Spherically Symmetric Wormhole Gravitational Lens Deflection Angle Signifying Braneworld Cosmology

2017 ◽  
Vol 34 (6) ◽  
pp. 060401 ◽  
Author(s):  
Anuar Alias ◽  
Wan Ahmad Tajuddin Wan Abdullah
Keyword(s):  
Deflection Angle ◽  
Gravitational Lens ◽  
Spherically Symmetric ◽  
Braneworld Cosmology

scholarly journals A Cusp—Counting Formula For Caustics Due To Multiplane Gravitational Lensing

1996 ◽  
Vol 173 ◽  
pp. 281-282
Author(s):  
A. O. Petters
Keyword(s):  
Light Source ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Gravitational Lens ◽  
Source Plane ◽  
Lens System ◽  
Light Rays ◽  
Counting Formula

Consider a gravitational lens system with K planes. If light rays are traced back from the observer to the light source plane, then the points on the first lens plane where a light ray either terminates, or, passes through and terminates before reaching the light source plane, are “obstruction points.” More precisely, tracing rays back to the source plane induces a K-plane lensing map η : U ⊆ R2 → R2 of the form η(x1) = x1 −∑i=1k αi(xi(xi)). We then define an obstruction point of η to be a point a of U where limx1→a |αi(xi(x1))| = ∞ for some “deflection angle” αi.

On strong field deflection angle by the massless Ellis–Bronnikov wormhole

2019 ◽  
Vol 34 (05) ◽  
pp. 1950040 ◽  
Author(s):  
Amrita Bhattacharya ◽  
Alexander A. Potapov
Keyword(s):  
Gravity Field ◽  
Deflection Angle ◽  
Strong Field ◽  
Spherically Symmetric ◽  
Light Deflection ◽  
Massless Limit ◽  
Strong Gravity

Tsukamoto [N. Tsukamoto, Phys. Rev. D 95, 064035 (2017)] developed a method, which is an improvement over that of Bozza [V. Bozza, Phys. Rev. D 66, 103001 (2002)], for calculating light deflection angle in the strong gravity field of a spherically symmetric static spacetime. The method is directly applicable to the massless Ellis–Bronnikov wormhole (EBWH), while Bozza’s method is not applicable. We wish to show that it is still possible to obtain the same deflection angle by applying Bozza’s method but only in an indirect way, that is, first calculate the deflection by the parent massive EBWH and then take its massless limit.

scholarly journals Testing Generalized Einstein-Cartan-Kibble-Sciama Gravity Using Weak Deflection Angle and Shadow Cast

2020 ◽  
Author(s):  
Ali Övgün ◽  
İzzet Sakallı
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Symmetric Solution ◽  
Deflection Angle ◽  
Spherically Symmetric ◽  
Plasma Medium ◽  
Asymptotically Flat ◽  
Spherically Symmetric Solution ◽  
Shadow Cast ◽  
Bonnet Theorem

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 effect of the ECKS parameter on the shadow of the black hole and weak deflection angle. 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.

scholarly journals First-Order Light Deflection by Einstein-Strauss Vacuole Method

2013 ◽  
Vol 2013 ◽  
pp. 1-4
Author(s):  
Debasish Saha ◽  
Amarjit Tamang ◽  
Ramil Izmailov ◽  
Carlo Cattani ◽  
Kamal K. Nandi
Keyword(s):  
Deflection Angle ◽  
Common Knowledge ◽  
Galactic Rotation ◽  
Spherically Symmetric ◽  
Light Deflection ◽  
Good Theory ◽  
Conformal Gravity ◽  
First Order ◽  
Outstanding Problem ◽  
Spherically Symmetric Solution

We resolve here an outstanding problem plaguing conformal gravity in its role in making consistent astrophysical predictions. Though its static spherically symmetric solution incorporates all the successes of Schwarzschild gravity, the fit to observed galactic rotation curves requires γ>0, while the observed increase in the Schwarzschild light deflection by galaxies appears to demand γ<0. Here we show that, contrary to common knowledge, there is an increase in the Schwarzschild deflection angle in the vicinity of galaxies due purely to the effect of γ>0, when the idea of the Einstein-Strauss vacuole model is employed. With the inconsistency now out of the way, conformal gravity should be regarded as a good theory explaining light deflection by galaxies.

scholarly journals On Gravitational Aberrations in Stellar Images

1972 ◽  
Vol 25 (6) ◽  
pp. 749
Author(s):  
MW Cook
Keyword(s):  
Cosmological Model ◽  
Null Geodesic ◽  
Average Density ◽  
Gravitational Lens ◽  
Light Sources ◽  
Spherically Symmetric ◽  
Dispersion Effect ◽  
Stellar Objects ◽  
Light Rays ◽  
The Universe

On the basis of a cosmological model which is fundamentally of the Friedmann expanding type with a spherically symmetric inhomogeneity superimposed, a study is made of three gravitational aberrations of purely relativistic origin observed in the images of stellar objects: (1) the "gravitational lens" effect, (2) a dispersion effect whereby a point source would produce a diffuse image, and (3) an 'apparent systematic motion of all light sources towards (or away from) the inhomogeneity. Admissable inhomogeneities in the model must satisfy PU ? 2�104 Mpc, where P is the ratio of the average density of matter within the inhomogeneity to the average density of the universe and U is its diameter in megaparsecs. The assumption is also made that the paths of light rays are described by the null-geodesic equations of the space-time under consideration.

scholarly journals Gravitational lensing by a black hole with torsion

2018 ◽  
Vol 27 (12) ◽  
pp. 1850110 ◽  
Author(s):  
Lu Zhang ◽  
Songbai Chen ◽  
Jiliang Jing
Keyword(s):  
Gravitational Lensing ◽  
Deflection Angle ◽  
Strong Field ◽  
Spherically Symmetric ◽  
Field Limit ◽  
Strong Gravitational Lensing ◽  
Spacetime Structure ◽  
Higher Order Terms ◽  
The Deflection Angle ◽  
Special Case

In this paper, we have investigated the gravitational lensing in a spherically symmetric spacetime with torsion in the generalized Einstein–Cartan–Kibble–Sciama (ECKS) theory of gravity by considering higher order terms. The torsion parameters change the spacetime structure, which affects the photon sphere, the deflection angle and the strong gravitational lensing. The condition of existence of horizons is not inconsistent with that of the photon sphere. Especially, there exists a novel case in which there is horizon but no photon sphere for the considered spacetime. In this special case, the deflection angle of the light ray near the event horizon also diverges logarithmically, but the coefficients in the strong-field limit are different from those in the cases with photon sphere. Moreover, in the far-field limit, we find that the deflection angle for certain torsion parameters approaches zero from the negative side, which is different from those in the usual spacetimes.

scholarly journals Hills and holes in the microlensing light curve due to plasma environment around gravitational lens

2019 ◽  
Vol 491 (4) ◽  
pp. 5636-5649 ◽  
Author(s):  
Oleg Yu Tsupko ◽  
Gennady S Bisnovatyi-Kogan
Keyword(s):  
Gravitational Field ◽  
Light Curve ◽  
Significant Influence ◽  
Deflection Angle ◽  
Inhomogeneous Plasma ◽  
Light Curves ◽  
Gravitational Lens ◽  
Remarkable Effect ◽  
The Deflection Angle ◽  
Hole Effect

ABSTRACT In this paper, we investigate the influence of the plasma surrounding the gravitational lens on the effect of microlensing. In presence of plasma around the lens, the deflection angle is determined by both the gravitational field of the lens and the chromatic refraction in the inhomogeneous plasma. We calculate microlensing light curves numerically for point-mass lens surrounded by power-law density distribution of plasma. A variety of possible curves is revealed, depending on the plasma density and frequency of observations. In the case of significant influence of plasma, the shape of microlensing light curve is strongly deformed in comparison with vacuum case. If the refractive deflection is large enough to compensate or to overcome the gravitational deflection, microlensing images can completely disappear for the observer. In this case, the remarkable effect occurs: formation of a ‘hole’ instead of a ‘hill’ in the center of microlensing light curve. Observational prospects of ‘hill-hole’ effect in different microlensing scenarios are discussed.

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