Seasons of Dark Matter Freeze-In Shaped by the Weather of the Early Universe

TL;DR

This paper explores how different early universe conditions influence the phase-space distribution of freeze-in dark matter, affecting its properties and mass bounds.

Contribution

It introduces a framework to understand how pre-nucleosynthesis cosmological variations shape dark matter's momentum distribution and warmness.

Findings

Distinct cosmological histories produce unique dark matter momentum distributions.

Early universe composition significantly impacts the mass bounds of freeze-in dark matter.

The study maps the relationship between early universe conditions and dark matter phase-space properties.

Abstract

Quantifying the imprints of freeze-in dark matter (DM) on cosmological structures requires knowledge of its phase-space distribution. We investigate how variations in the cosmological history before nucleosynthesis, the "weather" of that epoch, give rise to distinct "seasons" in the DM momentum distribution that govern its warmness. Studying decay-driven production across diverse cosmological histories, we map how these conditions shape DM phase-space properties. Our study quantifies how the early universe composition plays a key role in determining the mass bound on freeze-in DM.