Penrose and super-Penrose energy extraction from a Reissner-Nordstr\"om black hole spacetime with a cosmological constant through the BSW mechanism: Full story

TL;DR

This paper investigates energy extraction from extremal Reissner-Nordström black holes with various cosmological constants using the Penrose and BSW mechanisms, revealing conditions for super-Penrose processes and effects of spacetime asymptotics.

Contribution

It provides a detailed analysis of energy extraction via collisional Penrose processes in higher-dimensional black holes with different cosmological constants, highlighting the possibility of super-Penrose processes.

Findings

Energy of particle 3 can be arbitrarily high but finite.

Particle 4 has negative energy within its ergosphere.

Results vary with cosmological constant and number of dimensions.

Abstract

The Penrose process, a process that transfers energy from a black hole to infinity, together with the BSW mechanism, which uses collisions of ingoing particles at the event horizon of a black hole to locally produce large amounts of energy, is studied in a combined description for a $d$ dimensional extremal Reissner-Nordstr\"om black hole spacetime with negative, zero, or positive cosmological constant, i.e., for an asymptotically anti-de Sitter (AdS), flat, or de Sitter (dS) spacetime. In an extremal Reissner-Nordstr\"om black hole background, in the vicinity of the horizon, several types of radial collisions between electrically charged particles can be considered. The most interesting one is between a critical particle, with its electric charge adjusted in a specific way, and a usual particle, as it gives a divergent center of mass frame energy locally, this being a favorable but not sufficient condition to extract energy from the black hole. To understand whether energy can be extracted in such a collisional Penrose process, we investigate in detail a collision between ingoing particles 1 and 2, from which particles 3 and 4 emerge, with the possibility that particle 3 can carry energy far out from the black hole horizon. One finds that the mass, energy, electric charge, and initial direction of motion of particle 3 can have different values, depending on the collision internal process, but these values lie within some range. Moreover, the energy of particle 3 can be arbitrarily high but not infinite, characterizing a super-Penrose process. It is also shown that particle 4 has negative energy, living in its own electric ergosphere before being engulfed by the event horizon. For zero cosmological constant the results do not depend on the number of dimensions, but they do for nonzero cosmological constant, which also introduces differences in the lower bound for the energy extracted.