Inflationary Particle Production and Implications for WIMP Substructure

TL;DR

This paper investigates how resonant particle production during inflation can create small-scale dark matter structures, which enhance annihilation signals detectable by gamma-ray telescopes, linking early universe physics with current observations.

Contribution

It introduces a novel connection between inflationary particle production and small-scale dark matter structure formation, providing new observational constraints on dark matter annihilation.

Findings

Enhanced small-scale dark matter structures due to inflationary particle production.

Upper limits on dark matter annihilation cross section from Fermi-LAT data.

Potential gamma-ray signatures of early universe processes.

Abstract

We explore the observational consequences of resonant particle production during inflation, focusing on its impact on dark matter annihilation signals today. A transient burst of particle production generates localised features in the primordial power spectrum, enhancing the formation of compact small-scale dark matter structures known as prompt cusps. If dark matter consists of thermal WIMPs, the resulting small-scale structures substantially boost annihilation rates, leaving potentially detectable imprints in gamma-ray observations. Using 15 years of Fermi-LAT data targeting the Virgo cluster, we derive upper limits on the thermally averaged annihilation cross section $\langle \sigma v \rangle$, connecting inflationary particle production in the early universe with present-day observations constraining dark matter annihilation.