scholarly journals The deflection angle of a gravitational source with a global monopole in the strong field limit

2010 ◽  
Vol 28 (1) ◽  
pp. 015001 ◽  
Author(s):  
Hongbo Cheng ◽  
Jingyun Man
Keyword(s):  
Deflection Angle ◽  
Strong Field ◽  
Global Monopole ◽  
Field Limit ◽  
Gravitational Source ◽  
The Deflection Angle ◽  
Strong Field Limit

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.

Deflection angle for charged wormhole in f(R,T) gravity

2021 ◽  
pp. 2150193
Author(s):  
Nisha Godani ◽  
Gauranga C. Samanta
Keyword(s):  
Gravitational Lensing ◽  
Deflection Angle ◽  
Strong Field ◽  
Energy Conditions ◽  
Field Limit ◽  
Strong Field Limit

This paper is focused on the study of charged wormholes which are combinations of Morris–Thorne wormhole and Reissner–Nordström spacetime. Gravitational lensing is an important tool which has been adopted to detect various objects like wormholes using the notion of deflection angle. In this work, we have evaluated deflection angle with and without using the strong field limit coefficients and compared the results. Further, exact charged wormhole solutions are obtained in [Formula: see text] gravity and the nature of the energy conditions is examined.

scholarly journals Null Geodesics and Strong Field Gravitational Lensing of Black Hole with Global Monopole

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
M. Sharif ◽  
Sehrish Iftikhar
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Time Delays ◽  
Deflection Angle ◽  
Orbital Motion ◽  
Strong Field ◽  
Global Monopole ◽  
Schwarzschild Black Hole ◽  
Field Limit ◽  
Null Geodesics

We study two interesting features of a black hole with an ordinary as well as phantom global monopole. Firstly, we investigate null geodesics which imply unstable orbital motion of particles for both cases. Secondly, we evaluate deflection angle in strong field regime. We then find Einstein rings, magnifications, and observables of the relativistic images for supermassive black hole at the center of galaxy NGC4486B. We also examine time delays for different galaxies and present our results numerically. It is found that the deflection angle for ordinary/phantom global monopole is greater/smaller than that of Schwarzschild black hole. In strong field limit, the remaining properties of these black holes are quite different from the Schwarzschild black hole.

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.

Charged traversable wormholes in f(R) gravity

2021 ◽  
pp. 2150098
Author(s):  
Nisha Godani ◽  
Gauranga C. Samanta
Keyword(s):  
Gravitational Lensing ◽  
Deflection Angle ◽  
Strong Field ◽  
Energy Condition ◽  
Weak Energy Condition ◽  
Exotic Matter ◽  
Field Limit ◽  
Traversable Wormholes ◽  
The Deflection Angle ◽  
Lensing Effect

This work is focused on the study of charged wormholes in the following two aspects: (i) to obtain exotic matter free effective charged wormhole solutions and (ii) to determine deflection angle for gravitational lensing effect. We have defined a novel redshift function, obtained wormhole solutions using the background of [Formula: see text] theory of gravity and found the regions obeying the weak energy condition. Further, the gravitational lensing effect is analyzed by determining the deflection angle in terms of strong field limit coefficients.

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.

scholarly journals Development of singularities of the Skyrme model

2020 ◽  
Vol 17 (01) ◽  
pp. 61-73
Author(s):  
Michael McNulty
Keyword(s):  
Sigma Model ◽  
Blow Up ◽  
Strong Field ◽  
Skyrme Model ◽  
Nonlinear Sigma Model ◽  
Field Limit ◽  
Wave Maps ◽  
Self Similar ◽  
Similar Solutions ◽  
Strong Field Limit

The Skyrme model is a geometric field theory and a quasilinear modification of the Nonlinear Sigma Model (Wave Maps). In this paper, we study the development of singularities for the equivariant Skyrme Model, in the strong-field limit, where the restoration of scale invariance allows us to look for self-similar blow-up behavior. After introducing the Skyrme Model and reviewing what’s known about formation of singularities in equivariant Wave Maps, we prove the existence of smooth self-similar solutions to the [Formula: see text]-dimensional Skyrme Model in the strong-field limit, and use that to conclude that the solution to the corresponding Cauchy problem blows-up in finite time, starting from a particular class of everywhere smooth initial data.

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