A Composite Fermion Description of Rotating Bose-Einstein Condensates

We study the properties of rotating Bose-Einstein condensates in parabolic traps, with coherence length large compared to the system size. In this limit, it has been shown that unusual groundstates form which cannot be understood within a conventional many-vortex picture. Using comparisons with exact numerical results, we show that these groundstates can be well-described by a model of non-interacting ``composite fermions''. Our work emphasises the similarities between the novel states that appear in rotating Bose-Einstein condensates and incompressible fractional quantum Hall states.