318 research outputs found
Gravitational collapse in anti de Sitter space
A numerical and analytic treatment is presented here of the evolution of
initial data of the kind that was conjectured by Hertog, Horowitz and Maeda to
lead to a violation of cosmic censorship. That initial data is essentially a
thick domain wall connecting two regions of anti de Sitter space. The evolution
results in no violation of cosmic censorship, but rather the formation of a
small black hole.Comment: 9 pages, 13 figure
Black Hole Criticality in the Brans-Dicke Model
We study the collapse of a free scalar field in the Brans-Dicke model of
gravity. At the critical point of black hole formation, the model admits two
distinctive solutions dependent on the value of the coupling parameter. We find
one solution to be discretely self-similar and the other to exhibit continuous
self-similarity.Comment: 4 pages, REVTeX 3.0, 5 figures include
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
Remark on formation of colored black holes via fine tuning
In a recent paper (gr-qc/9903081) Choptuik, Hirschmann, and Marsa have
discovered the scaling law for the lifetime of an intermediate attractor in the
formation of n=1 colored black holes via fine tuning. We show that their result
is in agreement with the prediction of linear perturbation analysis. We also
briefly comment on the dependence of the mass gap across the threshold on the
radius of the event horizon.Comment: 2 pages, RevTex, 2 postscript figure
On Equivalence of Critical Collapse of Non-Abelian Fields
We continue our study of the gravitational collapse of spherically symmetric
skyrmions. For certain families of initial data, we find the discretely
self-similar Type II critical transition characterized by the mass scaling
exponent and the echoing period . We
argue that the coincidence of these critical exponents with those found
previously in the Einstein-Yang-Mills model is not accidental but, in fact, the
two models belong to the same universality class.Comment: 7 pages, REVTex, 2 figures included, accepted for publication in
Physical Review
Critical Phenomena Inside Global Monopoles
The gravitational collapse of a triplet scalar field is examined assuming a
hedgehog ansatz for the scalar field. Whereas the seminal work by Choptuik with
a single, strictly spherically symmetric scalar field found a discretely
self-similar (DSS) solution at criticality with echoing period ,
here a new DSS solution is found with period . This new critical
solution is also observed in the presence of a symmetry breaking potential as
well as within a global monopole. The triplet scalar field model contains
Choptuik's original model in a certain region of parameter space, and hence his
original DSS solution is also a solution. However, the choice of a hedgehog
ansatz appears to exclude the original DSS.Comment: 5 pages, 5 figure
Collapse and dispersal in massless scalar field models
The phenomena of collapse and dispersal for a massless scalar field has drawn
considerable interest in recent years, mainly from a numerical perspective. We
give here a sufficient condition for the dispersal to take place for a scalar
field that initially begins with a collapse. It is shown that the change of the
gradient of the scalar field from a timelike to a spacelike vector must be
necessarily accompanied by the dispersal of the scalar field. This result holds
independently of any symmetries of the spacetime. We demonstrate the result
explicitly by means of an example, which is the scalar field solution given by
Roberts. The implications of the result are discussed.Comment: revised version, Accepted for publication in Int. Journ. of Mod.
Phys. D, 6 pages, 3 figure
Critical Collapse of the Massless Scalar Field in Axisymmetry
We present results from a numerical study of critical gravitational collapse
of axisymmetric distributions of massless scalar field energy. We find
threshold behavior that can be described by the spherically symmetric critical
solution with axisymmetric perturbations. However, we see indications of a
growing, non-spherical mode about the spherically symmetric critical solution.
The effect of this instability is that the small asymmetry present in what
would otherwise be a spherically symmetric self-similar solution grows. This
growth continues until a bifurcation occurs and two distinct regions form on
the axis, each resembling the spherically symmetric self-similar solution. The
existence of a non-spherical unstable mode is in conflict with previous
perturbative results, and we therefore discuss whether such a mode exists in
the continuum limit, or whether we are instead seeing a marginally stable mode
that is rendered unstable by numerical approximation.Comment: 11 pages, 8 figure
Critical collapse of a massive vector field
We perform numerical simulations of the critical gravitational collapse of a
massive vector field. The result is that there are two critical solutions. One
is equivalent to the Choptuik critical solution for a massless scalar field.
The other is periodic.Comment: 7 pages, 4 figure
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