Mixed Symmetry Nuclear Shell Model

Abstract

A mixed-symmetry nuclear shell-model scheme for carrying out calculations in regimes where there is a competition between two or more modes is proposed. A one-dimensional toy model is used to demonstrate the concept. The theory is then applied to ${}^{24}Mg$ and ${}^{44}Ti$. For lower pf-shell nuclei such as ${}^{44-48}Ti$ and ${}^{48}Cr$ there is strong SU(3) symmetry breaking due to the spin-orbit interaction. However, the quadrupole collectivity as measured by B(E2) transition strengths in the yrast band remain high even though SU(3) appears to be broken. Some results for the so-called X(5) symmetry that falls along the U(5) $\leftrightarrow$ SU(3) leg of the Interacting Boson Model are also considered. The results show that the mixed-symmetry concept is effective, even when strong symmetry breaking occurs.

Comments: 23 pages, 12pt article style, 14 figures, talk presented at the XV International School on Nuclear Physics, Neutron Physics and Nuclear Energy, September 9 - 13, 2003, Varna, Bulgaria