SUPERDEFORMATIONS AND FERMION DYNAMIC SYMMETRIES

In this talk, I will present a link between nuclear collective motions and their underlying fermion dynamical symmetries. In particular, I will focus on the microscopic understanding of deformations. It is shown that the SU3 of the one major shell fermion dynamical symmetry model (FDSM) is responsible for the physics of low and high spins in normal deformation. For the recently observed phenomena of superdeformation, the physics of the problem dictates a generalization to a supershell structure (SFDSM), which also has an SU3 fermion dynamical symmetry. Many recently discovered features of superdeformation are found to be inherent in such an SU3 symmetry. In both cases the dynamical Pauli effect plays a vital role. A particularly noteworthy discovery from this model is that the superdeformed ground band is not the usual unaligned band but the D-pair aligned (DPA) band, which sharply crosses the excited bands. The existence of such DPA band is a key point to understand many properties of superdeformation. Our studies also pose new experimental challenge. This is particularly interesting since there are now plans to build new and exciting gamma-ray detecting systems, like the GAMMASPHERE, which could provide answers to some of these challenges.