Strong excitations of a Bose--Einstein condensate: Barrier resonances
  We study the dynamics of a forced condensed atom cloud and relate the behavior to a classical Mathieu oscillator in a singular potential. It is found that there are wide resonances which can strongly affect the dynamics even when dissipation is present. The behavior is characteristic of condensed clouds of any shape and has experimental relevance. 
Juan J. G. Ripoll, Victor M. Perez-Garcia