We examine the evolution of perturbations on the kink configuration in <FONT FACE=Symbol>l f</FONT>4 theory and of the Nielsen-Olesen vortex in scalar electrodynamics through the Galerkin method. The problem is reduced to a finite dynamical system for which the linear and nonlinear regimes are studied. The linear stability of both is associated to a motion in a stable torus present in phase space, whereas the nonlinear evolution of perturbations can be viewed as a consequence of the breakdown of the tori structure and the onset of chaos. We discuss this regime in connection with the stability of the configurations. Also, the Galerkin method is used to obtain approximate analytical expressions for the vortex profile.
Stability of solitons; Nielsen-Olesen vortex; Galerkin model
