Self-interacting Dark Matter from Primordial Black Holes

TL;DR

This paper explores how primordial black holes can produce dark matter and how thermalization processes in the dark sector can significantly increase dark matter abundance, affecting constraints on dark matter properties.

Contribution

It provides a model-independent estimate of dark matter boost from PBH evaporation considering thermalization effects, impacting dark matter abundance and mass constraints.

Findings

Dark matter abundance can be enhanced by thermalization effects.

Smaller initial PBH densities are needed to produce observed dark matter.

Light dark matter in the keV range becomes viable due to thermalization.

Abstract

The evaporation of primordial black holes (PBH) with masses ranging from $\sim 10^{-1}$ to $\sim 10^9$ g could have generated the whole observed dark matter (DM) relic density. It is typically assumed that after being produced, its abundance freezes and remains constant. However, thermalization and number-changing processes in the dark sector can have a strong impact, in particular enhancing the DM population by several orders of magnitude. Here we estimate the boost from general arguments such as the conservation of energy and entropy, independently from the underlying particle physics details of the dark sector. Two main consequences can be highlighted: $i)$ As the DM abundance is increased, a smaller initial energy density of PBHs is required. $ii)$ Thermalization in the dark sector decreases the mean DM kinetic energy, relaxing the bound from structure formation and hence, allowing light DM with mass in the keV ballpark.