Black hole ringdown in higher-derivative gravity

by Dr Pablo Cano (ICC, University of Barcelona)

Monday Feb 24, 2025, 2:00 PM → 3:00 PM Europe/Rome

Aula Galileo

After a perturbation, black holes emit gravitational radiation of certain characteristic frequencies corresponding to their quasinormal modes (QNMs). These modes depend on the underlying gravitational dynamics and hence their observation in gravitational wave detectors provides an excellent test for deviations of Einstein gravity. In the case of Kerr black holes in General Relativity (GR), the study of QNMs is made possible by the Teukolsky equation. However, the study of perturbations of rotating black holes in theories beyond GR is a very challenging problem. In this talk I will present a resolution to this problem by introducing  a "universal" Teukolsky equation that holds in modifications of GR. I will use this equation to obtain the QNM frequencies of black holes with substantial angular momentum in higher-derivative extensions of GR. I will also identify a special theory that preserves the isospectrality of QNMs in the eikonal limit. Using the connection between QNMs and modified null geodesics, I will obtain the QNMs of this theory for arbitrary values of the angular momentum, unveiling interesting behavior near extremality.