scholarly journals ARE BLACK HOLES IN BRANS-DICKE THEORY PRECISELY THE SAME AS IN GENERAL RELATIVITY?

1993 ◽  
Vol 02 (04) ◽  
pp. 451-462 ◽  
Author(s):  
M. CAMPANELLI ◽  
C.O. LOUSTO
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Solar System ◽  
Parameter Family ◽  
Spherically Symmetric ◽  
Field Equations

We study a three-parameter family of solutions of the Brans-Dicke field equations. They are static and spherically symmetric. We find the range of parameters for which this solution represents a black hole different from the Schwarzschild one. We find a subfamily of solutions which agrees with experiments and observations in the solar system. We discuss some astrophysical applications and the consequences on the “no hair” theorems for black holes.

AN ANSWER TO THE MAIN BLACK HOLE PATHOLOGY: FORMING NONSINGULAR BLACK HOLES FROM DUST COLLAPSE

2009 ◽  
Vol 18 (14) ◽  
pp. 2221-2229 ◽  
Author(s):  
R. MAIER ◽  
I. DAMIÃO SOARES
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Event Horizon ◽  
Nonlinear Resonance ◽  
Space Time ◽  
Low Energy ◽  
Spherically Symmetric ◽  
Energy Limit ◽  
Exterior Space

The dynamics of gravitational collapse is examined in the realm of string-based formalism of D-branes which encompasses general relativity as a low energy limit. A complete analytical solution is given to the spherically symmetric collapse of a pure dust star, including its matching with a corrected Schwarzschild exterior space–time. The collapse forms a black hole (an exterior event horizon) enclosing not a singularity but perpetually bouncing matter in the infinite chain of space–time maximal analytical extensions inside the outer event horizon. This chain of analytical extensions has a structure analogous to that of the Reissner–Nordstrom solution. The interior trapped bouncing matter has the possibility of being expelled by disruptive nonlinear resonance mechanisms.

scholarly journals Quasi-normal modes of static spherically symmetric black holes in f(R) theory

2020 ◽  
Vol 80 (1) ◽  
Author(s):  
Sayak Datta ◽  
Sukanta Bose
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Gravitational Wave ◽  
Normal Modes ◽  
Einstein Frame ◽  
Spherically Symmetric ◽  
Inhomogeneous Term ◽  
Binary Black Hole ◽  
Special Case

AbstractWe study the quasi-normal modes (QNMs) of static, spherically symmetric black holes in f(R) theories. We show how these modes in theories with non-trivial f(R) are fundamentally different from those in general relativity. In the special case of $$f(R) = \alpha R^2$$f(R)=αR2 theories, it has been recently argued that iso-spectrality between scalar and vector modes breaks down. Here, we show that such a break down is quite general across all f(R) theories, as long as they satisfy $$f''(0)/(1+f''(0)) \ne 0$$f′′(0)/(1+f′′(0))≠0, where a prime denotes derivative of the function with respect to its argument. We specifically discuss the origin of the breaking of isospectrality. We also show that along with this breaking the QNMs receive a correction that arises when $$f''(0)/(1+f'(0)) \ne 0$$f′′(0)/(1+f′(0))≠0 owing to the inhomogeneous term that it introduces in the mode equation. We discuss how these differences affect the “ringdown” phase of binary black hole mergers and the possibility of constraining f(R) models with gravitational-wave observations. We also find that even though the iso-spectrality is broken in f(R) theories, in general, nevertheless in the corresponding scalar-tensor theories in the Einstein frame it is unbroken.

QUANTUM ERGOSPHERE AND HAWKING PROCESS

1999 ◽  
Vol 14 (28) ◽  
pp. 1951-1960 ◽  
Author(s):  
ZHONG-HENG LI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Thermal Radiation ◽  
Radiation Spectrum ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Stationary Black Hole ◽  
Symmetric Black Hole ◽  
Hawking Process ◽  
Nonstationary Black Hole

We study both spherically symmetric and rotating (Kerr) nonstationary black holes and discuss the radiation of these black holes via the Hawking process. We find that the thermal radiation spectrum of a nonstationary black hole is obviously dependent on the spin state of a particle and is different from the case of a stationary black hole. This effect originates from the quantum ergosphere. We also find that the field equations of spin s=0,1/2,1 and 2 can combine into a generalized Teukolsky-type master equation with sources for any spherically symmetric black hole.

scholarly journals NONEXTREME BLACK HOLES FROM INTERSECTING M-BRANES

1998 ◽  
Vol 13 (08) ◽  
pp. 1305-1328 ◽  
Author(s):  
NOBUYOSHI OHTA ◽  
TAKASHI SHIMIZU
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Higher Dimensions ◽  
Symmetric Case ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Deformation Parameters ◽  
Special Cases ◽  
Two Parameter ◽  
Black Hole Solutions

We investigate the possibility of extending nonextreme black hole solutions made of intersecting M-branes to those with two nonextreme deformation parameters, similar to Reissner–Nordstrøm solutions. General analysis of possible solutions is carried out to reduce the problem of solving field equations to a simple algebraic one for static spherically-symmetric case in D dimensions. The results are used to show that the extension to two-parameter solutions is possible for D= 4,5 dimensions but not for higher dimensions, and that the area of horizon always vanishes in the extreme limit for black hole solutions for D≥6 except for two very special cases which are identified. Various solutions are also summarized.

scholarly journals Charged and Non-Charged Black Hole Solutions in Mimetic Gravitational Theory

Symmetry ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 559 ◽  
Author(s):  
Gamal Nashed
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Gravitational Theory ◽  
Relativity Theory ◽  
Charged Black Hole ◽  
Field Equations ◽  
General Relativity Theory ◽  
Mimetic Theory ◽  
Black Hole Solutions

In this study, we derive, in the framework of mimetic theory, charged and non-charged black hole solutions for spherically symmetric as well as flat horizon spacetimes. The asymptotic behavior of those black holes behave as flat or (A)dS spacetimes and coincide with the solutions derived before in general relativity theory. Using the field equations of non-linear electrodynamics mimetic theory we derive new black hole solutions with monopole and quadrupole terms. The quadruple term of those black holes is related by a constant so that its vanishing makes the solutions coincide with the linear Maxwell black holes. We study the singularities of those solutions and show that they possess stronger singularity than the ones known in general relativity. Among many things, we study the horizons as well as the heat capacity to see if the black holes derived in this study have thermodynamical stability or not.

Black holes

2019 ◽  
pp. 80-91
Author(s):  
Steven Carlip
Keyword(s):  
Black Hole ◽  
Solar System ◽  
Symmetric Solution ◽  
Vacuum Solution ◽  
Interior Solution ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Killing Horizon ◽  
Spherically Symmetric Solution ◽  
Trapped Surface

Chapter 3 used the Schwarzschild metric to obtain predictions for the Solar System. In this chapter, that metric is derived as the unique static, spherically symmetric solution of the vacuum Einstein field equations. For the Solar System, this vacuum solution must be joined to an “interior solution” describing the interior of the Sun. Such solutions are discussed briefly. If, on the other hand, one assumes “vacuum all the way down,” the solution describes a black hole. The chapter analyzes the geometry and physics of the nonrotating black hole: the event horizon, the Kruskal-Szekeres extension, the horizon as a trapped surface and as a Killing horizon. Penrose diagrams are introduced, and a short discussion is given of the four laws of black hole mechanics.

Geometrodynamics of Lovelock black holes

2013 ◽  
Vol 91 (6) ◽  
pp. 461-462
Author(s):  
Gabor Kunstatter
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Fast Track ◽  
Mass Function ◽  
Spherically Symmetric ◽  
Hole Formation ◽  
Lovelock Gravity ◽  
Higher Dimensional ◽  
Classical Quantum

Lovelock gravity is arguably the most natural higher curvature, higher dimensional generalization of Einstein's theory of gravity. As shown in a previous paper (Kunstatter et al. arXiv:1210.1566; Kunstatter et al. Classical Quantum Gravity, 29, 092001 (2012) (Fast Track); arXiv:1201.4904.), the Hamiltonian for spherically symmetric Lovelock gravity is as simple as that of general relativity when written in terms of geometrodynamical variables (i.e., the areal radius and mass function). This result paves the way to the study of critical phenomena in black hole formation and the quantum mechanics of Lovelock black holes.

Solar System Tests in Einstein- Æther gravity

2021 ◽  
Author(s):  
Tuhina Manna ◽  
Bidisha Samanta ◽  
Amna Ali ◽  
Farook Rahaman
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Time Delay ◽  
Solar System ◽  
Coupling Constants ◽  
Spherically Symmetric ◽  
Tests Of General Relativity ◽  
Range Of Values ◽  
Vast Range ◽  
Black Hole Solutions

In the current paper we analyze the three classical tests of general relativity, viz. the precession of perihelion, deflection of light and time delay in Einstein Æther gravity. Einstein Æther gravity has two static, spherically symmetric, charged solutions of black hole solutions corresponding to different constraints on its coupling constants c<sub>14</sub>, and c<sub>123</sub>. We investigate the aforementioned tests for both these solutions, graphically and analytically. We also tabulate our results and discuss the outcome which is promising. We evaluate the results, when the coupling constants are varied over a vast range of values, both within the constraints set by the recent observational data, and also beyond, for a comparative study.

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.

scholarly journals Mimicking Black Holes in General Relativity

2021 ◽  
Author(s):  
Thomas Berry
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Thin Shell ◽  
Classical General Relativity ◽  
Regular Black Hole ◽  
Regular Black Holes ◽  
Traversable Wormholes ◽  
Hole Model ◽  
Linearised Stability

<p><b>The central theme of this thesis is the study and analysis of black hole mimickers. The concept of a black hole mimicker is introduced, and various mimicker spacetime models are examined within the framework of classical general relativity. The mimickers examined fall into the classes of regular black holes and traversable wormholes under spherical symmetry. The regular black holes examined can be further categorised as static spacetimes, however the traversable wormhole is allowed to have a dynamic (non-static) throat. Astrophysical observables are calculated for a recently proposed regular black hole model containing an exponential suppression of the Misner-Sharp quasi-local mass. This same regular black hole model is then used to construct a wormhole via the "cut-and-paste" technique. The resulting wormhole is then analysed within the Darmois-Israel thin-shell formalism, and a linearised stability analysis of the (dynamic) wormhole throat is undertaken. Yet another regular black hole model spacetime is proposed, extending a previous work which attempted to construct a regular black hole through a quantum "deformation" of the Schwarzschild spacetime. The resulting spacetime is again analysed within the framework of classical general relativity. </b></p><p>In addition to the study of black hole mimickers, I start with a brief overview of the theory of special relativity where a new and novel result is presented for the combination of relativistic velocities in general directions using quaternions. This is succeed by an introduction to concepts in differential geometry needed for the successive introduction to the theory of general relativity. A thorough discussion of the concept of spacetime singularities is then provided, before analysing the specific black hole mimickers discussed above.</p>

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