607 research outputs found
Relaciones - Propiedades reológicas y estructuras.
Relaciones, propiedades y estructuras de la reología textil.Peer Reviewe
Gravitational quasinormal radiation of higher-dimensional black holes
We find the gravitational resonance (quasinormal) modes of the higher
dimensional Schwarzschild and Reissner-Nordstrem black holes. The effect on the
quasinormal behavior due to the presence of the term is investigated.
The QN spectrum is totally different for different signs of . In more
than four dimensions there excited three types of gravitational modes: scalar,
vector, and tensor. They produce three different quasinormal spectra, thus the
isospectrality between scalar and vector perturbations, which takes place for
D=4 Schwarzschild and Schwarzschild-de-Sitter black holes, is broken in higher
dimensions. That is the scalar-type gravitational perturbations, connected with
deformations of the black hole horizon, which damp most slowly and therefore
dominate during late time of the black hole ringing.Comment: 13 pages, 2 figures, several references are adde
Nonlinear Gravitational Waves: Their Form and Effects
A gravitational wave must be nonlinear to be able to transport its own
source, that is, energy and momentum. A physical gravitational wave, therefore,
cannot be represented by a solution to a linear wave equation. Relying on this
property, the second-order solution describing such physical waves is obtained.
The effects they produce on free particles are found to consist of nonlinear
oscillations along the direction of propagation.Comment: 15 pages, no figures. v2: presentation changes aiming at clarifying
the text; matches published versio
Quasinormal modes of black holes immersed in a strong magnetic field
We found quasinormal modes, both in time and frequency domains, of the Ernst
black holes, that is neutral black holes immersed in an external magnetic
field. The Ernst solution reduces to the Schwarzschild solution, when the
magnetic field vanishes. It is found that the quasinormal spectrum for massless
scalar field in the vicinity of the magnetized black holes acquires an
effective "mass" , where m is the azimuthal number and B is
parameter describing the magnetic field. We shall show that in the presence of
a magnetic field quasinormal modes are longer lived and have larger oscillation
frequencies. The perturbations of higher dimensional magnetized black holes by
Ortaggio and of magnetized dilaton black holes by Radu are considered.Comment: 5 pages, RevTe
Quasinormal behavior of the D-dimensional Schwarzshild black hole and higher order WKB approach
We study characteristic (quasinormal) modes of a -dimensional Schwarzshild
black hole. It proves out that the real parts of the complex quasinormal modes,
representing the real oscillation frequencies, are proportional to the product
of the number of dimensions and inverse horizon radius . The
asymptotic formula for large multipole number and arbitrary is derived.
In addition the WKB formula for computing QN modes, developed to the 3rd order
beyond the eikonal approximation, is extended to the 6th order here. This gives
us an accurate and economic way to compute quasinormal frequencies.Comment: 15 pages, 6 figures, the 6th order WKB formula for computing QNMs in
Mathematica is available from https://goo.gl/nykYG
Quasinormal modes of a Schwarzschild black hole surrounded by free static spherically symmetric quintessence: Electromagnetic perturbations
In this paper, we evaluated the quasinormal modes of electromagnetic
perturbation in a Schwarzschild black hole surrounded by the static spherically
symmetric quintessence by using the third-order WKB approximation when the
quintessential state parameter in the range of . Due to
the presence of quintessence, Maxwell field damps more slowly. And when at
, it is similar to the black hole solution in the ds/Ads
spacetime. The appropriate boundary conditions need to be modified.Comment: 6 pages, 3 figure
Holographic conductivity of zero temperature superconductors
Using the recently found by G. Horowitz and M. Roberts (arXiv:0908.3677)
numerical model of the ground state of holographic superconductors (at zero
temperature), we calculate the conductivity for such models. The universal
relation connecting conductivity with the reflection coefficient was used for
finding the conductivity by the WKB approach. The dependence of the
conductivity on the frequency and charge density is discussed. Numerical
calculations confirm the general arguments of (arXiv:0908.3677) in favor of
non-zero conductivity even at zero temperature. In addition to the
Horowitz-Roberts solution we have found (probably infinite) set of extra
solutions which are normalizable and reach the same correct RN-AdS asymptotic
at spatial infinity. These extra solutions (which correspond to larger values
of the grand canonical potential) lead to effective potentials that also vanish
at the horizon and thus correspond to a non-zero conductivity at zero
temperature.Comment: 9 pages, 10 figure
Gravitational spectrum of black holes in the Einstein-Aether theory
Evolution of gravitational perturbations, both in time and frequency domains,
is considered for a spherically symmetric black hole in the non-reduced
Einstein-Aether theory. It is shown that real oscillation frequency and damping
rate are larger for the Einstein-Aether black hole than for the Schwarzschild
black hole. This may provide an opportunity to observe aether in the
forthcoming experiments with new generation of gravitational antennas.Comment: 4 pages, RevTex, to be published in Phys. Lett.
A note on quasinormal modes: A tale of two treatments
There is an apparent discrepancy in the literature with regard to the
quasinormal mode frequencies of Schwarzschild-de Sitter black holes in the
degenerate-horizon limit. On the one hand, a Poschl-Teller-inspired method
predicts that the real part of the frequencies will depend strongly on the
orbital angular momentum of the perturbation field whereas, on the other hand,
the degenerate limit of a monodromy-based calculation suggests there should be
no such dependence (at least, for the highly damped modes). In the current
paper, we provide a possible resolution by critically re-assessing the limiting
procedure used in the monodromy analysis.Comment: 11 pages, Revtex format; (v2) new addendum in response to reader
comments, also references, footnote and acknowledgments adde
Perturbations and quasi-normal modes of black holes in Einstein-Aether theory
We develop a new method for calculation of quasi-normal modes of black holes,
when the effective potential, which governs black hole perturbations, is known
only numerically in some region near the black hole. This method can be applied
to perturbations of a wide class of numerical black hole solutions. We apply it
to the black holes in the Einstein-Aether theory, a theory where general
relativity is coupled to a unit time-like vector field, in order to observe
local Lorentz symmetry violation. We found that in the non-reduced
Einstein-Aether theory, real oscillation frequency and damping rate of
quasi-normal modes are larger than those of Schwarzschild black holes in the
Einstein theory.Comment: 6 pages, 3 figures, RevTex, to be published in Phys. Lett.
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