Stretched Horizon Dissipation and the Fate of Echoes

Abstract: We examine the dissipation of infalling particles near black holes under the assumption that the equivalence principle breaks down at the stretched horizon. This violation allows partial reflection of particles just outside the event horizon, as suggested by models such as the fuzzball and firewall proposals. We show that scattering with blue-shifted Hawking radiation leads to moderate dissipation when the particle energy is comparable to the Hawking temperature. The decay rate is independent of the Planck mass, and therefore gravitational wave echoes-arising from such partial reflection-may survive despite the presence of quantum gravitational effects. Our result is universal and does not rely on the detailed microphysics of the horizon.