Maximum efficiency of the collisional Penrose process

Abstract

We consider collision of two particles that move in the equatorial plane near a general stationary rotating axially symmetric extremal black hole. One of particles is critical (with fine-tuned parameters) and moves in the outward direction. The second particle (usual, not fine-tuned) comes from infinity. We examine the efficiency $\eta$ of the collisional Penrose process. There are two relevant cases here: (i) a particle falling into a black hole after collision is heavy, (ii) it has a finite mass. We show that the maximum of $\eta$ in case (ii) is less or equal to that in case (i). It is argued that for superheavy particles, the bound applies to nonequatorial motion as well. As an example, we analyze collision in the Kerr-Newman background. When the bound is the same for processes (i) and (ii), $\eta =3$ for this metric. For the Kerr black hole, recent results in literature are reproduced.

18 pages. Typos corrected. Title somewhat modified according to suggestions of editors of PRD

References in corpus (7)

• Collisional Penrose process near the horizon of extreme Kerr black holes
• Revised upper limit to energy extraction from a Kerr black hole
• Ultra-high-energy debris from the collisional Penrose process
• Are black holes totally black?
• Super-Penrose collisions are inefficient - a Comment on: Black hole fireworks: ultra-high-energy debris from super-Penrose collisions
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Cited by in corpus (2)

• Fifty years of energy extraction from rotating black hole: revisiting magnetic Penrose process
• The Collisional Penrose Process