788 research outputs found
Mobile Localization in nonlinear Schrodinger lattices
Using continuation methods from the integrable Ablowitz-Ladik lattice, we
have studied the structure of numerically exact mobile discrete breathers in
the standard Discrete Nonlinear Schrodinger equation. We show that, away from
that integrable limit, the mobile pulse is dressed by a background of resonant
plane waves with wavevectors given by a certain selection rule. This background
is seen to be essential for supporting mobile localization in the absence of
integrability. We show how the variations of the localized pulse energy during
its motion are balanced by the interaction with this background, allowing the
localization mobility along the lattice.Comment: 10 pages, 11 figure
Flexible and dynamic replication control for interdependent distributed real-time embedded systems
Replication is a proven concept for increasing the availability of distributed
systems. However, actively replicating every software component in distributed
embedded systems may not be a feasible approach. Not only the available
resources are often limited, but also the imposed overhead could significantly degrade
the systemâs performance.
This paper proposes heuristics to dynamically determine which components to
replicate based on their significance to the system as a whole, its consequent
number of passive replicas, and where to place those replicas in the network. The
activation of passive replicas is coordinated through a fast convergence protocol
that reduces the complexity of the needed interactions among nodes until a new
collective global service solution is determined
Holography and Eternal Inflation
We show that eternal inflation is compatible with holography. In particular,
we emphasize that if a region is asymptotically de Sitter in the future,
holographic arguments by themselves place no bound on the number of past
e-foldings. We also comment briefly on holographic restrictions on the
production of baby universes.Comment: 14 pages, 3 figures, revtex4, (v2 relation with work of Banks and
Fischler clarified, references added
Generation of atom-photon entangled states in atomic Bose-Einstein condensate via electromagnetically induced transparency
In this paper, we present a method to generate continuous-variable-type
entangled states between photons and atoms in atomic Bose-Einstein condensate
(BEC). The proposed method involves an atomic BEC with three internal states, a
weak quantized probe laser and a strong classical coupling laser, which form a
three-level Lambda-shaped BEC system. We consider a situation where the BEC is
in electromagnetically induced transparency (EIT) with the coupling laser being
much stronger than the probe laser. In this case, the upper and intermediate
levels are unpopulated, so that their adiabatic elimination enables an
effective two-mode model involving only the atomic field at the lowest internal
level and the quantized probe laser field. Atom-photon quantum entanglement is
created through laser-atom and inter-atomic interactions, and two-photon
detuning. We show how to generate atom-photon entangled coherent states and
entangled states between photon (atom) coherent states and atom-(photon-)
macroscopic quantum superposition (MQS) states, and between photon-MQS and
atom-MQS states.Comment: 9 pages, 1 figur
Longitudinal broadening of near side jets due to parton cascade
Longitudinal broadening along direction on near side in
two-dimensional () di-hadron correlation
distribution has been studied for central Au+Au collisions at =
200 GeV, within a dynamical multi-phase transport model. It was found that the
longitudinal broadening is generated by a longitudinal flow induced by strong
parton cascade in central Au+Au collisions, in comparison with p+p collisions
at = 200 GeV. The longitudinal broadening may shed light on the
information about strongly interacting partonic matter at RHIC.Comment: 5 pages, 4 figures; accepted by Eur. Phys. J.
Radiative falloff of a scalar field in a weakly curved spacetime without symmetries
We consider a massless scalar field propagating in a weakly curved spacetime
whose metric is a solution to the linearized Einstein field equations. The
spacetime is assumed to be stationary and asymptotically flat, but no other
symmetries are imposed -- the spacetime can rotate and deviate strongly from
spherical symmetry. We prove that the late-time behavior of the scalar field is
identical to what it would be in a spherically-symmetric spacetime: it decays
in time according to an inverse power-law, with a power determined by the
angular profile of the initial wave packet (Price falloff theorem). The field's
late-time dynamics is insensitive to the nonspherical aspects of the metric,
and it is governed entirely by the spacetime's total gravitational mass; other
multipole moments, and in particular the spacetime's total angular momentum, do
not enter in the description of the field's late-time behavior. This extended
formulation of Price's falloff theorem appears to be at odds with previous
studies of radiative decay in the spacetime of a Kerr black hole. We show,
however, that the contradiction is only apparent, and that it is largely an
artifact of the Boyer-Lindquist coordinates adopted in these studies.Comment: 17 pages, RevTeX
State transfer in dissipative and dephasing environments
By diagonalization of a generalized superoperator for solving the master
equation, we investigated effects of dissipative and dephasing environments on
quantum state transfer, as well as entanglement distribution and creation in
spin networks. Our results revealed that under the condition of the same
decoherence rate , the detrimental effects of the dissipative
environment are more severe than that of the dephasing environment. Beside
this, the critical time at which the transfer fidelity and the
concurrence attain their maxima arrives at the asymptotic value
quickly as the spin chain length increases. The transfer
fidelity of an excitation at time is independent of when the system
subjects to dissipative environment, while it decreases as increases when
the system subjects to dephasing environment. The average fidelity displays
three different patterns corresponding to , and . For
each pattern, the average fidelity at time is independent of when the
system subjects to dissipative environment, and decreases as increases when
the system subjects to dephasing environment. The maximum concurrence also
decreases as increases, and when , it arrives at an
asymptotic value determined by the decoherence rate and the structure
of the spin network.Comment: 12 pages, 6 figure
Foliations of Isonergy Surfaces and Singularities of Curves
It is well known that changes in the Liouville foliations of the isoenergy
surfaces of an integrable system imply that the bifurcation set has
singularities at the corresponding energy level. We formulate certain
genericity assumptions for two degrees of freedom integrable systems and we
prove the opposite statement: the essential critical points of the bifurcation
set appear only if the Liouville foliations of the isoenergy surfaces change at
the corresponding energy levels. Along the proof, we give full classification
of the structure of the isoenergy surfaces near the critical set under our
genericity assumptions and we give their complete list using Fomenko graphs.
This may be viewed as a step towards completing the Smale program for relating
the energy surfaces foliation structure to singularities of the momentum
mappings for non-degenerate integrable two degrees of freedom systems.Comment: 30 pages, 19 figure
Plasmonic nanoparticle monomers and dimers: From nano-antennas to chiral metamaterials
We review the basic physics behind light interaction with plasmonic
nanoparticles. The theoretical foundations of light scattering on one metallic
particle (a plasmonic monomer) and two interacting particles (a plasmonic
dimer) are systematically investigated. Expressions for effective particle
susceptibility (polarizability) are derived, and applications of these results
to plasmonic nanoantennas are outlined. In the long-wavelength limit, the
effective macroscopic parameters of an array of plasmonic dimers are
calculated. These parameters are attributable to an effective medium
corresponding to a dilute arrangement of nanoparticles, i.e., a metamaterial
where plasmonic monomers or dimers have the function of "meta-atoms". It is
shown that planar dimers consisting of rod-like particles generally possess
elliptical dichroism and function as atoms for planar chiral metamaterials. The
fabricational simplicity of the proposed rod-dimer geometry can be used in the
design of more cost-effective chiral metamaterials in the optical domain.Comment: submitted to Appl. Phys.
Challenges and Obstacles for a Bouncing Universe in Brane Models
A Brane evolving in the background of a charged AdS black-hole displays in
general a bouncing behaviour with a smooth transition from a contracting to an
expanding phase. We examine in detail the conditions and consequences of this
behaviour in various cases. For a cosmological-constant-dominated Brane, we
obtain a singularity-free, inflationary era which is shown to be compatible
only with an intermediate-scale fundamental Planck mass. For a
radiation-dominated Brane, the bouncing behaviour can occur only for
background-charge values exceeding those allowed for non-extremal black holes.
For a matter-dominated Brane, the black-hole mass affects the proper volume or
the expansion rate of the Brane. We also consider the Brane evolving in an
asymmetric background of two distinct charged AdS black hole spacetimes being
bounded by the Brane and find that, in the case of an empty critical Brane,
bouncing behaviour occurs only if the black-hole mass difference is smaller
than a certain value. The effects of a Brane curvature term on the bounce at
early and late times are also investigated.Comment: 23 pages, Latex file, comments and references added, version to
appear in Phys. Rev.
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