Fumio Yoshida

Computer-Simulated Scattering of Lattice Solitons from a Mass Interface in a One-Dimensional Nonlinear Lattice

The scattering of lattice solitons from a mass interface is numerically investigated. For this purpose, a rarefactive soliton solution for the generalized KdV equation is introduced in a one-dimensional nonlinear lattice as the incident soliton. The simulated results show that when the incident soliton propagates into an interface, it disintegrates into a reflected and a transmitted soliton. It is also found that the dependence of the reflected and transmitted soliton amplitudes on the mass ratio of the interface agrees quite well with that obtained from the boundary value problem of a simple linear wave equation. This is probably due to the weak nonlinearity of our lattice.

Computer-Simulated Scattering of Lattice Solitons from Impurity at Free Boundary

The scattering of solitons from a mass-impurity at a free boundary in a one-dimensional nonlinear lattice is investigated numerically. A rarefactive soliton solution for the generalized Korteweg-de Vries equation is introduced in this lattice as the incident soliton. The results show that the soliton interacts strongly with heavy impurity but very weakly with light one. These are discussed in terms of the spectral analysis of the incident soliton amplitude.

Thermodynamic Properties of Anisotropic Two-Dimensional Sine-Gordon Lattice: Molecular-Dynamics Calculations

By the use of molecular dynamics technique, we studied the thermodynamic properties of the anisotropic two-dimensional (2D) sine-Gordon lattice. Anisotropy parameter γ is introduced as the ratio of the strength of stretching to that of shear coupling. Energy-temperature curves are caleulated with varying γ. We found that the peak temperature of specific heat changes with γ. These observed thermodynamic propertics are analyzed in the case of 1D and nearly isotropic 2D system.

Molecular-Dynamics Calculations of Two-Dimensional Sine-Gordon Lattice

We have performed the molecular-dynamics calculations for the two-dimensional sine-Gordon lattice and obtained the internal energies and the time correlation functions of displacements. The experimental results at low temperatures are in good agreement with the analysis in terms of the self-consistent phonon approximation.

Computer-Simulated Scattering of Envelope Soliton from Impurity and Interface in a One-Dimensional Nonlinear Lattice

In 1970, Tappert and Varma[1] showed that the behavior of heat pulse propagation in solids is governed by the nonlinear Schrodinger equation under certain conditions on phonon dispersions and lattice anharmonicity in a continuum limit. The solitary wave (soliton) solution resulting from the equation is called envelope soliton (E soliton). The real crystals, however, contain some impurities or interfaces, so that the soliton propagating in this anharmonic crystals will suffer considerable perturbation from them. In this paper, we investigate numerically the interaction of E soliton with a mass impurity and an interface in a one-dimensional nonlinear lattice.