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 ground states form which cannot be understood within a conventional many-vortex picture. Using comparisons with exact numerical results, we show that these ground states can be well-described by a model of noninteracting ``composite fermions.'' Our work emphasizes the similarities between the unusual states that appear in rotating Bose-Einstein condensates and incompressible fractional quantum Hall states.