Internal solitary waves in the ocean: Analysis using the periodic,inverse scattering transform

The periodic, inverse scattering transform (PIST) is a powerful analytical tool in the theory of integrable, nonlinear evolution equations. Osborne pioneered the use of the PIST in the analysis of data form inherently nonlinear physical processes. In particular, Osborne's so-called nonlinear Fourier analysis has been successfully used in the study of waves whose dynamics are (to a good approximation) governed by the Korteweg–de Vries equation. In this paper, the mathematical details and a new application of the PIST are discussed. The numerical aspects of and difficulties in obtaining the nonlinear Fourier (i.e., PIST) spectrum of a physical data set are also addressed. In particular, an improved bracketing of the “spectral eigenvalues” (i.e., the ±1 crossings of the Floquet discriminant) and a new root-finding algorithm for computing the latter are proposed. Finally, it is shown how the PIST can be used to gain insightful information about the phenomenon of soliton-induced acoustic resonances, by computing the nonlinear Fourier spectrum of a data set from a simulation of internal solitary wave generation and propagation in the Yellow Sea.     

Extended nonlinear waves in multidimensional dynamical lattices

We explore spatially extended dynamical states in the discrete nonlinear Schrödinger lattice in two- and three-dimensions, starting from the anti-continuum limit. We first consider the “core” of the relevant states (either a two-dimensional “tile” or a three-dimensional “stone”), and examine its stability analytically. The predictions are corroborated by numerical results. When the core is stable, we propose a method allowing the extension of the structure to as many sites as may be desired. In this way, various patterns of excited sites can be formed. The stability of the full extended nonlinear structures is studied numerically, which yields instability thresholds for such structures, which are attained with the increase of the lattice coupling constant. Finally, in cases of instability, direct numerical simulations are used to elucidate the evolution of the pattern; it is found that, typically, the unstable extended nonlinear pattern breaks up in an oscillatory way, leading to “lattice turbulence”.     

Applications of complete discrimination system for polynomial for classifications of traveling wave solutions to nonlinear differential equations

If a partial differential equation is reduced to an ordinary differential equation in the form u^′(ξ)=G(u,θ₁,…,θm) under the traveling wave transformation, where θ₁,…,θm are parameters, its solutions can be written as an integral form . Therefore, the key steps are to determine the parameters' scopes and to solve the corresponding integral. When G is related to a polynomial, a mathematical tool named complete discrimination system for polynomial is applied to this problem so that the parameter's scopes can be determined easily. The complete discrimination system for polynomial is a natural generalization of the discrimination △=b²−4ac of the second degree polynomial ax²+bx+c. For example, the complete discrimination system for the third degree polynomial F(w)=w³+d₂w²+d₁w+d₀ is given by and . In the paper, we give some new applications of the complete discrimination system for polynomial, that is, we give the classifications of traveling wave solutions to some nonlinear differential equations through solving the corresponding integrals. In finally, as a result, we give a partial answer to a problem on Fan's expansion method.     

Hidden solitons in the Zabusky–Kruskal experiment: Analysis using the periodic,inverse scattering transform

Recent numerical work on the Zabusky–Kruskal experiment has revealed, amongst other things, the existence of hidden solitons in the wave profile. Here, using Osborne’s nonlinear Fourier analysis, which is based on the periodic, inverse scattering transform, the hidden soliton hypothesis is corroborated, and the exact number of solitons, their amplitudes and their reference level is computed. Other “less nonlinear” oscillation modes, which are not solitons, are also found to have nontrivial energy contributions over certain ranges of the dispersion parameter. In addition, the reference level is found to be a non-monotone function of the dispersion parameter. Finally, in the case of large dispersion, we show that the one-term nonlinear Fourier series yields a very accurate approximate solution in terms of Jacobian elliptic functions.     

Collision dynamics of elliptically polarized solitons in Coupled Nonlinear Schrödinger Equations

We investigate numerically the collision dynamics of elliptically polarized solitons of the System of Coupled Nonlinear Schrödinger Equations (SCNLSE) for various different initial polarizations and phases. General initial elliptic polarizations (not sech$sech$-shape) include as particular cases the circular and linear polarizations. The elliptically polarized solitons are computed by a separate numerical algorithm. We find that, depending on the initial phases of the solitons, the polarizations of the system of solitons after the collision change, even for trivial cross-modulation. This sets the limits of practical validity of the celebrated Manakov solution. For general nontrivial cross-modulation, a jump in the polarization angles of the solitons takes place after the collision (‘polarization shock’). We study in detail the effect of the initial phases of the solitons and uncover different scenarios of the quasi-particle behavior of the solution. In majority of cases the solitons survive the interaction preserving approximately their phase speeds and the main effect is the change of polarization. However, in some intervals for the initial phase difference, the interaction is ostensibly inelastic: either one of the solitons virtually disappears, or additional solitons are born after the interaction. This outlines the role of the phase, which has not been extensively investigated in the literature until now.     

Impact of the large cross-modulation parameter on the collision dynamics of quasi-particles governed by vector NLSE

For the Coupled Nonlinear Schrödinger Equations (CNLSE) we construct a conservative fully implicit scheme (in the vein of the scheme with internal iterations proposed in [C.I. Christov, S. Dost, G.A. Maugin, Inelasticity of soliton collisions in system of coupled nls equations, Physica Scripta 50 (1994) 449–454.]). Our scheme makes use of complex arithmetic which allows us to reduce the computational time fourfold. The scheme conserves the “mass”, momentum, and energy.     

Excited Bose–Einstein condensates: Quadrupole oscillations and dark solitons

We study the dynamics of atomic Bose–Einstein condensates (BECs), when the quadrupole mode is excited. Within the Thomas–Fermi approximation, we derive an exact first-order system of differential equations that describes the parameters of the BEC wave function. Using perturbation theory arguments, we derive explicit analytical expressions for the phase, density and width of the condensate. Furthermore, it is found that the observed oscillatory dynamics of the BEC density can even reach a quasi-resonance state when the trap strength varies according to a time-periodic driving term. Finally, the dynamics of a dark soliton on top of a breathing BEC are also briefly discussed.     

A non-trivial relation between some many-dimensional chaotic discrete dynamical systems and some one-dimensional chaotic discrete dynamical systems

Chaotic maps are very useful in practical applications. In this paper, we present a method for constructing the many-dimensional chaotic discrete dynamical systems using semiconjugacy property. The chaotic property in one dimension may be influenced the chaotic property in higher-dimensions. In fact, using the one-dimensional chaotic maps and semiconjugacy property, we construct some many-dimensional chaotic discrete dynamical systems. These systems may be used as random number generators in Monte Carlo simulations. Also, these systems may be used in practical applications such as chaotic cryptography and evolutionary algorithms.     

Self-correction of errors in discrete dynamic systems

The ability of a discrete dynamic system for correcting functional errors is investigated. A method for enhancing the degree of self-correction is described.     

Propagation of conic model uncertainty in hierarchical systems

Conic sectors are used for analysis of stability and modeling uncertainty propagation in interconnected systems with a hierarchical structure. For large systems that can be readily decomposed into sparsely interconnected groups subsystems, sub-subsystems, sub-sub-subsystems, etc., analysis is greatly facilitated: formulas for conic uncertainty propagation and stability analysis are applied successively to the various groups, beginning at the bottom of the hierarchy and moving up one level at a time. At each level of the hierarchy the results both test stability and yield tight cone bounds on the modeling uncertainty in terms of the cone parameters at the level immediately below.     

Auto-Bäcklund transformation and exact solutions of the generalized variable-coefficient Kadomtsev-Petviashvili equation

Based on the idea of the homogeneous balance (HB) method, an auto-Bäcklund transformation (BT) to the generalized variable-coefficient Kadomtsev-Petviashvili (GvcKP) equation is obtained with symbolic computation. By the use of the auto-BT and the ε-expansion method, we can obtain a soliton-like solution including N-solitary wave of the GvcKP equation. Especially, we get a soliton-like solution including two-solitary wave as an illustrative example in detail. Since the cylindrical KP (cKP) equation, the generalized cKP (GcKP) equation and the spherical KP (SKP) equation are all special cases of the GvcKP equation, we can also obtain the corresponding results of these equations respectively.     

Multisymplectic numerical method for the regularized long-wave equation

In this paper, we derive a 6-point multisymplectic Preissman scheme for the regularized long-wave equation from its Bridges' multisymplectic form. Backward error analysis is implemented for the new scheme. The performance and the efficiency of the new scheme are illustrated by solving several test examples. The obtained results are presented and compared with previous methods. Numerical results indicate that the new multisymplectic scheme can not only obtain satisfied solutions, but also keep three invariants of motion very well.     

Parameter functionalization and its application to the problem of local bifurcations in dynamic systems

The method of parameter functionalization suggested by M.A. Krasnosel’skii for solving problems with parameters and continuums of fixed points is considered. A general scheme of constructing the functionals in the bifurcation problem of small solutions to operator equations is suggested. As an application, we consider problems of local bifurcations in dynamic systems that are topical for the control theory: bifurcations of double equilibrium and forced oscillations and bifurcations of cycles of discrete systems. New sufficient criteria of bifurcations are indicated, an iteration procedure for constructing the solutions and their asymptotic representations are elaborated, and new stability conditions are stated.     

Nonlinear dynamic systems: Their canonical decomposition based on invariant functions

Decomposition of nonlinear dynamic systems based on invariant functions similar to the canonical decomposition of uncontrollable nonobservable linear systems is described.     

Predictive non-iterative coordinations in hierarchical systems

Predictive and goal-oriented coordinations are primarily used in multilevel systems. In this paper, they are developed in non-iterative form. Proof for the predictive coordination strategy is given. Properties and disadvantages of real-time control for a two-level system are analyzed. For optimization problems, load and coordination rate are estimated in terms of the number of floating-point operations per second.     

Scilab software package for the study of dynamical systems

This work presents a new software package for the study of chaotic flows and maps. The codes were written using Scilab, a software package for numerical computations providing a powerful open computing environment for engineering and scientific applications. It was found that Scilab provides various functions for ordinary differential equation solving, Fast Fourier Transform, autocorrelation, and excellent 2D and 3D graphical capabilities. The chaotic behaviors of the nonlinear dynamics systems were analyzed using phase-space maps, autocorrelation functions, power spectra, Lyapunov exponents and Kolmogorov-Sinai entropy. Various well known examples are implemented, with the capability of the users inserting their own ODE.

Program summary

Program title: ChaosCatalogue identifier: AEAP_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAP_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 885No. of bytes in distributed program, including test data, etc.: 5925Distribution format: tar.gzProgramming language: Scilab 3.1.1Computer: PC-compatible running Scilab on MS Windows or LinuxOperating system: Windows XP, LinuxRAM: below 100 MegabytesClassification: 6.2Nature of problem: Any physical model containing linear or nonlinear ordinary differential equations (ODE).Solution method: Numerical solving of ordinary differential equations. The chaotic behavior of the nonlinear dynamical system is analyzed using Poincaré sections, phase-space maps, autocorrelation functions, power spectra, Lyapunov exponents and Kolmogorov-Sinai entropies.Restrictions: The package routines are normally able to handle ODE systems of high orders (up to order twelve and possibly higher), depending on the nature of the problem.Running time: 10 to 20 seconds for problems that do not involve Lyapunov exponents calculation; 60 to 1000 seconds for problems that involve high orders ODE and Lyapunov exponents calculation.