arXiv subjects

Yizhi Zhan

Publications and source records attributed to Yizhi Zhan.

4 recordsLinked to original sources

arXiv2026

Electric Penrose process in spherically symmetric regular black holes with and without a cosmological constant

We investigate the electric Penrose process in Ayón-Beato-García (ABG) black holes, both in the presence and absence of a cosmological constant, presenting, to the best of our knowledge, the first such analysis within the context of regular black holes. Our study systematically examines the effects of black hole charge and the cosmological constant on the formation of negative-energy states and the efficiency of energy extraction. Compared to Reissner-Nordström (RN) black holes, ABG black holes exhibit a significantly larger negative-energy region, enabling the electric Penrose process to operate at larger distances from the event horizon and achieve higher energy extraction efficiency. This enhancement is particularly pronounced near the event horizon, where the performance gap widens with increasing black hole charge. Notably, even for astrophysically realistic values of charge and cosmological constant that approach vanishingly small values, distinct differences persist, yielding a maximum efficiency ratio of approximately $23/8$. These results suggest that, in realistic astrophysical scenarios, ABG black holes can accelerate charged particles more efficiently and serve as more powerful engines for energy extraction than their RN counterparts.

gr-qc↗

arXiv2026

Charged Superradiant Instability of Spherically Symmetric Regular Black Holes in de Sitter Spacetime: Time- and Frequency-Domain Analysis

We investigate the superradiant instability of Ayón-Beato-García-de Sitter (ABG-dS) black holes under massless charged scalar perturbations using both time-domain evolutions and frequency-domain computations. We show that the instability occurs only for the spherically symmetric mode with $\ell=0$, whereas asymptotically flat ABG black holes remain stable in the massless limit, which underscores the essential role of the cosmological horizon in providing a confining boundary. We further study the dependence of the growth rate on the cosmological constant $Λ$, the scalar charge $q$, and the black hole charge $Q$, finding that it reaches a maximum at intermediate values of $Λ$ and $q$ and increases monotonically with $Q$. Compared with Reissner-Nordström-de Sitter black holes, ABG-dS black holes exhibit distinct instability characteristics due to the modified electrostatic potential induced by nonlinear electrodynamics.

gr-qc↗

arXiv2024

Charged superradiant instability in a spherical regular black hole

We examine the stability of a spherically symmetric regular black hole when subjected to perturbations from a charged scalar field. This particular black hole is constructed by deforming the Minkowski spacetime. It has been observed that the charged superradiant instability arises only within a specific range of the deformation parameter, potentially resulting in an instability growth rate with a maximum magnitude of approximately $\text{Im} (M ω) \sim 10^{-3}$. This growth rate significantly exceeds the instability identified in ABG black holes discussed in prior research, suggesting a notable timescale for detecting this phenomenon in astrophysical scenarios. Additionally, we conduct a thorough investigation into how the three parameters of the model influence the onset and intensity of the instability. Our analysis offers further insights into the possible emergence of this instability in spherically regular black holes and its association with the nonlinear effects of the electromagnetic field.

gr-qc↗

arXiv2024

Tachyonic instability and spontaneous scalarization in parameterized Schwarzschild-like black holes

We study the phenomenon of spontaneous scalarization in parameterized Schwarzschild-like black holes. Two metrics are considered, the Konoplya-Zhidenko metric and the Johannsen-Psaltis metric. While these metrics can mimic the Schwarzschild black hole well in the weak-field regime, they have deformed geometries in the near-horizon strong-field region. Such deformations notably influence the emergence of tachyonic instability and subsequent spontaneous scalarization, enabling a clear distinction between these parameterized metrics and the standard Schwarzschild metric. These results suggest a possible way to test the parameterized black holes and thus the Kerr hypothesis by observing the phenomenon of spontaneous scalarization.

gr-qc↗