431 research outputs found
Decay of a charged scalar and Dirac fields in the Kerr-Newman-de Sitter background
We find the quasinormal modes of the charged scalar and Dirac fields in the
background of the rotating charged black holes, described by the Kerr-Newman-de
Sitter solution. The dependence of the quasinormal spectrum upon the black hole
parameters mass M, angular momentum a, charge Q, as well as on values of the
\Lambda-term and field charge q is investigated. Special attention is given to
the near extremal limit of the black hole charge. In particular, we find that
for both scalar and Dirac fields, charged perturbations decay quicker for q>0
and slower for q<0 for values of black holes charge Q less than than some
threshold value, which is close to the extremal value of charge and depend on
parameters of the black holes.Comment: Phys. Rev. D, in pres
How to tell the shape of a wormhole by its quasinormal modes
Here we shall show how to reconstruct the shape function of a spherically
symmetric traversable Lorenzian wormhole near its throat if one knows high
frequency quasinormal modes of the wormhole. The wormhole spacetime is given by
the Morris-Thorne ansatz. The solution to the inverse problem via fitting of
the parameters within the WKB approach is unique for arbitrary tideless
wormholes and some wormholes with non-zero tidal effects, but this is not so
for arbitrary wormholes. As examples, we reproduce the near throat geometries
of the Bronnikov-Ellis and tideless Morris-Thorne metrics by their quasinormal
modes at high multipole numbers .Comment: 8 pages, revtex4, 1 figure; version accepted for publication in
Physics Letters
Long life of Gauss-Bonnet corrected black holes
Dictated by the string theory and various higher dimensional scenarios, black
holes in -dimensional space-times must have higher curvature corrections.
The first and dominant term is quadratic in curvature, and called the
Gauss-Bonnet (GB) term. We shall show that although the Gauss-Bonnet correction
changes black hole's geometry only softly, the emission of gravitons is
suppressed by many orders even at quite small values of the GB coupling. The
huge suppression of the graviton emission is due to the multiplication of the
two effects: the quick cooling of the black hole when one turns on the GB
coupling and the exponential decreasing of the grey-body factor of the tensor
type of gravitons at small and moderate energies. At higher the tensor
gravitons emission is dominant, so that the overall lifetime of black holes
with Gauss-Bonnet corrections is many orders larger than was expected. This
effect should be relevant for the future experiments at the Large Hadron
Collider (LHC). Keywords: Hawking radiation, black hole evaporation.Comment: 13 pages, 14 figure
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