Faculty Publications
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Item Repulsive interactions in the microstructure of regular Hayward black hole in anti-de Sitter spacetime(Elsevier B.V., 2020) Naveena Kumara, A.N.; Ahmed Rizwan, C.L.A.; Hegde, K.; Ajith, K.M.We study the interaction between the microstructures of Hayward-AdS black hole using Ruppeiner geometry. Our investigation shows that the dominant interaction between the black hole molecules is attractive in most part of the parametric space of temperature and volume, as in van der Waals system. However, in contrast to the van der Waals fluid, there exists a weak dominant repulsive interaction for small black hole phase in some parameter range. This result clearly distinguishes the interactions in a magnetically charged black hole from that of van der Waals fluid. However, these sort of interactions are characteristic for charged black holes since they do not dependent on magnetic charge or temperature. © 2020 The Author(s)Item Coexistent physics and microstructure of the regular Bardeen black hole in anti-de Sitter spacetime(Academic Press Inc. apjcs@harcourtbrace.com, 2020) Ahmed Rizwan, C.L.A.; Naveena Kumara, A.N.; Hegde, K.; Vaid, D.We study the phase structure and the microscopic interactions of a regular Bardeen–AdS black hole. The stable and metastable phases in the black hole are analysed through coexistence and spinodal curves. The solutions are obtained numerically as the analytic solution to the coexistence curve is not feasible. The Pr?Tr coexistence equation is obtained using a fitting formula. The coexistence and spinodal curves are plotted in Pr?Tr and Tr?Vr planes to explore the phase structure of the black hole. In the second part of our study, we were able to probe the microscopic interactions of the regular Bardeen–AdS black hole using the novel Ruppeiner geometry proposed by Wei et al. (2019). It is found that the microscopic interactions are not the same in small black hole (SBH) and large black hole (LBH) phases. In the SBH phase, there exists a repulsive interaction in the microstructure in the low temperature regime. In contrast, the microstructure associated with the LBH phase has an attractive interaction throughout the parameter space. We found that, along the coexistence temperature, both the SBH and LBH branches diverge to negative infinity with a critical exponent equal to 1?2. © 2020 Elsevier Inc.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 Dynamics and kinetics of phase transition for regular AdS black holes in general relativity coupled to nonlinear electrodynamics(World Scientific, 2023) Naveena Kumara, A.N.; Punacha, S.; Hegde, K.; Ahmed Rizwan, C.L.A.; Ajith, K.M.; Ali, M.S.We study the stochastic dynamics and kinetics of the phase transition of the regular black holes in Anti-de Sitter spacetime by employing the free energy landscape. Our investigation focuses on two important classes of regular black hole solutions, namely the Hayward and Bardeen, which can be obtained from coupling of non-linear electrodynamics. The dynamics of the phase transition is described by the Fokker-Planck equation, using which, we investigate the probabilistic evolution of regular AdS black holes. We solve this equation numerically by imposing both reflecting and absorbing boundary conditions and appropriate initial conditions. In this context, the on-shell Gibbs free energy is treated as a function of the event horizon radius, where the difference of the event horizon radii in different phases serves as the order parameter for the phase transition. The study allows us to probe the dynamic process of transitioning between coexisting small and large black hole phases due to thermal fluctuations, as quantified by the calculation of the first passage time. Furthermore, we explore the influence of temperature on this dynamic process. This research contributes to a deeper understanding of the microstructures of regular AdS black holes. © 2023 World Scientific Publishing Company.Item Dynamic phase transition of black holes in massive gravity(Academic Press Inc., 2023) Safir, T.K.; Naveena Kumara, A.N.; Punacha, S.; Ahmed Rizwan, C.L.A.; Fairoos, C.; Vaid, D.The dynamical properties of small-large black hole phase transition in dRGT non-linear massive gravity theory are studied based on the underlying free energy landscape. The free energy landscape is constructed by specifying the Gibbs free energy to every state, and the free energy profile is used to study the different black hole phases. The small-large black hole states are characterized by probability distribution functions and the kinetics of phase transition are described by the Fokker–Planck equation. Further, a detailed study of the first passage process is presented which describes the dynamics of phase transitions. Finally, we have investigated the effect of mass and topology on the dynamical properties of phase transitions of black holes in dRGT non-linear massive gravity theory. © 2023 Elsevier Inc.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.