arXiv subjects

X. G. Lan

Publications and source records attributed to X. G. Lan.

4 recordsLinked to original sources

arXiv2026

Additional Observational Signatures of Asymmetric Thin-Shell Wormholes within 4D Einstein-Gauss-Bonnet Gravity

In this paper, we study the optical appearance of a 4D Einstein-Gauss-Bonnet asymmetric thin-shell wormhole. Using Visser's cut-and-paste construction, we determine the photon sphere radius and critical impact parameter for different values of the Gauss-Bonnet coupling $α$. We then investigate the effective potential and photon motion inside the wormhole spacetime. It is found that the effective potential, light ray paths, and azimuthal angle are closely tied to the mass ratio of the two spacetimes. Considering an optically thin accretion disk as the only light source, we find that the asymmetric thin-shell wormhole's images exhibit additional photon rings and lensing bands that are absent for a 4D Einstein-Gauss-Bonnet black hole. Furthermore, the size of these extra rings increases with $α$, contrary to the black hole case. Such exceptionally bright rings provide a reliable criterion for distinguishing and characterizing a thin-shell wormhole spacetime. We also verify that the mass ratio and throat radius significantly tune the morphology of these extra photon rings.

gr-qc↗

arXiv2025

Asymmetric thin-shell wormholes in the Kalb-Ramond background: Observational characteristics and extra photon rings

In this paper, we utilize the ray-tracing method to conduct an in-depth study of the observational images of asymmetric thin-shell wormholes in the Kalb-Ramond field. Initially, we calculate the null geodesics and effective potential energy of the asymmetric thin-shell wormhole, and investigate the variations in the photon sphere radius and critical impact parameter under different values of charge $Q$ and Lorentz-violation parameter $l$. Based on these calculations, we determine the photon deflection angles and trajectories within this space-time structure. Specifically, depending on the photon impact parameters, the photon trajectories can be categorized into three types. By using a thin accretion disk as the sole background light source and incorporating two classical observational radiation models, we find that under conditions of equal mass $M$, charge quantity $Q$, and Lorentz-violation parameter $l$, the asymmetric thin-shell wormholes exhibit unique observational features such as additional lensing rings and photon ring clusters. Furthermore, distinct from black holes, as the charge quantity $Q$ and the Lorentz-violation parameter $l$ increase, the coverage area of the specific additional halo also expands correspondingly.

gr-qc↗

arXiv2025

Charged Black Holes in the Kalb-Ramond Background with Lorentz Violation: Null Geodesics and Optical Appearance of a Thin Accretion Disk

In this paper, we investigate the optical appearance of a charged black hole in the Kalb-Ramond background, incorporating a Lorentz-violating parameter $l=0.01$. By analyzing the null geodesics, we derive the photon sphere, event horizon, effective potential, and critical impact parameters. We then employ a ray-tracing technique to study the trajectories of photons surrounding a thin accretion disk. Three different emission models are considered to explore the observed intensity profiles of direct rings, lensing rings, and photon sphere. By comparing these results with those of the standard Reissner-Nordström black hole ($l=0$) and the Kalb-Ramond black hole with different values of Lorentz-violating parameter (specifically, $l=0.05$ and $l=0.1$ respectively), we find that the Lorentz symmetry breaking will lead to a decrease in the radii of the photon sphere, the event horizon, and the innermost stable circular orbit. Consequently, this makes the detection of these black holes more challenging.

gr-qc↗

arXiv2014

Measuring Hawking Radiation of a Kerr-Newman Black Hole in a Superconducting Transmission Line

Applying a dimensional reduction technique and a coordinates transformation approach, we deduce the Kerr-Newman space-time into a Painlevé-like form, and obtain its corresponding event horizon and the Hawking radiation temperature. We find that, the event horizon of a Kerr-Newman black hole can be simulated in a superconducting transmission line. Moreover, by running some numerical simulation, we confirm that the Hawking radiation of a Kerr-Newman Black Hole can be experimentally measured in a superconducting transmission line.

gr-qc↗