FREE PARTICLE CHAOTIC SCATTERING OFF 2 OSCILLATING DISKS

We investigate the two-dimensional classical dynamics of the scatterin g of point particles by two periodically oscillating disks. The dynami cs exhibits regular and chaotic scattering properties, as a function o f the initial conditions and parameter values of the system. The energ y is not conserved, since the particles can gain and lose energy from the collisions with the disks. We find that for incident particles who se velocity is on the order of the oscillating disk velocity, the ener gy of the exiting particles displays nonmonotonic gaps of allowed ener gies, and the distribution of exiting particle velocities shows signif icant fluctuations in the low energy regime. We also considered the ca se when the initial velocity distribution is Gaussian, and found that for high energies the exit velocity distribution is Gaussian with the same mean and variance. When the initial particle velocities are in th e irregular regime the exit velocity distribution is Gaussian, but wit h a smaller mean and variance. The latter result can be understood as an example of stochastic cooling. In the intermediate regime the exit velocity distribution differs significantly from Gaussian. A compariso n of the results presented in this paper to previous chaotic static sc attering problems is also discussed.