Parametric Resonance Production of Ultralight Vector Dark Matter

TL;DR

This paper demonstrates that ultralight vector dark matter can be efficiently produced via parametric resonance from a dark Higgs field after inflation, allowing for a broad viable mass range and motivating experimental searches.

Contribution

It introduces a natural production mechanism for ultralight vector dark matter involving parametric resonance from a dark Higgs field, with detailed analysis of transverse and longitudinal components.

Findings

Vector mass can be as low as 10^{-18} eV and still account for dark matter.

The production mechanism is efficient if the dark Higgs has a large post-inflation field value.

The resulting spectra and abundance depend on detailed dynamics of vector components.

Abstract

Vector bosons heavier than $10^{-22}$ eV can be viable dark matter candidates with distinctive experimental signatures. Ultralight dark matter generally requires a non-thermal origin to achieve the observed density, while still behaving like a pressureless fluid at late times. We show that such a production mechanism naturally occurs for vectors whose mass originates from a dark Higgs. If the dark Higgs has a large field value after inflation, the energy in the Higgs field can be efficiently transferred to vectors through parametric resonance. Computing the resulting abundance and spectra requires careful treatment of the transverse and longitudinal components, whose dynamics are governed by distinct differential equations. We study these equations in detail and find that the mass of the vector may be as low as $10 ^{ - 18 }$ eV, while making up the dominant dark matter abundance. This opens up a wide mass range of vector dark matter as cosmologically viable, further motivating their experimental search.