Coherent state approach to the interacting boson model: Test of its validity in the transitional region

The predictive power of the coherent state (CS) approach to the interacting boson model (IBM) is tested far from the IBM dynamical symmetry limits. The transitional region along the γ-unstable path from U(5) to O(6) is considered. Excitation energy of the excited β band and intraband and interband transitions obtained within the CS approach are compared with the exact results as a function of the boson number N. We find that the CS formalism provides approximations to the exact results that are correct up to the order 1/N in the transitional region, except in a narrow region close to the critical point.