scholarly journals Quasiequatorial gravitational lensing by spinning black holes in the strong field limit

2003 ◽  
Vol 67 (10) ◽  
Author(s):  
V. Bozza
Keyword(s):  
Black Holes ◽  
Gravitational Lensing ◽  
Strong Field ◽  
Field Limit ◽  
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.

scholarly journals Time delay in the strong field limit for null and timelike signals and its simple interpretation

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Haotian Liu ◽  
Junji Jia
Keyword(s):  
Time Delay ◽  
Gravitational Lensing ◽  
Strong Field ◽  
Critical Value ◽  
Field Limit ◽  
Signal Velocity ◽  
Perturbative Method ◽  
Sgr A ◽  
The Impact ◽  
Strong Field Limit

AbstractGravitational lensing can happen not only for null signals but also timelike signals such as neutrinos and massive gravitational waves in some theories beyond GR. In this work we study the time delay between different relativistic images formed by signals with arbitrary asymptotic velocity v in general static and spherically symmetric spacetimes. A perturbative method is used to calculate the total travel time in the strong field limit, which is found to be a quasi-power series of the small parameter $$a=1-b_c/b$$ a = 1 - b c / b where b is the impact parameter and $$b_c$$ b c is its critical value. The coefficients of the series are completely fixed by the behaviour of the metric functions near the particle sphere $$r_c$$ r c and only the first term of the series contains a weak logarithmic divergence. The time delay $$\Delta t_{n,m}$$ Δ t n , m to the leading non-trivial order was shown to equal the particle sphere circumference divided by the local signal velocity and multiplied by the winding number and the redshift factor. By assuming the Sgr A* supermassive black hole is a Hayward one, we were able to validate the quasi-series form of the total time, and reveal the effects of the spacetime parameter l, the signal velocity v and the source/detector coordinate difference $$\Delta \phi _{sd}$$ Δ ϕ sd on the time delay. It is found that as l increases from 0 to its critical value $$l_c$$ l c , both $$r_c$$ r c and $$\Delta t_{n,m}$$ Δ t n , m decrease. The variation of $$\Delta t_{n+1,n}$$ Δ t n + 1 , n for l from 0 to $$l_c$$ l c can be as large as $$7.2\times 10^1$$ 7.2 × 10 1 [s], whose measurement then can be used to constrain the value of l. While for ultra-relativistic neutrino or gravitational wave, the variation of $$\Delta t_{n,m}$$ Δ t n , m is too small to be resolved. The dependence of $$\Delta t_{n,-n}$$ Δ t n , - n on $$\Delta \phi _{sd}$$ Δ ϕ sd shows that to temporally resolve the two sequences of images from opposite sides of the lens, $$|\Delta \phi _{sd}-\pi |$$ | Δ ϕ sd - π | has to be larger than a certain value, or equivalently if $$|\Delta \phi _{sd}-\pi |$$ | Δ ϕ sd - π | is small, the time resolution of the observatories has to be good.

scholarly journals Strong Field Limit of Black Hole Gravitational Lensing

2001 ◽  
Vol 33 (9) ◽  
pp. 1535-1548 ◽  
Author(s):  
V. Bozza ◽  
S. Capozziello ◽  
G. Iovane ◽  
G. Scarpetta
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Strong Field ◽  
Field Limit ◽  
Strong Field Limit

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 GRAVITATIONAL LENSING BY WORMHOLES

2008 ◽  
Vol 23 (13) ◽  
pp. 953-962 ◽  
Author(s):  
TUSHAR KANTI DEY ◽  
SURAJIT SEN
Keyword(s):  
Gravitational Lensing ◽  
Strong Field ◽  
Field Limit ◽  
Strong Field Limit

We have investigated the gravitational lensing by two wormholes, viz., Janis–Newman–Winnicour (JNW) wormhole and Ellis wormhole. The deflection angles in the strong field limit are calculated and various lens parameters of two wormholes are compared. It is shown that the JNW wormhole exhibits the relativistic images, while the Ellis wormhole does not have any relativistic image due to the absence of its photon sphere.

scholarly journals Gravitational Lensing in the Strong Field Limit for Kar’s Metric

2015 ◽  
Vol 55 (4) ◽  
pp. 2219-2236 ◽  
Author(s):  
Carlos A. Benavides ◽  
Alejandro Cárdenas-Avendaño ◽  
Alexis Larranaga
Keyword(s):  
Gravitational Lensing ◽  
Strong Field ◽  
Field Limit ◽  
Strong Field Limit
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