scholarly journals Efficient gravitational lens optical scalars calculation of black holes with angular momentum

2019 ◽  
Vol 492 (3) ◽  
pp. 3763-3778
Author(s):  
Ezequiel F Boero ◽  
Osvaldo M Moreschi
Keyword(s):  
Black Hole ◽  
Null Geodesic ◽  
Space Time ◽  
Gravitational Lens ◽  
Hidden Symmetries ◽  
Kerr Geometry ◽  
Deviation Equation ◽  
Efficient Calculation ◽  
Efficient Integration ◽  
Kerr Space

ABSTRACT We provide new very simple and compact expressions for the efficient calculation of gravitational lens optical scalars for Kerr space–time, which are exact along any null geodesic. These new results are obtained recurring to well-known results on geodesic motion that exploit obvious and hidden symmetries of Kerr space–time and contrast with the rather long and cumbersome expressions previously reported in the literature, providing a helpful improvement for the sake of an efficient integration of the geodesic deviation equation on Kerr geometry. We also introduce a prescription for the observer frame that captures a new notion of centre of the black hole, which can be used for any position of the observer, including those near the black hole. We compare the efficient calculation of weak lens optical scalars with the exact equations, finding an excellent agreement.

scholarly journals Shadow of a Kerr-like black hole

2014 ◽  
Vol 10 (S312) ◽  
pp. 135-136
Author(s):  
Farruh Atamurotov
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Deformation Parameter ◽  
Space Time ◽  
Black Hole Spin ◽  
Spin Parameter ◽  
Kerr Space ◽  
The One

AbstractThe shadow of a Kerr-like black hole has been considered and it was shown that in addition to the specific angular momentum a, deformation parameter of Kerr-like space-time essentially deforms the shape of the black hole shadow. For a given value of the black hole spin parameter a, the presence of a deformation parameter ε reduces the shadow and enlarges its deformation with respect to the one in the Kerr space-time.

The gravitational perturbations of the Kerr black hole IV. The completion of the solutiont

1980 ◽  
Vol 372 (1751) ◽  
pp. 475-484 ◽  
Keyword(s):  
Black Hole ◽  
Kerr Black Hole ◽  
Space Time ◽  
Gravitational Perturbations ◽  
Kerr Space ◽  
The One

This paper eliminates the last remaining lacuna in the information that was needed to make the solution for the perturbations in the metric coefficients of the Kerr space-time fully explicit. The requisite information is obtained from a pair of equations which is complementary to the one considered in paper III; and the solution of the Newman-Penrose equations governing the perturbations is, thus, completed.

scholarly journals CAN GRAVITATIONAL COLLAPSE SUSTAIN SINGULARITY-FREE TRAPPED SURFACES?

2008 ◽  
Vol 17 (01) ◽  
pp. 165-177 ◽  
Author(s):  
MANASSE R. MBONYE ◽  
DEMOS KAZANAS
Keyword(s):  
Black Hole ◽  
Gravitational Collapse ◽  
Null Geodesic ◽  
Space Time ◽  
Test Case ◽  
Hole Center ◽  
Singularity Formation ◽  
Trapped Surfaces ◽  
Type D ◽  
Fluid Formation

In singularity-generating space–times both the outgoing and the ingoing expansions of null geodesic congruences θ+ and θ- should become increasingly negative without bound, inside the horizon. This behavior leads to geodetic incompleteness, which in turn predicts the existence of a singularity. In this work we inquire whether, in gravitational collapse, space–time can sustain singularity-free trapped surfaces, in the sense that such a space–time remains geodetically complete. As a test case, we consider a type D space–time of Dymnikova which is Schwarzschild-like at large distances and consists of a fluid with a p = -ρ equation of state near r = 0. By following both the expansion parameters θ+ and θ- across the horizon and into the black hole, we find that both θ+ and θ+θ- have turning points inside the trapped region. Further, we find that deep inside the black hole there is a region, 0 ≤ r < r0 (which includes the black hole center), which is not trapped. Thus the trapped region is bounded from both outside and inside. The space–time is geodetically complete, a result which violates a condition for singularity formation. It is inferred that, in general, if gravitational collapse were to proceed with a p =-ρ fluid formation, the resulting black hole might be singularity-free.

Geodesic structure of the Clifton–Barrow black hole space–time

2019 ◽  
Vol 34 (22) ◽  
pp. 1950123
Author(s):  
Li-Li Shi ◽  
Jian-Ping Hu ◽  
Yu Zhang ◽  
Chen Ma ◽  
Peng-Fei Duan
Keyword(s):  
Black Hole ◽  
Circular Orbit ◽  
Orbital Motion ◽  
Null Geodesic ◽  
Space Time ◽  
Circular Orbits ◽  
Test Particles ◽  
Stable Circular Orbit ◽  
Geodesic Structure ◽  
Bound Orbits

In this paper, we investigate the geodesic structure of Clifton–Barrow black hole space–time. Through the numerical analysis of the effective potential and the motion equation, the orbital types of test particles and photons and the corresponding orbital motion diagrams of each orbital types under certain conditions are obtained. We find that angular momentum [Formula: see text] and [Formula: see text] determine the existence of bound orbits and circular orbits. And we also find that the radius of unstable circular orbit decreases with increases in [Formula: see text] while the radius of stable circular orbit increases. Furthermore, as [Formula: see text] increases, the radius of unstable circular orbit increases, while the radius of stable circular orbit decreases. For null geodesic, parameters [Formula: see text] and [Formula: see text] do not affect the types of null orbits. The radius of the unstable circular orbits increases with the increase of [Formula: see text]. However, the radius of the unstable circular orbits remains unchanged as [Formula: see text] increases. Also, we show that the precession direction of the bound orbits of the test particles is counterclockwise for [Formula: see text], but clockwise with [Formula: see text]. Moreover, different energy values have an effect on the curvature of escape and absorb orbits curve.

scholarly journals Bargmann–Wigner formulation and superradiance problem of bosons and fermions in Kerr space–time

2015 ◽  
Vol 30 (11) ◽  
pp. 1550052 ◽  
Author(s):  
Masakatsu Kenmoku ◽  
Y. M. Cho
Keyword(s):  
Negative Energy ◽  
Space Time ◽  
The Other ◽  
Positive Energy ◽  
Independent Components ◽  
Consistent Description ◽  
Other Hand ◽  
Kerr Space

The superradiance phenomena of massive bosons and fermions in the Kerr space–time are studied in the Bargmann–Wigner formulation. In case of bi-spinor, the four independent components spinors correspond to the four bosonic freedom: one scalar and three vectors uniquely. The consistent description of the Bargmann–Wigner equations between fermions and bosons shows that the superradiance of the type with positive energy (0 < ω) and negative momentum near horizon (p H < 0) is shown not to occur. On the other hand, the superradiance of the type with negative energy (ω < 0) and positive momentum near horizon (0 < p H ) is still possible for both scalar bosons and spinor fermions.

scholarly journals BLACK HOLE EVAPORATION BASED UPON A q-DEFORMATION DESCRIPTION

2005 ◽  
Vol 20 (26) ◽  
pp. 6039-6049 ◽  
Author(s):  
XIN ZHANG
Keyword(s):  
Black Hole ◽  
Degrees Of Freedom ◽  
Radiation Spectrum ◽  
Correlation Effect ◽  
Space Time ◽  
Noncommutative Space ◽  
Schwarzschild Black Hole ◽  
Black Hole Evaporation ◽  
Starting Point ◽  
New Distribution

A toy model based upon the q-deformation description for studying the radiation spectrum of black hole is proposed. The starting point is to make an attempt to consider the space–time noncommutativity in the vicinity of black hole horizon. We use a trick that all the space–time noncommutative effects are ascribed to the modification of the behavior of the radiation field of black hole and a kind of q-deformed degrees of freedom are postulated to mimic the radiation particles that live on the noncommutative space–time, meanwhile the background metric is preserved as usual. We calculate the radiation spectrum of Schwarzschild black hole in this framework. The new distribution deviates from the standard thermal spectrum evidently. The result indicates that some correlation effect will be introduced to the system if the noncommutativity is taken into account. In addition, an infrared cutoff of the spectrum is the prediction of the model.

Sign in / Sign up

Export Citation Format

Share Document