Asymmetric dark matter annihilation as a test of non-standard cosmologies

TL;DR

This paper investigates how non-standard early universe cosmologies can significantly influence the relic abundance and annihilation rates of asymmetric dark matter, challenging previous assumptions about their detectability.

Contribution

It demonstrates that the relic density and annihilation signals of asymmetric dark matter are highly sensitive to the universe's expansion history before BBN, providing new ways to test cosmological models.

Findings

Relic abundance of asymmetric dark matter depends on the early universe expansion rate.

Annihilation rates of asymmetric dark matter can surpass those of symmetric dark matter in non-standard cosmologies.

The transition temperature between non-standard and standard cosmology affects dark matter relic density.

Abstract

We show that the relic abundance of the minority component of asymmetric dark matter can be very sensitive to the expansion rate of the Universe and the temperature of transition between a non-standard pre-Big Bang Nucleosynthesis cosmological phase and the standard radiation dominated phase, if chemical decoupling happens before this transition. In particular, because the annihilation cross section of asymmetric dark matter is typically larger than that of symmetric dark matter in the standard cosmology, the decrease in relic density of the minority component in non-standard cosmologies with respect to the majority component may be compensated by the increase in annihilation cross section, so that the annihilation rate at present of asymmetric dark matter, contrary to general belief, could be larger than that of symmetric dark matter in the standard cosmology.