Extended Axion Dark Matter Landscape from Post-Inflationary Field Dynamics

This thesis analyzes axions as a possible candidate for Dark Matter. A brief introduction of axions, which emerge in physics consequently to the strong CP problem, is initially proposed, together with a sum up of of the inflationary epoch, followed by the reheating phase. The main work of the thesis focuses on the production of axions during the Reheating phase, both through the standard misalignment mechanism and through gravitational production. Assuming that during Reheating the inflaton is decaying into three main channels, the assumption of axions as DM allows us to impose some upper bounds on the couplings of these interactions. Moreover, knowing that the DM abundance has an experimental upper bound, assuming DM to be made of axions translates into finding constraints on other parameters used in the study, such as the reheating temperature. Lastly a comparison between inflaton- and PBH-driven inflation is presented.