Production of Hot Axions in the Early Universe

We numerically compute the abundance of hot axions produced in the early Universe and we assess whether their presence can be inferred by the next CMB surveys. We will focus on axion interactions with heavy fermions of the standard model, also with EW corrections, and with couplings suppressed by the scale of Peccei-Quinn breaking. Once we establish for what parameter space region the signal is detectable, we will investigate whether this region is compatible with cold axions accounting for the observed abundance of dark matter.