Intermittent movement of localized excitations of a nonlinear lattice.

The mobility of localized high-amplitude excitations of the discrete nonlinear Schrödinger equation is studied. The excitations can either be pinned at the lattice or they can propagate depending on their energy and particle number. Such localized excitation can emit or absorb waves with a low amplitude which changes the amount of these quantities in the excitation. For statistical reasons, the excitations absorb a high amount of energy per particle through their interaction with low-amplitude waves. They can only move if their energy decreases temporarily either by a random fluctuation or by an external force.