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

TL;DR

This paper investigates the conditions under which particles and debris resulting from ultrahigh energy collisions near black hole ergospheres can escape to infinity, highlighting potential observational signatures of new physics.

Contribution

It demonstrates that certain high-inclination geodesics are unbound, enabling debris escape, and shows that Penrose processes can facilitate high-energy ejections in near-extremal Kerr black holes.

Findings

Unbound geodesics at high inclinations allow debris escape.

Penrose process can produce high-energy ejections consistent with Wald inequalities.

Potential observability of new physics effects from black hole 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.