Unbound geodesics from the ergosphere and potential observability of debris from ultrahigh energy particle collisions

Abstract

Particle collisions in black hole ergoregions may result in extremely high center-of-mass energies that could probe new physics if escape to infinity were possible. Here we show that some geodesics at high inclinations to the equatorial plane may be unbound. Hence a finite flux of annihilation debris is able to escape, especially in the case of near-extremal Kerr black holes and if the Penrose process plays a role. For a class of Penrose processes, we show that the Wald inequalities are satisfied, allowing the Penrose process to have a key role in high-energy ejection. Hence the possibility of observing new physics effects from a black hole accelerator at unprecedentedly high particle collision energies remains a tantalizing, if futuristic, experimental vision.