The formation of black holes in nonspherical collapse and cosmic censorship

1986 ◽  
Vol 64 (2) ◽  
pp. 120-127 ◽  
Author(s):  
Werner Israel
Keyword(s):  
Black Holes ◽  
Gravitational Collapse ◽  
Cosmic Censorship ◽  
Circumstantial Evidence ◽  
Event Horizons ◽  
Causal Influence ◽  
Fixed Area

Circumstantial evidence favouring the broad conjecture that event horizons always form in gravitational collapse is summarized along with the mounting counterevidence to a more restrictive cosmic censorship principle, which would compel every singularity formed in the collapse to be enclosed within a horizon. A confinement theorem is presented, stating that a closed, initially-trapped 2-surface of fixed area that remains regular will act as a wall that permanently seals off its interior contents from causal influence on the environment.

Black holes

2021 ◽  
pp. 274-300
Author(s):  
Andrew M. Steane
Keyword(s):  
Black Holes ◽  
Event Horizon ◽  
Gravitational Collapse ◽  
Symmetric Spaces ◽  
Proper Time ◽  
Cosmic Censorship ◽  
General Nature ◽  
Spherically Symmetric ◽  
Event Horizons ◽  
Killing Horizon

We discuss event horizons and black holes. First Birkhoff’s theorem is derived, and we consider the general nature of spherically symmetric spaces. Then the concepts of null surface, Killing horizon and event horizon are defined and related to one another. Cosmic censorship is briefly discussed. The Schwarzshild horizon is discussed in detail. The divergence or otherwise of redshift, acceleration, speed and proper time is obtained for infalling observers and for Schwarzschild observers. Eddington-Finkelstein coordinates are introduced and used to discuss gravitational collapse. The growth of the horizon is noted, and the causality structure is briefly considered via an introduction to the conformal (Penrose-Carter) diagram. The maximal extension is then presented, with the Kruskal-Szekeres coordinates and associated diagram. Wormholes are briefly discussed. The chapter finishes with a survey of astronomical evidence for black holes.

scholarly journals COSMIC CENSORSHIP: A CURRENT PERSPECTIVE

2002 ◽  
Vol 17 (15n17) ◽  
pp. 1067-1079 ◽  
Author(s):  
PANKAJ S. JOSHI
Keyword(s):  
Black Holes ◽  
Gravitational Collapse ◽  
Cosmic Censorship ◽  
Final State ◽  
Open Problems ◽  
Naked Singularities ◽  
Physical Constraints ◽  
Current Perspective ◽  
Collapse Models ◽  
A Current

End state of gravitational collapse and the related cosmic censorship conjecture continue to be amongst the most important open problems in gravitation physics today. My purpose here is to bring out several aspects related to gravitational collapse and censorship, which may help towards a better understanding of the issues involved. Possible physical constraints on gravitational collapse scenarios are considered. It is concluded that the best hope for censorship lies in analyzing the genericity and stability properties of the currently known classes of collapse models which lead to the formation of naked singularities, rather than black holes, as the final state of collapse and which develop from a regular initial data.

scholarly journals Vacuum Semiclassical Gravity Does Not Leave Space for Safe Singularities

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 281
Author(s):  
Julio Arrechea ◽  
Carlos Barceló ◽  
Valentin Boyanov ◽  
Luis J. Garay
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Gravitational Collapse ◽  
Spacetime Singularities ◽  
Cosmic Censorship ◽  
Semiclassical Gravity ◽  
Strong Cosmic Censorship

General relativity predicts its own demise at singularities but also appears to conveniently shield itself from the catastrophic consequences of such singularities, making them safe. For instance, if strong cosmic censorship were ultimately satisfied, spacetime singularities, although present, would not pose any practical problems to predictability. Here, we argue that under semiclassical effects, the situation should be rather different: the potential singularities which could appear in the theory will generically affect predictability, and so one will be forced to analyse whether there is a way to regularise them. For these possible regularisations, the presence and behaviour of matter during gravitational collapse and stabilisation into new structures will play a key role. First, we show that the static semiclassical counterparts to the Schwarzschild and Reissner–Nordström geometries have singularities which are no longer hidden behind horizons. Then, we argue that in dynamical scenarios of formation and evaporation of black holes, we are left with only three possible outcomes which could avoid singularities and eventual predictability issues. We briefly analyse the viability of each one of them within semiclassical gravity and discuss the expected characteristic timescales of their evolution.

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 COLLAPSING SCALAR FIELD WITH KINEMATIC SELF-SIMILARITY OF THE SECOND KIND IN (2+1) GRAVITY

2005 ◽  
Vol 14 (06) ◽  
pp. 1049-1061 ◽  
Author(s):  
R. CHAN ◽  
M. F. A. DA SILVA ◽  
J. F. VILLAS DA ROCHA ◽  
ANZHONG WANG
Keyword(s):  
Black Holes ◽  
Scalar Field ◽  
Gravitational Collapse ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Field Equations ◽  
Self Similarity ◽  
Global Properties ◽  
Scalar Field Equations

All the (2+1)-dimensional circularly symmetric solutions with kinematic self-similarity of the second kind to the Einstein-massless-scalar field equations are found and their local and global properties are studied. It is found that some of them represent gravitational collapse of a massless scalar field, in which black holes are always formed.

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