Quasiperiodic versus irreversible dynamics of an optically confined Bose-Einstein condensate

We consider the evolution of a dilute Bose-Einstein condensate in an optical trap formed by a doughnut laser mode. By solving a one-dimensional Gross-Pitaevskii equation and looking at the variance and the statistical entropy associated with the position of the system, we can study the dynamical behavior of the system. It is shown that for small condensates nonlinear revivals of the macroscopic wave function are expected. For sufficiently large and dense condensates irreversible dynamics takes place for which revivals of regular dynamics appear as predicted in P. Villain and M. Lewenstein, Phys. Rev. A 62, 043601 (2000). These results are confirmed by a two-dimensional simulation in which the scales of energy associated with the two different directions mimic the experimental situation.