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Ali Ovgun - One of the best experts on this subject based on the ideXlab platform.

  • effect of the brane dicke coupling parameter on weak gravitational lensing by wormholes and naked singularities
    Physical Review D, 2019
    Co-Authors: Wajiha Javed, Ali Ovgun, Rimsha Babar
    Abstract:

    In this paper, we analyze the deflection angle of light by the Brane-Dicke wormhole in the weak field limit approximation to find the effect of the Brane-Dicke coupling parameter on the weak gravitation lensing. For this purpose, we consider new geometric techniques, i.e., Gauss-Bonnet Theorem and optical geometry in order to calculate the deflection angle. Furthermore, we verify our results by considering the most familiar geodesic technique. Moreover, we establish the quantum corrected metric of the Brane-Dicke wormhole by replacing the classical geodesic with Bohmian trajectories, whose matter source and anisotropic pressure are influenced by Bohmian quantum effects and calculate its quantum corrected deflection angle. Then, we calculate the deflection angle by naked singularities and compare with the result of the wormhole. Such a novel lensing feature might serve as a way to detect wormholes, naked singularities and also the evidence of Brane-Dicke theory.

  • the effect of the brane dicke coupling parameter on weak gravitational lensing by wormholes and naked singularities
    Physical Review D, 2019
    Co-Authors: Wajiha Javed, Rimsha Babar, Ali Ovgun
    Abstract:

    In this paper, we analyze the deflection angle of light by Brane-Dicke wormhole in the weak field limit approximation to find the effect of the Brane-Dicke coupling parameter on the weak gravitation lensing. For this purpose, we consider new geometric techniques, i.e., Gauss-Bonnet Theorem and optical geometry in order to calculate the deflection angle. Furthermore, we verify our results by considering the most familiar geodesic technique. Moreover, we establish the quantum corrected metric of Brane-Dicke wormhole by replacing the classical geodesic with Bohmian trajectories, whose matter source and anisotropic pressure are influenced by Bohmian quantum effects and calculate its quantum corrected deflection angle. Then, we calculate the deflection angle by naked singularities and compare with the result of wormhole's. Such a novel lensing feature might serve as a way to detect wormholes, naked singularities and also the evidence of Brane-Dicke theory.

  • gravitational lensing under the effect of weyl and bumblebee gravities applications of gauss bonnet Theorem
    Annals of Physics, 2018
    Co-Authors: Kimet Jusufi, Ali Ovgun, Izzet Sakalli
    Abstract:

    Abstract In this paper, we use the Gauss–Bonnet Theorem to obtain the deflection angle by the photons coupled to Weyl tensor in a Schwarzschild black hole and Schwarzschild-like black hole in bumblebee gravity in the weak limit approximation. To do so, we first calculate the corresponding optical metrics, and then we find the Gaussian curvature to use in Gauss–Bonnet Theorem, which is first done by Gibbons and Werner. Hence, in the leading order terms we show the deflection angle, that is affected by the coupling between the photon and Weyl tensor, and there is a deviation from the deflecting angle as compared with Schwarzschild black hole with Schwarzschild-like black hole in bumblebee gravity. Moreover, we investigate the deflection angle by Einstein–Rosen type wormhole in Weyl gravity and in bumblebee gravity. Interestingly, the deflection angle by Einstein–Rosen type wormhole in bumblebee gravity is found as larger than the deflection angle by Einstein–Rosen type wormhole in Weyl gravity.

  • gravitational lensing under the effect of weyl and bumblebee gravities applications of gauss bonnet Theorem
    arXiv: General Relativity and Quantum Cosmology, 2018
    Co-Authors: Kimet Jusufi, Ali Ovgun, Izzet Sakalli
    Abstract:

    In this paper, we use the Gauss Bonnet Theorem to obtain the deflection angle by the photons coupled to Weyl tensor in a Schwarzschild black hole and Schwarzschild-like black hole in bumblebee gravity in the weak limit approximation. To do so, we first calculate the corresponding optical metrics, and then we find the Gaussian curvature to use in Gauss-Bonnet Theorem, which is first done by Gibbons and Werner. Hence, in the leading order terms we show the deflection angle, that is affected by the coupling between the photon and Weyl tensor, and there is a deviation from the deflecting angle as compared with Schwarzschild black hole with Schwarzschild-like black hole in bumblebee gravity. Moreover, we investigate the deflection angle by Einstein-Rosen type wormhole in Weyl gravity and in bumblebee gravity. Interestingly, the deflection angle by Einstein-Rosen type wormhole in bumblebee gravity is found as larger than the the deflection angle by Einstein-Rosen type wormhole in Weyl gravity.

  • effect of the cosmological constant on the deflection angle by a rotating cosmic string
    Physical Review D, 2018
    Co-Authors: Kimet Jusufi, Ali Ovgun
    Abstract:

    In this article, we report the effect of the cosmological constant and the internal density energy of the cosmic string in the deflection angle of light in the spacetime of a rotating cosmic string with an internal structure. Furthermore, we revisit the deflection angle by a rotating cosmic string and provide a generalization to the deflection angle in the cosmic string spacetime using the geodesic equations and the Gauss-Bonnet Theorem and show an agreement between two methods in the case of higher order terms of the linear density mass of the cosmic string. By modifying the integration domain due to the global conical topology, we were able to solve the inconsistency between these two methods regarding the effect of the rotating of the cosmic string previously reported in the literature. We show that the deflection angle is not affected by the rotating of the cosmic string however, the cosmological constant $\Lambda$ completely affect the deflection angle and generalizes the well known result.

Kimet Jusufi - One of the best experts on this subject based on the ideXlab platform.

  • shadow and deflection angle of rotating black holes in perfect fluid dark matter with a cosmological constant
    Physical Review D, 2019
    Co-Authors: Kimet Jusufi, Sumarna Haroon, Mubasher Jamil, Kai Lin, Robert B Mann
    Abstract:

    The presence of dark matter around a black hole remarkably affects its spacetime. We consider the effects of dark matter on the shadow of a new solution to the Einstein equations that describes a rotating black hole in the background of perfect dark matter fluid, along with its extension to nonzero cosmological constant $\mathrm{\ensuremath{\Lambda}}$. Working in Boyer-Lindquist coordinates, we consider the effects of the perfect dark matter fluid parameter $\ensuremath{\alpha}$ on the shadow cast by a black hole with respect to an observer at position $({r}_{o},{\ensuremath{\theta}}_{o})$. By applying the Gauss-Bonnet Theorem to the optical geometry, we find that notable distortions from a Kerr black hole can occur. We describe their dependence on $\ensuremath{\alpha}$ and $\mathrm{\ensuremath{\Lambda}}$.

  • shadow and deflection angle of rotating black holes in perfect fluid dark matter with a cosmological constant
    Physical Review D, 2019
    Co-Authors: Sumarna Haroon, Kimet Jusufi, Mubasher Jamil, Robert B Mann
    Abstract:

    The presence of dark matter around a black hole remarkably affects its spacetime. We consider the effects of dark matter on the shadow of a new solution to the Einstein equations that describes a rotating black hole in the background of perfect dark matter fluid (PFDM), along with its extension to nonzero cosmological constant $\Lambda$. Working in Boyer-Lindquist coordinates, we consider the effects of the PFDM parameter $\alpha$ on the shadow cast by a black hole with respect to an observer at position $(r_o,\theta_o)$. By applying the Gauss-Bonnet Theorem to the optical geometry we find that notable distortions from a Kerr black hole can occur. We describe their dependence on $\alpha$ and $\Lambda$.

  • Distinguishing rotating naked singularities from Kerr-like wormholes by their deflection angles of massive particles
    SpringerOpen, 2019
    Co-Authors: Kimet Jusufi, Ayan Banerjee, Galin Gyulchev, Muhammed Amir
    Abstract:

    Abstract We study the gravitational deflection of relativistic massive particles by Janis–Newman–Winicour (JNW) spacetimes (also known as a rotating source with a surface-like naked singularity), and a rotating Kerr-like wormholes. Based on the recent article (Jusufi in Phys Rev D 98:064017, 2018), we extend some of these results by exploring the effects of naked singularity and Kerr-like objects on the deflection of particles. We start by introducing coordinate transformation leading to an isotropic line element which gives the refraction index of light for the corresponding optical medias. On the other hand, the refraction index for massive particles is found by considering those particles as a de Broglie wave packets. To this end, we apply the Gauss–Bonnet Theorem to the isotropic optical metrics to find the deflection angles. Our analysis shows that, in the case of the JNW spacetime the deflection angle is affected by the parameter $$0

  • gravitational lensing under the effect of weyl and bumblebee gravities applications of gauss bonnet Theorem
    Annals of Physics, 2018
    Co-Authors: Kimet Jusufi, Ali Ovgun, Izzet Sakalli
    Abstract:

    Abstract In this paper, we use the Gauss–Bonnet Theorem to obtain the deflection angle by the photons coupled to Weyl tensor in a Schwarzschild black hole and Schwarzschild-like black hole in bumblebee gravity in the weak limit approximation. To do so, we first calculate the corresponding optical metrics, and then we find the Gaussian curvature to use in Gauss–Bonnet Theorem, which is first done by Gibbons and Werner. Hence, in the leading order terms we show the deflection angle, that is affected by the coupling between the photon and Weyl tensor, and there is a deviation from the deflecting angle as compared with Schwarzschild black hole with Schwarzschild-like black hole in bumblebee gravity. Moreover, we investigate the deflection angle by Einstein–Rosen type wormhole in Weyl gravity and in bumblebee gravity. Interestingly, the deflection angle by Einstein–Rosen type wormhole in bumblebee gravity is found as larger than the deflection angle by Einstein–Rosen type wormhole in Weyl gravity.

  • gravitational deflection of relativistic massive particles by kerr black holes and teo wormholes viewed as a topological effect
    Physical Review D, 2018
    Co-Authors: Kimet Jusufi
    Abstract:

    We consider the problem of gravitational deflection of a propagating relativistic massive particles by rotating black holes (Kerr black holes) and rotating wormholes (Teo wormholes) in the weak limit approximation. In particular we have introduced an alternative way to calculate the deflection angle for massive particles based on the refractive index of the optical media and the Gauss-Bonnet Theorem applied to the isotropic optical metrics. The refractive index governing the propagation of massive particles is calculated by considering those particles as a de Broglie wave packets. Finally applying the Gauss-Bonnet Theorem leads to an exact result for the deflection angle in both geometries. Put in other words, the trajectory of light rays as well as the trajectory of massive particles in a given spacetime background can be viewed as a global spacetime effect, namely as a topological effect.

Övgün Ali - One of the best experts on this subject based on the ideXlab platform.

  • Weak deflection angle by Casimir wormhole using Gauss-Bonnet Theorem and its shadow
    'World Scientific Pub Co Pte Lt', 2021
    Co-Authors: Javed Wajiha, Hamza Ali, Övgün Ali
    Abstract:

    In this paper, we calculate the weak deflection angle by Casimir wormhole and its shadow. To do so, we derive the Gaussian optical curvature and use the Gauss-Bonnet Theorem. Then we find the deflection angle by Casimir wormhole in weak field limits. Moreover, we obtain the weak deflection angle in the presence of plasma medium and see the effect of the plasma medium on the weak deflection angle. Moreover, we study a shadow of Casimir wormhole and we plot and discuss them. We show the shadow of Casimir wormhole's behavior when changing the value of $a$.Comment: Accepted for publication in Modern Physics Letters

  • Deriving Weak Deflection Angle by Black Holes or Wormholes using Gauss-Bonnet Theorem
    'The Scientific and Technological Research Council of Turkey', 2021
    Co-Authors: Kumaran Yashmitha, Övgün Ali
    Abstract:

    In this review, various researches on finding the bending angle of light deflected by a massive gravitating object which regard the Gauss-Bonnet Theorem as the premise have been revised. Primarily, the Gibbons and Werner method is studied apropos of the gravitational lensing phenomenon in the weak field limits. Some exclusive instances are deliberated while calculating the deflection angle, beginning with the finite-distance corrections on non-asymptotically flat spacetimes. Effects of plasma medium is then inspected to observe its contribution to the deflection angle. Finally, the Jacobi metric is explored as an alternative method, only to arrive at similar results. All of the cases are probed in three constructs, one as a generic statement of explanation, one for black holes, and one for wormholes, so as to gain a perspective on every kind of influence.Comment: 22 pages. Review Article. Accepted for publication in Turkish Journal of Physic

  • Weak Deflection angle and Shadow by Tidal Charged Black Hole
    'MDPI AG', 2021
    Co-Authors: Javed Wajiha, Hamza Ali, Övgün Ali
    Abstract:

    In this article, we calculate the deflection angle of tidal charged black hole (TCBH) in weak field limits. First we obtain the Gaussian optical curvature and then apply the Gauss-Bonnet Theorem on it. With the help of Gibbons-Werner method, we are able to calculate the light's deflection angle by TCBH in weak field limits. After calculating the deflection angle of light, we check the graphical behavior of TCBH. Moreover, we further find the light's deflection angle in the presence of plasma medium and also check the graphical behavior in the presence of plasma medium. Moreover, we investigate the shadow of TCBH. For calculating the shadow, we first find the null geodesics around the TCBH and then find its shadow radius. We also obtain TCBH's shadow in the plasma medium. Hence, we discuss the shadow of the TCBH using the $M87^{*}$ parameters announced by the Event Horizon Telescope.Comment: 14 pages, 4 figures. Accepted for publication in Universe. https://www.mdpi.com/2218-1997/7/10/38

  • Testing Generalized Einstein-Cartan-Kibble-Sciama Gravity using Weak Deflection Angle and Shadow Cast
    'IOP Publishing', 2020
    Co-Authors: Övgün Ali, Sakallı İzzet
    Abstract:

    In this paper, we use a new asymptotically flat and spherically symmetric solution in the generalized Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity to study the weak gravitational lensing and its shadow cast. To this end, we first compute the weak deflection angle of generalized ECKS black hole using the Gauss-Bonnet Theorem in plasma medium and in vacuum. Next by using the Newman-Janis algorithm without complexification, we derive the rotating generalized ECKS black hole and in the sequel study its shadow. Then, we discuss the effects of the ECKS parameter on the weak deflection angle and shadow of the black hole. In short, the goal of this paper is to give contribution to the ECKS theory and look for evidences to understand how the ECKS parameter effects the gravitational lensing. Hence, we show that the weak deflection of black hole is increased with the increase of the ECKS parameter.Comment: 16 pages. Accepted for publication in Classical and Quantum Gravit

  • Weak Gravitational lensing by stringy black holes
    'Springer Science and Business Media LLC', 2020
    Co-Authors: Javed Wajiha, Khadim, Muhammad Bilal, Övgün Ali
    Abstract:

    In this paper, we discuss the weak gravitational lensing in the context of stringy black holes. Initially, we examine the deflection angle of photon by charged stringy black hole. For this desire, we compute the Gaussian optical curvature and implement the Gauss-Bonnet Theorem to investigate the deflection angle for spherically balanced spacetime of stringy black hole. We also analyze the influence of plasma medium in the weak gravitational lensing for stringy black hole. Moreover, the graphical impact of impact parameter $b$ , black hole charge $Q$ on deflection angle by charged stringy black hole has been studied in plasma as well as non-plasma medium.Comment: 7 pages. Published in EPJPlu

Robert B Mann - One of the best experts on this subject based on the ideXlab platform.

  • shadow and deflection angle of rotating black holes in perfect fluid dark matter with a cosmological constant
    Physical Review D, 2019
    Co-Authors: Sumarna Haroon, Kimet Jusufi, Mubasher Jamil, Robert B Mann
    Abstract:

    The presence of dark matter around a black hole remarkably affects its spacetime. We consider the effects of dark matter on the shadow of a new solution to the Einstein equations that describes a rotating black hole in the background of perfect dark matter fluid (PFDM), along with its extension to nonzero cosmological constant $\Lambda$. Working in Boyer-Lindquist coordinates, we consider the effects of the PFDM parameter $\alpha$ on the shadow cast by a black hole with respect to an observer at position $(r_o,\theta_o)$. By applying the Gauss-Bonnet Theorem to the optical geometry we find that notable distortions from a Kerr black hole can occur. We describe their dependence on $\alpha$ and $\Lambda$.

  • shadow and deflection angle of rotating black holes in perfect fluid dark matter with a cosmological constant
    Physical Review D, 2019
    Co-Authors: Kimet Jusufi, Sumarna Haroon, Mubasher Jamil, Kai Lin, Robert B Mann
    Abstract:

    The presence of dark matter around a black hole remarkably affects its spacetime. We consider the effects of dark matter on the shadow of a new solution to the Einstein equations that describes a rotating black hole in the background of perfect dark matter fluid, along with its extension to nonzero cosmological constant $\mathrm{\ensuremath{\Lambda}}$. Working in Boyer-Lindquist coordinates, we consider the effects of the perfect dark matter fluid parameter $\ensuremath{\alpha}$ on the shadow cast by a black hole with respect to an observer at position $({r}_{o},{\ensuremath{\theta}}_{o})$. By applying the Gauss-Bonnet Theorem to the optical geometry, we find that notable distortions from a Kerr black hole can occur. We describe their dependence on $\ensuremath{\alpha}$ and $\mathrm{\ensuremath{\Lambda}}$.

Sumarna Haroon - One of the best experts on this subject based on the ideXlab platform.

  • shadow and deflection angle of rotating black holes in perfect fluid dark matter with a cosmological constant
    Physical Review D, 2019
    Co-Authors: Sumarna Haroon, Kimet Jusufi, Mubasher Jamil, Robert B Mann
    Abstract:

    The presence of dark matter around a black hole remarkably affects its spacetime. We consider the effects of dark matter on the shadow of a new solution to the Einstein equations that describes a rotating black hole in the background of perfect dark matter fluid (PFDM), along with its extension to nonzero cosmological constant $\Lambda$. Working in Boyer-Lindquist coordinates, we consider the effects of the PFDM parameter $\alpha$ on the shadow cast by a black hole with respect to an observer at position $(r_o,\theta_o)$. By applying the Gauss-Bonnet Theorem to the optical geometry we find that notable distortions from a Kerr black hole can occur. We describe their dependence on $\alpha$ and $\Lambda$.

  • shadow and deflection angle of rotating black holes in perfect fluid dark matter with a cosmological constant
    Physical Review D, 2019
    Co-Authors: Kimet Jusufi, Sumarna Haroon, Mubasher Jamil, Kai Lin, Robert B Mann
    Abstract:

    The presence of dark matter around a black hole remarkably affects its spacetime. We consider the effects of dark matter on the shadow of a new solution to the Einstein equations that describes a rotating black hole in the background of perfect dark matter fluid, along with its extension to nonzero cosmological constant $\mathrm{\ensuremath{\Lambda}}$. Working in Boyer-Lindquist coordinates, we consider the effects of the perfect dark matter fluid parameter $\ensuremath{\alpha}$ on the shadow cast by a black hole with respect to an observer at position $({r}_{o},{\ensuremath{\theta}}_{o})$. By applying the Gauss-Bonnet Theorem to the optical geometry, we find that notable distortions from a Kerr black hole can occur. We describe their dependence on $\ensuremath{\alpha}$ and $\mathrm{\ensuremath{\Lambda}}$.