Remarks on shape phase transitions in nuclei

Various aspects of shape phase transitions in even as well as odd systems are reviewed. Firstly, the case of an odd j 3/2 particle coupled to an even-even boson core that undergoes a transition from spherical limit (U(5)) to the γ-unstable limit (0(6)) is illustrated. Energy spectrum and electromagnetic transitions, in correspondence of the critical point, display behaviors qualitatively similar to those of the even core and they agree qualitatively with the model based on the E(5/4) boson-fermion symmetry. Secondly, we describe a study on two-particle transfer reactions: the evolution of the transfer spectroscopic intensities within the interacting boson model is analyzed as a possible signature of shape phase transitions In correspondence to the critical points characterizing the phase transitions, the two-particl transfer matrix elements to both ground and excited 0 + states display a rapid dicontinuit that might help validating the experimental search for the critical point.