Challenging the Stability of Light Millicharged Dark Matter

TL;DR

This paper examines the stability of light millicharged bosonic dark matter, revealing that parametric resonance can cause fragmentation or destruction of dark matter in certain models, challenging its viability.

Contribution

It provides a detailed analysis of how parametric resonance impacts the stability of millicharged dark matter, especially in kinetic mixing scenarios.

Findings

Parametric resonance can fragment or destroy dark matter in kinetic mixing models.

Observational constraints are stronger than resonance effects for direct coupling cases.

Large regions of parameter space are affected by resonance, threatening dark matter stability.

Abstract

We investigate the cosmological stability of light bosonic dark matter carrying a tiny electric charge. In the wave-like regime of high occupation numbers, annihilation into gauge bosons can be drastically enhanced by parametric resonance. The millicharged particle can either be minimally coupled to photons or its electromagnetic interaction can be mediated via kinetic mixing with a massless hidden photon. In the case of a direct coupling current observational constraints on the millicharge are stronger than those arising from parametric resonance. For the (theoretically preferred) case of kinetic mixing large regions of parameter space are affected by the parametric resonance leading at least to a fragmentation of the dark matter field if not its outright destruction.