TAPIR Seminar

In person: 370 Cahill. To Join via Zoom: 851 0756 7442

Abstract: Trapping is one of the most striking features of wave propagation in strong gravity, and it can shape physics in dramatically different ways. In this talk, I will explore two such manifestations. On the one hand, unstable trapping at the photon sphere of a black hole controls the structure of photon rings, whose characterization can provide direct information about the spacetime and, in particular, the spin of black holes through horizon-scale imaging. On the other hand, stable trapping can lead to long-lived perturbations and turbulent dynamics. By studying scalar waves on a fixed background with stable trapping, I will discuss how gravitational turbulence can develop and what this may teach us about the nonlinear stability of exotic compact objects and higher-dimensional spacetimes. These two scenarios illustrate how the properties of trapped waves can reveal both observable signatures of astrophysical black holes and fundamental properties of gravitational dynamics.