arXiv subjects

Chao-Hui Wang

Publications and source records attributed to Chao-Hui Wang.

10 recordsLinked to original sources

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

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

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↗

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. 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↗

arXiv2025

Equatorial periodic orbits and gravitational waveforms in a black hole free of Cauchy horizon

In this paper, we study the periodic orbits and gravitational wave radiation in an extreme mass ratio inspiral system, where a stellar-mass object orbits a supermassive black hole without Cauchy horizons. Firstly, by using the effective potential, the marginally bound orbits and the innermost stable circular orbits are investigated. It is found that the radius, orbital angular momentum, and energy increase with the hair parameter for both orbits. Based on these results, we examine one special type of orbit, the periodic orbit, around the black hole without the Cauchy horizon. The results show that, for a fixed rational number, the energy and angular momentum of the periodic orbit increase with the hair parameter. In particular, we observe a significant deviation from the Schwarzschild case for small hair parameter with a large amount of external mass outside the black hole horizon. Moreover, we examine the waveforms in the extreme mass ratio inspiral system to explore the orbital information of the periodic orbits and the constraints on the parameters of the black holes. The results reveal that the gravitational waveforms can fully capture the zoom-whirl behavior of periodic orbits. Moreover, the phase of the gravitational waves imposes constraints on the parameters of the black hole solutions. As the system evolves, the phase shift of the waveforms becomes increasingly significant, with cumulative deviations becoming more pronounced over time. Compared to the Schwarzschild black hole background, the waveform phase will advance for the central supermassive black hole without a Cauchy horizon.

gr-qc↗

arXiv2024

Imprints of black hole charge on the precessing jet nozzle of M87*

The observed jet precession period of approximately 11 years for M87* strongly suggests the presence of a supermassive rotating black hole with a tilted accretion disk at the center of the galaxy. By modeling the motion of the tilted accretion disk particle with the spherical orbits around a Kerr-Newman black hole, we study the effect of charge on the observation of the precession period, thereby exploring the potential of this strong-gravity observation in constraining multiple black hole parameters. Firstly, we study the spherical orbits around a Kerr-Newman black hole and find that their precession periods increase with the charge. Secondly, we utilize the observed M87* jet precession period to constrain the relationship between the spin, charge, and warp radius, specifically detailing the correlations between each pair of these three quantities. Moreover, to further refine constraints on the charge, we explore the negative correlation between the maximum warp radius and charge. A significant result shows that the gap between the maximum warp radii of the prograde and retrograde orbits decrease with the black hole charge. If the warp radius is provided by other observations, different constraints on the charge can be derived for the prograde and retrograde cases. These results suggest that in the era of multi-messenger astronomy, such strong-gravity observation of precessing jet nozzle presents a promising avenue for constraining black hole parameters.

gr-qc↗

arXiv2023

Extracting spinning wormhole energy via magnetic reconnection

Magnetic reconnection has been extensively shown to be a promising approach to extract spinning black hole energy. In this paper, we focus on extracting spinning wormhole energy via such mechanism. The study shows that it is indeed possible to extract rotating energy from a spinning wormhole with small regularization parameter $\ell$ of the central singularity. The efficiency and power of the energy extraction are also evaluated. Quite different from the Kerr black hole, the spin of the wormhole can take arbitrarily large value. However, the increasing of wormhole spin not always improves the efficiency and power of energy extraction. By further comparing with the Kerr black hole, we find the wormhole is more efficient when the magnetic reconnection happens within radial distance $r/M<1$. These studies reveal the features of extracting spinning wormhole energy, and more underlying properties are expected to be disclosed for the horizonless objects.

gr-qc↗

arXiv2023

Extracting energy via magnetic reconnection from Kerr-de Sitter black holes

It has been recently shown that magnetic reconnection can provide us a novel mechanism to extract black hole rotational energy from a Kerr black holes. In this paper, we study the energy extraction from the Kerr-de Sitter black hole via this magnetic reconnection process. The result shows that, with the increase of the cosmological constant, a slowly spinning Kerr-de Sitter black hole can implement the energy extraction better than its Kerr counterpart. Interestingly, although the numerical results show that the maximum values of the power and efficiency slightly decrease with the cosmological constant, Kerr-de Sitter black hole still has significant advantages when the black hole spin is larger than 1 and the dominant reconnection $X$-point is far away from the event horizon. This is mainly attributed to the higher upper spin bound and wider ergosphere in the presence of the cosmological constant. These results uncover the significant effects of the cosmological constant on the energy extraction via the magnetic reconnection process.

gr-qc↗

arXiv2019

Prediction for $5^{++}$ mesons

In this paper, we study the spectrum and decay behavior of $5^{++}$ meson family which is still missing in experiment. By the modified Godfrey-Isgur model with a color screening effect, we obtain the mass spectrum of $a_5$, $f_5$ and $f_5^\prime$ mesons. And we predict their two-body strong decays by means of a phenomenology quark pair creation model. This study is crucial to establish $J^{PC}=5^{++}$ meson family and it is also helpful to search for these states in the future.

hep-ph↗