arXiv subjects

A. Guvendi

Publications and source records attributed to A. Guvendi.

5 recordsLinked to original sources

arXiv2025

Ergosphere Dynamics and Rotational Energy Extraction in Bumblebee Kerr-Newman-AdS Black Holes

We present a comprehensive analysis of the thermodynamic and optical properties of the Bumblebee Kerr-Newman-Anti-de Sitter (AdS) black hole, a rotating and charged configuration arising in Lorentz symmetry-violating (LSV) gravity. The influence of the black hole parameters on the horizon structure, thermodynamic stability, and geometric deformation of spacetime is systematically investigated. Explicit expressions for the Hawking temperature, entropy, and heat capacity are derived, revealing the formation of black hole remnants and extended stability phases induced by Lorentz symmetry-violating (LSV) effects. The sparsity of Hawking radiation is quantified, showing that Lorentz violation suppresses the continuum limit and produces a more discrete, less thermal emission spectrum. A detailed analysis of null geodesics is performed to determine the photon region and shadow morphology, indicating that increasing l and Q compresses and distorts the shadow boundary, while rotation diminishes its overall size. The ergosphere geometry is analyzed in detail, showing that increases in a, l, and Q not only enlarge and distort the ergoregion but also intensify frame-dragging, thereby maximizing the efficiency of energy extraction via the Penrose process. These results reveal clear and potentially observable deviations from standard Kerr-Newman-AdS predictions, providing a powerful new avenue to probe Lorentz symmetry breaking and test the fundamental structure of gravity in extreme strong field regimes.

gr-qc↗

arXiv2025

Fermion-antifermion pairs in magnetized spacetime generated by a point source

In this research, we study fermion-antifermion pairs in a magnetized spacetime induced by a point-like source and characterized by an angular deficit parameter, \(\alpha\). In the rest frame, the relative motion (\(\propto r\)) of these pairs is analyzed using exact solutions of a two-body Dirac equation with a position-dependent mass expressed as \(m(r) = m_0 + \mathcal{S}(r)\). We select the Lorentz scalar potential \(\mathcal{S}(r) = -\alpha_c/r\), which modifies the rest mass in a manner analogous to an attractive Coulomb potential, and derive analytical solutions to the resulting radial wave equation. Our findings are applicable to pairs in flat spacetime when \(\alpha = 1\) without loss of generality. We elucidate how the spectra of such pairs are influenced by the spacetime background. Additionally, we observe that even the well-known non-relativistic energy (\(\propto \alpha_c^2\)) reflects the influence of the parameter \(\alpha\) in positronium-like fermion-antifermion systems. We propose that our results can also be extended to study charge carriers in magnetized monolayer materials. Furthermore, we demonstrate that the metric for a 2+1-dimensional spinning point source background can be transformed into the metric describing the near-horizon region of a rotating BTZ black hole, a result not previously reported in the literature. This metric holds potential for providing meaningful insights into topics such as holographic superconductivity and quantum critical phenomena in future research

gr-qc↗

arXiv2025

Investigating quantum criticality through charged scalar fields near the BTZ black hole horizon

We examine a charged scalar field with a position-dependent mass \( m(\rho) = m_0 + \mathcal{S}(\rho) \), where \(\mathcal{S}(\rho)\) represents a Lorentz scalar potential, near a BTZ black hole in the presence of an external magnetic field. By deriving the Klein-Gordon equation for this setup, we explore two scenarios: (i) a mass-modified scalar field with \(m(\rho) = m_0 - a/\rho\) (an exactly solvable case), and (ii) a scenario involving both mass modification and an external magnetic field (conditionally exactly solvable). We identify quantum critical points (QCPs) associated with the coupling constant \(a\). In the first scenario, for massless charged scalar fields, critical points occur at \(a = n + 1/2\) for all radial quantum numbers \(n \geq 0\) and magnetic quantum numbers \(|m| \geq 0\). In the second scenario, these critical points shift to \(a = n + 3/2\) for \(n \geq 0\) and \(|m| > 0\), with the case \(m = 0\) excluded. For massive scalar fields, QCPs emerge at \(a = (n + 1/2)/2\), leading to non-propagating fields at zero frequency. At these QCPs, the field frequencies drop to zero, marking transitions from stable oscillatory modes to non-propagating states. Below the critical points, the system exhibits instability, characterized by negative imaginary frequencies that suggest rapid decay and high dissipation. Above the critical points, the modes stabilize and propagate, indicating a transition to a superconducting-like phase, where dissipation vanishes and stable excitations dominate.

hep-th↗

arXiv2025

Photonic Modes in Twisted Graphene Nanoribbons

This study investigates the behavior of photonic modes in twisted graphene nanoribbons (TGNRs) using an analytical approach based on solving the fully covariant vector boson equation. We present a model that demonstrates how helical twisting in TGNRs significantly affects the evolution of photonic modes. Our analytical solutions yield detailed expressions for mode profiles, energy spectra, and decay characteristics. We find that increasing the twist parameter shortens the decay times (\(\tau_{ns}\)) for damped modes, indicating enhanced photonic coupling due to the twisted geometry. Conversely, longer nanoribbons (NRs) exhibit increased decay times, showing a length (\(L\))-dependent effect, where \(\tau_{ns} \propto L / c\), with \(c\) representing the speed of light. These findings may enhance the understanding of light control in nanostructures and suggest potential applications in tunable photonic devices, topological photonics, and quantum optical systems.

physics.optics↗

arXiv2025

On the Klein-Gordon scalar field oscillators in a spacetime with spiral-like dislocations in external magnetic fields

We investigate the effects of two types of spiral dislocation (the distortion of the radial line, labeled as spiral dislocation I, and the distortion of a circle, labeled as spiral dislocation II) on the relativistic dynamics of the Klein-Gordon (KG) oscillator fields, both in the presence and absence of external magnetic fields. In this context, our investigations show that while spiral dislocation I affects the energies of the KG oscillators (with or without the magnetic field), spiral dislocation II has, interestingly, no effect on the KG oscillator's energies unless a magnetic field is applied. However, for both types of spiral dislocations, we observe that the corresponding wave functions incorporate the effects of the dislocation parameter. Our findings are based on the exact solvability and conditional exact solvability (associated with the biconfluent Heun polynomials) of the KG oscillators (with or without the magnetic field, respectively) for spiral dislocation I, and the exact solvability of the KG oscillators (with or without the magnetic field) for spiral dislocation II. The exact solvability of the latter suggests that the oscillator's frequency is solely determined by the magnetic field strength.

gr-qc↗