# Extreme Dark Matter Tests with Extreme Mass Ratio Inspirals

## TL;DR

Future space-based gravitational wave detectors like LISA could detect dark matter spikes around massive black holes via EMRI signals, providing new constraints on dark matter particle properties.

## Contribution

This paper demonstrates how EMRI gravitational wave signals can be used to test and constrain various dark matter models through their effects on dark matter spikes.

## Key findings

- Detection of dark matter spikes can constrain ultralight bosons and fermions.
- Gravitational wave signals can rule out certain self-annihilating dark matter models.
- Dark matter spikes influence EMRI waveforms, enabling particle property inference.

## Abstract

Future space-based laser interferometry experiments such as LISA are expected to detect $\cal O$(100--1000) stellar-mass compact objects (e.g., black holes, neutron stars) falling into massive black holes in the centers of galaxies, the so-called extreme-mass-ratio inspirals (EMRIs). If dark matter forms a "spike" due to the growth of the massive black hole, it will induce a gravitational drag on the inspiraling object, changing its orbit and gravitational-wave signal. We show that detection of even a single dark matter spike from the EMRIs will severely constrain several popular dark matter candidates, such as ultralight bosons, keV fermions, MeV--TeV self-annihilating dark matter, and sub-solar mass primordial black holes, as these candidates would flatten the spikes through various mechanisms. Future space gravitational wave experiments could thus have a significant impact on the particle identification of dark matter.