498 research outputs found
Higher dimensional dust collapse with a cosmological constant
The general solution of the Einstein equation for higher dimensional (HD)
spherically symmetric collapse of inhomogeneous dust in presence of a
cosmological term, i.e., exact interior solutions of the Einstein field
equations is presented for the HD Tolman-Bondi metrics imbedded in a de Sitter
background. The solution is then matched to exterior HD Scwarschild-de Sitter.
A brief discussion on the causal structure singularities and horizons is
provided. It turns out that the collapse proceed in the same way as in the
Minkowski background, i.e., the strong curvature naked singularities form and
that the higher dimensions seem to favor black holes rather than naked
singularities.Comment: 7 Pages, no figure
Topological Charged Black Holes in High Dimensional Spacetimes and Their Formation from Gravitational Collapse of a Type II Fluid
Topological charged black holes coupled with a cosmological constant in
spacetimes are studied, where is an Einstein
space of the form . The global structure for
the four-dimensional spacetimes with is investigated systematically.
The most general solutions that represent a Type fluid in such a high
dimensional spacetime are found, and showed that topological charged black
holes can be formed from the gravitational collapse of such a fluid. When the
spacetime is (asymptotically) self-similar, the collapse always forms black
holes for , in contrast to the case , where it can form
either balck holes or naked singularities.Comment: 14 figures, to appear in Phys. Rev.
Non-adiabatic collapse of a quasi-spherical radiating star
A model is proposed of a collapsing quasi-spherical radiating star with
matter content as shear-free isotropic fluid undergoing radial heat-flow with
outgoing radiation. To describe the radiation of the system, we have considered
both plane symmetric and spherical Vaidya solutions. Physical conditions and
thermodynamical relations are studied using local conservation of momentum and
surface red-shift. We have found that for existence of radiation on the
boundary, pressure on the boundary is not necessary.Comment: 8 Latex pages, No figures, Revtex styl
Gravitational collapse of null fluid on the brane
We first obtain the analogue of Vaidya's solution on the brane for studying
the collapse of null fluid onto a flat Minkowski cavity on the brane. Since the
back-reaction of the bulk onto the brane is supposed to strengthen gravity on
the brane, it would favour formation of black hole as against naked
singularity. That is the parameter window in the initial data set giving rise
to naked singularity in the 4D Vaidya case would now get partially covered.Comment: 12 pages, latex, 3 figures, submitted to Phys.Lett.
Spherical Dust Collapse in Higher Dimensions
We consider here the question if it is possible to recover cosmic censorship
when a transition is made to higher dimensional spacetimes, by studying the
spherically symmetric dust collapse in an arbitrary higher spacetime dimension.
It is pointed out that if only black holes are to result as end state of a
continual gravitational collapse, several conditions must be imposed on the
collapsing configuration, some of which may appear to be restrictive, and we
need to study carefully if these can be suitably motivated physically in a
realistic collapse scenario. It would appear that in a generic higher
dimensional dust collapse, both black holes and naked singularities would
develop as end states as indicated by the results here. The mathematical
approach developed here generalizes and unifies the earlier available results
on higher dimensional dust collapse as we point out. Further, the dependence of
black hole or naked singularity end states as collapse outcomes, on the nature
of the initial data from which the collapse develops, is brought out explicitly
and in a transparent manner as we show here. Our method also allows us to
consider here in some detail the genericity and stability aspects related to
the occurrence of naked singularities in gravitational collapse.Comment: Revtex4, Title changed, To appear in Physical Review
Nature of singularity formed by the gravitational collapse in Husain space-time with electromagnetic field and scalar field
In this work, we have investigated the outcome of gravitational collapse in
Husain space-time in the presence of electro-magnetic and a scalar field with
potential. In order to study the nature of the singularity, global behavior of
radial null geodesics have been taken into account. The nature of singularities
formed has been thoroughly studied for all possible variations of the
parameters. These choices of parameters has been presented in tabular form in
various dimensions. It is seen that irrespective of whatever values of the
parameters chosen, the collapse always results in a naked singularity in all
dimensions. There is less possibility of formation of a black hole. Hence this
work is a significant counterexample of the cosmic censorship hypothesis.Comment: 9 pages, 19 figure
Radiating black hole solutions in arbitrary dimensions
We prove a theorem that characterizes a large family of non-static solutions
to Einstein equations in -dimensional space-time, representing, in general,
spherically symmetric Type II fluid. It is shown that the best known
Vaidya-based (radiating) black hole solutions to Einstein equations, in both
four dimensions (4D) and higher dimensions (HD), are particular cases from this
family. The spherically symmetric static black hole solutions for Type I fluid
can also be retrieved. A brief discussion on the energy conditions,
singularities and horizons is provided.Comment: RevTeX 9 pages, no figure
Higher dimensional radiation collapse and cosmic censorship
We study the occurrence of naked singularities in the spherically symmetric
collapse of radiation shells in a higher dimensional spacetime. The necessary
conditions for the formation of a naked singularity or a black hole are
obtained. The naked singularities are found to be strong in the Tipler's sense
and thus violating cosmic censorship conjecture.Comment: 4 pages, ReVTeX, Phys Rev D Vol 62 107502 (2000
Gravitational Collapse of Null Radiation and a String fluid
We consider the end state of collapsing null radiation with a string fluid.
It is shown that, if diffusive transport is assumed for the string, that a
naked singularity can form (at least locally). The model has the advantage of
not being asymptotically flat. We also analyse the case of a radiation-string
two-fluid and show that a locally naked singularity can result in the collapse
of such matter. We contrast this model with that of strange quark matter.Comment: RevTeX 4.0 (8 pages - no figures). submitted to Phys Rev D. Some
changes to abstract, introduction and conclusion - references update
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