Phase diffusion in a chaotic pendulum

The rate of expansion of the phase coordinate for a harmonically driven pendulum is considered. The mean-squared displacement is found to grow as a linear function of time during chaotic motion, indicating deterministic diffusion. The diffusion coefficient can be significantly influenced by the proximity of a window containing a periodic solution. We find that diffusion associated with intermittent chaos can be described in terms of an interleaving of the diffusion properties of the separate modes taking part in the intermittency. copyright 1996 The American Physical Society