Is the super-Penrose process possible near black holes?

TL;DR

This paper investigates the theoretical possibility of achieving unlimited energy extraction near extremal black holes through particle collisions, concluding that such super-Penrose processes cannot occur from finite-mass particle collisions.

Contribution

It demonstrates that the super-Penrose process cannot be realized from collisions involving particles with finite masses and angular momenta near extremal black holes.

Findings

Super-Penrose process is not feasible from finite-mass particle collisions.

Indefinitely large energy extraction cannot be achieved near extremal black holes.

Various collision scenarios do not produce states suitable for super-Penrose process.

Abstract

We consider collisions of particles near generic axially symmetric extremal black holes. We examine possibility of indefinitely large extraction of energy (the so-called super-Penrose process) in the limit when the point of collision approaches the horizon. Three potential options are considered (fractional powers of the lapse function in the relations between the energies and the angular momenta of particles in the point of collision), collision between outgoing particles and ingoing ones, collision in the ergoregion far from the horizon). It turns out in all three cases that states suitable for the super-Penrose process cannot be obtained from the previous collision of particles with finite masses and angular momenta.