scholarly journals Divergent reflections around the photon sphere of a black hole

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Albert Snepppen

AbstractFrom any location outside the event horizon of a black hole there are an infinite number of trajectories for light to an observer. Each of these paths differ in the number of orbits revolved around the black hole and in their proximity to the last photon orbit. With simple numerical and a perturbed analytical solution to the null-geodesic equation of the Schwarzschild black hole we will reaffirm how each additional orbit is a factor $$e^{2 \pi }$$ e 2 π closer to the black hole’s optical edge. Consequently, the surface of the black hole and any background light will be mirrored infinitely in exponentially thinner slices around the last photon orbit. Furthermore, the introduced formalism proves how the entire trajectories of light in the strong field limit is prescribed by a diverging and a converging exponential. Lastly, the existence of the exponential family is generalized to the equatorial plane of the Kerr black hole with the exponentials dependence on spin derived. Thereby, proving that the distance between subsequent images increases and decreases for respectively retrograde and prograde images. In the limit of an extremely rotating Kerr black hole no logarithmic divergence exists for prograde trajectories.

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
M. Sharif ◽  
Sehrish Iftikhar

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.


2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
M. Sharif ◽  
Sehrish Iftikhar

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.


2016 ◽  
Vol 12 (S324) ◽  
pp. 45-46
Author(s):  
Vojtěch Witzany ◽  
Claus Lämmerzahl

AbstractSince the first investigations into accretion onto black holes, astrophysicists have proposed effective Newtonian-like potentials to mimic the strong-field behavior of matter near a Schwarzschild or Kerr black hole. On the other hand, the fields of neutron stars or black holes in many of the alternative gravity theories differ from the idealized Schwarzschild or Kerr field which would require a number of new potentials. To resolve this, we give a Newtonian-like Hamiltonian which almost perfectly mimics the behavior of test particles in any given stationary space-time. The properties of the Hamiltonian are excellent in static space-times such as the Schwarzschild black hole, but become worse for space-times with gravito-magnetic or dragging effects such as near the Kerr black hole.


2016 ◽  
Vol 31 (01) ◽  
pp. 1650006
Author(s):  
Jin-Ling Geng ◽  
Yu Zhang ◽  
En-Kun Li ◽  
Peng-Fei Duan

Using the strong field limit approach, the strong field gravitational lensing in a black hole with deficit solid angle (DSA) and surrounded by quintessence-like matter (QM) has been investigated. The results show that the DSA [Formula: see text], the energy density of QM [Formula: see text] and the equation of state (EOS) parameter [Formula: see text] have some distinct effects on the strong field gravitational lensing. As [Formula: see text] or [Formula: see text] increases, the deflection angle and the strong field limit coefficients all increase faster and faster. Moreover, the evolution of the main observables also has been studied, which shows that the curves at [Formula: see text] are more steepy than those of [Formula: see text]. Compared with the Schwarzschild black hole, the black hole surrounded by QM has smaller relative magnitudes, and at [Formula: see text] both the angular position and angular separation are slightly bigger than those of Schwarzschild black hole, but when [Formula: see text], the angular position and the relative magnitudes all diminish significantly. Therefore, by studying the strong gravitational lensing, we can distinguish the black hole with a DSA and surrounded by QM from the Schwarzschild black hole and the effects of the DSA and QM on the strong gravitational lensing by black holes can be known better.


2021 ◽  
Author(s):  
◽  
Del Rajan

<p>In this thesis, we explore the subject of complex spacetimes, in which the mathematical theory of complex manifolds gets modified for application to General Relativity. We will also explore the mysterious Newman-Janis trick, which is an elementary and quite short method to obtain the Kerr black hole from the Schwarzschild black hole through the use of complex variables. This exposition will cover variations of the Newman-Janis trick, partial explanations, as well as original contributions.</p>


2019 ◽  
Vol 134 (8) ◽  
Author(s):  
Ramil N. Izmailov ◽  
Amrita Bhattacharya ◽  
Eduard R. Zhdanov ◽  
Alexander A. Potapov ◽  
Kamal K. Nandi

2014 ◽  
Vol 92 (1) ◽  
pp. 46-50
Author(s):  
De-Jiang Qi

Recently, via adiabatic invariance, Majhi and Vagenas quantized the horizon area of the general class of a static spherically symmetric space–time. Very recently, applying the period of the gravity system with respect to the Euclidean time, Zeng and Liu derived area spectra of a Schwarzschild black hole and a Kerr black hole. It is noteworthy that the preceding methods are not useful for the quasi-normal modes. In this paper, based on those works, and as a further study, adopting near horizon approximation, applying the laws of black hole thermodynamics, we would like to investigate the black hole spectroscopy from a class of Plebański and Demiański space–times by using two different methods. The result shows that the area spectrum of the black hole is [Formula: see text], which confirms the initial proposal of Bekenstein, and the result is consistent with that already obtained by Maggiore with quasi-normal modes.


2020 ◽  
Vol 80 (6) ◽  
Author(s):  
Guansheng He ◽  
Chaohong Pan ◽  
Xia Zhou ◽  
Weijun Li ◽  
Lin Li

2001 ◽  
Vol 33 (9) ◽  
pp. 1535-1548 ◽  
Author(s):  
V. Bozza ◽  
S. Capozziello ◽  
G. Iovane ◽  
G. Scarpetta

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