14,595 research outputs found
Late time tails of the massive vector field in a black hole background
We investigate the late-time behavior of the massive vector field in the
background of the Schwarzschild and Schwarzschild-de Sitter black holes. For
Schwarzschild black hole, at intermediately late times the massive vector field
is represented by three functions with different decay law , ,
, while at asymptotically late times
the decay law is universal, and does not
depend on the multipole number . Together with previous study of massive
scalar and Dirac fields where the same asymptotically late-time decay law was
found, it means, that the asymptotically late-time decay law \emph{does not depend} also \emph{on the spin} of the field under
consideration. For Schwarzschild-de Sitter black holes it is observed two
different regimes in the late-time decay of perturbations: non-oscillatory
exponential damping for small values of and oscillatory quasinormal mode
decay for high enough . Numerical and analytical results are found for these
quasinormal frequencies.Comment: one author and new material are adde
Bulk and surface magnetoinductive breathers in binary metamaterials
We study theoretically the existence of bulk and surface discrete breathers
in a one-dimensional magnetic metamaterial comprised of a periodic binary array
of split-ring resonators. The two types of resonators differ in the size of
their slits and this leads to different resonant frequencies. In the framework
of the rotating-wave approximation (RWA) we construct several types of breather
excitations for both the energy-conserved and the dissipative-driven systems by
continuation of trivial breather solutions from the anticontinuous limit to
finite couplings. Numerically-exact computations that integrate the full model
equations confirm the quality of the RWA results. Moreover, it is demonstrated
that discrete breathers can spontaneously appear in the dissipative-driven
system as a results of a fundamental instability.Comment: 10 pages, 16 figure
Scalar field evolution in Gauss-Bonnet black holes
It is presented a thorough analysis of scalar perturbations in the background
of Gauss-Bonnet, Gauss-Bonnet-de Sitter and Gauss-Bonnet-anti-de Sitter black
hole spacetimes. The perturbations are considered both in frequency and time
domain. The dependence of the scalar field evolution on the values of the
cosmological constant and the Gauss-Bonnet coupling is
investigated. For Gauss-Bonnet and Gauss-Bonnet-de Sitter black holes, at
asymptotically late times either power-law or exponential tails dominate, while
for Gauss-Bonnet-anti-de Sitter black hole, the quasinormal modes govern the
scalar field decay at all times. The power-law tails at asymptotically late
times for odd-dimensional Gauss-Bonnet black holes does not depend on ,
even though the black hole metric contains as a new parameter. The
corrections to quasinormal spectrum due to Gauss-Bonnet coupling is not small
and should not be neglected. For the limit of near extremal value of the
(positive) cosmological constant and pure de Sitter and anti-de Sitter modes in
Gauss-Bonnet gravity we have found analytical expressions.Comment: 10 pages, to be published in Phys. Rev.
Effect of nonlinearity on the dynamics of a particle in dc field-induced systems
Dynamics of a particle in a perfect chain with one nonlinear impurity and in
a perfect nonlinear chain under the action of dc field is studied numerically.
The nonlinearity appears due to the coupling of the electronic motion to
optical oscillators which are treated in adiabatic approximation.
We study for both the low and high values of field strength. Three different
range of nonlinearity is obtained where the dynamics is different. In low and
intermediate range of nonlinearity, it reduces the localization. In fact in the
intermediate range subdiffusive behavior in the perfect nonlinear chain is
obtained for a long time. In all the cases a critical value of nonlinear
strength exists where self-trapping transition takes place. This critical value
depends on the system and the field strength. Beyond the self-trapping
transition nonlinearity enhances the localization.Comment: 9 pages, Revtex, 6 ps figures include
Quasinormal modes of black holes in anti-de Sitter space: a numerical study of the eikonal limit
Using series solutions and time-domain evolutions, we probe the eikonal limit
of the gravitational and scalar-field quasinormal modes of large black holes
and black branes in anti-de Sitter backgrounds. These results are particularly
relevant for the AdS/CFT correspondence, since the eikonal regime is
characterized by the existence of long-lived modes which (presumably) dominate
the decay timescale of the perturbations. We confirm all the main qualitative
features of these slowly-damped modes as predicted by Festuccia and Liu
(arXiv:0811.1033) for the scalar-field (tensor-type gravitational)
fluctuations. However, quantitatively we find dimensional-dependent correction
factors. We also investigate the dependence of the QNM frequencies on the
horizon radius of the black hole (brane) and the angular momentum (wavenumber)
of vector- and scalar-type gravitational perturbations.Comment: 5 pages, RevTex4. v2: References added and minor typos corrected.
Published versio
Time evolution of models described by one-dimensional discrete nonlinear Schr\"odinger equation
The dynamics of models described by a one-dimensional discrete nonlinear
Schr\"odinger equation is studied. The nonlinearity in these models appears due
to the coupling of the electronic motion to optical oscillators which are
treated in adiabatic approximation. First, various sizes of nonlinear cluster
embedded in an infinite linear chain are considered. The initial excitation is
applied either at the end-site or at the middle-site of the cluster. In both
the cases we obtain two kinds of transition: (i) a cluster-trapping transition
and (ii) a self-trapping transition. The dynamics of the quasiparticle with the
end-site initial excitation are found to exhibit, (i) a sharp self-trapping
transition, (ii) an amplitude-transition in the site-probabilities and (iii)
propagating soliton-like waves in large clusters. Ballistic propagation is
observed in random nonlinear systems. The effect of nonlinear impurities on the
superdiffusive behavior of random-dimer model is also studied.Comment: 16 pages, REVTEX, 9 figures available upon request, To appear in
Physical Review
Stationary Localized States Due to a Nonlinear Dimeric Impurity Embedded in a Perfect 1-D Chain
The formation of Stationary Localized states due to a nonlinear dimeric
impurity embedded in a perfect 1-d chain is studied here using the appropriate
Discrete Nonlinear Schrdinger Equation. Furthermore, the nonlinearity
has the form, where is the complex amplitude. A proper
ansatz for the Localized state is introduced in the appropriate Hamiltonian of
the system to obtain the reduced effective Hamiltonian. The Hamiltonian
contains a parameter, which is the ratio of stationary
amplitudes at impurity sites. Relevant equations for Localized states are
obtained from the fixed point of the reduced dynamical system. = 1 is
always a permissible solution. We also find solutions for which . Complete phase diagram in the plane comprising of both
cases is discussed. Several critical lines separating various regions are
found. Maximum number of Localized states is found to be six. Furthermore, the
phase diagram continuously extrapolates from one region to the other. The
importance of our results in relation to solitonic solutions in a fully
nonlinear system is discussed.Comment: Seven figures are available on reques
Changes of the topological charge of vortices
We consider changes of the topological charge of vortices in quantum
mechanics by investigating analytical examples where the creation or
annihilation of vortices occurs. In classical hydrodynamics of non-viscous
fluids the Helmholtz-Kelvin theorem ensures that the velocity field circulation
is conserved. We discuss applicability of the theorem in the hydrodynamical
formulation of quantum mechanics showing that the assumptions of the theorem
may be broken in quantum evolution of the wavefunction leading to a change of
the topological charge.Comment: 5 pages, 2 figures, version accepted for publication in J. Phys.
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