Quantum spherical spins with local symmetry.

We construct a quantum system of spherical spins with a continuous local symmetry. The model is exactly soluble in the thermodynamic limit and exhibits a number of interesting properties. We show that the local symmetry is spontaneously broken at finite as well as zero temperatures, implying the existence of classical and quantum phase transitions with a nontrivial critical behavior. The dynamical generation of gauge fields and the equivalence with the CP((N-1)) model in the limit N→∞ are investigated. The dynamical generation of gauge fields is a consequence of the restoration of the local symmetry.