scholarly journals Gravitational collapse of type N spacetime, the naked singularity, and causality violation

2017 ◽  
Vol 2017 (9) ◽  
Author(s):  
Faizuddin Ahmed
Keyword(s):  
Gravitational Collapse ◽  
Naked Singularity ◽  
Causality Violation

scholarly journals GENERICITY ASPECTS IN GRAVITATIONAL COLLAPSE TO BLACK HOLES AND NAKED SINGULARITIES

2012 ◽  
Vol 21 (08) ◽  
pp. 1250066 ◽  
Author(s):  
PANKAJ S. JOSHI ◽  
DANIELE MALAFARINA ◽  
RAVINDRA V. SARAYKAR
Keyword(s):  
Black Holes ◽  
Initial Data ◽  
Gravitational Collapse ◽  
Naked Singularity ◽  
Matter Field ◽  
Einstein Equations ◽  
Type I ◽  
Naked Singularities ◽  
Physical Conditions ◽  
Perfect Fluids

Here we investigate the genericity and stability aspects for naked singularities and black holes that arise as the final states for a complete gravitational collapse of a spherical massive matter cloud. The form of the matter considered is a general Type I matter field, which includes most of the physically reasonable matter fields such as dust, perfect fluids and such other physically interesting forms of matter widely used in gravitation theory. Here, we first study in some detail the effects of small pressure perturbations in an otherwise pressure-free collapse scenario, and examine how a collapse evolution that was going to the black hole endstate would be modified and go to a naked singularity, once small pressures are introduced in the initial data. This allows us to understand the distribution of black holes and naked singularities in the initial data space. Collapse is examined in terms of the evolutions allowed by Einstein equations, under suitable physical conditions and as evolving from a regular initial data. We then show that both black holes and naked singularities are generic outcomes of a complete collapse, when genericity is defined in a suitable sense in an appropriate space.

scholarly journals The Negative Energy in Generalized Vaidya Spacetime

Universe ◽  
2020 ◽  
Vol 6 (9) ◽  
pp. 155
Author(s):  
Vitalii Vertogradov
Keyword(s):  
Gravitational Collapse ◽  
Naked Singularity ◽  
Negative Energy ◽  
Matter Field ◽  
The State ◽  
Energy Problem

In this paper we consider the negative energy problem in generalized Vaidya spacetime. We consider several models where we have the naked singularity as a result of the gravitational collapse. In these models we investigate the geodesics for particles with negative energy when the II type of the matter field satisfies the equation of the state P=αρ (α∈[0,1]).

scholarly journals NONSTATIC CHARGED BTZ-LIKE BLACK HOLES IN N+1 DIMENSIONS

2012 ◽  
Vol 21 (03) ◽  
pp. 1250022 ◽  
Author(s):  
SUSHANT G. GHOSH
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Collapse ◽  
Naked Singularity ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Btz Black Hole ◽  
Sitter Spacetime ◽  
Apparent Horizons ◽  
Sitter Background

We find an exact nonstatic charged BTZ-like solutions, in (N+1)-dimensional Einstein gravity in the presence of negative cosmological constant and a nonlinear Maxwell field defined by a power s of the Maxwell invariant, which describes the gravitational collapse of charged null fluid in an anti-de Sitter background. Considering the situation that a charged null fluid injects into the initially an anti-de Sitter spacetime, we show that a black hole form rather than a naked singularity, irrespective of spacetime dimensions, from gravitational collapse in accordance with cosmic censorship conjecture. The structure and locations of the apparent horizons of the black holes are also determined. It is interesting to see that, in the static limit and when N = 2, one can retrieve 2+1 BTZ black hole solutions.

GRAVITATIONAL COLLAPSE OF A SELF-INTERACTING SCALAR FIELD

2007 ◽  
Vol 22 (01) ◽  
pp. 65-74 ◽  
Author(s):  
RITUPARNO GOSWAMI ◽  
PANKAJ S. JOSHI
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Gravitational Collapse ◽  
Energy Condition ◽  
Dynamical Evolution ◽  
Naked Singularity ◽  
Cosmic Censorship ◽  
Weak Energy Condition ◽  
Scalar Field Models ◽  
Cosmic Censorship Conjecture

We construct and study here a class of collapsing scalar field models with a nonzero potential. The weak energy condition is satisfied by the collapsing configuration and it is shown that the end state of collapse could be either a black hole or a naked singularity. It is seen that physically it is the rate of collapse that governs these outcomes of the dynamical evolution. The implications for the cosmic censorship conjecture are discussed.

scholarly journals Stability of naked singularity arising in gravitational collapse of Type I matter fields

Pramana ◽  
2005 ◽  
Vol 65 (1) ◽  
pp. 17-33 ◽  
Author(s):  
Sanjay B. Sarwe ◽  
R. V. Saraykar
Keyword(s):  
Gravitational Collapse ◽  
Naked Singularity ◽  
Type I ◽  
Matter Fields

scholarly journals Critical phenomena in gravitational collapse of Husain–Martinez–Nunez scalar field

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
Xiaobao Wang ◽  
Xiaoning Wu ◽  
Sijie Gao
Keyword(s):  
Scalar Field ◽  
Critical Phenomena ◽  
Gravitational Collapse ◽  
Naked Singularity ◽  
Extrinsic Curvature ◽  
Analytical Models ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Self Similarity ◽  
Metric Function

Abstract We construct analytical models to study the critical phenomena in gravitational collapse of the Husain-Martinez-Nunez massless scalar field. We first use the cut-and-paste technique to match the conformally flat solution ($$c=0$$c=0 ) onto an outgoing Vaidya solution. To guarantee the continuity of the metric and the extrinsic curvature, we prove that the two solutions must be joined at a null hypersurface and the metric function in Vaidya spacetime must satisfy certain constraints. We find that the mass of the black hole in the resulting spacetime takes the form $$M\propto (p-p^*)^\gamma $$M∝(p-p∗)γ, where the critical exponent $$\gamma $$γ is equal to 0.5. For the case $$c\ne 0$$c≠0, we show that the scalar field must be joined onto two pieces of Vaidya spacetimes to avoid a naked singularity. We also derive the power-law mass formula with $$\gamma =0.5$$γ=0.5. Compared with previous analytical models which were constructed from a different scalar field with continuous self-similarity, we obtain the same value of $$\gamma $$γ. However, we show that the solution with $$c\ne 0$$c≠0 is not self-similar. Therefore, we provide a rare example that a scalar field without self-similarity also possesses the features of critical collapse.

Static axisymmetric discs and gravitational collapse

1987 ◽  
Vol 413 (1844) ◽  
pp. 251-262 ◽  
Keyword(s):  
Gravitational Collapse ◽  
Energy Condition ◽  
Naked Singularity ◽  
Cosmic Censorship ◽  
Field Equations ◽  
Exterior Field ◽  
Thin Disc ◽  
Cosmic Censorship Hypothesis ◽  
Hoop Conjecture ◽  
Vacuum Solutions

Regular static axisymmetric vacuum solutions of Einstein’s field equations representing the exterior field of a finite thin disc are found. These are used to describe the slow collapse of a disc-like object. If no conditions are placed on the matter, a naked singularity is formed and the cosmic censorship hypothesis would be violated. Imposition of the weak energy condition, however, prevents slow collapse to a singularity and preserves the validity of this hypothesis. The validity of the hoop conjecture is also discussed.

NAKED SINGULARITY IN HIGHER-DIMENSIONAL CHARGED-VAIDYA SPACETIME

2012 ◽  
Vol 27 (26) ◽  
pp. 1250148 ◽  
Author(s):  
ZAHID AHMAD
Keyword(s):  
Gravitational Collapse ◽  
Naked Singularity ◽  
Higher Dimensions ◽  
Cosmic Censorship ◽  
Strong Form ◽  
Singularity Formation ◽  
Higher Dimensional

In this paper, the gravitational collapse has been studied in the context of higher-dimensional charged-Vaidya spacetime. It is shown that naked singularity always exists in this case and strong form of cosmic censorship is violated. This work extends the earlier studies on naked singularity formation in higher dimensions.

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