Energy extraction from the Reissner-Nordstr\"om de Sitter black hole

TL;DR

This paper investigates the conditions and efficiency of energy extraction from Reissner-Nordström de Sitter black holes via charged particle decay, highlighting the roles of ergospheres and optimal parameters.

Contribution

It provides a general expression for extraction efficiency and analyzes specific cases, including the influence of cosmological horizons on energy extraction.

Findings

Energy extraction is possible in regions defined by ergospheres.

Efficiency can be maximized and is consistent across different breakup points.

Connected ergospheres enable extraction at any point near the black hole.

Abstract

The energy extraction from an electrostatic black hole by the decay or splitting of electrically charged particles is analyzed. We determine the energetic conditions that make the extraction process viable and present a general expression for the efficiency in terms of the parameters of the electrostatic black hole and the decaying particles. We also examine the conditions that optimize the efficiency of the extraction process. We analyze two particular cases, the first one is the extraction process from a Reissner Nordstr\"om black hole, for charged test particles with nonvanishing angular momentum; the second one and more interesting corresponds to the energy extraction from a Reissner Nordstr\"om de Sitter black hole. For the latter there are two regions where the energy extraction is possible, the generalized ergosphere and a cosmological ergosphere induced by the cosmological horizon. Under certain conditions the two ergospheres get connected and cover the whole region between the event horizon and the cosmological horizon, and therefore the energy extraction is possible at any point in the vicinity of the black hole. Moreover, the efficiency of the energy extraction can be the same for different break up points and also there is the possibility of a different efficiency for the same break up point. The conditions that maximize the efficiency are determined as well.