2025/08/05 by Tiwari, Avinash, Chanda, Prolay, Kapadia, Shasvath J. +3 · 1 citation
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #High Energy Physics - Phenomenology (hep-ph)
paper · doi:10.48550/arxiv.2508.03803
Dark matter halos can develop a density spike, e.g., around a galactic supermassive black hole, with the profile ρ∝ r^-γ\rm sp determined both by the galaxy's formation history and the microphysics of dark matter. We show that future LISA/DECIGO observations, of intermediate/stellar-mass binary mergers inside the spike around the supermassive black hole, can measure γ\rm sp at a few-percent--level precision. The spike induces a distinctive time-dependent acceleration along the non-circular orbit taken by the binary's center of mass, which is observable as a secular modulation of the gravitational wave signal. This method -- insensitive to confounding astrophysical effects (dynamical friction, tidal effects, etc.) and not reliant on unknown dark matter particle physics -- provides a clean diagnostic of density spikes and a new probe of dark matter.