Speaker
Description
Black hole spectroscopy is a central part of testing gravity in the strong-field regime and plays a key role in gravitational wave astronomy. With the next generation of detectors, we have a unique opportunity to test modifications of General Relativity (GR). This motivates a timely question from an effective field theory perspective: where are higher-derivative corrections most strongly amplified, while the expansion itself remains reliable? In this talk, I will show that this question can be answered by investigating the quasinormal modes of highly-spinning (i.e. near extremal) black holes. I will show how perturbatively-small higher-derivative corrections to the Einstein-Hilbert action can lead to order-one modifications of the quasinormal mode spectrum of near-extremal Kerr black holes. These effects originate from shifts in the critical point controlling the bifurcation structure of Kerr quasinormal modes, which reorganizes the spectrum and changes the number between zero-damped and damped modes. We show that these large effects can take place in a regime in which the higher-derivative expansion remains under control.