Phase transitions and thermodynamic geometry of a Kerr–Newman black hole in a cavity
Center for Theoretical Physics, College of Physics, Sichuan University, 610065, Chengdu, China
2 Department of Astronomy, School of Physical Sciences, University of Science and Technology of China, 230026, Hefei, China
3 Department of Physics, Chongqing University, 401331, Chongqing, China
Accepted: 3 March 2023
Published online: 23 March 2023
Being placed in a cavity is an effective way of reaching thermodynamic equilibrium for black holes. We investigate a Kerr–Newman black hole in a cavity as well as compare it with two reduced cases, i.e., a RN black hole in a cavity and a Kerr black hole in a cavity. We derive the quasi-local energy from the Hamiltonian, and construct the first law of thermodynamics accordingly. In a canonical ensemble, these black holes could undergo a van der Waals-like phase transition, which is very similar to that in AdS space. We further investigate the black holes’ thermodynamic geometry, which is a powerful tool to diagnose microscopic interactions of a thermodynamic system. Our results show that in a cavity, although phase structures of these black holes are similar, their thermodynamic geometry show strong dissimilarities, implying that the microstructure of a black hole is sensitive to its states.
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