Why Do We Need Instantons in Strangeness Hadron Physics?

Strangeness nuclear physics has reached a new era, which requires elevation of phenomenological analyses of hypernuclear phenomena to a deeper understanding of the fundamental interactions from QCD viewpoint. Recent coordinated efforts in experimental and theoretical researches revealed several interesting features of hyperon-nucleon and hyperon-hyperon interactions. For instance, it is established by now that the spin-orbit interaction of Λ in nuclear medium is very weak, suggesting cancellation of two types of spin-orbit interactions, spin-flavor symmetric and antisymmetric ones. Discovery of pentaquarks triggers revisiting inter-quark correlations, such as diquarks and triquarks. It is urgent to establish foundations of such possibilities directly from QCD. In this talk, I would like to review a new type of quark-quark interaction mediated by instantons in the QCD vacuum. The instanton idea is not new, but its applications to hadron spectroscopy and to hadronic interactions are being developed in these years. I concentrate on the instanton induced interactions among quarks, and stress that the strangeness plays an important role as the third flavor for the quark dynamics under the instanton induced interactions. In sect. 2, instanton and instanton induced interaction are introduced in the context of hadron physics. In sect. 3, we discuss consequences of