Enhanced Small-Scale Structure in the Cosmic Dark Ages

TL;DR

This paper explores how a rising small-scale matter power spectrum, influenced by dark matter microphysics, leads to early nonlinear structure formation, increased dark matter annihilation, and earlier star formation in the universe.

Contribution

It demonstrates that microphysical effects can significantly enhance small-scale dark matter structures and early star formation, providing new insights into the dark ages.

Findings

Nonlinear structures form abundantly at high redshifts.

Dark matter annihilation is substantially increased after matter-radiation equality.

First star forming halos may form earlier than in standard models.

Abstract

We consider the consequences of a matter power spectrum which rises on small scales until eventually being cutoff by microphysical processes associated with the particle nature of dark matter. Evolving the perturbations of a weakly interacting massive particle from before decoupling until deep in the nonlinear regime, we show that nonlinear structure can form abundantly at very high redshifts. In such a scenario, dark matter annihilation is substantially increased after matter-radiation equality. Furthermore, since the power spectrum can be increased over a broad range of scales, the first star forming halos may form earlier than usual as well. The next challenge is determining how early Universe observations may constrain such enhanced dark matter perturbations.