Catastrophic Emission of Charges from Near-Extremal Charged Nariai Black Holes. II. Rotation Effect
Kerr-Newman black holes in a de Sitter (dS) space have the limit of rotating Nariai black holes with the near-horizon geometry of a warped ${\rm dS}_3 \times {\rm S}^1/Z_2$ when the black hole horizon and the cosmological horizon coincide or approach close to each other. We study the rotation effect on the spontaneous emission of charges in the near-extremal rotating charged Nariai black hole and compare it to those from the near-extremal Nariai black hole in Phys. Rev. D \textbf{110}, 085020 (2024) and near-extremal Kerr-Newman black hole in de Sitter space in Eur. Phys. J. C \textbf{83}, 219 (2023). In strong contrast to the near-extremal Kerr-Newman black hole in dS space, the near-extremal rotating Nariai black hole also has an exponential amplification for the emission of high energy charges, which becomes catastrophic regardless of angular momentum when two horizons coincide. The radius of rotating Nariai black holes monotonically increases as the angular momentum and charge of black holes increase, which gives a weaker electric field on the horizon than Nariai black holes. Thus the angular momentum of black holes that drags particles on the horizon decreases the mean number of charges by a factor not by an order. We observe a catastrophic emission of boson condensation for charges with an effective energy equal to the chemical potential in the spacelike outer region of the cosmological horizon. Remarkably, the Schwinger emission of charges in the standard particle model may prevent the rotating Nariai black holes from evolving into spacetimes with a naked singularity when the angular momentum is close to the allowed maximum, which Nariai black holes cannot avoid.