Time-dependent properties of a simplified Fermi-Ulam accelerator model.

The chaotic low-energy region of a simplified Fermi-Ulam accelerator model is investigated numerically to determine the average energy and number of collisions as functions of time. We find that these properties exhibit scaling when the oscillation amplitude of the moving wall is small. Following a transient regime, the average energy increases in time, reaches a maximum and then shows a surprising slow decay.