ON THE WING BEHAVIOR OF THE OVERTONES OF SELF-LOCALIZED MODES

In this paper the solutions for self-localized modes in a nonlinear ch ain are investigated. We present a converging iteration procedure, whi ch is based on analytical information of the wings and which takes int o account higher overtones of the solitonic oscillations. The accuracy is controlled in a step by step manner by means of a Gaussian error a nalysis. Our numerical procedure allows for highly accurate solutions, in all anharmonicity regimes, and beyond the rotating-wave approximat ion (RWA). It is found that the overtone wings change their analytical behaviour at certain critical values of the energy of the self-locali zed mode: there is a turnover in the exponent of descent. The results an shown for a Fermi-Pasta-Ulam (FPU) chain with quartic anharmonicity . (C) 1998 Elsevier Science B.V.