MODIFIED NEWTONIAN POTENTIALS FOR OPTICALLY THIN ACCRETION DISKS AROUND BLACK HOLES

1998 ◽  
Vol 07 (03) ◽  
pp. 471-488 ◽  
Author(s):  
T. LØVÅS
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Gravitational Field ◽  
Accretion Disks ◽  
Rotating Black Holes ◽  
Relativistic Result ◽  
Do So

The use of modified Newtonian potentials to describe the gravitational field around black holes has proven successful. I will present here an investigation of the accuracy of several modified Newtonian potentials proposed in the literature, by comparing the result with the exact relativistic solution. I will do so for optically thin accretion disks that are more sensitive to the form of the potential than optically thick standard disks. I find that simple modified Newtonian potentials capture the essential features of general relativity, and the results from using the modified Newtonian potentials deviate from the relativistic result only by 20% at most for nonrotating black holes. For rotating black holes the accuracy depends on the rotation of the black hole.

3. Characterizing black holes

2015 ◽  
Author(s):  
Katherine Blundell
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Gravitational Field ◽  
Curved Spacetime ◽  
Remarkable Feature ◽  
Static Limit ◽  
Frame Dragging ◽  
Axis Of Rotation ◽  
Different Types

‘Characterizing black holes’ describes the two different types of black holes: Schwarzschild black holes that do not rotate and Kerr black holes that do. The only distinguishing characteristics of black holes are their mass and their spin. A remarkable feature of a spinning black hole is that the gravitational field pulls objects around the black hole’s axis of rotation, not merely in towards its centre—an effect called frame dragging. The static limit and ergosphere regions of black holes are also described. Einstein’s equations of General Relativity allow many different solutions describing alternative versions of curved spacetime. Could white holes and worm holes exist in our universe?

scholarly journals Twisted light, a new tool for general relativity and beyond — Revealing the properties of rotating black holes with the vorticity of light —

2021 ◽  
Author(s):  
F. Tamburini ◽  
F. Feleppa ◽  
B. Thidé
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Angular Momentum ◽  
Orbital Angular Momentum ◽  
Gravitational Lensing ◽  
Compact Object ◽  
Additional Tool ◽  
Physical Observable ◽  
Rotating Black Holes

We describe and present the first observational evidence that light propagating near a rotating black hole is twisted in phase and carries orbital angular momentum. The novel use of this physical observable as an additional tool for the previously known techniques of gravitational lensing allows us to directly measure, for the first time, the spin parameter of a black hole. With the additional information encoded in the orbital angular momentum, not only can we reveal the actual rotation of the compact object, but we can also use rotating black holes as probes to test general relativity.

scholarly journals Dynamics of particles in slowly rotating black holes with dipolar halos

2007 ◽  
Vol 3 (S248) ◽  
pp. 498-499
Author(s):  
W. B. Han
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Field Structure ◽  
Resonant Orbits ◽  
Test Particles ◽  
Rotating Black Holes ◽  
Fast Lyapunov Indicator ◽  
Dynamical Parameters ◽  
Dynamics Of Particles

AbstractIn general, the model of galaxy assumes a central huge black hole surrounded by a massive halo, disk or ring. In this paper, we investigate the gravitational field structure of a slowly rotating black hole with a dipolar halo, and the dynamics and chaos of test particles moving in it. Using Poincaré sections and fast Lyapunov indicator (FLI) in general relativity, we investigate chaos under different dynamical parameters, and find that the FLI is suitable for detecting chaos and even resonant orbits.

BLACK HOLES: OBSERVATIONAL PROPERTIES

2005 ◽  
Vol 20 (11) ◽  
pp. 2321-2325 ◽  
Author(s):  
A. F. ZAKHAROV
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Field ◽  
Spectral Line ◽  
Accretion Disks ◽  
Seyfert Galaxies ◽  
Kerr Metric ◽  
X Ray ◽  
Line Shapes ◽  
Inclination Angles

In the article we review observational features of black holes where an influence of a gravitational field is dominant and we must use strong gravitational field approach for GR. Recent X-ray observations of microquasars and Seyfert galaxies reveal broad emission lines in their spectra, which can arise in the innermost parts of accretion disks. Simulations indicate that at low inclination angle the line is measured by a distant observer as characteristic two-peak profile. However, at high inclination angles (> 85°) two additional peaks arise. This phenomenon was discovered by Matt et al. (1993) using the Schwarzschild black hole metric to analyze such an effect. They assumed that the effect is applicable to a Kerr metric far beyond the range of parameters that they exploited. We check and confirm their hypothesis about such a structure of the spectral line shape for the Kerr metric case. We discuss how analysis of the iron spectral line shapes could give an information about an upper limit of magnetic field near black hole horizon.

Dark Bodies and Black Holes, Magic Circles and Montgolfiers: Light and Gravitation from Newton to Einstein

1993 ◽  
Vol 6 (1) ◽  
pp. 83-106
Author(s):  
Jean Eisenstaedt
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Gravitational Field ◽  
Important Place ◽  
Propagation Of Light ◽  
History Of ◽  
Theory Of Gravitation ◽  
The 1960S ◽  
Bending Of Light

The ArgumentThe question of the possible existence of black holes is closely related to the question of the action of gravitation on the propagation of light. It has been raised recurrently from the when that Newton referred to a possible bending of light in his Opticks. And it relies on apparently simple questions: Is light subject to gravitation? What is the effect of a gravitational field on the propagation of light? Could a particle of light emitted by a star be retained by its gravitational field?From the end of the 1960s, the black hole idea has had a very important place in the relativistic literature, not to speak of the popularization of the theory. It turned out to be not only an important concept but also a tool that permitted us to understand general relativity better, indeed a tool that contributed greatly to changing the interpretation of Einstein's theory of gravitation. Here too I want to use this concept of the black hole to assist our understanding of the history of general relativity: the black hole is a fundamental milestone in the evolution of general relativity.

Rotating black holes in the teleparallel equivalent of general relativity

2016 ◽  
Vol 25 (07) ◽  
pp. 1650079 ◽  
Author(s):  
Gamal G. L. Nashed
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Unique Solution ◽  
Conserved Quantities ◽  
Cartan Geometry ◽  
Rotating Black Holes

We derive set of solutions with flat transverse sections in the framework of a teleparallel equivalent of general relativity which describes rotating black holes. The singularities supported from the invariants of torsion and curvature are explained. We investigate that there appear more singularities in the torsion scalars than in the curvature ones. The conserved quantities are discussed using Einstein–Cartan geometry. The physics of the constants of integration is explained through the calculations of conserved quantities. These calculations show that there is a unique solution that may describe true physical black hole.

scholarly journals Thin accretion disks around rotating black holes in 4D Einstein–Gauss–Bonnet gravity

2021 ◽  
Vol 81 (5) ◽  
Author(s):  
Mohaddese Heydari-Fard ◽  
Malihe Heydari-Fard ◽  
Hamid Reza Sepangi
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Coupling Parameter ◽  
Energy Conversion Efficiency ◽  
Bonnet Gravity ◽  
Stable Circular Orbit ◽  
Rotating Black Holes ◽  
Kerr Black Holes

AbstractRecently, Kumar and Ghosh have derived Kerr-like rotating black hole solutions in the framework of four-dimensional Einstein–Gauss–Bonnet theory of gravity and investigated the black hole shadow. Using the steady-state Novikov–Thorne model, we study thin accretion disk processes for such rotating black holes including the energy flux, temperature distribution, emission spectrum, energy conversion efficiency as well as the radius of the innermost stable circular orbit. We also study the effects of the Gauss–Bonnet coupling parameter $$\alpha $$ α on these quantities. The results are compared to slowly rotating relativistic Kerr black holes which show that for a positive Gauss–Bonnet coupling, thin accretion disks around rotating black holes in four-dimensional Einstein–Gauss–Bonnet gravity are hotter and more efficient than that for Kerr black holes with the same rotation parameter a, while for a negative coupling they are cooler and less efficient. Thus the accretion disk processes may be considered as tools for testing Einstein–Gauss–Bonnet gravity using astrophysical observations.

scholarly journals Retrograde versus Prograde Models of Accreting Black Holes

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
David Garofalo
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Magnetic Fields ◽  
Observational Data ◽  
Accretion Disks ◽  
General Consensus ◽  
Rotating Black Holes

There is a general consensus that magnetic fields, accretion disks, and rotating black holes are instrumental in the generation of the most powerful sources of energy in the known universe. Nonetheless, because magnetized accretion onto rotating black holes involves both the complications of nonlinear magnetohydrodynamics that currently cannot fully be treated numerically, and uncertainties about the origin of magnetic fields that at present are part of the input, the space of possible solutions remains less constrained. Consequently, the literature still bears witness to the proliferation of rather different black hole engine models. But the accumulated wealth of observational data is now sufficient to meaningfully distinguish between them. It is in this light that this critical paper compares the recent retrograde framework with standard “spin paradigm” prograde models.

scholarly journals Many accelerating distorted black holes

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Marco Astorino ◽  
Adriano Viganò
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Gravitational Field ◽  
Analytical Solution ◽  
Inverse Scattering ◽  
Inverse Scattering Method ◽  
Scattering Method ◽  
Schwarzschild Black Hole ◽  
Hole Configuration

AbstractAn analytical solution of four-dimensional General Relativity, representing an array of collinear and accelerating black holes, is constructed with the inverse scattering method. The metric can be completely regularised from any conical singularity, thanks to the presence of an external gravitational field. Therefore the multi-black hole configuration can be maintained at equilibrium without the need of strings or struts. Some notable subcases such as the accelerating distorted Schwarzschild black hole and the distorted double C-metric are explicitly presented. The Smarr law and the thermodynamics of these systems is studied. The Bonnor–Swaminarayan and the Bičák–Hoenselaers–Schmidt particle metrics are recovered, through appropriate limits, from the multi-black holes solutions.

scholarly journals Driven black holes: from Kolmogorov scaling to turbulent wakes

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Tomas Andrade ◽  
Christiana Pantelidou ◽  
Julian Sonner ◽  
Benjamin Withers
Keyword(s):  
Nonlinear Dynamics ◽  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Strong Field ◽  
De Sitter ◽  
Event Horizons ◽  
Binary Mergers ◽  
Tidal Deformations ◽  
Proof Of Principle

Abstract General relativity governs the nonlinear dynamics of spacetime, including black holes and their event horizons. We demonstrate that forced black hole horizons exhibit statistically steady turbulent spacetime dynamics consistent with Kolmogorov’s theory of 1941. As a proof of principle we focus on black holes in asymptotically anti-de Sitter spacetimes in a large number of dimensions, where greater analytic control is gained. We focus on cases where the effective horizon dynamics is restricted to 2+1 dimensions. We also demonstrate that tidal deformations of the horizon induce turbulent dynamics. When set in motion relative to the horizon a deformation develops a turbulent spacetime wake, indicating that turbulent spacetime dynamics may play a role in binary mergers and other strong-field phenomena.

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