title: Robust regularity in γ-soft nuclei and its microscopic realization.
abstract: γ softness in atomic nuclei is investigated in the framework of energy density functionals. By mapping constrained microscopic energy surfaces for a set of representative nonaxial medium-heavy and heavy nuclei to a Hamiltonian of the proton-neutron interacting boson model (IBM-2) containing up to three-body interactions, low-lying collective spectra and transition rates are calculated. Observables are analyzed that distinguish between the two limiting geometrical pictures of nonaxial nuclei: the rigid-triaxial rotor and the γ-unstable rotor. It is shown that neither of these pictures is realized in actual nuclei, and that a microscopic description leads to results that are almost exactly in between the two geometrical limits. This finding points to the optimal choice of the IBM Hamiltonian for γ-soft nuclei.
authors.affiliation: Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nomura
authors.forename: N
authors.initials: N
authors.lastname: Shimizu
authors.forename: D
authors.initials: D
authors.lastname: Vretenar
authors.forename: T
authors.initials: T
authors.lastname: Nikšić
authors.forename: T
authors.initials: T
authors.lastname: Otsuka