Axion constraints in non-standard thermal histories
Abstract
It is usually assumed that dark matter is produced during the radiation dominated era. There is, however, no direct evidence for radiation domination prior to big-bang nucleosynthesis. Two non-standard thermal histories are considered. In one, the low-temperature-reheating scenario, radiation domination begins as late as 1 MeV, and is preceded by significant entropy generation. Thermal axion relic abundances are then suppressed, and cosmological limits to axions are loosened. For reheating temperatures less than 35 MeV, the large-scale structure limit to the axion mass is lifted. The remaining constraint from the total density of matter is significantly relaxed. Constraints are also relaxed for higher reheating temperatures. In a kination scenario, a more modest change to cosmological axion constraints is obtained. Future possible constraints to axions and low-temperature reheating from the helium abundance and next-generation large-scale-structure surveys are discussed.
Cite
@article{arxiv.0711.1352,
title = {Axion constraints in non-standard thermal histories},
author = {Daniel Grin and Tristan L. Smith and Marc Kamionkowski},
journal= {arXiv preprint arXiv:0711.1352},
year = {2008}
}
Comments
10 pages, 7 figures, revised to match version published in Phys. Rev. D. Fig. 7 and Eq. (20) modified