Liberating Energy from Black Holes: Jets, Bombs, and Gravitational Waves

Will East (Perimeter Institute) // July 5, 2018

Abstract: Rotating black holes have a large reservoir of energy which can be liberated to fuel powerful astrophysical events. This includes the Blandford-Znajek process, a mechanism for producing relativistic jets, and superradiance, a related process for waves. I will discuss these ways of tapping into a black hole’s rotational energy. I will focus on the exciting possibility that observations of astrophysical black holes can be used to probe the existence of new particles. In the presence of a massive bosonic field, a spinning black hole is in fact unstable to superradiance. This provides a novel way to look for axions, dark photons, and other ultralight bosons with Compton wavelength comparable to the black hole’s radius. I will describe black hole superradiance in the linear and nonlinear regimes, including how the superradiant instability saturates by slowing the rotation of the black hole to match the frequency of the bosonic cloud that spontaneously forms around it. I will also discuss how such bosonic clouds decay through the emission of gravitational radiation, which could be an interesting target for LIGO and other gravitational wave detectors.

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