Faculty Publications
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Item Microstructure of five-dimensional neutral Gauss–Bonnet black hole in anti-de Sitter spacetime via P- V criticality(Springer, 2023) Naveena Kumara, A.N.; Ahmed Rizwan, C.L.A.; Hegde, K.; Ali, M.S.; Ajith, K.M.In this article, we analytically investigate the microstructure of a five-dimensional neutral Gauss–Bonnet black hole, in the background of anti-de Sitter spacetime, by using the scalar curvature of the Ruppeiner geometry constructed via adiabatic compressibility. The microstructure details associated with the small-large black hole phase transition are probed in the parameter space of pressure and volume. The curvature scalar shows similar properties for both phases of the black hole, it diverges at the critical point with a critical exponent 2, and approaches zero for extremal black holes. We show that the dominant interaction among black hole molecules is attractive. This study also confirms that the nature of the microstructure interaction remains unchanged during the small-large black hole phase transition, even though the microstructures are different for both phases. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Item Thermodynamics, phase transition and Joule Thomson expansion of 4-D GaussBonnet AdS black hole(World Scientific, 2024) Hegde, K.; Ahmed Rizwan, C.L.A.; Ajith, K.M.; Naveena Kumara, A.N.; Ali, M.S.; Punacha, S.In this paper, we explore the thermodynamic and phase transition properties of asymptotically AdS black holes within Einstein Gauss Bonnet gravity, focusing on Joule{Thomson expansion. Thermodynamics is studied in the extended phase space, where the cosmological constant serves as thermodynamic pressure. We observe that the black hole undergoes a phase transition similar to that of a van der Waals system. We analyze charged and neutral cases separately to distinguish the effect of charge and Gauss{Bonnet parameter on critical behavior and examine the phase structure. We find that the Gauss Bonnet coupling parameter behaves similarly to black hole charge or spin, guiding the phase structure. To understand the underlying phase structure determined by the Gauss Bonnet coefficient, we introduce a new order parameter. We discover that the change in the conjugate variable to the Gauss Bonnet parameter acts as an order parameter, demonstrating a critical exponent of 1=2 in the vicinity of the critical point. Since the phase structure is analogous to that of a van der Waals °uid, we investigate the Joule Thomson expansion of the black hole. We analytically study the Joule Thomson expansion, focusing on three key characteristics: the Joule{Thomson coefficient, inversion curves and isenthalpic curves. We obtain isenthalpic curves in the T P plane and illustrate the cooling{heating regions. © 2024 World Scientific Publishing Company.Item Thermodynamics, photon sphere and thermodynamic geometry of Ayón-Beato-Garcia space-time(World Scientific, 2025) Hegde, K.; Naveena Kumara, A.N.; Ajith, K.M.; Ahmed Rizwan, C.L.A.; Ali, M.S.; Punacha, S.We study the thermodynamics of the Ayón-Beato-García black hole and the relationship between photon orbits and the thermodynamic phase transitions of the black hole in AdS space-time. We then examine the interactions between the microstructures of the black hole using Ruppeiner geometry. The radius of the photon orbit and the minimum impact parameter behave nonmonotonically below the critical point, mimicking the behavior of Hawking temperature and pressure in extended thermodynamics. Their changes during the large black hole-small black hole phase transition serve as the order parameter, possessing a critical exponent of 1=2. The results demonstrate that the gravity and thermodynamics of the Ayón-Beato-García black hole are closely related. Furthermore, we explore the thermodynamic geometry, which provides insight into the microstructure interactions of the black hole. We find that the large black hole phase is analogous to a bosonic gas with a dominant attractive interaction, while the small black hole phase behaves like an anyonic gas with both attractive and repulsive interactions. © 2025 World Scientific Publishing Company.