Black-hole hair from vector dark matter accretion

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Hauptverfasser: Hancock, Fredric, Witek, Helvi
Format: Preprint
Veröffentlicht: 2025
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author Hancock, Fredric
Witek, Helvi
author_facet Hancock, Fredric
Witek, Helvi
contents We model a single black hole in equilibrium with a dark photon-cold dark matter environment. Representing the dark photon as a Proca field, we show that a Schwarzschild black hole grows vector-field "hair" when allowed to accrete from an infinite homogeneous bath of particles far from the horizon. We solve the Proca equation in linear perturbation theory, separating it using the vector spherical harmonics and Frolov-Krtouš-Kubizňák-Santos approaches for the odd-parity and even-parity sectors, respectively. In the "particle" dark matter regime, the field is purely infalling and exhibits a sharply peaked density profile, in concordance with the particle dark matter "spikes" studied in the literature. In the "wave" regime, the field exhibits standing waves, and the profile is smeared. We find a dark-matter density amplification upward of $10^7$ near the horizon. Though small for most black holes, we find the mass enclosed in the cloud can reach $\sim 1 \%$ of the black hole mass for large supermassive black holes. These black holes are also most susceptible to vector dark matter accretion, with mass accretion rates as large as $10 M_\odot/$yr.
format Preprint
id arxiv_https___arxiv_org_abs_2506_06554
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Black-hole hair from vector dark matter accretion
Hancock, Fredric
Witek, Helvi
General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
High Energy Physics - Theory
We model a single black hole in equilibrium with a dark photon-cold dark matter environment. Representing the dark photon as a Proca field, we show that a Schwarzschild black hole grows vector-field "hair" when allowed to accrete from an infinite homogeneous bath of particles far from the horizon. We solve the Proca equation in linear perturbation theory, separating it using the vector spherical harmonics and Frolov-Krtouš-Kubizňák-Santos approaches for the odd-parity and even-parity sectors, respectively. In the "particle" dark matter regime, the field is purely infalling and exhibits a sharply peaked density profile, in concordance with the particle dark matter "spikes" studied in the literature. In the "wave" regime, the field exhibits standing waves, and the profile is smeared. We find a dark-matter density amplification upward of $10^7$ near the horizon. Though small for most black holes, we find the mass enclosed in the cloud can reach $\sim 1 \%$ of the black hole mass for large supermassive black holes. These black holes are also most susceptible to vector dark matter accretion, with mass accretion rates as large as $10 M_\odot/$yr.
title Black-hole hair from vector dark matter accretion
topic General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
High Energy Physics - Theory
url https://arxiv.org/abs/2506.06554