scholarly journals Weak Deflection Angle of Black-bounce Traversable Wormholes Using Gauss-Bonnet Theorem in the Dark Matter Medium

2020 ◽  
Author(s):  
Ali Övgün
Keyword(s):  
Dark Matter ◽  
Gaussian Curvature ◽  
Deflection Angle ◽  
Light Bending ◽  
Traversable Wormholes ◽  
Topological Effect ◽  
Bonnet Theorem

In this paper, first we use the optical metrics of black-bounce traversable wormholes to calculate the Gaussian curvature. Then we use the Gauss-Bonnet theorem to obtain the weak deflection angle of light from the black-bounce traversable wormholes. Then we investigate the effect of dark matter medium on weak deflection angle using the Gauss-Bonnet theorem. We show how weak deflection angle of wormhole is affected by the bounce parameter $a$. Using the Gauss-bonnet theorem for calculating weak deflection angle shows us that light bending can be thought as a global and topological effect.

scholarly journals Weak deflection angle of black-bounce traversable wormholes usingGauss–Bonnet theorem in the dark matter medium

2020 ◽  
Vol 44 (5) ◽  
pp. 465-471
Author(s):  
ALİ ÖVGÜN
Keyword(s):  
Dark Matter ◽  
Deflection Angle ◽  
Light Bending ◽  
Traversable Wormholes ◽  
Bonnet Theorem

In this paper, we first use the optical metrics of black-bounce traversable wormholes to calculate the Gaussiancurvature. Then we use the Gauss–Bonnet theorem to obtain the weak deflection angle of light from the black-bouncetraversable wormholes. We investigate the effect of dark matter medium on weak deflection angle using the Gauss–Bonnet theorem. We show how weak deflection angle of wormhole is affected by the bounce parametera. Using theGauss–Bonnet theorem for calculating weak deflection angle shows us that light bending can be thought as a global andtopological effect.

scholarly journals Deflection Angle of Photons through Dark Matter by Black Holes and Wormholes Using Gauss–Bonnet Theorem

Universe ◽  
2019 ◽  
Vol 5 (5) ◽  
pp. 115 ◽  
Author(s):  
Ali Övgün
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Compact Objects ◽  
Asymptotically Flat ◽  
Optical Geometry ◽  
Topological Effect ◽  
Bonnet Theorem ◽  
Fish Eye

In this research, we used the Gibbons–Werner method (Gauss–Bonnet theorem) on the optical geometry of a black hole and wormhole, extending the calculation of weak gravitational lensing within the Maxwell’s fish eye-like profile and dark-matter medium. The angle is seen as a partially topological effect, and the Gibbons–Werner method can be used on any asymptotically flat Riemannian optical geometry of compact objects in a dark-matter medium.

scholarly journals Effect of the Dilaton Field on Deflection Angle of Massive Photons by Black Holes in Einstein-Maxwell-Dilaton-Axion Theory

2019 ◽  
Author(s):  
Wajiha Javed ◽  
Rimsha Babar ◽  
Ali Övgün
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Deflection Angle ◽  
Weak Field ◽  
Dilaton Field ◽  
Plasma Medium ◽  
The Deflection Angle ◽  
Bonnet Theorem ◽  
Massive Photons

In this paper, we argue that one can calculate the weak deflection angle in the background of Einstein-Maxwell-Dilaton-Axion black hole using the Gauss-Bonnet theorem. To support this, the optical geometry of the black hole with the Gibbons-Werner method are used to obtain the deflection angle of light in the weak field limits. Moreover, we investigate the effect of a plasma medium on deflection of light for a given black hole. Because of dilaton and axion are one of the candidate of the dark matter, it can give us a hint on observation of dark matter which is supported the black hole. Hence we demonstrate the observational viability via showing the effect of the dark matter on the weak deflection angle.

scholarly journals Weak gravitational lensing by Einstein-nonlinear-Maxwell–Yukawa black hole

2020 ◽  
Vol 17 (12) ◽  
pp. 2050182
Author(s):  
Wajiha Javed ◽  
Muhammad Bilal Khadim ◽  
Ali Övgün
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Gaussian Curvature ◽  
Deflection Angle ◽  
Weak Field ◽  
Plasma Medium ◽  
Weak Gravitational Lensing ◽  
The Deflection Angle ◽  
Bonnet Theorem

In this paper, we analyze the weak gravitational lensing in the context of Einstein-nonlinear-Maxwell–Yukawa black hole. To this desire, we derive the deflection angle of light by Einstein-nonlinear-Maxwell–Yukawa black hole using the Gibbons and Werner method. For this purpose, we obtain the Gaussian curvature and apply the Gauss–Bonnet theorem to find the deflection angle of Einstein-nonlinear-Maxwell–Yukawa black hole in weak field limits. Moreover, we derive the deflection angle of light in the influence of plasma medium. We also analyze the graphical behavior of deflection angle by Einstein-nonlinear-Maxwell–Yukawa black hole in the presence of plasma as well as non-plasma medium.

scholarly journals Effect of Aether Field on Weak Deflection Angle of Black Holes

2019 ◽  
Author(s):  
Ali Övgün ◽  
İzzet Sakallı ◽  
Joel Saavedra
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Weak Limit ◽  
Spherically Symmetric ◽  
Light Rays ◽  
Topological Effect ◽  
The Deflection Angle ◽  
Bonnet Theorem ◽  
Limit Approximation

We study the light rays in a static and spherically symmetric gravitational field of null aether theory (NAT). To this end, we employ the Gauss-Bonnet theorem to compute the deflection angle by a NAT black hole in the weak limit approximation. Using the optical metrics of the NAT black hole, we first obtain the Gaussian curvature and then calculate the leading terms of the deflection angle. Our calculations show how gravitational lensing is affected by the NAT field. We also show once again that the bending of light stems from a global and topological effect.

scholarly journals Weak Deflection Angle of some Classes of non-linear Electrodynamics Black Holes via Gauss-Bonnet Theorem

2020 ◽  
Author(s):  
Hasan El Moumni ◽  
Karima Masmar ◽  
Ali Övgün
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Weak Field ◽  
Leading Order ◽  
Plasma Medium ◽  
Non Linear ◽  
The Deflection Angle ◽  
Bonnet Theorem

In this paper, we study the gravitational lensing by some black hole classes within the non-linear electrodynamics in weak field limits. First, we calculate an optical geometry of the non-linear electrodynamics black hole then we use the Gauss-Bonnet theorem for finding deflection angle in weak field limits. The effect of non-linear electrodynamics on the deflection angle in leading order terms is studied. Furthermore, we discuss the effects of the plasma medium on the weak deflection angle.

scholarly journals Deflection of light by a rotating black hole surrounded by “quintessence”

2020 ◽  
Vol 35 (26) ◽  
pp. 2050155 ◽  
Author(s):  
Prateek Sharma ◽  
Hemwati Nandan ◽  
Radouane Gannouji ◽  
Rashmi Uniyal ◽  
Amare Abebe
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Deflection Angle ◽  
Energy Condition ◽  
Additional Parameter ◽  
Deviation Angle ◽  
Extremal Case ◽  
Rotating Black Hole ◽  
State Formula ◽  
Kerr Space

We present a detailed analysis of a rotating black hole surrounded by “quintessence.” This solution represents a fluid with a constant equation of state, [Formula: see text], which can for example describe an effective warm dark matter fluid around a black hole. We clarify the conditions for the existence of such a solution and study its structure by analyzing the existence of horizons as well as the extremal case. We show that the deflection angle produced by the black hole depends on the parameters [Formula: see text] which need to obey the condition [Formula: see text] because of the weak energy condition, where [Formula: see text] is an additional parameter describing the hair of the black hole. In this context, we found that for [Formula: see text] (consistent with warm dark matter) and [Formula: see text], the deviation angle is larger than that in the Kerr space–time for direct and retrograde orbits. We also derive an exact solution in the case of [Formula: see text].

scholarly journals Possible formation of wormholes from dark matter in an isothermal galactic halo and void

2019 ◽  
Vol 34 (23) ◽  
pp. 1950188
Author(s):  
Nayan Sarkar ◽  
Susmita Sarkar ◽  
Farook Rahaman ◽  
P. K. F. Kuhfittig ◽  
G. S. Khadekar
Keyword(s):  
Dark Matter ◽  
Galactic Halo ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Galactic Rotation ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Rotation Curves ◽  
Galactic Rotation Curves ◽  
Traversable Wormholes

It is well-known that traversable wormholes are valid solutions of the Einstein field equations, but these structures can only be maintained by violating the null energy condition. In this paper, we have obtained such wormhole solutions in an isothermal galactic halo, as well as in a void. We have shown that the null energy condition is violated, with the help of a suitable redshift function obtained from flat galactic rotation curves.

scholarly journals Traversable wormholes supported by GUP corrected Casimir energy

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
Kimet Jusufi ◽  
Phongpichit Channuie ◽  
Mubasher Jamil
Keyword(s):  
Deflection Angle ◽  
Equations Of State ◽  
Generalized Uncertainty Principle ◽  
Casimir Energy ◽  
Energy Conditions ◽  
Strong Condition ◽  
Asymptotically Flat ◽  
Wormhole Throat ◽  
Classical Energy ◽  
Traversable Wormholes

Abstract In this paper, we investigate the effect of the Generalized Uncertainty Principle (GUP) in the Casimir wormhole spacetime recently proposed by Garattini (Eur Phys J C 79: 951, 2019). In particular, we consider three types of GUP relations, firstly the Kempf, Mangano and Mann (KMM) model, secondly the Detournay, Gabriel and Spindel (DGS) model, and finally the so-called type II model for the GUP principle. To this end, we consider three specific models of the redshift function along with two different equations of state (EoS), given by $${\mathcal {P}}_r(r)=\omega _r(r) \rho (r)$$Pr(r)=ωr(r)ρ(r) and $${\mathcal {P}}_t(r)=\omega _t (r){\mathcal {P}}_r(r)$$Pt(r)=ωt(r)Pr(r) and obtain a class of asymptotically flat wormhole solutions supported by Casimir energy under the effect of GUP. Furthermore we check the null, weak, and strong condition at the wormhole throat with a radius $$r_0$$r0, and we show that in general the classical energy conditions are violated by some arbitrary quantity at the wormhole throat. Importantly, we examine the wormhole geometry with semiclassical corrections via embedding diagrams. We also consider the ADM mass of the wormhole, the volume-integral quantifier to calculate the amount of the exotic matter near the wormhole throat, and the deflection angle of light.

scholarly journals Deflection angle of light by wormholes using the Gauss–Bonnet theorem

2017 ◽  
Vol 14 (12) ◽  
pp. 1750179 ◽  
Author(s):  
Kimet Jusufi
Keyword(s):  
Deflection Angle ◽  
Weak Limit ◽  
Space Time ◽  
Geometrical Method ◽  
Optical Geometry ◽  
The Deflection Angle ◽  
Bonnet Theorem ◽  
Limit Approximation

In this paper, we have investigated the deflection angle of light by wormholes using a new geometrical method known as Gibbons–Werner method (GW). In particular, we have calculated the deflection angle of light in the weak limit approximation in two wormhole space–time geometries: Ellis wormhole and Janis–Newman–Winnicour (JNW) wormhole. We have employed the famous Gauss–Bonnet theorem (GBT) to the Ellis wormhole optical geometry and JNW wormhole optical geometry, respectively. By using GBT, we computed the deflection angles in leading orders by these wormholes and our results were compared with the ones in the literature.

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