arXiv subjects

Pabitra Tripathy

Publications and source records attributed to Pabitra Tripathy.

7 recordsLinked to original sources

arXiv2025

Modified first law of charged dilaton black hole

We investigate the thermodynamics of a charged dilaton black hole arising from Einstein-Maxwell-dilaton theory, where the dilaton couples exponentially to the Maxwell field via a dimensionless parameter a. Treating a as a continuous solution parameter, we extend the black hole first law to include a term Psi^A da, where Psi^A is the thermodynamic potential conjugate to a. We derive Psi^A explicitly through a differential analysis of the mass, charge, and entropy, and confirm its form via an independent Hamiltonian calculation. Additionally, by promoting a to a spacetime-dependent scalar and introducing auxiliary gauge fields, we provide a geometric interpretation of Psi^A as a conserved Noether charge. We further analyze the implications of treating a as a thermodynamic variable within the extended phase space. Despite the modification to the first law, we demonstrate that the Smarr relation remains unaffected due to the dimensionless nature of a, highlighting the distinction between variational and scaling symmetries. Our analysis supports the thermodynamic relevance of coupling constants and enriches the framework of extended black hole thermodynamics.

gr-qc↗

arXiv2025

Lower bound of black hole hair in pure Lovelock theory of gravity

As an alternative to the "no hair conjecture," the "no short hair conjecture" for hairy black holes was established earlier. This theorem stipulates that hair must be present above 3/2 of the event horizon radius for a hairy black hole. It is assumed that the nonlinear behavior of the matter field plays a key role in the presence of such hair. Subsequently, it was established that the hair must extend beyond the photon sphere of the corresponding black hole. We have investigated the validity of the "no short hair conjecture" in pure Lovelock gravity. Our analysis has shown that irrespective of dimensionality and Lovelock order, the hair of a static, spherically symmetric black hole extends at least up to the photon sphere.

gr-qc↗

arXiv2024

Exploring critical behavior of thermodynamic variables of the Kerr-Newman-AdS black hole in the restricted phase space

The present work delves into examining the thermodynamic properties of the four-dimensional Kerr-Newmann-AdS black hole, employing the recently proposed framework of restricted phase space thermodynamics (RPST). This approach introduces a novel set of paired thermodynamic variables: the central charge $C$ of the corresponding dual conformal field theory (CFT) and the chemical potential $μ$. Through simple analysis, we establish fundamental relationships such as the Euler relation, Gibbs-Duhem relation, and the zeroth order homogeneity of intensive variables. Employing numerical techniques, we explore the thermodynamic processes between these conjugate variables. Our investigation reveals the first-order and second-order phase transitions across various macroscopic processes. Despite the absence of complete analytical expressions, our findings unveil striking similarities in behavior between RN-AdS and Kerr-AdS, underscoring the presence of underlying universality within the RPST formalism.

hep-th↗

arXiv2023

Hawking temperature of black holes with multiple horizons

There are several well-established methods for computing thermodynamics in single-horizon spacetimes. However, understanding thermodynamics becomes particularly important when dealing with spacetimes with multiple horizons. Multiple horizons raise questions about the existence of a global temperature for such spacetimes. Recent studies highlight the significant role played by the contribution of all the horizons in determining Hawking temperature. Here we explore the Hawking temperature of a rotating and charged black hole in four spacetime dimensions and a rotating BTZ black hole. We also find that each horizon of those black holes contributes to the Hawking temperature. The effective Hawking temperature for a four-dimensional rotating and charged black hole depends only on its mass. This temperature is the same as the Hawking temperature of a Schwarzschild black hole. In contrast, the effective Hawking temperature depends on the black hole mass and angular momentum for a rotating BTZ hole.

gr-qc↗

arXiv2023

Local first law of black hole

We investigated the form and implications of the local first law of black hole thermodynamics in relation to an observer located at a finite distance from the black hole horizon. Our study is based on the quasilocal form of the first law for black hole thermodynamics, given by $δE=\frac{\barκ}{8π}δA$, where $δE$ and $δA$ represent the changes in the black hole mass and area, respectively, and $\barκ$ denotes the quasilocal surface gravity. We show that even at a finite distance, the quasilocal law still holds. It shows how the first law scales with the observer's location.

gr-qc↗

arXiv2023

Hawking radiation in multi-horizon spacetimes using Hamilton Jacobi method

It has been recently shown that the contribution between the horizons determines the Hawking temperature for a multi-horizon spacetime. In this article, we apply the Hamiltonian Jacobi method to compute the Hawking temperature for some multi-horizon spacetimes like Schwarzschild-de Sitter spacetime (SdS), Reissner-Nordstrom-de Sitter spacetime (RNdS), and rotating BTZ black hole spacetime (RBTZ) and also arrive at the same conclusion. There are two contributions to the tunneling process of radiation. The combination of these two contributions gives the radiation with the Hawking temperature with an effective surface gravity.

gr-qc↗

arXiv2022

Hawking radiation as quantum mechanical reflection

In this article, we explore an alternative derivation of Hawking radiation. Instead of the field-theoretic derivation, we have suggested a simpler calculation based on quantum mechanical reflection from a one-dimensional potential. The reflection coefficient shows an exponential fall in energy which, in comparison with the Boltzmann probability distribution, yields a temperature. The temperature is the same as Hawking temperature for spherically symmetric black holes. The derivation gives an exact local calculation of Hawking temperature that involves a region lying entirely outside the horizon. This is a crucial difference from the tunneling calculation, where it is necessary to involve a region inside the horizon.

gr-qc↗