Shell Structure of Exotic Nuclei and Nuclear Force

The effect of the tensor force on the single-particle energies is presented, exhibiting how spherical single-particle energies are shifted as protons or neutrons occupy certain orbits. An analytic relation for such monopole shifts is shown, and their general features are explained intuitively. Single-particle levels are shown to change in a systematic and robust way, by using the π+ρ meson exchange tensor potential. Several examples are shown with the corresponding experimental data.