Mean-field derivation of the interacting boson model and exotic nuclear shapes

The interacting boson model (IBM), where correlated pairs of valence nucleons are represented by bosons, has been remarkably successful in phenomenological description of collective excitations in medium-heavy and heavy nuclei. Microscopic foundation of the IBM, starting from nucleonic degrees of freedom, has been extensively studied within the shell model, but has been somewhat limited to nearly-spherical nuclei.

We have developed a comprehensive method to derive the Hamiltonian of the IBM from nuclear energy density functional (EDF) theory. In this method, results of the constrained self-consistent mean-field calculations with a choice of EDF are used as microscopic input to completely determine the Hamiltonian of the IBM for nuclear spectroscopy.

Since the EDF framework allows for a global mean-field description of many nuclear properties over the entire region of the nuclear chart, it has become possible to derive the IBM Hamiltonian for any arbitrary nuclei. I would like to highlight important applications of this method, that include the phenomena of shape transitions and coexistence in the mass A~100 region, octupole deformations in actinides and rare-earth regions, and the extensions to nuclei with odd nucleon numbers.