Shapes and phase transitions in generalized boson models

Abstract

Geometrical properties of the interacting boson model with arbitrary kinds of bosons (s, d, g, …) are investigated. A general expression for the energy surface is derived and the effects of various multipole interactions on the equilibrium shape are discussed. It is shown that a quadrupole interaction alone always leads to an axial shape and a hexadecapole interaction is needed in order to induce a triaxial shape. Another interesting feature that is not possible in the standard sd model is the emergence of prolate-oblate shape co-existence in the extended boson models which may be relevant in the study of high spin states.