# Can black hole superradiance be induced by galactic plasmas?

## TL;DR

This paper explores how galactic plasmas can induce superradiant instabilities in spinning black holes, potentially leading to observable astrophysical phenomena like Fast Radio Bursts.

## Contribution

It demonstrates that galactic plasma environments can trigger superradiance in Kerr black holes, revealing a new astrophysical context for black hole instabilities.

## Key findings

- Galactic plasmas can induce superradiance in black holes with millisecond instability timescales.
- Photon clouds around black holes could contain significant mass, affecting their evolution.
- Potential link between superradiance and Fast Radio Bursts is discussed.

## Abstract

Highly spinning Kerr black holes with masses $M = 1 - 100\ M_{\odot}$ are subject to an efficient superradiant instability in the presence of bosons with masses $\mu \sim 10^{-10} - 10^{-12}\ {\rm eV}$. We observe that this matches the effective plasma-induced photon mass in diffuse galactic or intracluster environments ($\omega_{\rm pl} \sim 10^{-10} - 10^{-12}\ {\rm eV}$). This suggests that bare Kerr black holes within galactic or intracluster environments, possibly even including the ones produced in recently observed gravitational wave events, are unstable to formation of a photon cloud that may contain a significant fraction of the mass of the original black hole. At maximal efficiency, the instability timescale for a massive vector is milliseconds, potentially leading to a transient rate of energy extraction from a black hole in principle as large as $\sim 10^{55} \ {\rm erg \, s}^{-1}$. We discuss possible astrophysical effects this could give rise to, including a speculative connection to Fast Radio Bursts.