arXiv subjects

Shao-Wen Wei

Publications and source records attributed to Shao-Wen Wei.

At least 19 recordsLinked to original sources

arXiv2026

Evolution and disruption of circular orbits during dynamic black hole scalarization

Dynamical black hole scalarization describes the process by which a ``no-hair" black hole transitions to a scalarized hairy state. This transition significantly alters the spacetime geometry, including the structure of stable circular orbits of the test particles, which are critical for astrophysical observations and tests of gravity. In this work, we employ numerical relativity simulations to model the time-dependent evolution of a vacuum black hole undergoing scalarization. By evolving timelike geodesic equations within the dynamically changing spacetime background, we investigate how the scalarization process impacts initially stable circular orbits. Our results reveal that the growth of the scalar hair destroys the circular nature of these orbits, forcing them to either become eccentric or plunge into the black hole. This orbital destabilization arises from the rapid change of spacetime curvature induced by the scalar field. Our findings provide novel insights into the interplay between scalar fields and black hole dynamics, with significant implications for gravitational-wave signatures, accretion disk stability, and observational tests of extended theories of gravity.

gr-qc↗

arXiv2026

Holographic complexity of de Sitter black holes

We investigate holographic complexity within the Schwarzschild-de Sitter (SdS) black hole spacetime. Two distinct de Sitter holography prescriptions are examined: the static patch scheme restricted to the stretched horizon and the de Sitter/Conformal Field Theory (dS/CFT) correspondence scheme defined at asymptotic future and past infinities. We evaluate the Complexity equals Volume (CV) conjecture and extend the analysis to codimension-zero proposals, specifically Complexity equals Spacetime Volume (CV2.0) and Complexity equals Action (CA), through the Wheeler-DeWitt (WDW) patch we construct. The behaviors of the complexity in the static patch holography at late time and in the dS/CFT at infinite spacelike boundary coordinate are studied, respectively. We find that under both the CV and CV2.0 conjectures, the static patch holographic complexity and the dS/CFT holographic complexity consistently exhibit linear growth. Conversely, regarding the CA conjecture, the holographic complexity growth rates for both the static patch and the dS/CFT correspondence vanish. This behavior is attributed to the finiteness of the (regularized) action within the restricted WDW region. Furthermore, we find that, in the limit in which the boundary coordinate is taken to infinity, the complexity growth rate in the static patch prescription coincides with its counterpart in the dS/CFT prescription. This agreement suggests a deeper connection between the two descriptions and may point toward a unified understanding of bulk dynamics in de Sitter holography.

hep-th↗

arXiv2026

Central charge and black hole entropy for regular extremal black-bounce spacetimes

The Bekenstein-Hawking entropy, proportional to one quarter of the horizon area, is fundamental in black hole thermodynamics and can also be understood via the AdS/CFT correspondence, such as the 3D BTZ black hole and 2D CFT. In this work, we adopt the Kerr/CFT approach to analyze the central charge and black hole entropy for regular extremal black-bounce spacetimes, including the counterparts of the Kerr, Kerr-Newman, and Reissner-Nordström black holes. These spacetimes are free of curvature singularities at $r=0$. We derive the near horizon geometries of these spacetimes and find that they exhibit enhanced symmetry, namely SL$(2,\mathbb{R})\times \mathrm{U}(1)$ or SL$(2,\mathbb{R}) \times \mathrm{SO}(3)$. By imposing appropriate boundary conditions, we analyze their asymptotic symmetry groups, which contain diffeomorphisms as well as the $\mathrm{U}(1)_{\rm gauge}$ symmetry arising from the electromagnetic field. We then extract the central charge from the charge algebra and evaluate the left-moving temperature of the Frolov-Thorne vacuum. It is worth emphasizing that in the black-bounce Kerr-Newman case, the central charge from the electromagnetic contribution vanishes. Furthermore, in the black-bounce Reissner-Nordström case, we uplift the 4D geometry to a 5D configuration by incorporating a $\mathrm{U}(1)$ gauge fiber. Our results show that the microscopic entropy calculated from the Cardy formula is consistent with the Bekenstein-Hawking entropy. This agreement suggests that the Kerr/CFT approach remains valid for certain regular spacetimes without curvature singularities, thereby providing a microscopic statistical understanding of black hole entropy.

hep-th↗

arXiv2026

Gravitational equal-area law and critical phenomena of cuspy black hole shadow

The formation of a cusp on a black hole shadow is a striking signature of physics beyond the Kerr paradigm. Using the Konoplya-Zhidenko metric, a general parametrized deformation of Kerr black hole, we demonstrate that this morphological change fundamentally alters the shadow's topology with the topological charge flipping from 1 to -1. To analyze this topological transition, we introduce a gravitational equal-area law, analogous to Maxwell's construction in thermodynamics, and identify a critical point for cusp formation. Near this point, we uncover universal behavior characterized by a critical exponent 1/2, which places this gravitational lensing system within the mean-field universality class. These results establish a new framework for testing fundamental physics of black hole shadows, reframing the search for deviations from general relativity as a targeted hunt for a distinct topological and critical phenomenon.

gr-qc↗

arXiv2026

The universal topological charge of black hole photon spheres in higher dimensions

A recently developed topological approach offers novel insights into photon spheres, which are fundamental to the formation of black hole shadows. In this study, we extend this topological analysis to higher-dimensional, static, spherically symmetric, and asymptotically flat black holes. By examining the asymptotic properties of the vector field associated with the photon spheres, we demonstrate that their topological charge is consistently -1. This result is a dimensionally independent invariant, guaranteeing the existence of at least one standard (unstable) photon sphere outside the event horizon. We further explore this conclusion by analyzing two distinct regular black hole solutions derived from pure gravity theory, confirming that the topological charge remains -1 irrespective of the spacetime dimension. These results provide a robust and universal characterization of photon spheres in higher-dimensional spacetimes.

gr-qc↗

arXiv2026

Enhanced energy extraction via magnetic reconnection in Kerr-AdS spacetime

In this paper, we study the energy extraction from Kerr-AdS black holes following the magnetic reconnection process. The parameter space regions that satisfy the energy extraction condition, as well as the efficiency and power of the extracted energy, are analyzed. The study shows that the presence of a negative cosmological constant extends the range of dominant reconnection radial locations where the energy extraction condition is met, and enables energy extraction even from black holes with relatively low spin. Furthermore, the influence of the negative cosmological constant on energy extraction is modulated by the extent of the dominant reconnection radial region: a more negative cosmological constant enhances the extracted energy, efficiency, and power, particularly for smaller dominant reconnection radii. These results demonstrate that the energy extraction from Kerr-AdS black holes is more favorable than that from their asymptotically flat counterparts. Our results highlight the crucial role of the cosmological constant in energy extraction via magnetic reconnection.

gr-qc↗

arXiv2026

A new type of multi-branch periodic orbits in dyonic black holes

We investigate bound timelike periodic orbits in dyonic black hole spacetimes arising from quasi-topological electromagnetism. By varying the coupling parameter $α_1$, we show that the exterior monotonicity of the metric function, rather than the number of horizons, controls the topology of the radial effective potential, which can exhibit either a single well or multiple wells separated by potential barriers. When $f(r)$ is non-monotonic outside the event horizon, the effective potential develops multiple wells, leading to multiple MBO branches and several coexisting periodic-orbit branches with the same rational number $q$. These branches are topologically equivalent but geometrically distinct, because they correspond to different energies or angular momenta, leading to different radial extents and eccentricities. In particular, bound periodic orbits with $E>1$ can occur, and up to three branches may coexist. We also find an inverted radial response: the innermost branch becomes more circular as the energy or angular momentum increases, whereas the outer branches become more eccentric. By contrast, when $f(r)$ is monotonic outside the event horizon, the effective potential has a single well and only one periodic orbit branch exists, even for black holes with multiple horizons. Our results identify metric non-monotonicity as the geometric origin of multi-branch periodic motion and suggest a timelike counterpart to the multiple photon ring signatures of nonstandard black hole geometries.

gr-qc↗

arXiv2026

Gravitational partition function under volume constraints

The Euclidean action provides a bridge between gravitational thermodynamics and the partition function. In this work, we further investigate the gravitational partition function under a fixed-volume constraint, generalizing the fixed-volume on-shell geometry in the massless case. Moving beyond this massless configuration, we construct solutions with nonvanishing mass functions, which give rise to a new class of volume-constrained Euclidean geometries (VCEGs). These geometries possess both a boundary and a horizon. However, closer inspection indicates that the boundary is not intrinsic, but rather artificially introduced and can be extended, leading to the extended volume-constrained Euclidean geometries (ECVEGs). The ECVEGs contain two horizons, each generically associated with a conical singularity. Their Euclidean action is given by one quarter of the sum of the areas of the two horizons. In general, the conical singularities at the two horizons cannot be simultaneously eliminated, except at a critical mass $m = m^*$, which defines the critical ECVEG. Configurations with unavoidable conical singularities are naturally interpreted as constrained gravitational instantons. An analysis of their contributions to the partition function, together with their topological properties, reveals a close analogy between the ECVEGs and the Euclidean Schwarzschild--de Sitter static patch. This suggests that the volume constraint effectively plays a role analogous to that of a cosmological constant in semiclassical quantum gravity.

hep-th↗

arXiv2026

Interior geometry of black holes as a probe of first-order phase transition

Traditional diagnostics of black hole phase transitions rely on thermodynamic quantities defined at the event horizon or asymptotic boundary. Here, we demonstrate that the near-singularity geometry offers a sharp, independent probe of both first-order phase transitions and supercritical crossover. For scalarized AdS black holes exhibiting a first-order phase transition, the Kasner exponent $p_t$, which characterizes the approach to the singularity, undergoes a dramatic transformation. On one side of the transition, $p_t$ oscillates strongly with temperature, reflecting violent interior dynamics. On the other side, it becomes a smooth, monotonically varying function. These two distinct behaviors converge as the critical point is approached. Beyond the critical point, in the supercritical region, $p_t(T)$ develops a distinct extremum, defining a Kasner crossover line that is entirely independent of traditional thermodynamic (Widom line) or dynamic (Frenkel line) criteria. Our work establishes the near geometry of singularity of scalarized black hole as a novel class of diagnostics for phase transitions, revealing that a change in the macroscopic thermodynamic state fundamentally reshapes the deepest interior structure of spacetime.

gr-qc↗

arXiv2026

Unifying topological, geometric, and complex classifications of black hole thermodynamics

Black hole thermodynamics has recently witnessed three distinct classification schemes: based on local geometric properties of the temperature function, global topological invariants, and Riemann surface foliations in the complex plane. We show that these schemes can be precisely mapped onto one another in the real domain via two dictionaries: one linking thermal stability to the monotonicity of the temperature curve, and the other connecting the number of black hole states to the foliation number of a Riemann surface. The number of extremal points of the temperature curve determines the classification in all three frameworks, tracing this unification to the critical point structure of the black hole solution space. As an illustration, several black holes demonstrate how counting extrema yields topological invariants and phase transition information. This unified framework simplifies black hole thermodynamic analysis and provides a foundation for exploring more complex black holes.

gr-qc↗

arXiv2026

Phase transitions in scalarized topological AdS black holes

We investigate the behavior of black hole scalarization induced by a charged scalar field in the extended phase space of the asymptotic AdS spacetime with three distinct horizon topologies. The results indicate that in all three cases, the charged black hole spacetime undergoes scalarization at low temperatures. Notably, the spherical topology is unique in that its domain of scalarization theoretically extends to much higher temperatures under low pressure in the extended phase space. Moreover, the scalarization process in the spherical case exhibits complex phase transition behaviors without additional non-linear terms, which are similar to those in the planar and hyperbolic topologies with the assistance of non-linear terms. With increasing pressure in the extended phase space, the condensate of the scalarization in all three cases undergoes a transition from the first-order style to a cave-of-wind style. This study provides deeper insight into the zeroth-order phase transition during black hole scalarization and reveals the complete phase structure of black holes in the extended phase space.

gr-qc↗

arXiv2026

Black Hole Entropy Beyond the Wald Term in Nonminimally Coupled Gravity: A Covariant Phase Space Decomposition

We study the entropy of static, spherically symmetric black holes in diffeomorphism-invariant theories with nonminimal matter--curvature couplings, using the covariant phase space formalism. For regular bifurcate Killing horizons, the Iyer--Wald construction gives the standard Wald entropy. If a matter field cannot be smoothly extended to the regular bifurcation surface, however, the entropy-sector horizon surface charge variation can contain finite contributions that are not included in the Wald entropy density. In the representative obtained by directly varying the action, and after ordinary non-gravitational boundary terms have been separated into the work sector, we decompose the entropy entering the first law of black hole thermodynamics as $\SH=\SW+\Sone+\DeltaS$. Here $\SW$ is the Wald entropy, $\Sone$ is the non-Wald part of the entropy-sector Noether charge, and $\DeltaS$ is the remaining integrable part of the entropy-sector horizon surface charge variation. Applying this criterion to Kalb--Ramond, bumblebee, and extended Gauss--Bonnet black holes, we find that the regular Kalb--Ramond branch has $\SH=\SW$, the bumblebee branches yield either $\Sone=0$ with $\DeltaS\neq0$ or a cancellation between $\Sone$ and $\DeltaS$, and the Weyl-vector extended Gauss--Bonnet examples require both corrections. This provides a direct test of whether the Wald density is sufficient or whether the full horizon surface charge variation is required.

gr-qc↗

arXiv2026

Topological perspective on bulk boundary thermodynamic equivalence

We establish an exact duality between the extended thermodynamics of five-dimensional charged Gauss-Bonnet AdS black holes and the thermodynamic framework of the dual boundary conformal field theory (CFT). The thermodynamics of the dual CFT involves two central charges originating from the trace anomaly. We demonstrate a precise correspondence between the extended first laws on the bulk and boundary sides. Moreover, the topological charges of the CFT thermodynamics, associated with the phase transition and critical point, coincide with those of the corresponding bulk black hole.

hep-th↗

arXiv2026

Exact Black Hole Solutions in Bumblebee Gravity with Lightlike or Spacelike VEVS

Motivated by recent developments in Lorentz-violating theories of gravity, we obtain new black hole solutions within the framework of bumblebee gravity, where the bumblebee vector field possesses two independent nonzero components and acquires either a lightlike or spacelike vacuum expectation value. Within this framework, we derive new Schwarzschild-like and Schwarzschild-(A)dS-like black hole solutions. By further incorporating a nonminimally coupled electromagnetic field, we generalize these to new charged black hole solutions. These solutions extend previous results by including additional Lorentz-violating parameters. A key finding is that even for lightlike vacuum expectation values, the black hole solutions exhibit distinct corrections from Lorentz violation. Furthermore, we present a preliminary analysis of their thermodynamic properties. Similar to previous studies that reported a discrepancy between the black hole entropy and the Wald entropy in bumblebee gravity with spacelike vacuum expectation values, our solutions in the spacelike case exhibit the same behavior. In contrast, for the lightlike case considered here, the two entropies coincide.

gr-qc↗

arXiv2026

Topology of black hole thermodynamics: A brief review

Recent explorations of topological aspects in black hole thermodynamics have achieved unprecedented progress. By utilizing topological numbers, different black hole systems can be categorized into distinct universality classes. This universal classification is particularly evident in thermodynamic limits, offering valuable insights for developing a comprehensive quantum gravity framework. This review highlights the latest advancements in this field. Specifically, we outline fundamental topological frameworks underlying black hole solutions, critical points, Davies points, and the Hawking-Page phase transition. For each scenario, we calculate the associated topological numbers and analyze their physical significance. Furthermore, we explore the practical implications arising from this research.

gr-qc↗

arXiv2026

Topologically equivalent yet radiatively distinct orbits in EMRI system

Multiple potential wells for massive test particles, allowing distinct families of bound orbits to coexist, are a characteristic feature of certain exotic compact objects beyond general relativity. Taking the dyonic black hole as a representative example, we demonstrate that such multi-well geometries generically support multiple coexisting branches of bound orbits, in contrast to the single-branch behavior observed in the Schwarzschild spacetime. Crucially, the periodic orbits sharing identical rational rotation number, and hence identical topological indices can nevertheless produce \emph{radiatively distinct} gravitational waves in a representative extreme-mass-ratio inspirals: their amplitude modulation and harmonic content differ because each branch spans different regions of spacetime curvature. These ``topologically equivalent yet waveform-distinguishable'' signatures provide a direct observational probe of strong field gravitational dynamics beyond general relativity, potentially accessible to future space-based gravitational wave detectors.

gr-qc↗

arXiv2026

Gravity/thermodynamics correspondence via black hole shadows

The shadow of a black hole serves as a pristine window into the strong-gravity regime, with cuspy feature emerging as a smoking-gun signature of physics beyond the Kerr paradigm. In this paper, we extend the work of [arXiv:2601.15612 [gr-qc]] and study the detailed properties of the cuspy shadow by using the parametric expressions of the shadow boundary. From a topological perspective, we provide a rigorous topological classification of these shadows, categorizing them into distinct ``rectangular" and ``8-shape" topologies. Crucially, we establish a formal gravity/thermodynamics correspondence by mapping the cuspy shadow to the swallowtail behavior observed in thermodynamic free energy. We demonstrate that the self-intersection of the shadow boundary, marking a geometric phase transition, can be precisely determined through three independent but equivalently thermodynamic-like approaches. Furthermore, we analytically derive the critical exponents governing the emergence of these cusps, revealing that they are consistent with the mean-field universality class. Our results suggest that the observational features of black hole shadows are deeply rooted in the underlying gravitational thermodynamics, offering a novel framework to probe the fundamental nature of spacetime.

gr-qc↗

arXiv2026

Magnetic field effects on spherical orbit in Kerr-Bertotti-Robinson spacetime: constraints from jet precession of M87*

The recently reported precession period of about $11.24$ years of the M87* jet provides a sensitive probe of strong field gravity and the electromagnetic environment in the immediate vicinity of supermassive black holes. In this work, we study the precession of the spherical orbit in the Kerr-Bertotti-Robinson geometry describing a rotating black hole immersed in a uniform electromagnetic field. Although the timelike geodesics is non-separable, we develop a Hamiltonian approach to investigate the spherical orbits. For sufficiently strong magnetic fields, the study shows that the spherical orbits can only exist within a finite radial range for given orbital inclination. Requiring the existence of the spherical orbits, we obtain an upper bound of the magnetic field, i.e., $B<0.33 M^{-1}$ for prograde and $B<0.0165 M^{-1}$ for retrograde motion. Furthermore, imposing the observed jet precession period, we obtain a significantly tighter constraint, $B\lesssim 0.0145 M^{-1}$, providing a new constrain on the magnetic field of M87* independent of the shadow. Our results provide unified constraints on the parameters of the KBR black hole and demonstrate that the jet precession offers a robust and complementary probe of magnetized black holes in the strong gravity regime.

gr-qc↗