A scalar two-level boson model to study the IBM phase diagram in the   Casten triangle
  We introduce a simple two-level boson model with the same energy surface as the Q-consistent Interacting Boson Model Hamiltonian. The model can be diagonalized for large number of bosons and the results used to check analytical finite-size corrections to the energy gap and the order parameter in the critical region. \ 
J. Vidal, J. M. Arias, J. Dukelsky, J. E. Garcia-Ramos