Gravity Seminar: The calm after the storm: the black hole ringdown beyond linear perturbation theory, Laura Sberna, AEI

When a binary merges to form a single black hole, the merger product emits a final burst of gravitational waves known as the “ringdown”. Ringdowns are currently being observed with LIGO and Virgo, and will be even stronger in future detectors like the Einstein Telescope or LISA. Observations of black hole ringdowns can be used to characterize binary merger remnants, and are particularly suited to test general relativity.

So far, analyses of the ringdown have assumed linear black hole perturbation theory. In this talk, I will explore nonlinear effects during the ringdown, which could potentially spoil (or enhance) ringdown analysis. I will focus on one nonlinear process, which we call “absorption-induced mode excitation” or AIME.  I will use numerical and analytic techniques to explore this process first in a toy model in anti-de Sitter, and then in asymptotically-flat Schwarzschild black holes. Our results so far indicate that nonlinear effects could play a role in the interpretation of current and future gravitational wave observations.