arXiv subjects

Wen-Xiang Chen

Publications and source records attributed to Wen-Xiang Chen.

At least 19 recordsLinked to original sources

arXiv2026

Canonical-Ensemble Stability of the Quantum Oppenheimer-Snyder Black-Hole Exterior

We study the local canonical thermodynamics of the quantum Oppenheimer--Snyder (qOS) black-hole exterior previously obtained from loop quantum cosmology. The spacetime is adopted from the literature; no new black-hole solution, regular extension, or singularity-resolution mechanism is claimed here. At fixed quantum parameter $α$, we rewrite the outer horizon in a dimensionless form and obtain exact expressions for the mass, Hawking temperature, entropy, and heat capacity. These expressions reproduce the logarithmic entropy term and the heat-capacity divergence reported in earlier analyses. We then place those results in an explicit, regulated canonical-ensemble framework. The off-shell canonical action has a local minimum on a near-extremal branch with positive heat capacity and a local maximum on a large-black-hole branch with negative heat capacity. The two saddles merge at $r_h/\sqrtα=\sqrt{(4+2\sqrt{7})/3}$, where the temperature is maximal and the heat capacity diverges. Because the asymptotically flat partition function is not normalizable without boundary data, this divergence is interpreted as a Davies-type local stability transition, not by itself as a global first-order phase transition. The principal contribution of this work is therefore a transparent canonical-saddle organization of known qOS thermodynamic results, together with a precise statement of its domain and limitations.

gr-qc↗

arXiv2026

Hawking Temperatures of Dynamical Black Holes from the RVB--Residue Method:Vaidya and Kinnersley Geometries

This paper develops a local residue-based extension of the Robson--Villari--Biancalana method for calculating Hawking temperatures of dynamical black holes. Since non-stationary black holes generally do not admit a global timelike Killing vector, their temperature must be understood in a local, near-horizon, and quasi-stationary sense. By analytically continuing the near-horizon radial function into the complex plane, the Hawking temperature can be extracted from the residue of the inverse horizon function at the simple pole corresponding to the local horizon. This residue prescription is first applied to the Vaidya black hole, where it reproduces the standard local trapping-horizon temperature (T=1/(8πM(v))). The method is then extended to the arbitrarily accelerating Kinnersley black hole, whose horizon depends on time and angular coordinates. In this case, the RVB--residue method yields a point-dependent local Hawking temperature consistent with the generalized tortoise-coordinate approach. The results show that the RVB--residue method can be naturally generalized from stationary black holes to dynamical and non-spherical black holes, provided that the temperature is interpreted as a local near-horizon quantity rather than a global equilibrium temperature.

gr-qc↗

arXiv2026

Thermodynamic Regulation of Superradiance in a Charged Two-Dimensional Black Hole

Within the framework of gravitational thermodynamicization, we investigate the propagation of charged scalar fields in static two-dimensional black-hole spacetimes. Starting from the scalar-field action, we derive the exact radial wave equation and show that a neutral, massless, minimally coupled scalar field in a genuinely two-dimensional geometry exhibits neither an angular-momentum barrier nor superradiant amplification. For a charged scalar field, the condition for amplification is governed by the electrostatic potential evaluated at the event horizon. In the case of the charged two-dimensional string black hole, the horizon electrostatic potential is directly related to the Hawking temperature, implying that the superradiant frequency window is determined by the thermodynamic state of the black hole. We further formulate a near-horizon residue criterion that provides a coordinate-independent characterization of the superradiant threshold. When a reflecting outer boundary is imposed, necessary frequency conditions for unstable modes are derived, together with an upper bound on their growth rates. Numerical calculations verify the corresponding flux relation and clearly distinguish superradiant scattering from genuine superradiant instability.

physics.gen-ph↗

arXiv2026

Non-Equilibrium Physics of Thermodynamicized Black Holes

This work presents a non-equilibrium framework for thermodynamicized black holes, inspired by the entropy-functional interpretation of emergent gravity and by residue-based methods in black hole thermodynamics. The main idea is to unify three components: an entropy functional principle for selecting physical on-shell backgrounds, a Euclidean and contour-based description of the horizon temperature through simple pole singularities, and a topological residue classification of multi-horizon black hole configurations. On this basis, the paper introduces a quasi-stationary non-equilibrium partition functional in which irreversible entropy production appears as an additional contribution to the singular action. The formalism reproduces the standard equilibrium relations in the adiabatic limit, while also extending them to dynamically driven black-hole systems with matter, charge, and rotational fluxes. The framework is then applied to Kerr Newman type black holes in constant curvature f(R) gravity, where the equilibrium entropy remains weighted by the derivative of f at the background curvature, while non-equilibrium corrections arise from flux-induced deformations of the effective thermodynamic action. The analysis further shows that the outer and inner horizons carry opposite topological orientations, so the non-extremal Kerr Newman family stays in the topological class W = 0 unless a horizon bifurcation or merger changes the singularity structure. Finally, several function plots are provided to illustrate the behavior of equilibrium and non-equilibrium free energy, the Kerr Newman temperature curve, and the entropy production law.

gr-qc↗

arXiv2026

Thermodynamic Consistency of Logarithmic Entropy Corrections on the Schwarzschild Branch of $f(\mathbb{Q})$ Gravity and a Superradiance No-Go Result

We present a concise and explicit analysis of logarithmically corrected black-hole thermodynamics and scalar scattering on the Schwarzschild branch of symmetric teleparallel gravity. Treating the metric and the flat, torsion-free affine connection as independent variables, we formulate the relevant nonmetricity geometry and field equations and show that the linear branch is dynamically equivalent to general relativity up to a boundary term. The vacuum solution is therefore the Schwarzschild spacetime. The leading entropy is derived from both the Noether-charge method and the classical first law, after which a logarithmic correction is introduced. When the geometry and ADM mass are kept fixed, the geometric Hawking temperature remains unchanged, whereas the temperature defined through the corrected first law is modified. The apparent divergence of the heat capacity occurs outside the regime in which the logarithmic expansion is reliable and therefore cannot be interpreted as a physical phase transition. We also derive the scalar radial equation, effective potential, conserved Wronskian, and reflection-transmission relation. For a neutral scalar field on a static neutral background, no superradiant amplification occurs, and the entropy correction produces no first-order change in the scattering amplitudes unless a genuine semiclassical backreaction or an explicit rotating or charged black-hole solution is provided.

gr-qc↗

arXiv2026

Thermodynamic-Geometric Phase Transition and Gravitational-Wave Quasinormal Modes of Schwarzschild Black Holes in $f(Q)$ Gravity: An RVB-Residue Approach

We construct a residue-based framework connecting the thermodynamic geometry of a Schwarzschild-type black hole in $f(Q)$ gravity with its gravitational-wave quasinormal-mode spectrum. The analysis is based on the symmetric teleparallel formulation of gravity, in which the gravitational field is encoded by the nonmetricity scalar $Q$ rather than by curvature or torsion. For the Schwarzschild branch, the Robson--Villari--Biancalana (RVB) method gives the Hawking temperature through the simple-pole residue of the inverse blackening function. We show explicitly that the same residue also controls the logarithmic monodromy of the tortoise coordinate near the event horizon, and therefore enters the ingoing quasinormal-mode boundary condition. In the strict general-relativistic Schwarzschild limit the heat capacity is negative and finite, the one-dimensional Ruppeiner geometry contains no intrinsic curvature singularity, and no genuine thermodynamic phase transition occurs. In the extended $f(Q)$ state space, however, the modified horizon function and the effective Wald entropy generate a non-trivial thermodynamic Hessian. Its degeneracy condition coincides with singular behavior of the thermodynamic curvature and is reflected in the quasinormal-mode spectrum through shifts of the photon-sphere frequency, Lyapunov exponent, damping time, and near-horizon monodromy. This gives a precise statement of the internal relation between thermodynamic-geometric phase structure and gravitational-wave ringdown: both are different projections of the same analytic structure of the corrected black-hole metric.

gr-qc↗

arXiv2026

Dirac-Field Black Hole Entropy in $f(Q)$ Gravity from the RVB Residue Method

We compute the entropy of a Dirac quantum field near a static, spherically symmetric black hole in (f(Q)) gravity by combining the residue-based Robson--Villari--Biancalana method with the thin-film state-counting approach. The RVB prescription introduces a residue correction to the Hawking temperature, while the Dirac field entropy is obtained from the near-horizon WKB mode density and fermionic free energy. For an (f(Q))-deformed metric, we derive the Hamilton--Jacobi equation, radial momentum, mode number, and entropy at the residue-corrected temperature. The result shows that the Dirac-field entropy remains proportional to the horizon area after regularization, but its coefficient is modified by a cubic RVB temperature factor. An explicit expression is obtained for the quadratic model (f(Q)=Q+αQ^{2}).

gr-qc↗

arXiv2026

Black Hole Entropy in f(Q) Gravity from the RVB Residue Method

We extend the residue-based Robson-Villari-Biancalana (RVB) method from the calculation of Hawking temperature to the determination of black hole entropy within f(Q) gravity. Starting from the residue-corrected temperature prescription developed in recent RVB analyses of f(Q) black holes, we combine this approach with the first law of black hole thermodynamics to derive a general expression for the entropy of static, spherically symmetric configurations. By expressing the metric in a standard Schwarzschild-like decomposition with an additional correction term, we show that the entropy satisfies a universal integral relation. The integrand depends explicitly on horizon data as well as on a residue-induced temperature shift parameter. For the specific quadratic model, we obtain an explicit closed-form expression for the entropy at first order in the residue parameter. In the limit where the residue contribution vanishes, the standard Bekenstein-Hawking area law is recovered. However, once the complex contour contribution is retained, a correction beyond the area law naturally emerges. This framework should be interpreted as a residue-induced thermodynamic extension of the temperature-based method, rather than as a universal Noether charge formulation applicable to all f(Q) black hole solutions.

gr-qc↗

arXiv2026

Canonical and Grand-Canonical Singular Ensembles within a Thermodynamicized Gravity Framework

This paper develops a gravitational-thermodynamic interpretation of two ensemble structures with singular behavior, denoted as canonical ensemble A and grand canonical ensemble B. Ensemble A is modeled as a stellar-type system in which energy plays the dominant thermodynamic role under an effectively fixed particle-number condition, whereas ensemble B is modeled as a galactic-type open system in which both energy and particle number participate nontrivially and relativistic effects become essential. Within this framework, the singular structures of the two ensembles are treated in a unified manner by contour integration and residue analysis. For ensemble A, the dominant contribution is associated with the mass-energy relation and the corresponding energy-driven singular sector. For ensemble B, the coupled influence of mass-energy equivalence and the invariance of the speed of light leads to a more intricate singular configuration in which particle exchange and relativistic kinematics must be incorporated simultaneously. We show that the gravitational-thermodynamic formulation provides a natural bridge between local singular behavior and global thermodynamic observables, allowing the two ensembles to be compared within a common variational and geometric language. The resulting description clarifies why the canonical sector is more suitable for closed or quasi-closed astrophysical systems, while the grand canonical sector is more appropriate for open large-scale structures with appreciable matter and energy exchange. This approach offers a mathematically coherent route for extending ensemble theory toward self-gravitating systems and suggests a broader singularity-based methodology for relativistic thermodynamics.

gr-qc↗

arXiv2026

Threshold Temperature for Neutron-Star Emergence in a Gravitational Thermodynamic Framework

Motivated by the entropy-functional formulation of emergent gravity, in which spacetime is endowed with a thermodynamic entropy that, upon extremization, yields the Einstein field equations, we reformulate the onset of a neutron star as a bulk gravitational-thermodynamic threshold problem. By combining the Jacobson-Padmanabhan perspective of gravity as an equation of state with Tolman redshift, Tolman-Oppenheimer-Volkoff hydrostatics, and a bulk binding versus thermal energy balance, we derive four characteristic temperature scales for a static compact object: the Newtonian virial threshold, the redshifted threshold as observed at infinity, the degenerate-matter threshold, and the surface screen temperature.The paper supplies a mathematically expanded derivation, explicit TOV and Fermi-gas formulae, and thermodynamic consistency relations.

gr-qc↗

arXiv2026

Energy Layers and Quasi-Superradiant Heat Engines of Schwarzschild Black Holes

We examine Schwarzschild black holes within the framework of gravitational thermodynamics, introducing an ``energy layer'' picture for black-hole mass-energy and exploring a possible energy-extraction mechanism termed ``quasi-superradiance.'' Building on the standard relations for Hawking temperature and Bekenstein--Hawking entropy, we formalize energy layers via quasi-local radial energy accounting (e.g.\ integrating an effective local energy density over spherical shells) and connect this bookkeeping to the free energy $\FHelm=M-Þ\SBH$. We then extend the entropy correction ansatz with explicit series inversion and derive higher-order expansions for $Þ(M)$ and $\FHelm(M)$, including logarithmic and inverse-mass terms. To enhance mathematical transparency, we add intermediate derivations, lemma/theorem statements, and appendices. The quasi-superradiant mechanism is framed as a Carnot-like thought experiment powered by the Tolman temperature gradient between the near-horizon region and infinity; we show that the generalized second law enforces the Carnot bound and yields integrated maximum-work inequalities. Throughout, we stress that the proposal is heuristic and intended as a consistency-checked framework for discussion rather than a claim of definitive new physics.

gr-qc↗

arXiv2026

Existence of Halos Outside Schwarzschild-$f(R)$ Black Holes

We investigate the possibility of photon halos (stable photon orbits) forming outside Schwarzschild-$f(R)$ black holes by analyzing null geodesics in these spacetimes. Using methods inspired by studies of spherical photon orbits around Kerr-Newman black holes, we derive conditions for the existence of such halos. We examine several f(R) gravity models, including quadratic, logarithmic, exponential, cubic, power-law, and hyperbolic forms, and find that multiple photon orbits -- both stable and unstable -- can appear outside the event horizon for certain parameter ranges. These additional orbits (halos) provide new insights into spacetime geometry and potential observational signatures of black holes in modified gravity. We present analytical expressions for the orbital radii, perform a numerical stability analysis, and discuss possible observational implications for black hole shadows. Our results indicate that while the standard Schwarzschild black hole admits only a single unstable light ring, Schwarzschild-$f(R)$ black holes can support an additional outer stable photon orbit (a halo) without triggering a black-hole bomb instability. This work deepens the understanding of photon-orbit structures in alternative theories of gravity and highlights how such effects could be detected through deviations in black hole shadow size or morphology.

gr-qc↗

arXiv2026

Comment on "Superradiant stability of the Kerr black holes" (arXiv:1907.09118)

We revisit the recent work of Huang on the superradiant stability of Kerr black holes coupled to massive scalar fields. While their analysis provides sufficient conditions for stability, it imposes an unnecessarily strong requirement by demanding that two roots of the relevant quartic equation be explicitly negative. By instead analyzing the polynomial's coefficients, we show that simpler constraints already exclude additional positive turning points, thereby slightly enlarging the region of guaranteed stability. We further present a near-extremal estimate that tightens the stability bound for rapidly spinning black holes. These refinements sharpen the analytic stability limits without introducing extra assumptions.

gr-qc↗

arXiv2025

Topological Complex Analysis of Kerr--Newman Black Hole Microstructure in f(R) Gravity

We investigate the microstructure of Kerr Newman black holes in modified gravity of the f(R) type using a topological complex analytic framework inspired by holography. In this approach, black hole microstates are identified with singularities of an analytically continued partition function, and the entropy is obtained from residues weighted by winding numbers. We show that the microstructure is characterized by a discrete topological index, which encodes both horizon structure and thermodynamic stability. Non extremal Kerr Newman black holes with both inner and outer horizons correspond to a vanishing topological index, while single horizon configurations correspond to a positive unit topological index. An explicit Starobinsky type modified gravity model demonstrates that this classification is robust under changes to the gravitational sector. We further discuss the limitations of the analytic continuation procedure and suggest that this topological classification may indicate a form of phase protection in black hole thermodynamics.

gr-qc↗

arXiv2025

Thermodynamic geometric analysis of D-dimensional RN black hole

This paper studies the thermodynamics and Ruppeiner geometry of D-dimensional RN black holes. We analyze the thermodynamic curvature scalar $R$ in various thermodynamic ensembles. It is found that in an ensemble of fixed charge (canonical ensemble), the Ruppeiner curvature is curved and diverges at a critical point, indicating the existence of a phase transition for $D > 4$. In contrast, when all extensive variables are allowed to fluctuate (for example, in a grand-canonical ensemble or with pressure fixed), the Ruppeiner geometry can appear flat. We also demonstrate that the thermodynamic geometric metric has a one-to-one correspondence with the periodicity of the Euclidean path integral method. In particular, the inverse temperature (the Euclidean time period) serves as a bridge connecting the thermodynamic geometry and the Euclidean action approach.

gr-qc↗

arXiv2025

Analysis and research on superradiant stability of Kerr-sen Black Hole

Kerr Sen black holes possess stretchon parameters and hidden conformal symmetries. The superradiant stability and steady state resonance of such black holes warrant further investigation and form the primary motivation for this study. In this work,we introduce an additional variable, referred to as y, to generalize the findings of the previous study. When the frequency of the perturbation lies within a specific range namely, above a certain threshold determined by the spin parameter and below the sum of the azimuthal quantum number times the angular velocity at the horizon and the product of the charge with the electric potential at the horizon,the Kerr Sen black hole exhibits superradiant stability. This behavior is similar to the superradiant characteristics previously observed in KN black holes.

gr-qc↗

arXiv2025

Calculating the Hawking Temperature of Black Holes in $f(Q)$ Gravity Using the RVB Method: A Residue-Based Approach

This paper investigates the computation of Hawking temperatures for black holes within various $f(Q)$ gravity models using the RVB method. This topological approach uncovers an additional term in the temperature calculation, which we propose originates from the residue of a specific contour integral related to the metric or curvature. By examining several specific $f(Q)$ models including quadratic, logarithmic, square root, and power law modifications as well as well known black hole solutions such as RN, Kerr, and KN black holes, we demonstrate that the correction term can consistently be interpreted as this residue. Our findings provide new insights into black hole thermodynamics within modified gravity frameworks.

gr-qc↗

arXiv2024

Verification of the First Law of Horizon Thermodynamics for Schwarzschild, Reissner-Nordström, Kerr, and Kerr-Newman Black Holes in Four-Dimensional f(R) Gravity with Dual Scalar Fields

This paper demonstrates the validity of the first law of horizon thermodynamics for Schwarzschild, RN, Kerr, and Kerr-Newman (KN) black holes within the framework of four-dimensional f(R) gravity coupled with dual scalar fields. Starting from a five-dimensional membrane world scenario, we derive the four-dimensional effective f(R) gravity action and obtain the corresponding black hole solutions. We then verify that these solutions satisfy the first law of black hole thermodynamics by explicitly calculating the variations of thermodynamic quantities. The analysis confirms the robustness of the horizon thermodynamics framework in extended gravitational theories, providing insights into the interplay between higher-dimensional theories and four-dimensional black hole thermodynamics.

gr-qc↗