4,822 research outputs found
Cosmic Censorship: The Role of Quantum Gravity
The cosmic censorship hypothesis introduced by Penrose thirty years ago is
still one of the most important open questions in {\it classical} general
relativity. In this essay we put forward the idea that cosmic censorship is
intrinsically a {\it quantum gravity} phenomena. To that end we construct a
gedanken experiment in which cosmic censorship is violated within the purely
{\it classical} framework of general relativity. We prove, however, that {\it
quantum} effects restore the validity of the conjecture. This suggests that
classical general relativity is inconsistent and that cosmic censorship might
be enforced only by a quantum theory of gravity.Comment: 7 pages. This essay received the Second Prize from the Gravity
Research Foundation 200
Strong cosmic censorship in vacuum space--times with compact, locally homogeneous Cauchy surfaces
We consider the question of strong cosmic censorship in spatially compact,
spatially locally homogeneous vacuum models. We show in particular that strong
cosmic censorship holds in Bianchi IX vacuum space--times with spherical
spatial topology.Comment: Latex, 38 page
Nature of singularities in gravitational collapse
We discuss several aspects of cosmic censorship hypothesis. There is evidence
both in favor and against the hypothesis. On one hand one can prove that cosmic
censorship holds in several special cases and on the other hand there is a
number of special solutions of Einstein equations in which it is violated. One
way to resolve cosmic censorship problem is to test it observationally. We
point out to several possibilities of such tests using present and future
instruments.Comment: 11 pages, PTPTeX, references added, typos corrected, submitted to
Proceedings of the Yukawa-Kyoto International Seminar 9
Wormhole Cosmic Censorship
We analyze the properties of a Kerr-like wormhole supported by phantom
matter, which is an exact solution of the Einstein-phantom field equations. It
is shown that the solution has a naked ring singularity which is unreachable to
null geodesics falling freely from the outside. Similarly to Roger Penrose's
cosmic censorship, that states that all naked singularities in the Universe
must be protected by event horizons, here we conjecture from our results that a
naked singularity can also be fully protected by the intrinsic properties of a
wormhole's throat
Strong Cosmic Censorship under Quasinormal Modes of Non-Minimally Coupled Massive Scalar Field
We investigate the strong cosmic censorship conjecture in lukewarm
Reissner-Nordstr\"{o}m-de Sitter black holes (and Mart\'{i}nez-Troncoso-Zanelli
black holes) using the quasinormal resonance of non-minimally coupled massive
scalar field. The strong cosmic censorship conjecture is closely related to the
stability of the Cauchy horizon governed by the decay rate of the dominant
quasinormal mode. Here, dominant modes are obtained in the limits of small and
large mass black holes. Then, we connect the modes by using the WKB
approximation. In our analysis, the strong cosmic censorship conjecture is
valid except in the range of the small-mass limit, in which the dominant mode
can be assumed to be that of the de Sitter spacetime. Particularly, the
coupling constant and mass of the scalar field determine the decay rate in the
small mass range. Therefore, the validity of the strong cosmic censorship
conjecture depends on the characteristics of the scalar field.Comment: 19 pages, 10 figures, published in EPJ
Numerical simulation of a possible counterexample to cosmic censorship
A numerical simulation is presented here of the evolution of initial data of
the kind that was conjectured by Hertog, Horowitz and Maeda to be a violation
of cosmic censorship. That initial data is essentially a thick domain wall
connecting two regions of anti-deSitter space. The initial data has a free
parameter that is the initial size of the wall. The simulation shows no
violation of cosmic censorship, but rather the formation of a small black hole.
The simulation described here is for a moderate wall size and leaves open the
possibility that cosmic censorship might be violated for larger walls.Comment: discussion clarifie
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