Quasiclassical localization of wave packets in nonlinear Schrodinger systems

We consider the nonlinear Schrodinger equation with several kinds of potent ials. For studying the existence and stability of the wave packets that cou ld support these systems, a certain functional is constructed, which in som e manner possesses the properties of the Lyapunov functional for analyzing the existence and stability of solutions. The general case of potential is considered and the appearance of pulsons is shown. Then we propose three ex amples of nonlinear classical field theories with potentials that exhibit q uartic, sextic and saturable nonlinearities. This method exhibits a criteri a for determining quasiclassically the self-localization of wave packets in nonintegrable systems. (C) 2000 Elsevier Science Ltd. All rights reserved.