Searching for ultra-light dark matter through frequency modulation of gravitational waves

TL;DR

This paper investigates how ultra-light dark matter can cause frequency modulation in gravitational waves, proposing a method to detect such effects with future interferometers like the Einstein Telescope and Cosmic Explorer.

Contribution

It introduces a detailed analysis of frequency modulation effects caused by ultra-light dark matter on gravitational waves and evaluates the detection prospects with upcoming gravitational-wave observatories.

Findings

Detection of frequency modulation can constrain ultra-light dark matter properties.

Neutron star gravitational waves at the Galactic Centre are promising signals.

Future interferometers could significantly improve dark matter constraints.

Abstract

Ultra-light bosons, naturally appearing in well-motivated extensions to the Standard Model, can constitute all the dark matter. Models with particle mass close to the smallest phenomenologically allowed exhibit coherent field configurations at (sub)galactic scales, oscillating at a frequency corresponding to the fundamental mass of the dark matter particle. The gravitational field of these structures inherits the dark matter field's coherent oscillations, leaving an imprint on gravitational (and electromagnetic) waves sourced close to (or in) such overdensities. This happens via a heterodyning frequency modulation, which can later be decoded in a gravitational-wave detector. An analogous effect occurs in models with universal (conformal) couplings of ultra-light bosons with ordinary matter, generated by the direct interaction with the oscillating field. In this work, we explore this phenomenon in detail and assess the capability of near-future interferometers to probe ultra-light dark matter and its potential conformal couplings to matter. Using astrophysical population models, together with results from cosmological simulations, we find that the observation of gravitational waves from spinning neutron stars at the Galactic Centre with the Einstein Telescope/Cosmic Explorer would be particularly effective in constraining ultra-light dark matter.