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 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 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 Gravitational lensing by charged black hole in regularized 4D Einstein–Gauss–Bonnet gravity

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Rahul Kumar ◽  
Shafqat Ul Islam ◽  
Sushant G. Ghosh
Keyword(s):  
Black Holes ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Strong Field ◽  
Angular Position ◽  
Angular Separation ◽  
Light Deflection ◽  
Charged Black Holes ◽  
The Deflection Angle ◽  
Sgr A

AbstractAmong the higher curvature gravities, the most extensively studied theory is the so-called Einstein–Gauss–Bonnet (EGB) gravity, whose Lagrangian contains Einstein term with the GB combination of quadratic curvature terms, and the GB term yields nontrivial gravitational dynamics in $$ D\ge 5$$ D ≥ 5 . Recently there has been a surge of interest in regularizing, a $$ D \rightarrow 4 $$ D → 4 limit of, the EGB gravity, and the resulting regularized 4D EGB gravity valid in 4D. We consider gravitational lensing by Charged black holes in the 4D EGB gravity theory to calculate the light deflection coefficients in strong-field limits $$\bar{a}$$ a ¯ and $$\bar{b}$$ b ¯ , while former increases with increasing GB parameter $$\alpha $$ α and charge q, later decrease. We also find a decrease in the deflection angle $$\alpha _D$$ α D , angular position $$\theta _{\infty }$$ θ ∞ decreases more slowly and impact parameter for photon orbits $$u_{m}$$ u m more quickly, but angular separation s increases more rapidly with $$\alpha $$ α and charge q. We compare our results with those for analogous black holes in General Relativity (GR) and also the formalism is applied to discuss the astrophysical consequences in the case of the supermassive black holes Sgr A* and M87*.

scholarly journals Null Geodesics and Strong Field Gravitational Lensing in a String Cloud Background

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
M. Sharif ◽  
Sehrish Iftikhar
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Galactic Center ◽  
Deflection Angle ◽  
Orbital Motion ◽  
Strong Field ◽  
Schwarzschild Black Hole ◽  
Field Limit ◽  
Null Geodesics ◽  
Supermassive Black Hole

This paper is devoted to studying two interesting issues of a black hole with string cloud background. Firstly, we investigate null geodesics and find unstable orbital motion of particles. Secondly, we calculate deflection angle in strong field limit. We then find positions, magnifications, and observables of relativistic images for supermassive black hole at the galactic center. We conclude that string parameter highly affects the lensing process and results turn out to be quite different from the Schwarzschild black hole.

OBSERVATIONAL CONSTRAINTS ON STRONG GRAVITY

2011 ◽  
Vol 20 (14) ◽  
pp. 2755-2760
Author(s):  
CHRIS DONE
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Strong Field ◽  
Field Tests ◽  
High Energy ◽  
Observational Constraints ◽  
Tests Of General Relativity ◽  
Strong Gravity ◽  
Accretion Flows ◽  
Spacetime Curvature

Accretion onto a black hole transforms the darkest objects in the universe to the brightest. The high energy radiation emitted from the accretion flow before it disappears forever below the event horizon lights up the regions of strong spacetime curvature close to the black hole, enabling strong field tests of General Relativity. I review the observational constraints on strong gravity from such accretion flows, and show how the data strongly support the existence of such fundamental General Relativistic features of a last stable orbit and the event horizon. However, these successes also imply that gravity does not differ significantly from Einstein's predictions above the event horizon, so any new theory of quantum gravity will be very difficult to test.

Design of freeform LED lens with large light deflection angle for road lighting application

2012 ◽  
Author(s):  
Shaoyun Yin ◽  
Zhongxun Wang ◽  
Xiuhui Sun ◽  
Liangping Xia ◽  
Hui Pang ◽  
...  
Keyword(s):  
Deflection Angle ◽  
Light Deflection ◽  
Road Lighting ◽  
Lighting Application

scholarly journals PARAMETRIC INSTABILITY IN SCALAR GRAVITATIONAL FIELDS

2012 ◽  
Vol 27 (24) ◽  
pp. 1230023 ◽  
Author(s):  
TREVOR B. DAVIES ◽  
CHARLES H.-T. WANG ◽  
ROBERT BINGHAM ◽  
J. TITO MENDONÇA
Keyword(s):  
Gravitational Field ◽  
Field Effect ◽  
Strong Field ◽  
Parametric Instability ◽  
Spherically Symmetric ◽  
Scalar Tensor Theory ◽  
Subsequent Work ◽  
Dynamical Mechanism ◽  
Gravitational Fields ◽  
Tensor Theory

We present a brief review on a new dynamical mechanism for a strong field effect in scalar–tensor theory. Starting with a summary of the essential features of the theory and subsequent work by several authors, we analytically investigate the parametric excitation of a scalar gravitational field in a spherically symmetric radially pulsating neutron star.

scholarly journals Perturbative deflection angle, gravitational lensing in the strong field limit and the black hole shadow

2021 ◽  
Vol 81 (3) ◽  
Author(s):  
Junji Jia ◽  
Ke Huang
Keyword(s):  
Gravitational Lensing ◽  
Deflection Angle ◽  
Strong Field ◽  
Distance Effect ◽  
Critical Value ◽  
Field Limit ◽  
Perturbative Method ◽  
The Deflection Angle ◽  
The Impact ◽  
Strong Field Limit

AbstractA perturbative method to compute the deflection angle of both timelike and null rays in arbitrary static and spherically symmetric spacetimes in the strong field limit is proposed. The result takes a quasi-series form of $$(1-b_c/b)$$ ( 1 - b c / b ) where b is the impact parameter and $$b_c$$ b c is its critical value, with coefficients of the series explicitly given. This result also naturally takes into account the finite distance effect of both the source and detector, and allows to solve the apparent angles of the relativistic images in a more precise way. From this, the BH angular shadow size is expressed as a simple formula containing metric functions and particle/photon sphere radius. The magnification of the relativistic images were shown to diverge at different values of the source-detector angular coordinate difference, depending on the relation between the source and detector distance from the lens. To verify all these results, we then applied them to the Hayward BH spacetime, concentrating on the effects of its charge parameter l and the asymptotic velocity v of the signal. The BH shadow size were found to decrease slightly as l increases to its critical value, and increase as v decreases from light speed. For the deflection angle and the magnification of the images however, both the increase of l and decrease of v will increase their values.

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