Thermal axion constraints in non-standard thermal histories

Abstract

There is no direct evidence for radiation domination prior to big-bang nucleosynthesis, and so it is useful to consider how constraints to thermally-produced axions change in non-standard thermal histories. In the low-temperature-reheating scenario, radiation domination begins at temperatures as low as 1 MeV, and is preceded by significant entropy generation. Axion abundances are then suppressed, and cosmological limits to axions are significantly loosened. In a kination scenario, a more modest change to axion constraints occurs. Future possible constraints to axions and low-temperature reheating are discussed.

Submitted conference proceedings, based on a talk presented at Dark Matter '08 in Marina del Rey. Based on work discussed in Phys.Rev.D77:085020,2008, as well as arXiv:0711.1352. Updated to correct title