The impact of nuclear shape on the emergence of the neutron dripline.

Atomic nuclei are composed of a certain number of protons Z and neutrons N. A natural question is how large Z and N can be. The study of superheavy elements explores the large Z limit, and we are still looking for a comprehensive theoretical explanation of the largest possible N for a given Z-the existence limit for the neutron-rich isotopes of a given atomic species, known as the neutron dripline.

Nature of isomerism in exotic sulfur isotopes.

We clarify the origin of the anomalously hindered E2 decay from the 4_{1}^{+} level in ^{44}S by performing a novel many-body analysis in the shell model. Within a unified picture about the occurrence of isomerism in neutron-rich sulfur isotopes, the 4_{1}^{+} state is demonstrated to be a K=4 isomer dominated by the two-quasiparticle configuration νΩ^{π}=1/2^{-}⊗νΩ^{π}=7/2^{-}. The 4_{1}^{+} state in ^{44}S is a new type of high-K isomer which has significant triaxiality.

Novel features of nuclear forces and shell evolution in exotic nuclei.

Novel simple properties of the monopole component of effective nucleon-nucleon interactions are presented, leading to the so-called monopole-based universal interaction. Shell structures are shown to change as functions of N and Z, consistent with experiments. Some key cases of this shell evolution are discussed, clarifying the effects of central and tensor forces.