Condensate Fragmentation in a New Exactly Solvable Model for Confined   Bosons
  Based on Richardson's exact solution of the pairing model and the Gaudin model for spin systems we derive a new class of exactly solvable models for finite boson system. As an example we solve a particular hamiltonian which displays a transition to a fragmented condensate for repulsive pairing interactions. 
J. Dukelsky and P. Schuck