Seminarium "High Energy, Cosmology and Astro-particle Physics (HECA)"

Axions can be produced via the interactions in the thermal plasma of the early Universe and their contribution to dark radiation can modify the cosmological observables and constrain the axion couplings to SM particles. In my talk I am going to outline an approach to calculate the axion cosmological abundance that goes beyond the approximations widely used in the literature on the topic and demonstrate how it affects the bounds on axion couplings on the example of axion interactions with leptons.