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Shavkat Karshiboev

Publications and source records attributed to Shavkat Karshiboev.

3 recordsLinked to original sources

Blandford-Znajek Scaling in a Power-Law Rotating Kalb-Ramond Geometry: Magnetic-Flux Systematics and Bayesian Identifiability

Relativistic jets from spinning black holes offer a possible strong-field probe of gravity through the Blandford-Znajek mechanism. We study the leading jet-power scaling in the four-dimensional power-law rotating Kalb-Ramond geometry introduced by Kumar, Ghosh, and Wang. The metric is used here as a stationary background, without assuming that it constitutes a newly established exact rotating solution. We first examine the deformation at the metric level. For $s=2$ it is absorbed completely by a mass redefinition, whereas for $s>2$ the correction decays more slowly than the usual mass term. Our main benchmark is therefore the nondegenerate $s=3/2$ case, whose correction falls faster than the Kerr mass term; $s=3$ is kept as a secondary comparison. We evaluate the BZ scaling under three magnetic assumptions: fixed total horizon flux, fixed local normal field with the proper horizon area, and a reduced radius-based flux proxy. The resulting trends differ appreciably, showing that the magnetic prescription is itself a leading systematic. For GRO J1655-40 and GRS 1915+105, the marginalized deformation posterior remains close to the horizon-conditioned effective prior for both a uniform prior and a truncated-Gaussian alternative. The jet-only profile likelihood is also nearly flat over the allowed deformation range, with the same qualitative behavior in the $s=3$ test. Thus, within the present setup, the jet-power proxies do not independently determine the Kalb-Ramond deformation. A stronger inference will require better control of the rotating background, source-dependent magnetic flux, non-Kerr spin estimates, and a larger sample.

gr-qc

Gravitational perturbations of a regular T-duality inspired black hole: Quasinormal modes, excitation factors, and time-domain evolution

We study axial gravitational perturbations of the neutral regular black hole generated by a non-local, T-duality-inspired zero-point length and the associated gravitational self-energy. In this geometry, the usual point source is replaced by a regular core, and the zero-point length controls the departure from the Schwarzschild limit. We compute the fundamental quasinormal modes and several overtones using high-order WKB--Padé methods, and we verify the dominant mode via direct time-domain evolution. When the zero-point length is turned on, the real parts of the ADM-scaled frequencies increase for the gravitational modes with $\ell=2,3,4$, so the ringdown oscillates faster than in the Schwarzschild limit. The damping rates change more gradually: they initially increase slightly and then decrease near the largest deformation values considered here. This behavior is consistent with the effective potential, whose barrier becomes higher as the deformation parameter increases. We also compute the corresponding excitation factors and find that their magnitudes vary much less strongly than the quasinormal frequencies.

gr-qc

Rotating Curzon-Chazy metric

We demonstrate that the Curzon metric for a positive mass configuration possesses a singular event horizon with infinite area. This singularity has significant implications, revealing that the three-dimensional spatial hypersurfaces, which are orthogonal to the Killing vector field, exhibit a multiply connected structure. Furthermore, we investigate the dynamics of a test particle orbiting a central $γ$-object within this spacetime. It is found that under certain conditions, the particle's velocity can approach the speed of light, leading to an exceptionally high total energy at a specific value of the deformation parameter governing the spacetime structure. Moreover, we uncover a causality issue for a critical value of the deformation parameter, where the test particle can exceed the speed of light, potentially offering new insights into the theoretical existence of tachyons. This study contributes to the understanding of relativistic objects in deformed spacetimes and suggests that such violations of causality could play a role in explaining the elusive nature of tachyonic phenomena in high-energy physics.

gr-qc