Speaker
Description
Author: Fazlollah Hajkarim
We provide a comprehensive analysis of thermal axion production in the early universe, focusing on the KSVZ and DFSZ models. We extend our calculations to incorporate multiple mass thresholds, including the QCD phase transition, and provide a continuous production rate across these regimes. Employing updated cosmological data, we refine constraints on axion mass and examine the implications for dark radiation quantified as an effective number of additional neutrino species (ΔNeff). Our rigorous approach revisits traditional approximations in axion production, highlighting the importance of precise calculations in anticipation of future CMB surveys and large scale structure observations. Also, we examine the validity of different computational approaches for the calculation of effective number of additional neutrino species.
