3,957 research outputs found
Reflection of Channel-Guided Solitons at Junctions in Two-Dimensional Nonlinear Schroedinger Equation
Solitons confined in channels are studied in the two-dimensional nonlinear
Schr\"odinger equation. We study the dynamics of two channel-guided solitons
near the junction where two channels are merged. The two solitons merge into
one soliton, when there is no phase shift. If a phase difference is given to
the two solitons, the Josephson oscillation is induced. The Josephson
oscillation is amplified near the junction. The two solitons are reflected when
the initial velocity is below a critical value.Comment: 3 pages, 2 figure
Notes on Five-dimensional Kerr Black Holes
The geometry of five-dimensional Kerr black holes is discussed based on
geodesics and Weyl curvatures. Kerr-Star space, Star-Kerr space and Kruskal
space are naturally introduced by using special null geodesics. We show that
the geodesics of AdS Kerr black hole are integrable, which generalizes the
result of Frolov and Stojkovic. We also show that five-dimensional AdS Kerr
black holes are isospectrum deformations of Ricci-flat Kerr black holes in the
sense that the eigenvalues of the Weyl curvature are preserved.Comment: 23 pages, 5 figures; analyses on the Weyl curvature of AdS Kerr black
holes are extended, an appendix and references are adde
Gap solitons in Bragg gratings with a harmonic superlattice
Solitons are studied in a model of a fiber Bragg grating (BG) whose local
reflectivity is subjected to periodic modulation. The superlattice opens an
infinite number of new bandgaps in the model's spectrum. Averaging and
numerical continuation methods show that each gap gives rise to gap solitons
(GSs), including asymmetric and double-humped ones, which are not present
without the superlattice.Computation of stability eigenvalues and direct
simulation reveal the existence of completely stable families of fundamental
GSs filling the new gaps - also at negative frequencies, where the ordinary GSs
are unstable. Moving stable GSs with positive and negative effective mass are
found too.Comment: 7 pages, 3 figures, submitted to EP
Multiple treg suppressive modules and their adaptability
Foxp3+ regulatory T cells (Tregs) are a constitutively immunosuppressive cell type critical for the control of autoimmunity and inflammatory pathology. A range of mechanisms of Treg suppression have been identified and it has not always been clear how these different mechanisms interact in order to properly suppress autoimmunity and excessive inflammation. In recent years it has become clear that, while all Tregs seem to share some core suppressive mechanisms, they are also able to adapt to their surroundings in response to a variety of stimuli by homing to the sites of inflammation and exerting ancillary suppressive functions. In this review, we discuss the relevance and possible modes of Treg adaptability and put forward a modular model of Treg suppressive function. Understanding this flexibility may hold the key to understanding the full spectrum of Treg suppressive behavior
Stochastic synchronization in globally coupled phase oscillators
Cooperative effects of periodic force and noise in globally Cooperative
effects of periodic force and noise in globally coupled systems are studied
using a nonlinear diffusion equation for the number density. The amplitude of
the order parameter oscillation is enhanced in an intermediate range of noise
strength for a globally coupled bistable system, and the order parameter
oscillation is entrained to the external periodic force in an intermediate
range of noise strength. These enhancement phenomena of the response of the
order parameter in the deterministic equations are interpreted as stochastic
resonance and stochastic synchronization in globally coupled systems.Comment: 5 figure
Quantum switches and quantum memories for matter-wave lattice solitons
We study the possibility of implementing a quantum switch and a quantum
memory for matter wave lattice solitons by making them interact with
"effective" potentials (barrier/well) corresponding to defects of the optical
lattice. In the case of interaction with an "effective" potential barrier, the
bright lattice soliton experiences an abrupt transition from complete
transmission to complete reflection (quantum switch) for a critical height of
the barrier. The trapping of the soliton in an "effective" potential well and
its release on demand, without loses, shows the feasibility of using the system
as a quantum memory. The inclusion of defects as a way of controlling the
interactions between two solitons is also reported
Resonant nonlinearity management for nonlinear-Schr\"{o}dinger solitons
We consider effects of a periodic modulation of the nonlinearity coefficient
on fundamental and higher-order solitons in the one-dimensional NLS equation,
which is an issue of direct interest to Bose-Einstein condensates in the
context of the Feshbach-resonance control, and fiber-optic telecommunications
as concerns periodic compensation of the nonlinearity. We find from
simulations, and explain by means of a straightforward analysis, that the
response of a fundamental soliton to the weak perturbation is resonant, if the
modulation frequency is close to the intrinsic frequency of the
soliton. For higher-order -solitons with and 3, the response to an
extremely weak perturbation is also resonant, if is close to the
corresponding intrinsic frequency. More importantly, a slightly stronger drive
splits the 2- or 3-soliton, respectively, into a set of two or three moving
fundamental solitons. The dependence of the threshold perturbation amplitude,
necessary for the splitting, on has a resonant character too.
Amplitudes and velocities of the emerging fundamental solitons are accurately
predicted, using exact and approximate conservation laws of the perturbed NLS
equation.Comment: 14 pages, 6 figure
Localized matter-waves patterns with attractive interaction in rotating potentials
We consider a two-dimensional (2D) model of a rotating attractive
Bose-Einstein condensate (BEC), trapped in an external potential. First, an
harmonic potential with the critical strength is considered, which generates
quasi-solitons at the lowest Landau level (LLL). We describe a family of the
LLL quasi-solitons using both numerical method and a variational approximation
(VA), which are in good agreement with each other. We demonstrate that kicking
the LLL mode or applying a ramp potential sets it in the Larmor (cyclotron)
motion, that can also be accurately modeled by the VA.Comment: 13 pages, 11 figure
Exact Solutions for Domain Walls in Coupled Complex Ginzburg - Landau Equations
The complex Ginzburg Landau equation (CGLE) is a ubiquitous model for the
evolution of slowly varying wave packets in nonlinear dissipative media. A
front (shock) is a transient layer between a plane-wave state and a zero
background. We report exact solutions for domain walls, i.e., pairs of fronts
with opposite polarities, in a system of two coupled CGLEs, which describe
transient layers between semi-infinite domains occupied by each component in
the absence of the other one. For this purpose, a modified Hirota bilinear
operator, first proposed by Bekki and Nozaki, is employed. A novel
factorization procedure is applied to reduce the intermediate calculations
considerably. The ensuing system of equations for the amplitudes and
frequencies is solved by means of computer-assisted algebra. Exact solutions
for mutually-locked front pairs of opposite polarities, with one or several
free parameters, are thus generated. The signs of the cubic gain/loss, linear
amplification/attenuation, and velocity of the coupled-front complex can be
adjusted in a variety of configurations. Numerical simulations are performed to
study the stability properties of such fronts.Comment: Journal of the Physical Society of Japan, in pres
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