CONTINUOUS-TIME RANDOM-WALK MODEL FOR STANDARD MAP DYNAMICS

In standard map dynamics, the time series x(t) are analyzed for chaoti c orbits bounded by Kolmogorov-Arnold-Moser barriers, for subcritical values of the stochasticity parameter. They can be described as a succ ession of rather regular oscillations of bounded amplitude in basins l ocated near island chains, and of jumps between basins, at ''random'' times. This motion can be adequately modeled by a continuous time rand om walk, using values of the parameters taken from the numerical data. The resulting theory describes a subdiffusive motion, for which the m ean square displacement tends towards a saturation value.