arXiv subjects

Prabwal Phukon

Publications and source records attributed to Prabwal Phukon.

At least 37 records · Page 2Linked to original sources

arXiv2025

Bifurcation and Critical Phenomena in Black Hole Thermodynamics

In this work, we treat black holes as bifurcation points and explore their thermodynamic phase structure using the framework of bifurcation theory which is a commonly used method from nonlinear dynamics. By constructing an appropriate bifurcating function, we analyze how black holes transition between different thermodynamic phases through changes in the number and stability of fixed points. Our study shows that stable fixed points correspond to thermodynamically stable black hole states, while unstable ones indicate instability and decay. The dynamical evolution of the system further supports this correspondence, with stable configurations approaching equilibrium and unstable ones diverging from it.

gr-qc↗

arXiv2025

Investigating Optical and Ring-Down Gravitational Wave Properties of a Rotating Black Hole in a Dehnen Galactic Dark Matter Halo

We present a comprehensive study of the optical and dynamical properties of a rotating black hole immersed in a Dehnen-type $(1,4,0)$ galactic dark matter halo, modeled by a double power-law density profile commonly used to describe realistic galactic cores. By extending our previous Schwarzschild-Dehnen solution using a modified Newman-Janis algorithm, we construct a Kerr-like axisymmetric spacetime that smoothly incorporates both black hole rotation and the influence of the surrounding dark matter halo. We systematically investigate the effects of the halo parameters-the central density and halo radius-on horizon structure, the shape and extent of the ergoregion, and the null geodesics associated with black hole shadows. Our results show that the presence of a dense or extended halo expands the event horizon and ergoregion, and significantly alters the size and distortion of the black hole shadow. Furthermore, by applying the WKB approximation to scalar field perturbations, we compute the quasinormal mode (QNM) spectra and demonstrate that the frequencies and damping times of ringdown signals are highly sensitive to the halo profile. These results open promising avenues for probing the dark matter environment of astrophysical black holes through black hole imaging and gravitational wave observations.

astro-ph.CO↗

arXiv2025

Observational Constraints on f(R,T) gravity coupled with NED from Black Hole Quasi Periodic Oscillations

In this work, we examine the influence of nonlinear electrodynamics (NED) and $f(R,T)$ gravity on quasi-periodic oscillations (QPOs) around a magnetically charged black hole. By analyzing the effective potential, specific energy, and angular momentum of circular orbits, we study how the NED parameter $α$ and the gravitational coupling parameter $β$ affect orbital dynamics. Increasing $α$ leads to systematic deviations from the Reissner Nordstrom behavior, reflected in shifts in the ISCO radius and orbital frequencies. We further explore QPO-generating radii using the Relativistic Precession (RP), Warped Disk (WD), and Epicyclic Resonance (ER2-ER4) models. We further extend our analysis by performing an MCMC-based parameter estimation using QPO data from black holes spanning a wide range of mass scales. This approach yields consistent observational constraints on the model parameters.

gr-qc↗

arXiv2025

Probing the Thermodynamic Phase Structure of Black Holes through Euler characteristic

In this work, we attempt to explore a possible connection between thermodynamic topology and the thermodynamic geometry formulation of black hole thermodynamics. We study the topological structure of black hole thermodynamic phase spaces by calculating the Euler characteristic (EC) using four well-known thermodynamic geometries: Weinhold, Ruppeiner, Geometrothermodynamics (GTD), and HPEM. We interpret the Euler characteristic as an indicator of the degree of microscopic interactions within the thermodynamic system. As the system approaches the spinoidal curve, the interaction strength increases significantly, eventually driving a phase transition. Beyond the spinoidal region, the interactions begin to weaken, and the system gradually stabilizes into a new phase configuration, reflected by a corresponding change in the topological structure of the thermodynamic state space.

hep-th↗

arXiv2025

Holographic Fractional Order Phase Transitions in CFTs Dual to AdS Black Holes

In this work, we investigate the CFT phase transitions of various AdS black hole solutions, including the Reissner-Nordström-AdS (RN-AdS) black hole, the ModMax-AdS black hole, and the RN-AdS black hole formulated within the framework of Kaniadakis statistics, through the lens of the AdS/CFT correspondence. Employing the generalized Ehrenfest classification scheme based on fractional-order derivatives, we analyze the nature of phase transitions at both Davies points and critical points. Davies points, defined as the loci of divergent heat capacity, are typically associated with second-order transitions in the classical Ehrenfest paradigm. However, a refined analysis reveals that these points can be categorized into two distinct types: the first corresponds to extrema in the temperature profile, while the second aligns with its inflection point, i.e., the thermodynamic critical point. Our findings demonstrate that the order of the phase transition is sensitive to this classification, with the first type corresponding to a fractional order of $3/2$, and the second to $4/3$, which is consistent across RN-AdS black holes. Notably, when a specific constraint is imposed, we observe a $3/2$-order phase transition for both the RN-AdS and ModMax-AdS black holes, whereas in the case of the RN-AdS black hole with Kaniadakis statistics, two critical points arise under constrained paths, each exhibiting a transition of order $4/3$. This generalized, fractional-order framework enables a more precise and discriminating characterization of CFT phase transitions in holographic settings, revealing distinctions that remain hidden under traditional classifications. The results provide deeper insight into the rich structure of black hole thermodynamics on the CFT side and highlight the significance of fractional calculus as a powerful tool for probing critical phenomena within the AdS/CFT framework.

hep-th↗

arXiv2025

The Interconnection of Cosmological Constant and Renyi Entropy in Kalb-Ramond Black Holes : Insights from Thermodynamic Topology

This paper seeks to establish a connection between the cosmological constant and Renyi entropy within the framework of Kalb-Raymond(K-R) gravity. Our analysis is supported by evidence showing the equivalence of the thermodynamic topology of K-R AdS black holes in the Gibbs-Boltzmann (GB) statistical framework and K-R flat black holes in the Renyi statistical framework. We begin by exploring the thermodynamic topology of K-R black holes in flat spacetimes, focusing on the topological characteristics and phase transition behavior in both statistical frameworks. We find that K-R flat black holes in Renyi statistics exhibit equivalent global and local topological properties to K-R AdS black holes in GB statistics. This equivalence points to a potential connection between the cosmological constant and the Renyi parameter. We derive an approximate relationship between the Renyi parameter and the cosmological constant, which is consistent with similar findings in the literature from a cosmological perspective.

gr-qc↗

arXiv2025

Holographic Einstein Rings of AdS black holes with higher derivative corrections in presence of string cloud

This paper seeks to explore the holographic optical appearance of an AdS black hole with higher derivative corrections in the presence of a string cloud, drawing on the AdS/CFT correspondence and wave optics. We introduce a Gaussian wave source that oscillates at the AdS boundary and propagates through the bulk. The resulting response function is then analyzed using an imaging system to study the optical properties of the black hole. Depending on the observer's position and variations in system parameters, the resulting holographic image takes on different forms, including a well defined Einstein ring, deformed luminous patterns, or isolated bright spots. Notably, when the observer is positioned at the north pole, the image consistently features a bright ring at the photon sphere, encircled by concentric stripes. Our findings reveal a strong correlation between the Einstein ring's location and the photon sphere radius predicted by geometric optics, reinforcing the connection between wave optics and gravitational lensing. Additionally, we examine the influence of higher-derivative corrections and string cloud parameters on the observed optical features.

hep-th↗

arXiv2025

Signatures of NED on Quasi periodic Oscillations of a Magnetically Charged Black Hole

In this work, we explore the influence of nonlinear electrodynamics (NED) on the quasi-periodic oscillations (QPOs) of a magnetic charged black hole by analyzing the motion of test particles and their epicyclic frequencies. Starting from the effective potential, angular momentum, and energy of circular orbits, we examine how the NED parameter b alters the orbital dynamics. We find that as b increases, the system transitions smoothly from the RN regime towards the Schwarzschild profile, with observable changes in the innermost stable circular orbit (ISCO) and Keplerian frequencies. We further investigate the variation in the radii of QPOs with respect to the NED parameter b by employing the RP, WD, and ER models. We also perform Markov Chain Monte Carlo (MCMC) analysis using observational QPO data from a diverse set of black hole sources spanning stellar-mass, intermediate-mass, and supermassive regimes. The MCMC results yield consistent constraints on the parameter b across all mass regimes, indicating that NED effects leave a distinguishable signature on the QPO structure of a charged black hole.

gr-qc↗

arXiv2025

Probing Thermodynamic Phase Transitions of 4D R-Charged Black Holes via Lyapunov Exponent

We investigate the thermodynamic phase structure of four-dimensional \textit{R}-charged black holes--characterized by four independent $U(1)$ charges--through the lens of Lyapunov exponents associated with unstable circular orbits of both massless and massive particles. Considering three distinct charge configurations (equal, partially unequal, and fully unequal), we show that the thermal profile of the Lyapunov exponent can effectively probe the black hole phase transitions. Furthermore, we demonstrate that the discontinuous jump in the Lyapunov exponent acts as an order parameter, with the associated critical exponent $δ= 1/2$ near the critical point--consistent across all charge configurations studied. This supports the proposed universality of the exponent and the broader connection between dynamical chaos and thermodynamic phase transitions.

gr-qc↗

arXiv2025

Holographic Einstein Ring of AdS Reissner Nordstr$\ddot{o}$m Black Holes with Euler Heisenberg Nonlinear Electrodynamics

This study, situated within the framework of the AdS/CFT correspondence, employs wave optics methods to investigate the Einstein ring structure of quantum corrected AdS Reissner Nordstr$\ddot{o}$m black holes governed by Euler Heisenberg nonlinear electrodynamics. A wave source placed on the AdS boundary yields a response function on the antipodal side, from which a virtual optical system with a convex lens reconstructs the holographic image of the Einstein ring. The analysis systematically explores the impact of physical parameters and observer position on the ring's morphology. As the observer's position varies, the image transitions from a complete ring to an arc and eventually to a single bright point. The Einstein ring radius is observed to decrease with increasing radial source position $ρ$, wave frequency $ω$, and chemical potential $μ$, while it increases with electric charge $e$ and temperature $T$. In contrast, the quantum correction parameter $a$ has negligible effect on the ring radius or response amplitude, as its contribution falls off rapidly near the boundary and remains subleading in the wave dynamics. The parameter $e$ enhances the electromagnetic lensing strength, leading to a broader ring, whereas increasing $ρ$ alters wavefront propagation, affecting both brightness peak and ring location. Geometric optics analysis confirms that the incident angle of the photon ring matches the Einstein ring angle, validating consistency across frameworks. Overall, the results highlight how nonlinear electromagnetic effects and bulk field configurations manifest in observable boundary features, providing a means to distinguish quantum-corrected black holes from classical solutions.

hep-th↗

arXiv2025

RPST-Inspired Formalism for Black Holes in Flat Spacetime

In this work, we propose a novel formalism for the thermodynamics of flat black holes, inspired by the Restricted Phase Space Thermodynamics (RPST) framework. Our construction is motivated by the observed similarities in the thermodynamic behavior of flat black holes within the Rényi entropy framework and that of AdS black holes described by the Bekenstein entropy regime. The RPST framework is, by construction, exclusive to AdS black holes because it depends on the cosmological constant $Λ$, which is linked to the central charge $C$ of the dual conformal field theory (CFT). However, for non-AdS black holes, where $Λ$ is absent, we introduce a deformation parameter $λ$ to replace the central charge $C$. This RPST-inspired formalism incorporates $λ$ and its conjugate variable, the response potential $ζ$, as a new pair of thermodynamic variables, analogous to the central charge $C$ and chemical potential $μ$ in the AdS case. To illustrate the applicability of this formalism, we analyze two examples: the Reissner-Nordström (RN) flat black hole and the Kerr black hole.

hep-th↗

arXiv2025

Thermodynamics of Rotating AdS black holes in Kaniadakis statistics

In this study, we advance the understanding of thermodynamic properties and phase transitions in rotating anti-de Sitter (AdS) black holes by applying the Kaniadakis(KD) entropy framework. This framework represents a non-extensive generalization of classical statistical mechanics, inspired by the symmetries of relativity and offering a novel perspective on black hole thermodynamics. Our focus is on investigating how Kaniadakis entropy modifies the thermodynamic phase space of rotating AdS black holes. To achieve this, we analyze three prominent rotating AdS black hole systems: the Kerr AdS black hole, the Kerr-Sen AdS black hole, and the Kerr-Newman AdS black hole. We assess their thermodynamic quantities, phase transitions, thermodynamic topology and thermodynamic geometry within the Kaniadakis statistical framework. Our analysis reveals notable deviations from the behaviour predicted by traditional Gibbs-Boltzmann(GB) statistics.

gr-qc↗

arXiv2025

Revisiting thermodynamic topology of Hawking-Page and Davies type phase transitions

In this work, we propose a common vector field to study the thermodynamic topology of the Davies type and Hawking-Page phase transitions. Existing literature has shown that studying these two types of phase transitions typically requires defining two separate vector fields . In our approach, we adopt Duan's $ϕ$-mapping topological current theory to define a novel vector field, denoted as $ϕ$, whose critical points exactly correspond to the Davies point and the Hawking-Page phase transition point. More importantly, we can differentiate between these two points by their topological charge. While, the topological charge for the critical point corresponding to the Davies-type phase transition is found to be $-1$, the same for the Hawking-Page phase transition point, it is $+1$. Although our analysis is applicable to all black hole systems where both types of phase transitions are found, we illustrate it using three simple systems as examples: the Schwarzschild AdS black hole, the Reissner-Nordström AdS black hole in the grand canonical ensemble, and finally the Kerr AdS black holes in the grand canonical ensemble. It is wellknown that these black holes exhibit both Davies and Hawking-Page phase transitions. With our proposed vector $ϕ$, the critical points obtained for these three systems exactly match the Davies-type and Hawking-Page phase transition points, and the associated topological charges are found to be $-1$ for the Davies point and $+1$ for the Hawking-Page phase transition point.

hep-th↗

arXiv2025

Topology of restricted phase space thermodynamics in Kerr-Sen-Ads black holes

In this study, we investigate the thermodynamic topology of the Kerr-Sen-Ads black hole in restricted phase space. In the restricted phase space, a new parameter, central charge $C$, and its conjugate parameter $μ$ are introduced, omitting the well-known $PdV$ term in the first law of black hole thermodynamics. We study the local and global topology of the black hole by considering the black hole solution as topological defects in the free energy landscape. We compute the winding number and the total topological number at the thermodynamic defects. For our analysis, we have considered five ensembles of Kerr-Sen-Ads black holes in restricted phase space: fixed $(Q, J, C)$, fixed $(ϕ, J, C)$, fixed $(Q,Ω, C)$, fixed $(Q, J, μ)$, and fixed $(ϕ,Ω, C)$, where $Q$ is the electric charge, $J$ is the angular momentum, $C$ is the central charge, $ϕ$ is the electric potential conjugate to charge, $Ω$ is the angular frequency conjugate to $J$, and finally, $μ$ is the chemical potential. In the fixed $(Q, J, C)$, fixed $(ϕ, J, C)$, and fixed $(Q, J, μ)$ ensembles, we find a topological charge of $+1$. In the fixed $(Q,Ω, C)$ and fixed $(ϕ, Ω, C)$ ensembles, depending on the values of the thermodynamic parameters, we find topological charges of $-1$, $0$, and $+1$. Interestingly, in ensembles where we find the topological charge to be $0$, we observe both Hawking-Page and Davies type phase transitions. We show that both types of these phase transitions can be studied using a common vector field, and the topological charges associated with Davies type and Hawking-Page phase transitions are $-1$ and $+1$, respectively.

hep-th↗

arXiv2025

Thermodynamic Properties and Shadows of Black Holes in $f(R,T)$ Gravity

In this paper, we explore two $f(R,T)$ gravity models and derive black hole solutions within these models. We focus on investigating how the $f(R,T)$ model influences the thermodynamic characteristics of black holes by studying their thermodynamic topology and thermodynamic geometry. We consider five specific values of the thermodynamic parameter $ω$, which signify five different classes of black hole solutions in general relativity (GR). We observe significant changes in the local topological properties of these black holes compared to GR, depending on the model parameters. Notably, we identify an additional topological class $W=0$ for some values of $ω$ that is absent in the GR framework. We also study the thermodynamic geometry of the black hole using the Geometrothermodynamics (GTD) formalism. Our analysis demonstrates that the singular point, where the GTD scalar curvature diverges, corresponds exactly to the point where the heat capacity changes sign. Additionally, we constrain the model parameters of both models considered by utilizing black hole shadow data from the Sgr A* black hole, measured by the Event Horizon Telescope (EHT).

gr-qc↗

arXiv2025

BTZ Black Hole In The Non-Extensive Generalizations of Gibbs Entropy

We study the thermodynamics and thermodynamic geometry of the (2+1) dimensional Banados-Teitelboim-Zanelli(BTZ) black hole within the framework of the non-extensive generalizations of Gibbs entropy. We investigate both the rotating (R-BTZ) and the charged (C-BTZ) BTZ black holes in these non-extensive entropy formalisms. We write down the Bekenstein-Hawking(BH) entropy of the black hole in terms of the non-extensive entropies namely: Kaniadakis entropy, Renyi entropy and Barrow entropy. We investigate their impact on the thermodynamic phase structure and geometry of the BTZ black holes in both the ensembles i.e. the fixed $(J)$ and fixed $(Ω)$ ensemble for the R-BTZ black hole and the fixed $(Q)$ and the fixed $(Φ)$ ensemble for the C-BTZ black hole where $ J$, $Ω$, $Q$ and $Φ$ represent the angular momentum, angular velocity, charge and the electric potential of the respective black holes . We investigate the Ruppeiner and geometrothermodynamic(GTD) geometries of the black hole for all the non-extensive entropy cases. We find that there are Davies type along with Hawking-Page phase transitions in both the charged and rotating BTZ black hole for the Kaniadakis entropy case in all the above mentioned thermodynamic ensembles. These phase transitions were not seen in the BH entropy case. We also find that the Ruppeiner and the GTD scalar for the Kaniadakis entropy show curvature singularities corresponding to the Davies type phase transitions in both the rotating and charged BTZ black holes.

hep-th↗

arXiv2025

CFT Phase Transition Analysis of Charged, Rotating Black Holes in $D=4$: A Holographic Thermodynamics Approach

We investigate the holographic thermodynamics of 4-D Kerr-Newman AdS black holes, focusing on the conformal thermal states that are dual to these black holes. We explore the thermodynamic behavior within specific ensembles characterized by fixed sets of variables: $(\mathcal{Q},\mathcal{J},\mathcal{V},C)$, $(\mathcal{Q},Ω,\mathcal{V},C)$, $(φ,Ω,\mathcal{V},C)$, $(φ,\mathcal{J},\mathcal{V},C)$, $(\mathcal{Q},Ω,p,C)$, and $(φ,Ω,p,C)$. Here, $φ$, $\mathcal{Q}$, $Ω$, $\mathcal{J}$, $p$, $\mathcal{V}$, and $C$ represent the electric potential, electric charge, angular velocity, angular momentum, CFT pressure, CFT volume, and central charge, respectively. The inclusion of both charge and momentum significantly enriches the regime of phase transitions, leading to a variety of phenomena including first-order Van der Waals-type phase transitions, (de)confinement phase transitions, Davies-type phase transitions, and second-order superfluid $λ$-type phase transitions. Notably, the introduction of the CFT pressure variable allows us to identify phase transitions and critical behavior in the $(\mathcal{Q},Ω,p,C)$ and $(φ,Ω,p,C)$ ensembles, which had not been previously observed. This study underscores the complexity and richness of phase transitions in these systems due to the inclusion of both charge and angular momentum.

hep-th↗

arXiv2024

Restricted Phase Space Thermodynamics of 4D Dyonic AdS Black Holes: Insights from Kaniadakis Statistics and Emergence of Superfluid $λ$-Phase Transition

We study the thermodynamics of $4D$ dyonic AdS black hole in the Kaniadakis statistics framework using the Restricted Phase Space (RPST) formalism. This framework provides a non-extensive extension of classical statistical mechanics, drawing inspiration from relativistic symmetries and presenting a fresh perspective on black hole thermodynamics. Our study analyzes how including Kaniadakis entropy modifies the phase transition of the dyonic black holes. We consider the central charge $C$ and its conjugate chemical potential $μ$ as the thermodynamic variable along with others except the pressure and volume. Due to the addition of the magnetic charge $\tilde{Q}_m$, the study of the phase transition becomes much richer by obtaining a non-equilibrium phase transition from an unstable small black hole to a stable large black hole along with the Van der Waals phase transition in the $T-S$ processes. In the $F-T$ plot, we get an extra Hawking-Page phase transition. Including the deformation parameter $κ$ introduces an unstable (ultra-large BH) branch seen in almost all the plots. Turning off the magnetic charge flips the direction of the phase transition seen during its presence. We observe a novel phenomenon that is the superfluid $λ$ phase transition in the mixed $(\tildeΦ_e,\tilde{Q}_m)$ which is due to the additional $\tilde{Q}_m$ inclusion. Also, in the plots varying $κ$ match with the plot varying $C$ which underlines some sort of correspondence in its meaning which is not possible to observe in Gibbs-Boltzmann statistics. As the entropy models change the homogeneity is not lost where mass is of the first order and the rest is zeroth order. Finally, the $μ-C$ processes in quite similar across black hole systems and entropy formulation marking some kind of universality of this process.

hep-th↗