Quantum Phase Transitions in Finite Nuclei
Hebrew Univ., Jerusalem, Israel
Quantum phase transitions (QPT) are structural changes occurring at zero temperature, driven by quantum fluctuations and governed by a control parameter in the quantum Hamiltonian. An example of QPT is the phase transitions between different shapes of nuclei, for which the equilibrium deformation plays the role of an order parameter. It has been recently recognized that systems exhibiting such shape-phase transitions are amenable to analytic descriptions at the critical-points, and empirical evidence of nuclei satisfying these "critical-point symmetries" have been presented. A key issue near criticality is to understand the modifications brought in by the fact that nuclei consist of a finite number of nucleons. In the present talk properties of critical Hamiltonians for first- and second- order QPT in finite nuclei will be examined. Special emphasis will be paid to symmetry aspects of the phase transition. While exact dynamical symmetries describe the dynamics of stable nuclear shapes, the notion of partial dynamical symmetry appears to be relevant for the dynamics of transitional nuclei at the critical-point.