The Irreversible Depletion of Dark Matter Spikes by Extreme-Mass-Ratio Inspirals

@misc{sharpe2026irreversible,
  title = {{The Irreversible Depletion of Dark Matter Spikes by Extreme-Mass-Ratio Inspirals}},
  author = {Charlie Sharpe and Yonadav Barry Ginat and Thomas F. M. Spieksma and Alexander Heger and Bence Kocsis},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.37234},
  eprint = {2609.37234},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.37234},
}

TY  - UNPB
TI  - The Irreversible Depletion of Dark Matter Spikes by Extreme-Mass-Ratio Inspirals
AU  - Charlie Sharpe
AU  - Yonadav Barry Ginat
AU  - Thomas F. M. Spieksma
AU  - Alexander Heger
AU  - Bence Kocsis
PY  - 2026
DA  - 2026/09/29
PB  - arXiv
DO  - 10.48550/arxiv.2609.37234
UR  - https://arxiv.org/abs/2609.37234
AB  - Dense dark matter spikes around massive black holes (MBHs) have been widely predicted to produce gravitational-wave dephasing in extreme-mass-ratio inspirals (EMRIs) that are potentially observable by LISA. We show that EMRIs, the very objects used to probe these spikes, also destroy them. Combining Fokker-Planck models of nuclear star clusters with post-Newtonian three-body simulations of EMRI-dark matter encounters, we demonstrate that repeated gravitational slingshots irreversibly eject dark matter particles from the cluster's loss cone over gigayear time-scales. For MBHs at z = 3 with masses ≲ 10^5 M_⊙, even conservative EMRI rates of 𝒪(1−10) Gyr^−1 suffice to deplete the spike density by orders of magnitude; for more realistic rates of 𝒪(100−300) Gyr^−1, the mass range extends to ≲ 10^6 M_⊙. As a result, the gravitational-wave dephasing expected from such systems is greatly reduced, narrowing the prospects of detecting DM through this channel. Only heavy, high-redshift systems with sufficiently low EMRI rates -- for example, a ∼ 10^6 M_⊙ MBH at z ≳ 5 with ≲ 100 EMRIs per Gyr -- can induce dephasing that exceeds one radian.
ER  -