB photons and axion field perturbations to second-order in the perturbation theory. A parity-violating imprint in the four-point correlation function of the latter is expected to be manifest.