Selfconsistent Treatment of Collective Vibrations in Terms of Boson Expansions

Abstract

Earlier, a rapidly converging boson series expansion of fermion pair operators was suggested, and application to collective vibrations was discussed. This theory is now extended by introducing a selfconsistency requirement in the determination of the structure of the boson vacuum to be used. In this way one is allowed to use a basic fermion representation which do not correspond to the actual shape of the system. Such a possibility becomes important in cases, where the shape of the system is not known beforehand, such as in the region of transition between spherical and deformed shape, and quite generally it allows a unified description of systems with different equilibrium shapes.