arXiv subjects

Shining Yang

Publications and source records attributed to Shining Yang.

7 recordsLinked to original sources

arXiv2025

Constraint on magnetized black bounce spacetime from HFQPOs data and the selection of resonance models via information criterion

This paper primarily explores the dynamics of charged particle in the magnetized SV spacetime, and constrains the parameters of the SV spacetime along with its surrounding magnetic fields. The constraints are given by using $\chi^2$ analysis combined with high-frequency quasi-periodic oscillation (HFQPO) data observed from three microquasars: GRS 1915+105, XTE 1550-564, and GRO J1655-40. The results indicate that the magnetic field significantly influences the position of the innermost stable circular orbit of charged particle and frequency distribution of epicyclic motion, which excites more resonance model variants, enhancing observational effects. Additionally, we employ the Akaike Information Criterion (AIC) to evaluate resonance model and its various variants. The support for different models from observational data shows significant variation: $E R_8$ as the best model is supported strongly, $ER_3$ model has moderate evidence of support, $ER_6$ and $ER_7$ models are considerably less support, while other resonance models have essentially no support. For models more supported by the observational data, the allowed ranges of the regularization parameter: $0\leq a<0.736$ ($68\%$ confidence level) suggests that HFQPOs data support the magnetized black bounce spacetime as a regular black hole, and the smaller value of the regularization parameter indicates a possibility of the presence of quantum effects. According to the constraint results, we get the best-fit values of magnetic field strength around $10^{-5}\sim 10^{-4}$ GS for electrons and around $10^{-2}\sim 10^{-1}$ GS for protons. Finally, as a comparison, we test the SV spacetime without a magnetic field using microquasar observational data, and the calculated results of AIC show that this case is incompatible with the HFQPOs data, further supporting the existence of a magnetic field in SV spacetime.

astro-ph.HE↗

arXiv2025

Optical Appearance and Shadow of Kalb-Ramond Black Hole: Effects of Plasma and Accretion Models

In this paper, we study the effect of the presence of plasma and different accretion models on the shadow and optical appearance of static spherically symmetric black holes containing the Kalb-Ramond field. We derive the motion equations for photons around the Kalb-Ramond black hole and constrain the Lorentz symmetry breaking parameters $\lambda$ and $\gamma$ using observational data released by the Event Horizon Telescope collaboration. The results indicate that, under the static spherical accretion model, as $\lambda$ or $\gamma$ increase, the peak value of the observed intensity for Kalb-Ramond black holes is enhanced and consistently exceeds that of the corresponding Schwarzschild black holes. In the presence of plasma, we find that as the plasma frequency increases, the photon sphere radius increases, whereas the black hole shadow radius decreases. In addition, compared to inhomogeneous plasma, the effect of homogeneous plasma on these features is more significant. Specifically, when the plasma is homogeneous, an increase in plasma frequency further enhances the observed intensity peaks. This suggests that the shadow of the Kalb-Ramond black hole is brighter due to the presence of plasma. Additionally, for the same Kalb-Ramond black hole model parameters and plasma frequency, the shadow of the Kalb-Ramond black hole in inhomogeneous plasma is larger than in the case of homogeneous plasma. Under the thin disk accretion model, an increase in the Lorentz symmetry breaking parameters decreases the observed intensity peak and increases the thickness of the photon ring and the lensed ring. The presence of plasma significantly alters the optical appearance of Kalb-Ramond black hole, providing a possible way to distinguish Kalb-Ramond black hole from Schwarzschild black hole.

gr-qc↗

arXiv2025

Observational constraints on the Kerr and its several single-parameter modified spacetimes using quasi-periodic oscillation data

This paper investigates the dynamical effects of particles moving in the Kerr spacetime and its nine single-parameter modified spacetimes, including Bardeen, Ayon-Beato and Garcia (ABG), Hayward, Kerr-Newman (KN), Kerr-Taub-NUT (KTN), Braneworld Kerr (BK), Kerr-MOG, Kerr-Sen, and Perfect Fluid Dark Matter (PFDM) black holes. Using quasi-periodic oscillation (QPO) observational data, we constrain the free parameters of the ten spacetimes through $\chi^2$ analysis under the relativistic precession model of QPO. We constrain the modification parameters for the nine single-parameter modified spacetimes and provide the spin and mass ranges of three microquasars within the ten spacetime models (including Kerr) at the $68\%$ confidence level (CL). The results demonstrate that, at the $68 \%$ CL, the QPO data impose stringent constraints on the free parameters, as evidenced by the narrow confidence intervals. Among them, only the KN spacetime yields a modification parameter constraint spanning both negative and positive values (encompassing the Kerr case at zero). In contrast, all other tested geometries mandate positive-definite parameters at $68 \%$ CL, demonstrating statistical deviation of the Kerr solution. This highlights the significance of exploring modifications to the Kerr spacetime. Finally, we evaluate the spacetime models using the Bayes factor and the Akaike Information Criterion (AIC). Based on the current QPO observational data, the Bayesian factor analysis indicates that the ABG, Hayward, KN, BK, and Kerr-MOG spacetime have a slight advantage over the Kerr solution, while the Bardeen, KTN, Kerr-Sen, and PFDM spacetime are somewhat inferior to the Kerr model. In contrast, the AIC analysis shows that the Kerr spacetime remains the optimal model under the current QPO data.

gr-qc↗

arXiv2024

Research on high-frequency quasi-periodic oscillations in black bounce-type spacetime

This paper investigates the high frequency quasi-periodic oscillations (HFQPOs) phenomenon around the black bounce-type (BBT) spacetime using the resonance models. We calculated the location of the innermost stable circular orbit (ISCO) for different types of celestial bodies, and derived the expression for the epicyclic frequencies of test particles. The results show that the BBT spacetime possesses unique observational characteristics, where the ordering of epicyclic frequencies varies with the regularization parameter $a$, enabling the excitation of low-order resonances and producing stronger observational signals. Using parametric and forced resonance models, we compared theoretical results with the observed 3:2 twin-peak HFQPOs in microquasars (GRO 1655-40, XTE 1550-564, GRS $1915+105$ ), analyzed the formation mechanisms of HFQPOs, constrained the parameters of the BBT model, and explored the possible types of celestial objects corresponding to microquasars. The study indicates that, certain parametric resonance conditions (e.g., $n=1, 2$) lead to traversable wormhole models in BBT that closely align with observations. And forced resonance corresponding to BH or wormhole models can be verified through observations. These results deviate from the data fits of the original black-bounce model. It is found that the oscillatory behavior of three types of microquasars can also be explained by particle oscillations generated in BBT theory, providing evidence for exploring the existence of wormholes, under the assumptions of parametric resonance and forced resonance.

gr-qc↗

arXiv2024

Study on high-frequency quasi-periodic oscillations in rotating black bounce spacetime

This study investigates the dynamical effects of particles orbiting a celestial body in rotating Simpson-Visser (RSV) spacetime. The results show that, compared to Kerr and rotating regular black holes, the innermost stable circular orbit (ISCO) of an RSV wormhole is closer to the central object. Using high-frequency quasi-periodic oscillation (HFQPO) data from microquasars and $\chi^2$ analysis, we constrain the spin of microquasars and the regularization parameter $l$ in RSV spacetime based on four HFQPO models and their variants, and evaluate the models using the Akaike Information Criterion and Bayes factor. Calculations indicate that $\mathrm{ER}_0$, $\mathrm{ER}_1$, $\mathrm{ER}_2$, $\mathrm{RP}_0$, $\mathrm{RP}_2$, and $\mathrm{WD}$ models have the same support by observational data as the best model $\mathrm{TD}$. Other models considered in this paper have less or no support from observational data. Concretely, for cases of $\mathrm{ER}_0$ and $\mathrm{RP}_0$ models, the observational constraints on RSV regularization parameter are respectively: $l^* = 0.908_{-0.073}^{+0.086}$ and $l^* <0.314$ at $68 \%$ confidence level, which correspond to the regular or the Kerr ($l^*=0$) BH. For $\mathrm{ER}_1$, $\mathrm{ER}_2$, $\mathrm{RP}_2$, $\mathrm{TD}$, and $\mathrm{WD}$ models, the observational data suggest that RSV objects should be the traversable wormhole, e.g. we have the limits: $l^* =1.850 \pm 0.036$, $l^* =4.964 \pm 0.046$, etc.

gr-qc↗

arXiv2024

Validity of energy conditions of matter in traversable wormholes under the $f(Q)$ modified gravity theory

In the framework of the theory of general relativity, in order to obtain stable traversable wormholes, matter needs to violate the null energy condition. It is well known that the violation of the energy condition (EC) of matter leads to various physical problems. To address this issue, researchers have turned their attention to exploring modified theories of gravity, aiming to avoid the violation of ECs by introducing geometric terms. In this paper, within the framework of the $f(Q)$ modified gravitational theory, we investigate the effectiveness of ECs for matter in traversable wormholes. We examine the compliance of four types of energy conditions (weak energy condition, null energy condition, dominant energy condition, and strong energy condition) in the model by selecting a power-law model for $f(Q)$ and considering different shape functions $b(r)$. Our study reveals that for traversable wormholes realized through the $f(Q)$ modified gravity theory using the power-law model $f(Q)=a(-Q)^n$, all four types of ECs for matter can be satisfied. There is no need to introduce exotic matter (violating the null energy condition) or special matter (violating other energy conditions) artificially in the physics of wormholes.

gr-qc↗

arXiv2023

Development of a resource-efficient FPGA-based neural network regression model for the ATLAS muon trigger upgrades

This paper reports on the development of a resource-efficient FPGA-based neural network regression model for potential applications in the future hardware muon trigger system of the ATLAS experiment at the Large Hadron Collider (LHC). Effective real-time selection of muon candidates is the cornerstone of the ATLAS physics programme. With the planned ATLAS upgrades for the High Luminosity LHC, an entirely new FPGA-based hardware muon trigger system will be installed that will process full muon detector data within a 10 $μs$ latency window. The large FPGA devices planned for this upgrade should have sufficient spare resources to allow deployment of machine learning methods for improving identification of muon candidates and searching for new exotic particles. Our neural network regression model promises to improve rejection of the dominant source of background trigger events in the central detector region, which are due to muon candidates with low transverse momenta. This model was implemented in FPGA using 157 digital signal processors and about 5,000 lookup tables. The simulated network latency and deadtime are 122 and 25 ns, respectively, when implemented in the FPGA device using a 320 MHz clock frequency. Two other FPGA implementations were also developed to study the impact of design choices on resource utilisation and latency. The performance parameters of our FPGA implementation are well within the requirements of the future muon trigger system, therefore opening a possibility for deploying machine learning methods for future data taking by the ATLAS experiment.

physics.ins-det↗