Phase Diagram of the Proton-Neutron Interacting Boson Model
  We study the phase diagram of the proton--neutron interacting boson model (IBM--2) with special emphasis on the phase transitions leading to triaxial phases. The existence of a new critical point between spherical and triaxial shapes is reported. 
J.M. Arias, J.E. Garcia-Ramos, and J. Dukelsky