Massive Boson Superradiant Instability of Black Holes: Nonlinear Growth, Saturation, and Gravitational Radiation

TL;DR

This study investigates the nonlinear development of superradiant instability caused by a massive boson around a rapidly spinning black hole, revealing efficient energy extraction and gravitational wave emission.

Contribution

First full general relativity simulation of boson superradiance without symmetry assumptions, showing nonlinear growth, saturation, and gravitational radiation.

Findings

Superradiant instability can spin down black holes significantly.

A large fraction of rotational energy is converted into gravitational waves.

Nonlinear effects are crucial in the evolution of the boson cloud.

Abstract

We study the superradiant instability of a massive boson around a spinning black hole in full general relativity without assuming spatial symmetries. We focus on the case of a rapidly spinning black hole in the presence of a vector boson with a Compton wavelength comparable to the black hole radius, which is the regime where relativistic effects are maximized. We follow the growth of the boson cloud through superradiance into the nonlinear regime as it spins down the black hole, reaches a maximum energy, and begins to dissipate through the emission of gravitational waves. We find that the superradiant instability can efficiently convert a significant fraction of a black hole's rotational energy into gravitational radiation.