Concentrated Dark Matter: Enhanced Small-scale Structure from Co-Decaying Dark Matter

TL;DR

This paper explores how co-decaying dark matter causes an early matter-dominated phase, leading to enhanced small-scale structures like micro-halos, which could boost signals in indirect detection experiments.

Contribution

It introduces the cosmological implications of co-decaying dark matter, showing its potential to produce observable small-scale structures and impact indirect detection.

Findings

Early matter-dominated phase enhances small-scale perturbations

Small-scale structures like micro-halos can survive to present day

Boost factors for indirect detection experiments are significantly increased

Abstract

We study the cosmological consequences of co-decaying dark matter - a recently proposed mechanism for depleting the density of dark matter through the decay of nearly degenerate particles. A generic prediction of this framework is an early dark matter dominated phase in the history of the universe, that results in the enhanced growth of dark matter perturbations on small scales. We compute the duration of the early matter dominated phase and show that the perturbations are robust against washout from free-streaming. The enhanced small scale structure is expected to survive today in the form of compact micro-halos and can lead to significant boost factors for indirect detection experiments, such as FERMI, where dark matter would appear as point sources.