Chao-Hui Wang’s research while affiliated with Government of the People's Republic of China and other places

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. First, using the Hamiltonian formalism, we derive the equations of motion for spherical orbits, along with the general forms of energy and angular momentum, in the general stationary axisymmetric black hole spacetime. Subsequently, taking the Kerr-Newman black hole as a specific example, we study the effect of charge on spherical orbits and find that the precession period increases with increasing charge. Furthermore, incorporating the constraints of EHT on the black hole charge, 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. 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 radius of the prograde and retrograde disk 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. Finally, we investigate the size of the inner disk. By making use of current observations, our study reveals that the size of the inner disk increases with the charge and spin, and the prograde disk is always larger than the retrograde one. These results provide significant effects of charge in the physics around M87*.

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.

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.

Recently, Comisso and Asenjo demonstrated that rapid magnetic reconnection is 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 ℓ 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 increase in 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.

In this work, we study higher Bc mesons to the L=S, P, D, F, G multiplets using the Cornell potential model, which takes account of the screening effect. The calculated mass spectra of Bc states are in reasonable agreement with the present experimental data. Based on the spectroscopy, partial widths of all allowed radiative transitions and strong decays of each state are also evaluated by applying our numerical wave functions. Comparing our results with the former results, we point out the difference among various models and derive new conclusions obtained in this paper. Our theoretical results are valuable for searching more Bc mesons in experiments.

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.

It has been recently shown that magnetic reconnection can provide us a novel mechanism to extract black hole rotational energy from 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, the 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.

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 some certain values of parameters, such mechanism is found to be more efficient than the Blandford-Znajek mechanism. In this paper, we study the energy extraction from the Kerr-de Sitter black hole via this magnetic reconnection process. With the increase of the cosmological constant, a slowly spinning Kerr-de Sitter black hole can implement the energy extraction than its Kerr counterpart. Of particular interest is that although the numerical calculation shows that the maximum values of the power and efficiency decrease with the cosmological constant, Kerr-de Sitter black hole still has advantages when the black hole spin $a/M>1$ and the dominant reconnection X-point is far away from the event horizon. These results uncover the significant effects of cosmological constant on the energy extraction via the magnetic reconnection process.

In this paper, we study the mass spectra and the decays of low-lying orbital excited $B_c$ mesons. We predict the mass spectra of the high excited $B_c$ states using Cornell potential model taking into account the screening effect. We adopt a wave function which is expanded with a set of complete Simple Harmonic Oscillator (SHO) bases to calculate the radiative decay width of the $B_c$ mesons. Furthermore, the widths of the two-body strong decays of $B_c$ mesons are calculated by the quark pair creation(QPC) model, and the branching ratio are given accordingly. We expect that our research have reference value for searching for the other $B_c$ mesons that have not been observed and establishing the $B_c$ meson family in the future.

When a Simple Harmonic Oscillator (SHO) wave function is used as an effective wave function, a very important parameter in the SHO wave function is the effective $\beta$ value. We obtain the analytical expression of $\beta_{eff}$ ($\beta_{effective}$) of the SHO wave function in coordinate space and momentum space. The expression is applied to the light meson system $(u\bar{u},~u\bar{s})$ to compare the behavior of $\beta_{eff}$. The results show that $\beta_ {eff(\mathbf{r})}$ in coordinate space and $\beta_ {eff(\mathbf{p})}$ in momentum space are significantly different in the ground state, however, similar in the highly excited states.