New sources of gravitational wave signals: The black hole graviton laser

TL;DR

This paper proposes that black holes could act as natural graviton lasers, emitting coherent gravitational waves through superradiance with potential astrophysical implications and new gravitational wave sources.

Contribution

It introduces the novel idea that black holes and WISPs can enable natural graviton lasers, providing a new mechanism for gravitational wave emission.

Findings

Black holes can act as efficient graviton lasers.

Superradiance from Kerr black holes with WISPs can amplify gravitons.

Directed graviton laser beams may be astrophysically significant.

Abstract

A graviton laser works, in principle, by the stimulated emission of coherent gravitons from a lasing medium. For significant amplification, we must have a very long path length and/or very high densities. Black holes and the existence of weakly interacting sub-eV dark matter particles (WISPs) solve both of these obstacles. Orbiting trajectories for massless particles around black holes are well understood \cite{mtw} and allow for arbitrarily long graviton path lengths. Superradiance from Kerr black holes of WISPs can provide the sufficiently high density \cite{ABH}. This suggests that black holes can act as efficient graviton lasers. Thus directed graviton laser beams have been emitted since the beginning of the universe and give rise to new sources of gravitational wave signals. To be in the path of particularly harmfully amplified graviton death rays will not be pleasant.