Repetitive Penrose process in Kerr-de Sitter black holes

TL;DR

This paper investigates the repetitive Penrose process in Kerr-de Sitter black holes, revealing the influence of the cosmological parameter on energy extraction efficiency and suggesting a thermodynamics-like law for the process.

Contribution

It introduces the study of the repetitive Penrose process in Kerr-de Sitter black holes and analyzes how the cosmological parameter affects energy extraction and efficiency.

Findings

Kerr-dS black holes have higher EROI and single-extraction energy capability than Kerr black holes.

Larger cosmological parameters increase EROI and single-extraction energy capability.

Energy utilization efficiency varies with decay radius and black hole type.

Abstract

Recently, references [1,2] found that the repetitive Penrose process cannot extract all the extractable rotational energy of a Kerr black hole, and reference [3] found that the repetitive electric Penrose process cannot extract all the electrical energy of a Reissner-Nordstr\"om (RN) black hole. This suggests that a law analogous to the third law of thermodynamics exists for the repetitive Penrose process. In this paper, we intend to study the repetitive Penrose process in the Kerr-de Sitter (Kerr-dS) black hole. We will explore influences of the cosmological parameter on the repetitive Penrose process. The results show that, in addition to a similar third law of thermodynamics, the Kerr-dS black hole yields a higher energy return on investment (EROI) and single-extraction energy capability compared to the Kerr black hole. Specifically, the larger the cosmological parameter, the stronger the EROI and the single-extraction energy capability. Furthermore, we also find that at a lower decay radius, the Kerr black hole exhibits a higher energy utilization efficiency (EUE) and more extracted energy after the repetitive Penrose process is completed. However, at a higher decay radius, the situation is reversed, i.e., the Kerr-dS black hole exhibits a higher EUE and more extracted energy, which is due to the existence of stopping condition of the iteration.