Uniformly frustrated bosonic Josephson-junction arrays
  We derive a uniformly frustrated $XY$ model that describes two-dimensional Josephson-junction arrays consisting of rotating Bose-Einstein condensates trapped by both a harmonic trap and a corotating deep optical lattice. The harmonic trap makes the coupling constant of the model have a nonuniform parabolic dependance. We study the ground state through Monte Carlo simulations in a wide range of the frustration parameter $f$, revealing a rich variety of vortex patterns. 
Kenichi Kasamatsu