Nucleon-Nucleon Interaction at Small Distances

In 1956, the one-pion-exchange potential (OPEP) at large internucleon distances was established and this first success in substantial understanding of nuclear forces has become the keystone in studying nuclear forces since then. As was reported in the review article in 1956, this success was obtained by our Japanese group following the Taketani theory, which proposes to approach nuclear forces from the outside of the nucleon by combining meson-theoretical predictions at large distances with phenomenological descriptions at small distances. In this article we intend to report basic thoughts of approaches and main results recently obtained, in the theoretical works in Japan concerning nuclear forces at small distances.