Updated Axion CDM energy density

TL;DR

This paper refines the cosmological constraints on axion cold dark matter by incorporating anharmonic effects and a new initial overshoot correction, providing an explicit formula for relic density based on fundamental parameters.

Contribution

It introduces a novel initial overshoot correction factor and an explicit relic density formula, improving the accuracy of axion CDM energy density estimates.

Findings

Updated bounds on axion energy density considering new effects

Explicit formula for relic density in terms of QCD scale and quark masses

Quantitative impact of initial overshoot correction on axion abundance

Abstract

We update cosmological bound on axion model. The contribution from the anharmonic effect and the newly introduced initial overshoot correction are considered. We present an explicit formula for the axion relic density in terms of the QCD scale Lambda_{QCD}, the current quark masses m_q's and the Peccei-Quinn scale F_a, including firstly introduced 1.85 factor which is from the initial overshoot.