7,411 research outputs found
Interior of Distorted Black Holes
We study the interior of distorted static axisymmetric black holes. We obtain
a general interior solution and study its asymptotics both near the horizon and
singularity. As a special example, we apply the obtained results to the case of
the so-called `caged' black holes.Comment: 12 pages, 16 figure
Generalised Bose-Einstein phase transition in large- component spin glasses
It is proposed to understand finite dimensional spin glasses using a
expansion, where is the number of spin components. It is shown that this
approach predicts a replica symmetric state in finite dimensions. The point
about which the expansion is made, the infinite- limit, has been studied in
the mean-field limit in detail and has a very unusual phase transition, rather
similar to a Bose-Einstein phase transition but with macroscopically
occupied low-lying states.Comment: 4 pages (plus a few lines), 3 figures. v2: minor error corrected. v3:
numerics supplemented by analytical arguments, references added, figure of
density of states adde
D-branes in Lorentzian AdS(3)
We study the exact construction of D-branes in Lorentzian AdS(3). We start by
defining a family of conformal field theories that gives a natural Euclidean
version of the SL(2,R) CFT and does not correspond to H(3)+, the analytic
continuation of AdS(3). We argue that one can recuperate the exact CFT results
of Lorentzian AdS(3), upon an analytic continuation in the moduli space of
these conformal field theories. Then we construct exact boundary states for
various symmetric and symmetry-breaking D-branes in AdS(3).Comment: JHEP style;21 pages, no figures; v2:some corrections, comments and
references adde
Light-like Signals in General relativity and Cosmology
The modelling of light-like signals in General Relativity taking the form of
impulsive gravitational waves and light-like shells of matter is examined.
Systematic deductions from the Bianchi identities are made. These are based
upon Penrose's hierarchical classification of the geometry induced on the null
hypersurface history of the surface by its imbedding in the space-times to the
future and to the past of it. The signals are not confined to propagate in a
vacuum and thus their interaction with matter (a burst of radiation propagating
through a cosmic fluid, for example) is also studied. Results are accompanied
by illustrative examples using cosmological models, vacuum space-times, the de
sitter univers and Minkowskian space-time.Comment: 21 pages, latex, no figure
On Scaling Solutions with a Dissipative Fluid
We study the asymptotic behaviour of scaling solutions with a dissipative
fluid and we show that, contrary to recent claims, the existence of stable
accelerating attractor solution which solves the `energy' coincidence problem
depends crucially on the chosen equations of state for the thermodynamical
variables. We discuss two types of equations of state, one which contradicts
this claim, and one which supports it.Comment: 8 pages and 5 figures; to appear in Class. Quantum Gra
Two-dimensional Quantum Black Holes, Branes in BTZ and Holography
We solve semiclassical Einstein equations in two dimensions with a massive
source and we find a static, thermodynamically stable, quantum black hole
solution in the Hartle-Hawking vacuum state. We then study the black hole
geometry generated by a boundary mass sitting on a non-zero tension 1-brane
embedded in a three-dimensional BTZ black hole. We show that the two geometries
coincide and we extract, using holographic relations, information about the CFT
living on the 1-brane. Finally, we show that the quantum black hole has the
same temperature of the bulk BTZ, as expected from the holographic principle.Comment: 10 pages, 2 figures, RevTex, ``point particle of mass \mu '' changed
with ``massive boundary source'' for better clarity. Action in (50) written
in Z_2 symmetric form. Appendix clarified. Minor corrections and references
added. Version accepted for pubblication in PRD15 (2006
Gravitational Trapping Near Domain Walls and Stable Solitons
In this work, the behavior of test particles near a domain wall of a stable
false vacuum bubble is studied. It is shown that matter is naturally trapped in
the vicinity of a static domain wall, and also, that there is a discontinuity
in the test particle's velocity when crossing the domain wall. The latter is
unexpected as it stands in contrast to Newtonian theory, where infinite forces
are not allowed. The weak field limit is defined in order to show that there is
no conflict with the non-relativistic behavior of gravitational fields and
particle motions under these conditions.Comment: 8 pages, 1 figure, problem is reanalyzed using a continuous
coordinate syste
Our World as an Expanding Shell
In the model where the Universe is considered as a thin shell expanding in
5-dimensional hyper-space there is a possibility to have just one scale for a
particle theory corresponding to the Universe thickness. From a realistic model
the relation of this parameter to the Universe size was found.Comment: RevTeX, 4 pages, no figure
Exactly solvable model of wormhole supported by phantom energy
We have found a simple exact solution of spherically-symmetrical Einstein
equations describing a wormhole for an inhomogeneous distribution of the
phantom energy. The equation of state is linear but highly anisotropic: while
the radial pressure is negative, the transversal one is positive. At infinity
the spacetime is not asymptotically flat and possesses on each side of the
bridge a regular cosmological Killing horizon with an infinite area,
impenetrable for any particles. This horizon does not arise if the wormhole
region is glued to the Schwarzschild region. In doing so, the wormhole can
enclose an arbitrary amount of the phantom energy. The configuration under
discussion has a limit in which the phantom energy turns into the string dust,
the areal radius tends to the constant. In this limit, the strong gravitational
mass defect is realized in that the gravitational active mass is finite and
constant while the proper mass integrated over the total manifold is infinite.Comment: 6 pages. Two references added, typos corrected. Accepted for
publication in Phys. Rev. D as Rapid Communicatio
New Geometric Formalism for Gravity Equation in Empty Space
In this paper, a complex daor field which can be regarded as the square root
of space-time metric is proposed to represent gravity. The locally complexified
geometry is set up, and the complex spin connection constructs a bridge between
gravity and SU(1,3) gauge field. Daor field equations in empty space are
acquired, which are one-order differential equations and not conflict with
Einstein's gravity theory.Comment: 20 pages, to appear in Int. J. Mod. Phys.
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