Microscopic Picture of Interacting Boson Model

Abstract

The Interacting Boson Model (IBM) is discussed from two viewpoints related to the microscopic nuclear structure. One is the derivation of the IBM using the OAI mapping method. The results of recent microscopic calculations along this line are presented for TeXe-Ba isotopes. The IBM-2 Hamiltonian is derived from a nucleon Hamiltonian comprised of single-particle energy, pairing and quadrupole-quadrupole interactions, by carrying out mapping from multi-nucleon systems to interacting-boson systems. The microscopic origin of the O(6) dynamical symmetry or γ-unstable deformation is discussed. The second major subject is a novel interpretation of nuclear rotation. It is shown that, both in IBM and nucleonic calcuations, the proton and neutron deformed ellipsoids are rotating in the opposite directions near the ground state. The rotational energy can then be interpreted in terms of inertial parameter against tilting of the proton rotaion axis towards the neutron axis.