Anomalous momentum diffusion in the classical kicked rotor

Numerical simulation for the classical kicked rotor is used to obtain the momentum diffusion over a region of the control parameters K from 0 to 100 that covers 15 fundamental accelerator modes. The numerical data for momentum diffusion is well fit by a power law DN ^β in the number of kicks N. In the anomalous momentum diffusion regions due to accelerator modes the exponent β(K) is slightly less than quadratic except for a slight dip, in agreement with the upper bound (K ²/2) N ². The corresponding coefficient D(K) in these regions has three distinct sections, most likely due to accelerator modes with period greater than one.