We discuss the prospects for constraining dark matter models with an EMRI-based dark matter spike measurement. In particular, many of the standard dark matter models predict the destruction or smoothening of the dark matter spike. That is, these dark matter models could not produce a dark matter spike detection through an EMRI.
We turn the problem around: Given that we have detected a dark matter spike through an EMRI measurement, can we constrain the common dark matter models?
As a proof-of-principle, 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.