Strongly nonlinear envelope soliton in a lattice model for periodic structure

Nonlinear waves in a periodic structure are investigated numerically in ter ms of a modified Toda lattice model incorporating external linear elastic e ffect. The inclusion of the external linear elasticity causes a drastic cha nge in wave properties, i.e. the wave packets, whose wavenumbers are determ ined by the relative importance of the external force to the internal force , play central roles instead of the Toda soliton. Numerically observed wave packets are well described by the nonlinear Schrodinger equation for weakl y nonlinear regime, but an up-and-down asymmetry develops in the envelope f or strongly nonlinear regime. The head-on collisions of such strongly nonli near wave packets show their solitonic properties and that they can be cons idered as strongly nonlinear envelope solitons having an up-acid-down asymm etry in amplitude. (C) 2001 Elsevier Science B.V. All rights reserved.