Super-Penrose process due to collisions inside ergosphere

TL;DR

This paper demonstrates that collisions inside the ergosphere can produce unbounded energy at infinity, enabling a super-Penrose process without needing to occur near the black hole horizon.

Contribution

It shows that unbounded energy extraction via the super-Penrose process is possible inside the ergosphere without proximity to the horizon, expanding previous understanding.

Findings

Unbounded Killing energy can be achieved inside the ergosphere.

Large negative angular momentum of particles facilitates energy extraction.

Proximity to the horizon is not necessary for the super-Penrose process.

Abstract

If two particles collide inside the ergosphere, the energy in the centre of mass frame can be made unbound provided at least one of particles has a large negative angular momentum (A. A. Grib and Yu. V. Pavlov, Europhys. Lett. 101, 20004 (2013)). We show that the same condition can give rise to unbounded Killing energy of debris at infinity, i.e. super-Penrose process. Proximity of the point of collision to the black hole horizon is not required.