Resonance effects in nonlinear lattices

We study a class of one-dimensional nonlinear lattices with nearest-neighbo ur interactions described by a potential of the binomial type. This potenti al contains a free parameter which can be chosen to reproduce a variety of models, such as the Toda, the Fermi-Pasta-Ulam and the Coulomb-like lattice s. Carrying out essentially numerical experiments, thr effects of soliton p ropagation on a lattice with defects are investigated. In particular, the p roperties of the localized mode, generated by the propagation of the solito n through the defect, are discussed with respect to the defect mass and the potential parameter, in the light of a simple theoretical model. Furthermo re, an interesting phenomenon is observed: the amplitude of the speed of th e mass defect shows a sequel of resonance peaks in terms of the mass defect . The positions of these peaks appear to be independent of the potential pa rameter.