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 lim it, it has been shown that unusual ground states form which cannot be under stood within a conventional many-vortex picture. Using comparisons with exa ct numerical results, we show that these ground states can be well-describe d by a model of noninteracting "composite fermions." Our work emphasizes th e similarities between the unusual states that appear in rotating Bose-Eins tein condensates and incompressible fractional quantum Hall states. [S0163- 1829(99)50148-3].