468 research outputs found
Internal structure of a Maxwell-Gauss-Bonnet black hole
The influence of the Maxwell field on a static, asymptotically flat and
spherically-symmetric Gauss-Bonnet black hole is considered. Numerical
computations suggest that if the charge increases beyond a critical value, the
inner determinant singularity is replaced by an inner singular horizon.Comment: 5 pages, 5 figures, published version with minor change
Black Hole Relics in String Gravity: Last Stages of Hawking Evaporation
One of the most intriguing problem of modern physics is the question of the
endpoint of black hole evaporation. Based on Einstein-dilaton-Gauss-Bonnet four
dimensional string gravity model we show that black holes do not disappear and
that the end of the evaporation process leaves some relic. The possibility of
experimental detection of the remnant black holes is investigated. If they
really exist, such objects could be a considerable part of the non baryonic
dark matter in our Universe.Comment: 15 pages, accepted to Class. Quant. Gra
Wormholes and Naked Singularities in Brans-Dicke cosmology
We perform analytical and numerical study of static spherically symmetric
solutions in the context of Brans-Dicke-like cosmological model by Elizalde et
al. with an exponential potential. In this model the phantom regime arises
without the appearance of any ghost degree of freedom due to the specific form
of coupling. For the certain parameter ranges the model contains a regular
solution which we interpret as a wormhole in an otherwise dS Universe. We put
several bounds on the parameter values: . The numerical
solution could mimic the Schwarzschild one, so the original model is consistent
with astrophysical and cosmological observational data. However differences
between our solution and the Schwarzschild one can be quite large, so black
hole candidate observations could probably place further limits on the
value.Comment: 20 pages, 6 figures, typos & errors correcte
Black Holes of a Minimal Size in String Gravity
A lower limit for a neutral black hole size is obtained in the frames of the
string gravity model with the second order curvature correction. It is shown
that this effect remains when the third order curvature correction is also
taken into account and argued that such restriction does exist in all
perturbative orders of curvature expansions.Comment: 6 LaTeX pages, 1 PostScript figure (epsfig.sty), minor changes in the
text and references, submitted to Int.J.Mod.Phy
Maeda-Dadhich Solutions as Real Black Holes
A four-dimensional static Schwarzschild-like solution obtained in [3]-[6] in
the frames of the Einstein-Gauss-Bonnet gravity at the Kaluza-Klein split is
analyzed. The matter in these solutions is created by auxiliary dimensions. The
main goal of our work is to study physically sensible characteristics, which
could be observable. Study of the perturbed equations demonstrates their
stability under linear perturbations. The specific combinations of the
parameters, permitting to construct black hole-like objects with one or two
horizons or naked singularities are determined. Stable orbits of test particles
around these black holes are presented. We show the exotic thermodynamical
properties of the solution, when the Hawking evaporation law has the behavior
opposite to usual one in General Relativity
Kerr-Gauss-Bonnet Black Holes: An Analytical Approximation
Gauss-Bonnet gravity provides one of the most promising frameworks to study
curvature corrections to the Einstein action in supersymmetric string theories,
while avoiding ghosts and keeping second order field equations. Although
Schwarzschild-type solutions for Gauss-Bonnet black holes have been known for
long, the Kerr-Gauss-Bonnet metric is missing. In this paper, a five
dimensional Gauss-Bonnet approximation is analytically derived for spinning
black holes and the related thermodynamical properties are briefly outlined.Comment: 5 pages, 1 figur
Gauss-Bonnet Black Holes at the LHC : Beyond the Dimensionality of Space
The Gauss - Bonnet invariant is one of the most promising candidates for a
quadratic curvature correction to the Einstein action in expansions of
supersymmetric string theory. We study the evaporation of such Schwarzschild -
Gauss - Bonnet black holes which could be formed at future colliders if the
Planck scale is of order a TeV, as predicted by some modern brane world models.
We show that, beyond the dimensionality of space, the corresponding coupling
constant could be measured by the LHC. This opens new windows for physics
investigation in spite of the possible screening of microphysics due to the
event horizon.Comment: Accepted by Phys. Lett.
- …