Description of Nuclear Collective Excitations with Multi-Reference Covariant Density Functional Theory (The 41st Nuclear Theory Seminar)

by Dr Jiangming Yao (Tohoku University, Japan and Southwest University, China)

Wednesday 9 Oct 2013, 13:30 → 14:30 Asia/Tokyo

RIBF Hall

During the past decades, the relativistic mean-field (RMF) approach has achieved great success in describing many nuclear phenomena for both stable and exotic nuclei over the entire nuclear chart with a few universal parameters. It incorporates many important relativistic effects, such as the presence of large Lorentz scalar and vector fields with approximately equal magnitude and opposite sign. This leads to a new saturation mechanism via the difference between the scalar and vector densities, and naturally to the large spin–orbit interaction needed for the understanding of magic numbers in finite nuclei. However, to go beyond the modeling of nuclear bulk properties and perform detailed calculations for nuclear excitation spectra and transition probabilities, one must extend the RMF approach which usually relies on a single-reference state to include dynamical correlations related to restoration of symmetries broken by the static mean-field and to fluctuations of collective degree-of-freedom around the mean-field energy minimum. In this case, the many-body energy is determined by a functional of transition density matrices among many Slater determinants generated by selected collective coordinates. This level of implementation is referred to as multi-reference (MR) covariant density functional theory (CDFT). Recently, we have implemented both particle number projection and 3D-angular momentum projections into the CDFT for nuclei with triaxial shapes. The fluctuation effects around the energy minimum are taken into account with the generator coordinate method (GCM). In the seminar, I shall introduce the beyond RMF approach and demonstrate the dynamical correlation effects on nuclear binding energies, density profiles and collective excitations of exotic nuclei. The systematic in the low-lying states of sd-shell nuclei and triaxiality in low-lying states of 76Kr will be discussed. If I have enough time, I shall also mention about the simultaneous quadrupole and octupole shape transitions in Th isotopes, the transition density in low-lying collective states and a preliminary calculation of nuclear matrix element (NME) in neutrinoless double beta decay within this framework.