Rotating Bose-Einstein condensate in an optical lattice: Formulation of vortex configuration for the ground state

We consider a rotating Bose-Einstein condensate in an optical lattice in the regime in which the system Hamiltonian can be mapped onto a Josephson junction array. In an approximate scheme where the couplings are assumed uniform, the ground state energy is formulated in terms of the vortex configuration. Application of the method for the ladder case presented and the results are compared with Monte-Carlo method.