scholarly journals Strong deflection limit analysis and gravitational lensing of an Ellis wormhole

2016 ◽  
Vol 94 (12) ◽  
Author(s):  
Naoki Tsukamoto
Keyword(s):  
Gravitational Lensing ◽  
Limit Analysis ◽  
Deflection Limit

scholarly journals Strong gravitational lensing of a 4-dimensional Einstein–Gauss–Bonnet black hole in homogeneous plasma

2020 ◽  
Vol 29 (09) ◽  
pp. 2050065 ◽  
Author(s):  
Xing-Hua Jin ◽  
Yuan-Xing Gao ◽  
Dao-Jun Liu
Keyword(s):  
Gravitational Lensing ◽  
Deflection Angle ◽  
Strong Field ◽  
The Novel ◽  
Coupling Constant ◽  
Homogeneous Plasma ◽  
Strong Gravitational Lensing ◽  
Image Separation ◽  
Unmagnetized Plasma ◽  
Deflection Limit

We investigate the strong gravitational lensing of spherically symmetric black holes in the novel Einstein–Gauss–Bonnet (EGB) gravity surrounded by unmagnetized plasma medium. The deflection angle in the strong deflection limit in EGB spacetime with homogeneous plasma is derived. We find that both the coupling constant [Formula: see text] in the novel EGB gravity and the presence of plasma can affect the radius of photon sphere, strong field limit coefficient and other lensing observables significantly, while plasma has little effect on the angular image separation and the relative magnifications as [Formula: see text] and [Formula: see text], respectively.

scholarly journals Null Geodesics and Gravitational Lensing in a Nonsingular Spacetime

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Shao-Wen Wei ◽  
Yu-Xiao Liu ◽  
Chun-E Fu
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Angular Position ◽  
Angular Separation ◽  
Null Geodesics ◽  
Astronomical Instruments ◽  
Black Hole Background ◽  
Deflection Limit ◽  
Near Future

The null geodesics and gravitational lensing in a nonsingular spacetime are investigated. According to the nature of the null geodesics, the spacetime is divided into several cases. In the weak deflection limit, we find the influence of the nonsingularity parameterqon the positions and magnifications of the images is negligible. In the strong deflection limit, the coefficients and observables for the gravitational lensing in a nonsingular black hole background and a weakly nonsingular spacetime are obtained. Comparing these results, we find that, in a weakly nonsingular spacetime, the relativistic images have smaller angular position and relative magnification but larger angular separation than those of a nonsingular black hole. These results might offer a way to probe the spacetime nonsingularity parameter and put a bound on it by the astronomical instruments in the near future.

Gravitational Lensing by Kerr-Sen Dilaton-Axion Black Hole in the Weak Deflection Limit

2010 ◽  
Author(s):  
G. N. Gyulchev ◽  
S. S. Yazadjiev ◽  
Michail D. Todorov ◽  
Christo I. Christov
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Deflection Limit

Evaluation of the Current Concrete Design Code on Shear and End Anchorage of Deep Beams by a Limit Analysis Based on Concrete Plasticity

2012 ◽  
Vol 18 (11) ◽  
pp. 1311-1318
Author(s):  
Hosoon Choi ◽  
Sung-Gul Hong ◽  
Young Hak Lee ◽  
Heecheul Kim ◽  
Dae-Jin Kim
Keyword(s):  
Limit Analysis ◽  
Design Code ◽  
Deep Beams

Nonlocal Gravity

2017 ◽  
Author(s):  
Bahram Mashhoon
Keyword(s):  
Gravitational Field ◽  
Gravitational Lensing ◽  
Past History ◽  
Lorentz Invariance ◽  
Minkowski Spacetime ◽  
Field Measurements ◽  
Local Principle ◽  
History Of ◽  
Expansion Of The Universe ◽  
Nearby Galaxies

A postulate of locality permeates through the special and general theories of relativity. First, Lorentz invariance is extended in a pointwise manner to actual, namely, accelerated observers in Minkowski spacetime. This hypothesis of locality is then employed crucially in Einstein’s local principle of equivalence to render observers pointwise inertial in a gravitational field. Field measurements are intrinsically nonlocal, however. To go beyond the locality postulate in Minkowski spacetime, the past history of the accelerated observer must be taken into account in accordance with the Bohr-Rosenfeld principle. The observer in general carries the memory of its past acceleration. The deep connection between inertia and gravitation suggests that gravity could be nonlocal as well and in nonlocal gravity the fading gravitational memory of past events must then be taken into account. Along this line of thought, a classical nonlocal generalization of Einstein’s theory of gravitation has recently been developed. In this nonlocal gravity (NLG) theory, the gravitational field is local, but satisfies a partial integro-differential field equation. A significant observational consequence of this theory is that the nonlocal aspect of gravity appears to simulate dark matter. The implications of NLG are explored in this book for gravitational lensing, gravitational radiation, the gravitational physics of the Solar System and the internal dynamics of nearby galaxies as well as clusters of galaxies. This approach is extended to nonlocal Newtonian cosmology, where the attraction of gravity fades with the expansion of the universe. Thus far only some of the consequences of NLG have been compared with observation.

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