Extracting energy via magnetic reconnection from Kerr-de Sitter black holes

Abstract: It has been recently shown that magnetic reconnection can provide us a novel mechanism to extract black hole rotational energy from a Kerr black holes. In this paper, we study the energy extraction from the Kerr-de Sitter black hole via this magnetic reconnection process. The result shows that, with the increase of the cosmological constant, a slowly spinning Kerr-de Sitter black hole can implement the energy extraction better than its Kerr counterpart. Interestingly, although the numerical results show that the maximum values of the power and efficiency slightly decrease with the cosmological constant, Kerr-de Sitter black hole still has significant advantages when the black hole spin is larger than 1 and the dominant reconnection $X$-point is far away from the event horizon. This is mainly attributed to the higher upper spin bound and wider ergosphere in the presence of the cosmological constant. These results uncover the significant effects of the cosmological constant on the energy extraction via the magnetic reconnection process.