arXiv subjects

Ahmad Al-Badawi

Publications and source records attributed to Ahmad Al-Badawi.

At least 73 records · Page 4Linked to original sources

arXiv2025

Gravitational Lensing Phenomena of Ellis-Bronnikov-Morris-Thorne Wormhole with Global Monopole and Cosmic String

In this paper, we theoretically investigate gravitational lensing within the space-time framework of traversable wormholes, focusing on the combined effects of a global monopole and a cosmic string. Specifically, we examine the Ellis-Bronnikov-Morris-Thorne wormhole metric and analyze how these topological defects influence photon trajectories. By considering the weak-field limit, we derive analytical expressions for the photon deflection angle, highlighting how factors such as the wormhole throat radius, the global monopole charge, and the cosmic string influence the gravitational lensing phenomenon. We also examine the weak-field limit of lensing phenomena for a zero wormhole throat radius and derive an analytical expression for the deflection angle of photon light in this scenario.

gr-qc↗

arXiv2025

Ayón-Beato-García black hole in AdS space-time surrounded by quintessence: geodesic, shadow and thermodynamics

In this study, we present a novel exact solution to the gravitational field equations, known as the Ayón-Beato-García black hole solution, set against the backdrop of anti-de Sitter space and surrounded by a quintessence field. This solution serves as an interpolation between three distinct anti-de Sitter black hole configurations, namely, the Ayón-Beato-García, Schwarzschild-Kiselev, and the standard Schwarzschild black hole solutions. The first aspect of our investigation focuses on the geodesic motion of particles, where we explore how the black hole's space-time geometry-incorporating the effects of nonlinear electrodynamics, the quintessence field, and the curvature radius-influences the dynamics of both massless and massive particles near the black hole. To further enrich our analysis, we extend the study to include the perturbative dynamics of a massless scalar field within the black hole solution, placing special emphasis on the scalar perturbative potential. Subsequently, we focus into the phenomenon of black hole shadows, examining how various parameters, such as the nonlinear electrodynamics, the curvature of space-time and the presence of the quintessence field, impact the size and shape of the shadow cast by the black hole. In the final segment of our study, we shift our attention to the thermodynamics of the black hole solution. We compute several essential thermodynamic quantities, including the Hawking temperature, specific heat capacity, and Gibbs free energy, analyzing how these properties evolve in response to changes in the various parameters that define the space-time geometry, which in turn affect the gravitational field when compared to the traditional black hole

gr-qc↗

arXiv2025

Motions of Test Particles in Gravitational Field, Perturbations and Greybody Factor of Bardeen-like AdS Black Hole with Phantom Global Monopoles

We investigate the dynamics of test particles, perturbations, and greybody factors within the framework of a Bardeen-like AdS black hole (BH) with a phantom global monopole. This study explores the interactions between nonlinear electrodynamics, the energy scale of symmetry breaking, and space-time topology. We analyze the geodesic motion of null and time-like particles, deriving effective potentials that describe their trajectories. Utilizing the Regge-Wheeler potential, we calculate the quasinormal modes (QNMs) for scalar, vector, and tensor perturbations, applying the sixth-order WKB approximation. Our findings highlight how the Bardeen-like parameter ($\mathrm{b}$) and the energy scale of symmetry breaking, characterized by the parameter ($η$), influence the QNM spectra, with potential implications for gravitational wave observations. We also examine greybody factors, focusing on the transmission and reflection coefficients for scalar and axial fields, and employ semi-analytic techniques to derive precise bounds. Furthermore, we assess the thermodynamic stability of the BH, emphasizing the role of these parameters in phase transitions and stability criteria.

hep-th↗

arXiv2025

Shadow properties and orbital dynamics around an effective quantum-modified black hole surrounded by quintessential dark energy

In this study, we investigate black holes (BHs) surrounded by a quintessence field (QF) within the framework of effective quantum gravity (EQG). We analyze the spacetime metric characterized by quantum correction parameter $ξ$ and quintessence parameters $(c,w)$, revealing a rich three-horizon structure whose properties depend on both quantum effects and dark energy. Our main focus is on understanding the observational signatures and dynamical behavior of these modified BHs. We derive analytical expressions for the photon sphere and shadow radius for various values of the state parameter, finding that quintessence fields increase the shadow radius while quantum corrections decrease it-a distinctive interplay that creates potentially observable effects. Using Event Horizon Telescope data from M87*, we establish constraints on the quantum correction parameter, showing that the allowable range for $ξ$ increases with the quintessence parameter $c$. We conduct a comprehensive analysis of null and timelike geodesics, demonstrating how quantum corrections enhance interactions between photons and the gravitational field while modifying the energy, angular momentum, and stability properties of massive particle orbits. Our investigation extends to periodic orbits characterized by zoom-whirl behavior, finding that quintessence allows such orbits to occur at lower energies compared to purely quantum-corrected BHs. We further analyze scalar perturbations and their effective potentials, which reveal how both quantum and quintessence effects shape the response characteristics of these BHs. Throughout our study, we find that quantum corrections and quintessence frequently produce counteracting effects on observables that could provide simultaneous tests of quantum gravity theories and dark energy models through future high-precision astronomical observations.

gr-qc↗

arXiv2025

Photon spheres, gravitational lensing/mirroring, and greybody radiation in deformed AdS-Schwarzschild black holes with phantom global monopole

In this study, we investigate the geodesic structure, gravitational lensing/mirroring phenomena, and scalar perturbations of deformed AdS-Schwarzschild black holes with global monopoles, incorporating both ordinary and phantom configurations. We introduce a modified black hole metric characterized by a deformation parameter $α$, a control parameter $β$, and a symmetry-breaking scale parameter $η$, which collectively influence the spacetime geometry. Through comprehensive geodesic analysis, we determine the photon sphere radius numerically for various parameter configurations, revealing significant differences between ordinary and phantom global monopoles. The stability of timelike circular orbits is assessed via the Lyapunov exponent, demonstrating how these parameters affect orbital dynamics. Our gravitational lensing analysis, employing the Gauss-Bonnet theorem, reveals a remarkable gravitational mirroring effect in phantom monopole spacetimes at high AdS curvature radii, where light rays experience negative deflection angles-being repelled rather than attracted by the gravitational field. Furthermore, we analyze massless scalar perturbations and derive the corresponding greybody factors, which characterize the transmission of Hawking radiation through the effective potential barrier surrounding the black hole. Our numerical results indicate that phantom global monopoles substantially modify both gravitational lensing/mirroring properties and the radiation spectrum compared to ordinary monopoles. The presence of the deformation parameter $α$ introduces additional complexity to the system, leading to distinct thermodynamic behavior that deviates significantly from the standard AdS-Schwarzschild solution.

gr-qc↗

arXiv2025

The static charged black holes with Weyl corrections

This study investigates static charged black holes with Weyl corrections to the Einstein-Maxwell action. By extending the classical solutions, we incorporate the influence of the Weyl tensor coupling with the electromagnetic field tensor, deriving novel black hole solutions under this framework. The characteristics of the derived spacetimes, including their geometrical structure and physical properties, are meticulously examined. Key features explored include geodesics, photon spheres, and quasinormal modes, providing insights into the stability and dynamics around such black holes. Additionally, the deflection of light and the corresponding shadow cast by these black holes are analyzed, revealing the modifications induced by Weyl corrections. This study aims to enrich the understanding of how higher-order tensor interactions can influence observable astrophysical phenomena in the vicinity of compact objects.

gr-qc↗

arXiv2025

A new black hole coupled with nonlinear electrodynamics surrounded by quintessence: Thermodynamics, Geodesics, and Regge-Wheeler Potential

We present a new exact solution to the gravitational field equations, where nonlinear electrodynamics (NLED) serves as the matter source in the presence of a quintessence field (QF). This solution describes a static, spherically symmetric black hole in the context of Anti-de Sitter (AdS) space, with the black hole (BH) surrounded by quintessence matter. The resulting black hole solution generalizes the AdS Schwarzschild-Kiselev black hole and reduces to the standard AdS-Schwarzschild black hole in the appropriate limits. Additionally, under certain conditions, this solution recovers the Bardeen-Kiselev regular black hole. We further explore the horizon structure and thermodynamic properties of this new black hole spacetime, accounting for the contributions from both NLED and the QF, including the state parameter of the QF. These contributions modify the spacetime geometry, thereby altering the thermodynamic behavior of the black hole. Moreover, we analyze the geodesic equations and show how NLED and the QF influence the effective potential for massless photon particles. Finally, we study the Regge-Wheeler (RW) potential for this regular black hole and demonstrate how variations in the parameters (NLED and QF) affect the RW potential for fields of different spins: spin-zero ($S=0$), spin-one ($S=1$), and spin-two ($S=2$). To illustrate the effects, we provide graphical representations of the RW potential for both multipole numbers $\ell=0$ and $\ell=1$.

gr-qc↗

arXiv2025

Dynamics of test particles and scalar perturbations around Ayón-Beato-García black hole coupled with cloud of strings

In this paper, we investigate the geodesic motion and scalar perturbations of the Ayón-Beato-García (ABG) black hole (BH) coupled with a cloud of strings (CS). By employing the effective potential approach, we analyze the trajectories of massless and massive test particles around this regular BH solution. The interplay between nonlinear electrodynamics (NLED) and CS significantly modifies the spacetime geometry, resulting in distinct dynamical properties for test particles. The behavior of null and timelike geodesics, including their stability and escape conditions, is thoroughly examined. In addition to the geodesic analysis, we study scalar perturbations by deriving the Klein-Gordon equation for massless scalar fields in this spacetime. The resulting Schrödinger-like wave equation reveals an effective potential that depends intricately on the NLED and CS parameters. Furthermore, we compute the greybody factors (GFs) to explore the energy transmission and absorption properties of theBH. Our results demonstrate that the NLED parameter $g$ and the CS parameter $α$ play pivotal roles in modulating the GFs, influencing the energy spectrum of scalar radiation. These results provide significant understanding of the observational characteristics of the ABG NLED-CS BH in astrophysical contexts.

gr-qc↗

arXiv2025

Astrophysical properties of static black holes embedded in a Dehnen type dark matter halo with the presence of quintessential field

From an astrophysical perspective, the composition of black holes (BHs), dark matter (DM), and dark energy can be an intriguing physical system. In this study, we consider Schwarzschild BHs embedded in a Dehnen-type DM halo exhibiting a quintessential field. This study examines the horizons, shadows, deflection angle, and quasinormal modes (QNMs) of the effective BH spacetime and how they are affected by the dark sector. The Schwarzschild BH embodied in a Dehnen-type DM halo exhibiting a quintessential field possesses two horizons: the event horizon and the cosmological horizon. We demonstrate that all dark sector parameters increase the event horizon while decreasing the cosmological horizon. We analyze the BH shadow and emphasize the impact of DM and quintessence parameters on them. We show that the dark sector casts larger shadows than a Schwarzschild BH in a vacuum. Further, we delve into the weak gravitational lensing deflection angle using the Gauss-Bonnet theorem (GBT). We then investigate QNMs using the 6th order WKB approach. To visually underscore the dark sector parameters, we present figures that illustrate the impact of varying the parameters of the Dehnen-type DM halo as well as quintessence. Our findings show that the gravitational waves emitted from BHs with a dark sector have a lower frequency and decay rate compared to those emitted from BHs in a vacuum.

gr-qc↗

arXiv2024

Scalar, Vector Perturbations and Effective Hawking Radiation of Cylindrical Black Holes in $f(\mathcal{R})$ and Ricci-Inverse Gravity

This paper investigates scalar perturbations and quasinormal modes (QNMs) associated with cylindrical black holes constructed within the frameworks of $f(\mathcal{R})$-gravity and Ricci-Inverse ($\mathcal{RI}$) gravity. Moreover, we study the modified Hawking radiation in these black hole solutions and analyze the effects of coupling constants. These modified theories, which extend general relativity by introducing higher-order curvature corrections and additional geometric terms, provide a rich platform for exploring deviations from standard gravitational physics. The study begins by revisiting the cylindrical black holes in these modified gravity theories, where the effective cosmological constants respectively, are represented by $Λ_m^{f(\mathcal{R})}$ and $Λ_m^{\mathcal{RI}}$ related to the coupling constants unique to each framework. Afterwards, the QNMs, intrinsic damped oscillations of the black hole space-time, are analyzed to probe the stability of the system, with the effective potential $V$ revealing the impact of the modified gravity parameters. Additionally, the thermodynamic properties of the black holes are examined through the lens of the Generalized Uncertainty Principle (GUP), which introduces quantum corrections to Hawking radiation. The GUP-modified Hawking temperature and entropy are derived, demonstrating significant deviations from classical results and highlighting the quantum gravitational effects in these modified frameworks. By linking QNMs, thermodynamics, and quantum corrections, this work not only deepens the understanding of modified gravity theories but also offers potential observational pathways to test their validity.

gr-qc↗

arXiv2024

Quasinormal modes and shadow of Schwarzschild black holes embedded in a Dehnen type dark matter halo exhibiting string cloud

In this paper, we consider a static spherically symmetric black hole (BH) embedded in a Dehnen-(1,4,0) type dark matter (DM) halo in the presence of a cloud string. We examine and present data on how the core density of the DM halo parameter and the cloud string parameter affect BH attributes such as quasinormal modes (QNMs) and shadow cast. To do this, we first look into the effective potential of perturbation equations for three types of perturbation fields with different spins: massless scalar field, electromagnetic field, and gravitational field. Then, using the 6th order WKB approximation, we examine quasinormal modes of the BH disturbed by the three fields and derive quasinormal frequencies. The changes of QNM versus the core density parameter and the cloud string parameter for three disturbances are explored. We also investigate how the core density and the cloud string parameters affect the photon sphere and shadow radius. Interestingly, the study shows that the influence of Dehnen type DM and cloud string increases both photon spheres and shadow radius. Finally, we employ observational data from Sgr $A{^\star}$ and $M87{^\star}$ to set limitations on the BH parameters.

gr-qc↗

arXiv2024

Spin-dependent Regge-Wheeler Potential and QNMs in Quantum Corrected AdS Black Hole with Phantom Global Monopoles

In this paper, we investigate the geodesic motion of test particles in the spacetime surrounding a static, spherically symmetric black hole, which is described by an AdS-Schwarzschild-like metric and incorporates a quantum correction. This black hole also features phantom global monopoles, which modify the structure of the black hole space-time. We begin by deriving the effective potential governing the motion of test particles in this system and carefully analyze the impact of quantum correction in the presence of both phantom and ordinary global monopoles. Furthermore, we extend our study to include the spin-dependent Regge-Wheeler (RW) potential, which characterizes the dynamics of perturbations in this quantum-corrected black hole background. By examining this RW potential for various spin fields, we show how quantum corrections affect its form in the presence of both phantom and ordinary global monopoles. Our analysis demonstrate that quantum correction significantly alter the nature of the RW-potential, influencing the stability, and behavior of test particles and perturbations around the black hole.

gr-qc↗

arXiv2024

Quasinormal Modes and GUP-Corrected Hawking Radiation of BTZ Black Holes within Modified Gravity Frameworks

This paper aims to explore the quasinormal modes (QNMs) and effective potential profiles of massless and rotating BTZ black holes within the frameworks of $f(\mathcal{R})$ and Ricci-Inverse ($\mathcal{RI}$) modified gravity theories, which, while producing similar space-time structures, exhibit variations due to distinct cosmological constants, $Λ_m$. We derive wave equations for these black hole perturbations and analyze the behavior of the effective potential $V_{\text{eff}}(r)$ under different values of mass $m$, cosmological constant $Λ_m$, and modified gravity parameters $α_1$, $α_2$, $β_1$, $β_2$, and $γ$. The findings indicate that increasing mass and parameter values results in a raised potential barrier, implying stronger confinement of perturbations and impacting black hole stability. Incorporating the generalized uncertainty principle, we also study its effect on the thermodynamics of rotating BTZ black holes, demonstrating how GUP modifies black hole radiation, potentially observable in QNM decay rates. Additionally, we investigate the motion of particles through null and timelike geodesics in static BTZ space-time, observing asymptotic behaviors for null geodesics and parameter-dependent shifts in potential for timelike paths. The study concludes that modified gravity parameters significantly influence QNM frequencies and effective potential profiles, offering insights into black hole stability and suggesting that these theoretical predictions may be tested through gravitational wave observations.

gr-qc↗

arXiv2024

Schwarzschild Black Hole in Galaxies Surrounded by a Dark Matter Halo

In this paper, we derive a novel Schwarzschild-like black hole (BH) solution describing a static and asymptotically flat BH surrounded by a dark matter (DM) halo with a Dehnen-type density distribution in the surrounding environment. We investigate the properties of the obtained BH by studying the curvature properties and energy conditions in Einstein gravity. Furthermore, we explore the features of a novel Schwarzschild-like BH embedded in a DM halo with Dehnen-type density profile by analyzing the timelike geodesics of particles along with BH observable properties.

gr-qc↗

arXiv2024

Shadows and weak gravitational lensing by the black hole in Einstein-Maxwell-scalar theory

In this paper, we investigate the optical properties of a charged black hole in Einstein-Maxwell-scalar (EMS) theory. We evaluate the shadow cast by the black hole and obtain analytical solutions for both the radius of the photon sphere and the shadow radius. We observe that the black hole parameters $γ$ and $β$ both influence the shadow of black hole. It is shown that the photon sphere and the shadow radius increase as a consequence of the presence of parameter $γ$. Interestingly, we show that shadow radius decreases first and then remains unchanged due to the impact of parameter $β$. Finally, we consider the weak gravitational lensing and the total magnification of lensed images around black hole. We find that the black hole charge and parameter $β$ both give rise to a significant effect, reducing the deflection angle. Similarly, the same behavior for the total magnification is observed due to the effect of black hole charge and parameter $β$.

gr-qc↗

arXiv2024

GUP corrected black holes with cloud of string

We investigate shadows, deflection angle, quasinormal modes (QNMs), and sparsity of Hawking radiation of the Schwarzschild string cloud black hole's solution after applying quantum corrections required by the Generalised Uncertainty Principle (GUP). First, we explore the shadow's behaviour in the presence of a string cloud using three alternative GUP frameworks: linear quadratic GUP (LQGUP), quadratic GUP (QGUP), and linear GUP. We then used the weak field limit approach to determine the effect of the string cloud and GUP parameters on the light deflection angle, with computation based on the Gauss-Bonnet theorem. Next, to compute the quasinormal modes of Schwarzschild string clouds incorporating quantum correction with GUP, we determine the effective potentials generated by perturbing scalar, electromagnetic and fermionic fields, using the sixth-order WKB approach in conjunction with the appropriate numerical analysis. Our investigation indicates that string and linear GUP parameters have distinct and different effects on QNMs. We find that the greybody factor increases due to the presence of string cloud while the linear GUP parameter shows the opposite. We then examine the radiation spectrum and sparsity in the GUP corrected black hole with the cloud of string framework, which provides additional information about the thermal radiation released by black holes. Finally, our inquiries reveal that the influence of the string parameter and the quadratic GUP parameter on various astrophysical observables is comparable, however the impact of the linear GUP parameter is opposite.

gr-qc↗

arXiv2024

Massless Dirac Perturbations of black holes in f(Q) gravity: quasinormal modes and weak deflection angle

This article considers a static and spherical black hole (BH) in f(Q) gravity. f(Q) gravity is the extension of symmetric teleparallel general relativity, where both curvature and torsion are vanishing, and gravity is described by nonmetricity. In this study, we investigate the possible implications of quasinormal modes (QNM) modified Hawking spectra, and deflection angles generated by the model. The WKB method is used to solve the equations of motion for massless Dirac perturbation fields and explore the impact of the nonmetricity parameter ($Q_{0}$). Based on the QNMs computation, we can ensure that the BH is stable against massless Dirac perturbations and as $Q_{0}$ increases the the oscillatory frequency of the mode decrease. We then discuss the weak deflection angle in the weak field limit approximation. We compute the deflection angle up to the fourth order of approximation and show how the nonmetricity parameter affects it. We find that the $Q_{0}$ parameter reduces the deflection angle.

gr-qc↗

arXiv2024

Quazinormal modes and greybody factor of black hole surrounded by a quintessence in the S-V-T modified gravity as well as shadow

The purpose of this study is to investigate the quasinormal modes (QNMs), greybody factors (GFs) and shadows in a plasma of a black hole (BH) surrounded by an exotic fluid of quintessence type in a scalar-vector-tensor modified gravity. The effects of a quintessence scalar field and the modified gravity (MOG) field on the QNM, GF, and shadow are examined. Using the sixth-order WKB approach, we investigate the QNMs of massless scalar and electromagnetic perturbations. Our findings show that as the quintessence and the MOG parameter ($ε$ and $α$) increase, the oscillation frequencies decrease significantly. Gravitational wave damping, on the other hand, decreases with increasing $ε$ and $α$. In addition, we obtain an analytical solution for the transmission coefficients (GF) and demonstrate that more thermal radiation reaches the observer at spatial infinity as both the $ε$ and $α$ parameters increase. We also investigate the effect of the plasma background on the BH shadow and show that as the plasma background parameter increases, the shadow radius slightly shrinks. Nevertheless, the shadow radius increases as $α$ and $ε$ increase. Particularly intriguing is the fact that increasing $ε$ has a greater impact on the shadow radius than increasing $α$, indicating that the quintessence parameter has a greater impact than the MOG parameter.

gr-qc↗