arXiv subjects

Sudhaker Upadhyay

Publications and source records attributed to Sudhaker Upadhyay.

At least 19 recordsLinked to original sources

arXiv2026

Rényi Entropy and the Topological Features of Charged AdS Black Hole

This study applies Duan's topological current $ϕ$-mapping theory to investigate a newly proposed charged modified AdS black hole using the Rényi entropy formalism, examining its thermodynamic properties across the canonical, mixed, and grand canonical ensembles.} Electric and magnetic charges are fixed in the canonical ensemble, whereas the mixed ensemble incorporates electric and magnetic potentials. The grand canonical ensemble, meanwhile, ensures consistency by employing these potentials exclusively. Initially, we compute topological charges by identifying critical points in each ensemble. In both the canonical and mixed ensembles, we identify a conventional critical point with a topological charge of $-1$. We then model the black hole's domain in the AdS regime as a topological defect in thermodynamic space and analyze its local and global topology by calculating the winding numbers at these defect locations. {Interestingly, the canonical and mixed ensembles exhibit identical black hole topologies, each possessing a total topological charge of $1$ within the framework of the Rényi entropy.} Finally, we characterize the canonical, mixed, and grand canonical ensembles based on the presence of generation/annihilation points: the canonical ensemble has one such point, the mixed ensemble has a negative one, and the grand canonical ensemble has none.

physics.gen-ph↗

arXiv2026

Systematic Light Propagation Bias from the Heliosphere and Its Impact on the Hubble Tension

The Hubble tension (HT) represents one of the most significant discrepancies in modern cosmology, with local distance measurements yielding $H_0 = 73.5 \pm 1.4$ km/s/Mpc while cosmic microwave background (CMB) observations predict $H_0 = 67.4 \pm 0.5$ km/s/Mpc. We propose that this tension arises from systematic effects introduced by our Solar System's heliospheric (HS) environment on local distance measurements. The HS creates a complex medium of heated plasma and energetic neutral atoms (ENAs) beyond the heliopause (HP), where interstellar medium (ISM) temperatures rise significantly. This thermal gradient and particle environment may systematically affect observations of Cepheid variables and Type Ia supernovae (SNe~Ia) used in the local cosmic distance ladder (CDL), biasing distance measurements and artificially inflating the measured Hubble constant. We present theoretical calculations showing how HS effects could account for up to $\sim 8\%$ of the observed 8--9\% discrepancy, with the realistic contribution lying in the $\sim 3$--$8\%$ range once anisotropy, partial calibration cancellation, and chromatic suppression are included, and discuss observational tests to validate this hypothesis.

gr-qc↗

arXiv2026

Perturbative and Non-Perturbative Contributions to Black Hole Thermodynamics with String Clouds and Dark Matter Backgrounds

We investigate the effects of perturbative and non-perturbative quantum corrections on the thermodynamics of black holes immersed in a perfect fluid dark matter (PFDM) background with a cloud of strings (CoS) in asymptotically anti-de Sitter spacetime. Starting from the Bekenstein-Hawking entropy as the semiclassical baseline, we incorporate two distinct classes of corrections arising from small thermal fluctuations about thermodynamic equilibrium. In the perturbative sector, we derive the logarithmically corrected entropy and systematically compute the resulting modifications to the mass, Helmholtz free energy, Gibbs free energy, heat capacity, and pressure. The stability structure of the system is analyzed through the sign behavior of the heat capacity, which reveals a transition from a thermodynamically unstable to a stable phase. In the non-perturbative sector, we introduce exponential corrections to the entropy and carry out a parallel analysis of all thermodynamic quantities. We demonstrate that non-perturbative effects are negligible for large black holes but become significant as the horizon radius shrinks toward the Planck regime. In both sectors, we investigate the equation of state and search for a van der Waals-like critical point by examining the simultaneous vanishing of the first and second pressure derivatives with respect to thermodynamic volume; no such inflection point is found within the physically admissible domain. Our results illuminate the contrasting roles of logarithmic and exponential entropy corrections in governing the thermodynamic stability and phase structure of PFDM black holes with a CoS.

gr-qc↗

arXiv2026

Thermodynamics, Shadow, and Quasinormal Modes of AdS Ayón--Beato--García Massive Black Hole

We investigate the thermodynamics, photon sphere, and dynamical stability of an AdS Ayón--Beato--García (ABG) massive black hole with graviton mass and magnetic charge. The Gibbs free energy exhibits distinct limiting behaviors: it reduces to that of an AdS massive black hole when magnetic charge vanishes, to that of an AdS ABG black hole when graviton mass is zero, and smoothly interpolates to the AdS massive Reissner-Nordström case in the asymptotic regime. Furthermore, the photon sphere and shadow analysis indicate that increasing the graviton mass expands their radii, while increasing the magnetic charge causes contraction, in agreement with earlier studies of black hole spacetimes. Quasinormal mode (QNM) calculations further confirm dynamical stability, as the imaginary part remains negative, ensuring decay of perturbations. Additionally, the real part of the frequency decreases with graviton mass, while the imaginary part initially grows before saturating at higher values. Together, these results provide meaningful insights into the interplay between graviton mass, magnetic charge, and stability, thereby enriching the understanding of black holes in modified gravity theories.

gr-qc↗

arXiv2026

More Exact Thermodynamic Analysis of Topological Black Holes in $R^2$ Gravity

This study investigates the thermodynamics of topological black hole solutions in $R^{2}$ gravity, incorporating the effects of small statistical fluctuations up to first-order corrections. We precisely calculate entropy, internal energy, Helmholtz free energy, specific heat, enthalpy, and Gibbs free energy, accounting for perturbative thermal corrections. Our results reveal that the internal energy of small black holes diverges asymptotically due to these fluctuations. The corrected Gibbs free energy attains asymptotically high values for small horizon radii. In contrast, the equilibrium Gibbs free energy approaches zero. Additionally, we assess the stability of the black hole in the presence of these thermal fluctuations. We find that, in contrast to the equilibrium state, the thermal fluctuation introduces a double phase transition to the stability of the black hole. Our analysis reveals that the influence of fluctuations is notably significant, primarily for small black holes. These findings offer new insights into the thermodynamic properties of topological black holes in the presence of thermal fluctuations.

gr-qc↗

arXiv2025

Holography and the Swampland: Constraints on Quantum Gravity from Holographic Principles

The Swampland Program aims to delineate the space of consistent low-energy effective field theories (EFTs) that admit a UV completion in quantum gravity from those that do not. In parallel, holography, and particularly the AdS/CFT correspondence, offers a non-perturbative definition of quantum gravity in asymptotically anti-de Sitter (AdS) spacetimes. In this paper, we explore the Swampland Conjectures through the lens of holography, focusing on how holographic consistency conditions, such as the convexity of the conformal field theory (CFT) spectrum, the averaged null energy condition (ANEC), and the modular bootstrap, map onto Swampland constraints in the bulk. We argue that the holographic principle provides a geometric realization of Swampland bounds, particularly on scalar field potentials and the absence of long-lived de Sitter vacua. Finally, we discuss how the emergent bulk locality in AdS/CFT provides evidence that the Swampland conjectures may themselves be manifestations of deeper holographic consistency conditions.

hep-th↗

arXiv2025

Phantom BTZ Black Holes: Thermal Properties Under Perturbative Corrections

This study investigates the thermodynamics of phantom BTZ black holes by incorporating leading-order perturbative corrections arising from small statistical fluctuations around equilibrium. Starting from the phantom BTZ black holes review, we describe a modified action in three-dimensional spacetime that includes coupling with a Maxwell or phantom field. The analysis derives the corresponding field equations and obtains exact solutions for the metric and thermodynamic quantities. The corrected entropy is computed using the steepest descent method. It is expressed in terms of the leading-order entropy and Hawking temperature. Standard thermodynamic relations yield the corrected mass, Helmholtz free energy, specific heat, and Gibbs free energy. These corrections reveal significant deviations from classical results, particularly in the small black hole regime where statistical effects become prominent. Graphical analysis shows that the corrected entropy becomes negative for sufficiently small black holes, indicating potential limitations in thermodynamic stability under perturbative corrections. Furthermore, the influence of thermal fluctuations proves substantial for the small black holes and negligible for larger black holes. In this work, we have also calculated critical points and critical compressibility factor ($Z_{c}$) of the phantom BTZ black hole, treating it as a Van der Waals fluid. This work provides a comprehensive understanding of how statistical fluctuations modify the thermodynamics of phantom BTZ black holes. It underscores the necessity of including such corrections in realistic models of black hole thermodynamics in $(2+1)$ dimensions.

hep-th↗

arXiv2025

Refined Thermodynamic Analysis of Perfect Fluid Dark Matter Black Holes in a Phantom Background

In this study, we examine the thermodynamics of black holes immersed in perfect fluid dark matter (PFDM) by employing the Misner-Sharp energy framework. We extend the analysis to include the thermal fluctuations of these black holes when size reduces to small size, redefining key thermodynamic variables such as pressure, volume, temperature, internal energy, and entropy within the context of PFDM. Using these newly defined variables, we systematically calculate the enthalpy, Gibbs free energy, and specific heat of PFDM black holes, incorporating perturbative thermal corrections. To assess the stability of these black holes, we perform a detailed graphical analysis of the specific heat as a function of the horizon radius, providing insights into the thermal stability of PFDM black holes. This comprehensive approach enhances our understanding of the thermodynamic properties and stability of black holes in the presence of dark matter.

gr-qc↗

arXiv2025

Exploring non-perturbative effects on quasi-topological black hole thermodynamics

We examine the impact of non-perturbative quantum corrections to the entropy of both charged and charged rotating quasi-topological black holes, with a focus on their thermodynamic properties. The negative-valued correction to the entropy for small black holes is found to be unphysical. Furthermore, we analyze the effect of these non-perturbative corrections on other thermodynamic quantities, including internal energy, Gibbs free energy, charge density, and mass density, for both types of black holes. Our findings indicate that the sign of the correction parameter plays a crucial role at small horizon radii. Additionally, we assess the stability and phase transitions of these black holes in the presence of non-perturbative corrections. Below the critical point, both the corrected and uncorrected specific heat per unit volume are in an unstable regime. This instability leads to a first-order phase transition, wherein the specific heat transitions from negative to positive values as the system reaches a stable state.

gr-qc↗

arXiv2025

Impact of Perfect Fluid Dark Matter on the Thermodynamics of $AdS$ Ayón--Beato--García Black Holes

In this paper, we derive the black hole solution in the context of nonlinear electrodynamics (NLED) coupled to a perfect fluid dark matter (PFDM) field. The resulting black hole solution interpolates between the $AdS$ Ayón--Beato--García (ABG) black hole in the absence of the PFDM field and the Schwarzschild black hole devoid of magnetic monopole charges and PFDM influence. A numerical investigation of the horizon structure and thermodynamic properties, including both local and global stability, is conducted for the obtained black hole solution. The thermodynamic quantities are shown to be modified by the presence of the NLED and PFDM fields. We observe that the behaviour of thermodynamical quantities of black holes depends on these parameters significantly. We also discuss the stability and phase transition dependency on these parameters.

gr-qc↗

arXiv2025

Schwinger's SUSY Oscillators: An Analysis

In this article, we explore the inconsistencies in the physics of fermionic oscillators and propose potential solutions to address them. By rigorously deriving the Hamiltonian and Lagrangian from first principles, we aim to provide a comprehensive and fundamental understanding of the system. Furthermore, we calculate the partition function for a system of fermionic oscillators by drawing a direct analogy to Planck's treatment of energy distribution in bosonic oscillators, offering a parallel approach to this well-established method. Our study extends beyond the conventional framework by investigating the generalized angular momentum algebra within the context of Schwinger's oscillator model. This includes a detailed examination of the algebraic structures for combinations of bosonic-bosonic, bosonic-fermionic, and fermionic-fermionic oscillators. Through this, we delve into these systems' underlying symmetries and algebraic richness, shedding light on the intricate relationships between these different types of oscillators. In addition to these foundational aspects, we explore the broader implications of this generalized Schwinger approach. Our analysis touches upon potential applications and consequences of this formalism, offering insights that could be relevant to various areas of theoretical physics. This work paves the way for a deeper understanding of quantum oscillators and their role in modern physics by bridging the gap between bosonic and fermionic oscillators.

quant-ph↗

arXiv2024

Quantum gravitational corrections to the geometry of charged AdS black holes

We study the quantum gravitational corrections to the geometry of a four-dimensionalcharged (Reissner-Nordström) Anti de Sitter black hole starting from an effective field theory approach to quantum gravity. We use the expression of the modified horizon radius to compute the quantum corrected Wald entropy, whose expression reproduces the logarithmic behaviour found by other methods. We perform a thermodynamics analysis and compute the quantum gravitational corrections to the temperature, pressure, specific heat and Helmholtz free energy. All these quantities are renormalisation group invariant. We find that a quantum charged AdS black hole can exist only for a bounded range of masses and that it can undergo a second order phase transition as it moves from a state with positive specific heat to a negative one.

hep-th↗

arXiv2024

Ayón--Beato--García black hole coupled with a cloud of strings: thermodynamics, shadows and quasinormal modes

We find an exact black hole solution for the Einstein gravity in the presence of Ayón--Beato--García non-linear electrodynamics and a cloud of strings. The resulting black hole solution is singular, and the solution becomes non-singular when gravity is coupled with Ayón--Beato--García non-linear electrodynamics only. This solution interpolates between Ayón--Beato--García black hole, Letelier black hole and Schwarzschild black hole { in the absence of cloud of strings parameter, magnetic monopole charge and both of them, respectively}. We also discuss the thermal properties of this black hole and find that the solution follows the modified first law of black hole thermodynamics. Furthermore, we estimate the solution's black hole shadow and quasinormal modes.

gr-qc↗

arXiv2024

Thermodynamics of a newly constructed black hole coupled with nonlinear electrodynamics and cloud of strings

This paper finds an exact singular black hole solution in the presence of nonlinear electrodynamics as the source of matter field surrounded by a cloud of strings in $4D$ $AdS$ spacetime. Here, the presence of the cloud of string, the usual Bardeen solution, becomes singular. The obtained black hole solution interpolates with the $AdS$ Letelier black hole in the absence of both the deviation parameter and magnetic charge and interpolates with the $AdS$ Bardeen black hole in the absence of the deviation parameter and a cloud of strings parameter. We analyse the horizon structure and thermodynamics properties, including the stability of the resulting black hole, numerically and graphically. Thermodynamical quantities associated with the black hole get modified due to the nonlinear electrodynamics and cloud of strings. Moreover, we study the effect of a cloud of strings parameter, magnetic charge and deviation parameter on critical points and phase transition of the obtained black hole where the cosmological constant is treated as the thermodynamics pressure. The critical radius increases with increasing deviation parameter values and magnetic charge values. In contrast, the critical pressure and temperature decrease with increasing deviation parameters and magnetic charge values.

gr-qc↗

arXiv2024

Holographic Thermodynamics of an Enhanced Charged AdS Black Hole in String Theory's Playground

In this paper, we consider an $α^{\prime}$ corrected Reissner-Nordström AdS black hole to study thermodynamics. We study the $P-V$ criticality and thermodynamical stability of the black hole. We obtained a first-order phase transition, which may be interpreted as the large/small black hole phase transition. Therefore, we obtained a van der Waals behaviour and obtained critical points. Finally, we calculate quantum work used to resolve the information loss paradox.

hep-th↗

arXiv2024

Thermal analysis of black hole in de Rham--Gabadadze--Tolley massive gravity in Barrow entropy framework

This study examines a recently hypothesized black hole solution in de Rham--Gabadadze--Tolley massive gravity. Firstly, we consider the negative cosmological constant as a thermodynamic pressure. We extract the thermodynamical properties such as Hawking temperature, heat capacity and Gibbs free energy using the Barrow entropy. We also obtain a new pressure associated to the perfect fluid dark matter and discuss the first-order van der Waals-like phase transition. This black hole's stability is investigated through specific heat and Gibbs free energy. Also, we analyze the thermodynamic curvatures behavior of black hole through geometry methods (Weinhold, Ruppeiner, Hendi-Panahiyah-Eslam-Momennia (HPEM), and geometrothermodynamics (GTD)).

gr-qc↗

arXiv2024

Non-perturbative correction to thermodynamics of conformally dressed 3D black hole

We extend the study of corrected thermodynamics for the 3D black holes conformally coupled to scalar field up to non-perturbative level. We calculate the exponential correction to entropy arises due to the microstate counting for quantum states on the boundary. This exponential correction in entropy attributes to the other thermodynamical quantities also. We study the stability and phase transition for this system of black hole under the influence of non-perturbative correction. We also discuss the quantum work associated with exponential corrected entropy. Finally, we justify the results from the view point of thermodynamic geometry.

gr-qc↗

arXiv2024

Non-perturbative correction on the black hole geometry

In this paper, we use the holographic principle to obtain a modified metric of black holes that reproduces the exponentially corrected entropy. The exponential correction of the black hole entropy comes from non-perturbative corrections. It interprets as a quantum effect which affects black hole thermodynamics especially in the infinitesimal scales. Hence, it may affect black hole stability at the final stage. Then, we study modified thermodynamics due to the non-perturbative corrections and calculate thermodynamics quantities of several non-rotating black holes.

gr-qc↗