arXiv subjects

H. Hassanabadi

Publications and source records attributed to H. Hassanabadi.

At least 19 recordsLinked to original sources

arXiv2026

Constrained thermodynamics and geodesic observables of an effective non-commutative Kerr-like black hole

We investigate the horizon structure, constrained thermodynamics, and geodesic properties of an effective Kerr-like black hole in a non-commutative background. Deformation modifies the radial geometry through a mass-dependent charge-like contribution, while preserving the separability of the geodesic equations. We determine the conditions for horizon existence, identify the extremal zero-temperature configuration, and analyze the stationary-limit surfaces and the ergoregion. Special attention is paid to the thermodynamic interpretation of the model, where the geometric Hawking quantities are distinguished from the conjugate variables associated with the constrained state space at fixed non-commutative deformation parameter. The canonical and grand-canonical heat capacities are derived to characterize their ensemble-dependent local thermal behavior. We also obtain the spherical photon region, equatorial light rings, and shadow boundary, showing that the deformation shifts the characteristic photon orbits inwards and reduces the overall size of the shadow. Timelike circular motion is studied through the innermost stable circular orbit, where non-commutative correction produces an inward shift of both the prograde and retrograde branches. Finally, invariant photon frequency shifts are obtained by treating the emitter's orbital direction and the photon's tangential emission direction as independent physical choices.

gr-qc↗

arXiv2026

GUP-corrected black holes: Thermodynamic properties, evaporation time and shadow constraint from EHT Observations of M87* and Sgr A*

In this manuscript, we implement the generalized uncertainty principle (GUP) with linear and quadratic moment for Schwarzschild black hole metric in order to study the influence of quantum effect on the thermodynamics and evaporation of black hole. To this end, we first derive the GUP-modified Hawking temperature of a black hole in the semi-classical framework. Due to the existence of the GUP effect, there is a maximum Hawking temperature. We determine the entropy, heat capacity and Helmholtz free energy with heuristic analysis that investigates the particle absorbed by black hole. Furthermore, we also verify that these quantities are modified by the GUP, the influence of quantum effect on the black hole phase transition is discussed in detail. Then, we analyze the black hole evaporation process in the mentioned framework and examine the obtained results by graphical methods and compare them with each other. We likewise explore the behavior of the event horizon radius, photon sphere radius, and shadow silhouette when influenced by the GUP-corrected Schwarzschild black hole (GCSBH) parameters. We intend to establish restrictions for $α$ by utilizing the event horizon telescope (EHT) data for M87* and Sagittarius A* (Sgr A*). Our findings show that Sgr A* provides more robust constraints. As the parameter $β$ grows, the range of constraints for $α$ expands. For Sgr A* one, we find that the shadow radius is close to the observed value at smaller values of $α$.

gr-qc↗

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

Optical, Dynamic and Topological Characteristics of Deformed Schwarzschild Black Holes

We investigate the temperature, photon and shadow radii, quasinormal modes (QNMs), time domain profiles, greybody factors, emission rates and topological characteristics of deformed black holes, focusing on the effects of the deformation parameter $ α$ and control parameter $ β$. Increasing $ α$ enhances the oscillation frequency and damping rate of gravitational waves, while $ β$ shows non-linear behaviour. Electromagnetic perturbations exhibit similar trends, though with lower frequencies and damping rates. Greybody factors are mainly influenced by multipole moment $l$ and $ α$, with $ β$ having a more subtle effect. These findings provide insights into black hole dynamics, mergers, and gravitational wave emissions.

hep-th↗

arXiv2025

Parity-deformed $sl(2,R)$, $su(2)$ and $so(3)$ Algebras: a Basis for Quantum Optics and Quantum Communications Applications

Having in mind the significance of parity (reflection) in various areas of physics, the single-mode and two-mode Wigner algebras are considered adding to them a reflection operator. The associated deformed $sl(2, R)$ algebra, $sl_ν(2,R)$ and the deformed $so(3)$ algebra, $so_ν(3)$, are constructed for the widely used Jordan-Schwinger and Holstein-Primakoff realizations, commenting on various aspects and ingredients of the formalism for both single-mode and two-mode cases. Finally, due to its potential application in the study of qubit and qutrit systems, the parity-deformed $so_ν(3)$ representation is analyzed based on the isomorphy of $so(3)$ and $su(2)$. Related applications are discussed as well.

math-ph↗

arXiv2025

The impact of an antisymmetric tensor on charged black holes: evaporation process, geodesics, deflection angle, scattering effects and quasinormal modes

In this paper, we investigate the influence of anti-symmetric tensor effects, which trigger the Lorentz symmetry breaking, on charged spherically symmetric black holes. Initially, we address an overview of the model, laying the groundwork for deriving solutions to black holes. With this, we analyze the horizons, critical orbits, and geodesics. We compute quasinormal modes and the time-domain solution with a particular emphasis on vectorial perturbations. In addition, we derive the Hawking temperature to perform the calculation of the remnant mass. Additionally, we estimate the lifetime of the black holes until they reach their final stage after the evaporation process. Finally, we explore the emission rate, the deflection angle and, we investigate the correlation between quasinormal modes and shadows.

gr-qc↗

arXiv2025

Black holes immersed in polytropic scalar field gas

By implementing the concept of polytropic structures as a scalar field gas with a dark energy-like behavior, we obtain a static spherically symmetric black hole solution in the framework of general relativity. In this paper, we study the quasinormal modes, the greybody bound process, the shadow behaviors, and the sparsity of black holes with a surrounding polytropic scalar field gas. Using the Wentzel-Kramers-Brillouin approach, we evaluate the impact of a particular set of polytropic parameters $(ξ, A)$ with a fixed setting of the polytropic index $n$ on the oscillation frequency and damping rate of gravitational waves. The results show that the effect of the parameter $ξ$ is much less significant than that of the parameter $A$ on the gravitational waves oscillation frequency and damping rate. Furthermore, the analysis of the greybody factor bounds reveals special insight into the effect of certain parameters where the multipole moments $l$ and the polytropic index $n$ have similar effects, in contrast to the pair of polytropic parameters ($ξ,A$). On the other hand, exploring the sparsity of Hawking radiation is another task that provides a better understanding of the behaviour of the black hole solution. In this respect, the results show that the black hole behaves like blackbody radiation for a sufficiently large entropy. And for $ξ=A=0$, the relevant sparsity acts exactly like the Schwarzschild sparsity. These results provide an insight into the dynamics of black holes with a surrounding polytropic scalar field gas from the analysis of their quasinormal modes, greybody factors, shadow behaviors, energy emission rate and sparsity process. Constraints on the associated BH parameters, derived from the Event Horizon Telescope observations of M87* and Sgr A*, indicate that this black hole model stands as a compelling candidate for representing astrophysical black holes.

gr-qc↗

arXiv2025

Thermodynamical properties of a deformed Schwarzschild black hole via Dunkl generalization

In this paper, we construct a deformed Schwarzschild black hole from the de Sitter gauge theory of gravity within Dunkl generalization and we determine the metric coefficients versus Dunkl parameter and parity operators. Since the spacetime coordinates are not affected by the group transformations, only fields are allowed to change under the action of the symmetry group. A particular ansatz for the gauge fields is chosen and the components of the strength tensor are computed as well. Additionally, we analyze the modifications on the thermodynamic properties to a spherically symmetric black hole due to Dunkl parameters for even and odd parities. Finally, we verify a novel remark highlighted from heat capacity: the appearance of a phase transition when the odd parity is taken into account.

gr-qc↗

arXiv2024

Influences of modified Chaplygin dark fluid around a black hole

In this work, we study a static, spherically charged AdS black hole within a modified cosmological Chaplygin gas (MCG), adhering to the calorific equation of state, as a unified dark fluid model of dark energy and dark matter. We explore the influence of model parameters on several characteristics of the MCG-motivated charged AdS black hole (MCG-AdSBH), including the geodesic structure and some astrophysical phenomena such as null trajectories, shadow silhouettes, light deflection angles, and the determination of greybody bounds. We then discuss how the model parameters affect the Hawking temperature, remnant radius, and evaporation process of the MCG-AdSBH. Quasinormal modes are also investigated using the eikonal approximation method. Constraints on the MCG-AdSBH parameters are derived from EHT observations of M87* and Sgr A*, suggesting that MCG-AdSBH could be strong candidates for astrophysical black hole.

astro-ph.HE↗

arXiv2024

Thermal, topological, and scattering effects of an AdS charged black hole with an antisymmetric tensor background

In this study, we explore a spherically symmetric charged black hole with a cosmological constant under the influence of a Kalb--Ramond field background. We compute the photon sphere and shadow radii, validating our findings using observational data from the Event Horizon Telescope (EHT), with a particular emphasis on the shadow images of Sagittarius $A^{*}$. Furthermore, we investigate the \textit{greybody} factors, emission rate, and partial absorption cross section. It is shown that the Lorentz-violating parameter $\bar{l}$ has an important effect on the absorption cross section. Our analysis also includes an examination of the topological charge, temperature-dependent topology, and generalized free energy. In particular, we regard the AdS charged black hole with an antisymmetric tensor background as a topological defect in the thermodynamic space, then the system has the same topological classification to the charged RN-AdS black hole.

gr-qc↗

arXiv2024

Fermions with Electric Dipole Moment in curved spacetime

This paper explores the relativistic behavior of spin--half particles possessing an Electric Dipole Moment (EDM) in a curved spacetime background induced by a spiral dislocation. A thorough review of the mathematical formulation of the Dirac spinor in the framework of quantum field theory sets the foundation for our investigation. By deriving the action that governs the interaction between the spinor field, the background spacetime, and an external electric field, we establish a framework to study the dynamics of the system. Solving the resulting wave equation reveals a set of coupled equations for the radial components of the Dirac spinor, which give rise to a modified energy spectrum attributed to the EDM. To validate our findings, we apply them to the geometric phase and thermodynamics.

gr-qc↗

arXiv2024

Shadows, greybody factors, emission rate, topological charge, and phase transitions for a charged black hole with a Kalb-Ramond field background

In this work, we investigate a spherically symmetric charged black hole in the presence of a Kalb--Ramond field background. We calculate the photon sphere and shadow radii and, corroborating our results, we constrain them from observational data from the Event Horizon Telescope (EHT), particularly focusing on the shadow images of Sagittarius $A^{*}$. Additionally, we analyze the greybody factors, emission rate, and partial absorption cross section. We also examine the topological charge and its application to the deflection angle. Finally, we conduct the analysis of the heat capacity and phase transitions.

gr-qc↗

arXiv2024

Scattering effects of bumblebee gravity in metric affine formalism

In this work, we explore a Schwarzschild-like black hole within the framework of metric--affine bumblebee gravity. First, we investigate the behavior of the Kretschmann scalar and singularities in this modified gravity approach. Next, we introduce a newly defined time coordinate related to a stationary asymptotically flat spacetime. We also analyze the scattering effects and numerically calculate and comprehensively examine the partial and total absorption cross sections. At the high--frequency approximation, we find that the absorption cross section tends to the geodesic capture cross section. The continued fraction method is applied to investigate the quasinormal modes, and we explore the deviations of both the real and imaginary terms of the quasinormal modes from the Schwarzschild case in detail. We verify the relation between the shadow radius and the real part of the quasinormal frequencies at the eikonal limit within this modified gravity framework. Finally, we examine the energy emission rate.

gr-qc↗

arXiv2024

Exploring Non--commutativity as a Perturbation in the Schwarzschild Black Hole: Quasinormal Modes, Scattering, and Shadows

In this work, by a novel approach to studying the scattering of a Schwarzschild black hole, the non-commutativity is introduced as a perturbation. We begin by reformulating the Klein-Gordon equation for the scalar field in a new form that takes into account the deformed non-commutative spacetime. Using this formulation, an effective potential for the scattering process is derived. To calculate the quasinormal modes, we employ the WKB method and also utilize fitting techniques to investigate the impact of non-commutativity on the scalar quasinormal modes. We thoroughly analyze the results obtained from these different methods. Moreover, the greybody factor and absorption cross section are investigated. Additionally, we explore the behavior of null geodesics in the presence of non-commutativity. Specifically, we examine the photonic, and shadow radius as well as the light trajectories for different non-commutative parameters. Therefore, by addressing these various aspects, we aim to provide a comprehensive understanding of the influence of non-commutativity on the scattering of a Schwarzschild-like black hole and its implications for the behavior of scalar fields and light trajectories.

gr-qc↗

arXiv2024

Exact solution of two dimensional Dunkl harmonic oscillator in Non-Commutative phase-space

In this paper, we examine the harmonic oscillator problem in non-commutative phase space (NCPS) by using the Dunkl derivative instead of the habitual one. After defining the Hamilton operator, we use the polar coordinates to derive the binding energy eigenvalue. We find eigenfunctions that correspond to these eigenvalues in terms of the Laguerre functions. We observe that the Dunkl-Harmonic Oscillator (DHO) in the NCPS differs from the ordinary one in the context of providing additional information on the even and odd parities. Therefore, we conclude that working with the Dunkl operator could be more appropriate because of its rich content.

hep-th↗

arXiv2024

Exploring antisymmetric tensor effects on black hole shadows and quasinormal frequencies

This study explores the impact of antisymmetric tensor effects on spherically symmetric black holes, investigating photon spheres, shadows, emission rate and quasinormal frequencies in relation to a parameter which triggers the Lorentz symmetry breaking. We examine these configurations without and with the presence of a cosmological constant. In the first scenario, the Lorentz violation parameter, denoted as $λ$, plays a pivotal role in reducing both the photon sphere and the shadow radius, while also leading to a damping effect on quasinormal frequencies. Conversely, in the second scenario, as the values of the cosmological constant ($Λ$) increase, we observe an expansion in the shadow radius. Also, we provide the constraints of the shadows based on the analysis observational data obtained from the Event Horizon Telescope (EHT) focusing on Sagittarius $A^{*}$ shadow images. Additionally, with the increasing $Λ$, the associated gravitational wave frequencies exhibit reduced damping modes.

gr-qc↗

arXiv2024

Accelerating AdS black holes in gravity's rainbow

Motivated by the effect of the energy of moving particles in $C-$metric, we first obtain exact accelerating black hole solutions in gravity's rainbow. Then, we study the effects of gravity's rainbow and $C-$metric parameters on the Ricci and Kretschmann scalars, and also the asymptotical behavior of this solution. Next, we indicate how different parameters of the obtained accelerating black holes in gravity's rainbow affect thermodynamics quantities (such as the Hawking temperature, and entropy) and the local stability (by evaluating the heat capacity). In the following, we extract the geodesic equations to determine the effects of various parameters on photon trajectory in the vicinity of this black hole, as well as obtain the radius of the photon sphere and the corresponding critical impact parameter to gain insight into AdS black hole physics by adding the gravity's rainbow to $C-$metric.

gr-qc↗

arXiv2024

Quasinormal Modes and Greybody factors of de Sitter Black holes surrounded by Quintessence in Rastall gravity

In this work, we have studied the quasinormal mode, greybody factors, and absorption cross section of de Sitter Reissner-Nordström black hole surrounded by quintessence field in Rastall gravity. The violation of energy-momentum conservation has a non-linear effect on the quasinormal modes. With an increase in the black hole charge, both real parts of quasinormal modes i.e. oscillation frequency of ring-down Gravitational Waves (GWs) and damping or decay rate of GWs increase non-linearly. A similar observation is made for the black hole structural parameter also, however in this case the variation is almost linear. The remnant mass of a black hole depends on different physical parameters of a black hole. In the case of greybody factors also, we observed that both parameters have similar impacts. With an increase in these parameters, greybody factors decrease. Moreover, the null geodesics and the impact of Rastall gravity on the light trajectory are also investigated. Our study suggests that the presence of a surrounding quintessence field may shadow the existence of black hole charges in such black hole configurations.

gr-qc↗