Gravitational dynamics of near-extreme Kerr (Anti-)de Sitter black holes (2505.02674v1)

Abstract: We analyze the thermodynamic response near extremality of black holes with angular momentum in (3+1)-dimensional de Sitter and Anti-de Sitter spacetimes. While Kerr-AdS$_4$ is characterized by a single extremal limit, for Kerr-dS$_4$ there are three different extremal scenarios (Cold, Nariai and Ultracold). These exhibit different near horizon geometries, with AdS$_2$, dS$_2$ and Mink$_2$ factors respectively. We analyze each extremal case and contrast the response once the black holes are taken out of extremality. We study the perturbations of the near horizon geometry at the level of the 4D metric, considering a consistent truncation for the metric fluctuations, and find solutions to the linearized Einstein equations. We characterize the perturbations that are responsible for the deviations away from extremality and show that their dynamics is governed by a Schwarzian theory. We treat the Ultracold case separately, detailing how the thermodynamics in 4D is reflected in the near horizon dynamics.