共查询到20条相似文献,搜索用时 31 毫秒
1.
M. R. Zhang X. Y. Jiang Y. L. Zhang L. Shi J. Zi J. Y. Zhou 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(3):269-278
We systematically investigate slowly moving matter-wave gap
soliton propagation in weak random optical lattices. With the weak
randomness, an effective-particle theory is constructed to show
that the motion of a gap soliton is similar to a particle moving
in random potentials. Based on the effective-particle theory, the
effects of the randomness on gap solitons are obtained and the
trajectories of gap solitons are well predicted. Moreover, the
general laws that describe the movement depending on the weak
randomness are obtained. We find that with an increase of the
random strength, the ensemble-average velocity reduces slowly and
the reflection probability becomes larger. The theoretical results
based on the effective-particle theory are confirmed by the
numerical simulations based on the Gross-Pitaevskii equation. 相似文献
2.
Oscillatory behavior of spatial soliton in a gradient refractive index waveguide with nonlocal nonlinearity 总被引:1,自引:0,他引:1
Oscillatory behavior of spatial solitons in a transverse parabolic gradient refractive index distribution (GRIN) waveguide with both local and nonlocal nonlinearity is investigated. Dynamics of such solitons are analyzed by the effective-particle approach method. For weak nonlocal nonlinearity, solitons oscillate in transverse direction periodically during propagation. The normalized width and maximum of refractive index variation of the waveguide play a key role in determining the oscillating period while the position of soliton oscillatory center is slightly influenced by the nonlocal nonlinearity. Stronger nonlocal nonlinearity leads to instability of the oscillatory solitons. Furthermore, the dynamics of the solitons are simulated numerically and good agreements are obtained between the analysis and numerical results. This behavior may be used in all-optical routers, switches etc. PACS 42.65.Tg; 42.65.Jx; 42.65.Wi 相似文献
3.
Oscillation of spatial solitons in a waveguide with a symmetrical refractive index profile
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Dynamics of (1+1)D spatial solitons in a Kerr medium with a
transversely symmetrical refractive index profile is investigated.
Propagation of solitons is analysed theoretically by using an
effective-particle approach. Analytical results show that the soliton
oscillates periodically with a variable acceleration. The expression
of oscillatory period is derived by introducing a concept of `average
acceleration'. Both acceleration and oscillatory period are
determined by the parameters of the input soliton and the waveguide.
Propagations of solitons are simulated numerically and good agreement
is obtained between the theoretical and numerical results. 相似文献
4.
P. Rose T. Richter B. Terhalle J. Imbrock F. Kaiser C. Denz 《Applied physics. B, Lasers and optics》2007,89(4):521-526
We investigate the formation of fundamental discrete solitons and dipole-mode gap solitons in triangular photonic lattices
imprinted in photorefractive nonlinear media. These lattices are strongly affected by the photorefractive anisotropy, resulting
in orientation-dependent refractive index structures with reduced symmetry. It is demonstrated that two different orientations
of the lattice wave enable the formation of fundamental discrete solitons in the total internal reflection gap. Furthermore,
it is shown that one lattice orientation additionally supports dipole-mode solitons in the Bragg reflection gap. The experimental
results are corroborated by numerical simulations using the full anisotropic model.
PACS 42.65.Tg; 42.65.Wi; 42.70.Qs 相似文献
5.
V. A. Gorodtsov 《Journal of Experimental and Theoretical Physics》2000,90(6):1105-1113
The example of Kadomtsev-Petviashvili equations with a random time-dependent force (stochastic Kadomtsev-Petviashvili equations) is used to show that the theory of Brownian particle motion can be applied to the theory of the stochastic behavior of solitons of model hydrodynamic equations which are completely integrable in the absence of forces and interrelated by the generalized Galilean transformation. The Brownian motion of two-dimensional algebraic solitons of the Kadomtsev-Petviashvili equations with positive dispersion leads to their diffusion broadening similar to the broadening of one-dimensional solitons of other fully integrable hydrodynamic equations. However, for longer times the rate of decay of algebraic solitons is higher because of the degeneracy of the momentum integral for these solitons. The behavior of a periodic chain of algebraic solitons is established under the action of a random force. Tilted plane solitons of the Kadomtsev-Petviashvili equations with negative dispersion vary under the action of a random force similar to the solitons of the Korteweg-de Vries equation. Several of these solitons interact via “virtual solitons” and generate new solitons provided that resonance conditions are satisfied whose dimensions increase as a result of the influence of the random force. 相似文献
6.
Light propagation in one-dimensional nonlinear waveguide arrays with self-defocusing intensity-resonant nonlinearity is investigated
theoretically. We study thoroughly conditions for existence and stability of both gap and discrete dark solitons. According
to the linear stability analysis both fundamental types (on-site and intersite) of gap solitons may be stable. Discrete dark
solitons are unstable except in the low-power regime and, depending on system parameters, evolve into either gray solitons,
breathers, or background radiation. Mobility of these solitons is analyzed by the free energy concept: gap solitons are immobile
but dark solitons can be easily set in motion. 相似文献
7.
We study the stabilization of the soliton
transported bio-energy by the dynamic equations in the improved Davydov
theory from four aspects containing the feature of free motion and states of
the soliton at the long-time motion and at biological temperature 300 K and
behaviors of collision of the solitons by Runge-Kutta method and physical
parameter values appropriate to the $\alpha$-helix protein molecules. We
prove that the new solitons can move without dispersion at a constant speed
retaining its shape and energy in free and long-time motions and can go
through each other without scattering. If considering further influence of
the temperature effect of heat bath on the soliton, it is still thermally
stable at biological temperature 300 K and in a time as long as
300 ps and amino acid spacings as large as 400,
which shows that the lifetime of the new
soliton is at least 300 ps, which is consistent with analytic result
obtained by quantum perturbation theory. These results exhibit that the new
soliton is a possible carrier of bio-energy transport and the improved model
is possibly a candidate for the mechanism of this transport. 相似文献
8.
A review is given of features and motion of two-dimensional dissipative solitons in lasers and laser amplifiers with saturable
absorption. We present a rich variety of stable complexes with weak, strong, and mixed coupling of individual laser solitons.
The type of coupling is determined by the topology of the distribution of energy flows within the complex. We reveal the existence
of stable dissipative soliton complexes with curvilinear motion of their centre of mass. This type of motion results from
the field distribution asymmetry and is well pronounced for complexes of laser solitons with strong and mixed types of coupling.
Similar complexes are expected to exist in different spatially distributed nonlinear dissipative systems, including schemes
with discrete dissipative solitons.
PACS 42.65.Tg 相似文献
9.
Asymptotic motion of a classical particle in a random potential in two dimensions: Landau model 总被引:2,自引:2,他引:0
Detlef Dürr Sheldon Goldstein Joel L. Lebowitz 《Communications in Mathematical Physics》1987,113(2):209-230
We consider the motion of a classical particle in a random isotropic potential arising from uniformly distributed scatterers in two dimensions. We prove that in the weak coupling limit the velocity process of the particle converges in distribution to Brownian motion on a surface of constant speed, i.e. on the circle. The resulting equation for the probability density of the particle is related to the Landau equation in plasmas.also: Department of PhysicsWork supported in part by National Science Foundation Grant No. DMS-85-12505 and AFOSR No. C010 相似文献
10.
Surface superlattice gap solitons 总被引:1,自引:0,他引:1
We demonstrate that specific surface superlattice gap solitons can be supported at an interface between a one-dimensional photonic superlattice and a uniform medium with saturable nonlinearity. The solitons are stable in the semi-infinite gap but do not exist in the first gap. With the decrease of the power, the solitons jump from the surface site to the next one, and they may continue the motion into the lattices, which offers potential applications for the routing of optical signals. 相似文献
11.
We study fundamental spectral properties of random block operators that are common in the physical modelling of mesoscopic disordered systems such as dirty superconductors. Our results include ergodic properties, the location of the spectrum, existence and regularity of the integrated density of states, as well as Lifshits tails. Special attention is paid to the peculiarities arising from the block structure such as the occurrence of a robust gap in the middle of the spectrum. Without randomness in the off-diagonal blocks the density of states typically exhibits an inverse square-root singularity at the edges of the gap. In the presence of randomness we establish a Wegner estimate that is valid at all energies. It implies that the singularities are smeared out by randomness, and the density of states is bounded. We also show Lifshits tails at these band edges. Technically, one has to cope with a non-monotone dependence on the random couplings. 相似文献
12.
We consider effects of random time modulation of the nonlinearity coefficient on the dynamics of one- and two-dimensional (1D and 2D) solitary waves in the nonlinear Schrödinger equation (NLSE). In particular, the cases of a single Gaussian random variable, and a temporally correlated Gaussian process are considered. In the 1D case, we demonstrate the robustness of solitons against the random nonlinearity management. In the 2D case, the share (percentage) of realizations that lead to collapse of a localized pulse is computed, in order to quantify the effect of the randomness in preventing the collapse. Dependences of this share on the mean value, standard deviation, and correlation length of the random process are obtained, and, whenever possible, compared to analytical predictions. 相似文献
13.
We use a multiple time scale boundary layer theory to derive the equation of motion for a dark (or grey) soliton propagating through an effectively one-dimensional cloud of Bose-Einstein condensate, assuming only that the background density and velocity vary slowly on the soliton scale. We show that solitons can exhibit viscous or radiative acceleration (antidamping), which we estimate as slow but observable on experimental time scales. 相似文献
14.
We propose a lattice model for Dirac fermions which allows us to break the degeneracy of the node structure. In the presence of a random gap we analyze the scaling behavior of the localization length as a function of the system width within a numerical transfer-matrix approach. Depending on the strength of the randomness, there are different scaling regimes for weak, intermediate and strong disorder. These regimes are separated by transitions that are characterized by one-parameter scaling. 相似文献
15.
S.L. Cornish N.G. Parker T.E. Judd T.M. Fromhold 《Physica D: Nonlinear Phenomena》2009,238(15):1299-1305
We propose the use of bright matter-wave solitons formed from Bose-Einstein condensates with attractive interactions to probe and study quantum reflection from a solid surface at normal incidence. We demonstrate that the presence of attractive interatomic interactions leads to a number of advantages for the study of quantum reflection. The absence of dispersion as the soliton propagates allows precise control of the velocity normal to the surface and for much lower velocities to be achieved. Numerical modelling shows that the robust, self-trapped nature of bright solitons leads to a clean reflection from the surface, limiting the disruption of the density profile and permitting accurate measurements of the reflection probability. 相似文献
16.
Yuichi Shiozawa 《Journal of statistical physics》2009,136(1):145-163
We introduce a model of branching Brownian motions in time-space random environment associated with the Poisson random measure.
We prove that, if the randomness of the environment is moderated by that of the Brownian motion, the population density satisfies
a central limit theorem and the growth rate of the population size is the same as its expectation with strictly positive probability.
We also characterize the diffusive behavior of our model in terms of the decay rate of the replica overlap. On the other hand,
we show that, if the randomness of the environment is strong enough, the growth rate of the population size is strictly less
than its expectation almost surely. To do this, we use a connection between our model and the model of Brownian directed polymers
in random environment introduced by Comets and Yoshida.
Partly supported by the Global COE program at Department of Mathematics and Research Institute for Mathematical Sciences,
Kyoto University. 相似文献
17.
M. Temple-Raston 《International Journal of Theoretical Physics》1997,36(1):249-258
A topological field theory with Bogomol'nyi solitons is examined. The Bogomol'nyi solitons have much in common with the instanton
in Yang-Mills theory; consequently we called them ‘topological instantons.’ When periodic boundary conditions are imposed,
the field theory comments indirectly on the speed of light within the theory. In this particular model the speed of light
is not a universal constant. This may or may not be relevant to the current debate in astronomy and cosmology over the large
values of the Hubble constant obtained by the latest generation of ground- and space-based telescopes. An experiment is proposed
to detect spatial variation in the speed of light. 相似文献
18.
针对真随机数生成问题,提出基于大气湍流光闪烁图像的真随机数提取方法。利用相机获取波长为532 nm的激光经过大气湍流传输后的光斑图像,根据其闪烁特性,分别采用固定间隔选取和多步长选取的方式选取光斑图像,固定间隔选择50帧,多步长选择30帧、70帧和100帧,得到的光斑图像相关性很弱,相关系数均小于0.3,由于湍流效应的影响,图像中的像素点发生无规则变化,通过对像素点作组合计算以提取随机序列;通过NIST(national institute of science and technology)随机性测试的方法,对提取的随机序列进行测试。实验结果表明:固定间隔选取的随机序列随机效果一般,测试结果存在P值小于0.01的情况,而多步长选取测试的P值均大于0.01,可以通过随机性测试。 相似文献
19.