Approach to the Rotation Driven Vibrational to Axially Rotational Shape   Phase Transition Along the Yrast Line of a Nucleus
  By analyzing the potential energy surface, the shape phase diagram and the energy spectrum of the nucleus in U(5) symmetry in the IBM, we propose that the U(5) symmetry with parameters $(A+B) < 0$ may be a model to describe the rotation driven vibrational to axially rotational phase transition along the yrast line. With such a model, we have described successfully the observed rotation driven shape phase transition along the yrast line of individual nucleus and proposed some other empirical evidences. 
Yu-xin Liu, Liang-zhu Mu, and Haiqing Wei