Acoustically driven dark matter freeze-out

TL;DR

This paper investigates how density perturbations influence dark matter freeze-out, revealing that primordial curvature perturbations can significantly enhance the required annihilation cross section to match observed relic abundance, impacting indirect detection signals.

Contribution

It extends the thermal dark matter freeze-out model by incorporating density perturbations, showing their effect on relic abundance calculations and potential observational consequences.

Findings

Approximately 10% increase in annihilation cross section needed due to perturbations

Primordial curvature perturbations of about 0.2 at relevant scales influence freeze-out

Corrections are significant near resonance regions affecting detection prospects

Abstract

We extend the study of the effect of density perturbations to the well known thermal dark matter freeze-out scenario. We find $\sim 10 \, \%$ enhancements in the cross section are required to match onto the observed relic abundance for primordial curvature perturbations $\sim 0.2$ at length scales $\sim 1/$Hubble at freeze-out. Such corrections may be of importance in scenarios in which such perturbations are present and observational signals, such as the indirect detection rate, depend sensitively on the DM mass and freeze-out cross section, e.g. near resonances associated with DM bound states.