Extracting Energy Via Magnetic Reconnection From Kerr-de Sitter Black Holes

Energy extraction from rotating black holes is a hot issue during the recent revival of black hole research with the influx of multimessenger observations and exascale nu-merical simulations of the black hole vicinity.Understanding how black holes lose energy is an important and popular problem in theoretical physics and astrophysics,and research on energy extraction from black holes will help to understand Einstein’s the-ory of gravity.In this thesis,we studied the conditions and parameter ranges of Kerr-de Sitter black hole energy extraction under the magnetic reconnection process,as well as the power and efficiency of Kerr-de Sitter black hole energy extraction and compared it with the energy extraction of a Kerr black hole under the magnetic reconnection pro-cess.First,the characteristics of Kerr-de Sitter black holes were studied,with a focus on their parameter range and some characteristic radius.Subsequently,the process of extracting energy from a Kerr-de Sitter black hole was analyzed using the magnetic reconnection mechanism.It was found that particles falling into the black hole with deceleration have negative energyε_-~∞<0,while particles accelerating away from the black hole have positive energyε_+~∞>0,relative to observers at infinity.Then,we used these two expressions to verify the conditions for extracting energy from black holes and explored the parameter range for energy extraction.We found that the range of black hole energy extraction does indeed fall within the ergospher,with the lower limit of the energy extraction parameter range given by the circular photon orbit.Finally,the impact of black hole spin,cosmological constant,plasma magnetization,orienta-tion angle of plasma particles,and the location of the reconnection region on magnetic reconnection processes were investigated using the black hole energy extraction evalu-ation method.The results show that with the increase of the cosmological constant,a slowly spinning Kerr-de Sitter black hole can implement the energy extraction 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 holes still have significant advantages when the black hole spin is larger than one and the dominant reconnection X-point is far away from the event horizon.This mainly due to the higher upper spin bound and wider ergosphere in the presence of the cosmological constant.These results uncover the significant effects of cosmological constant on the energy extraction via the magnetic reconnection process.