Gravitational-wave signatures of non-violent non-locality from the ringdown

Gravitational waves precisely probe the dynamical spacetime near compact objects. Motivated by the black hole information paradox, Giddings' non-violent non-locality posits order-unity, stochastic metric fluctuations at length scales ~GM/c^2 outside astrophysical black holes — in contrast to Planck-scale modifications at the horizon. In this talk, we will analyze how the ringdown gravitational waves are changed. The Zerilli equation can compute the modified gravitational waves by doing a multiscale expansion. We show that the deviations induced by non-violent non-locality can be understood as the background gravitational waves scatter off the random metric fluctuations. Our ringdown calculation complements prior inspiral-phase estimates for the non-violent non-locality, providing a unified framework for parameterizing and constraining it across the full signal. We conclude by discussing prospects for upper limits on metric fluctuations using LIGO or LISA detectors.