1,004 research outputs found
Asymptotically AdS brane black holes
We study the possibility of having a static, asymptotically AdS black hole
localized on a braneworld with matter fields, within the framework of the
Randall and Sundrum scenario. We attempt to look for such a brane black hole
configuration by slicing a given bulk spacetime and taking Z_2 symmetry about
the slices. We find that such configurations are possible, and as an explicit
example, we provide a family of asymptotically AdS brane black hole solutions
for which both the bulk and brane metrics are regular on and outside the black
hole horizon and brane matter fields are realistic in the sense that the
dominant energy condition is satisfied. We also find that our braneworld models
exhibit signature change inside the black hole horizon.Comment: 21 pages, 6 figures, RevTex; v2: clarifications added, figures
updated, eq.31 corrected, comment on small four dimensional cosmological
constant limit added, character size increased, results unchanged. v3:
reference added, version accepted in Phys. Rev. D (2006
On the Onset of Inflation in Loop Quantum Cosmology
Using a Liouville measure, similar to the one proposed recently by Gibbons
and Turok, we investigate the probability that single-field inflation with a
polynomial potential can last long enough to solve the shortcomings of the
standard hot big bang model, within the semiclassical regime of loop quantum
cosmology. We conclude that, for such a class of inflationary models and for
natural values of the loop quantum cosmology parameters, a successful
inflationary scenario is highly improbable.Comment: 16 pages, 6 figures Amended version to appear in Phys. Rev.
Preferred foliation effects in Quantum General Relativity
We investigate the infrared (IR) effects of Lorentz violating terms in the
gravitational sector using functional renormalization group methods similar to
Reuter and collaborators. The model we consider consists of pure quantum
gravity coupled to a preferred foliation, described effectively via a scalar
field with non-standard dynamics. We find that vanishing Lorentz violation is a
UV attractive fixed-point of this model in the local potential approximation.
Since larger truncations may lead to differing results, we study as a first
example effects of additional matter fields on the RG running of the Lorentz
violating term and provide a general argument why they are small.Comment: 12 pages, no figures, compatible with published versio
On-brane data for braneworld stars
Stellar structure in braneworlds is markedly different from that in ordinary
general relativity. As an indispensable first step towards a more general
analysis, we completely solve the ``on brane'' 4-dimensional Gauss and Codazzi
equations for an arbitrary static spherically symmetric star in a
Randall--Sundrum type II braneworld. We then indicate how this on-brane
boundary data should be propagated into the bulk in order to determine the full
5-dimensional spacetime geometry. Finally, we demonstrate how this procedure
can be generalized to solid objects such as planets.Comment: 5 pages, RevTeX4, v2: Main algorithm and results substantially
simplified, further discussion and references adde
Brane inflation without slow-roll
The scenario of brane inflation without using the conventional slow-roll
approximations has been investigated. Based on the mechanism of generating the
curvature perturbations at the end of inflation, a new brane inflation paradigm
was developed. The conditions for making a sufficiently large enough number of
e-foldings and for generating the curvature perturbations without producing
dangerous relics were also examined. Benefits of our scenario are subsequently
discussed in detail.Comment: 21 pages, 2 figures, added an appendix, accepted for publication in
JHE
Gravitational collapse and evolution of holographic black holes
Gravitational collapse is analyzed in the Brane-World by arguing that
regularity of five-dimensional geodesics require that stars on the brane have
an atmosphere. For the simple case of a spherically symmetric cloud of
non-dissipating dust, conditions are found for which the collapsing star
evaporates and approaches the Hawking behavior as the (apparent) horizon is
being formed. The effective energy of the star vanishes at a finite radius and
the star afterwards re-expands and "anti-evaporates". Israel junction
conditions across the brane (holographically related to the matter trace
anomaly) and the projection of the Weyl tensor on the brane (holographically
interpreted as the quantum back-reaction on the brane metric) contribute to the
total energy as, respectively, an "anti-evaporation" and an "evaporation" term.Comment: 6 pages; Talk given at QG05, Cala Gonone (Italy), September 200
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
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