Structure of the QCD vacuum and hadrons

Abstract

Recent studies have provided strong arguments in favor of the idea that most hadrons (including the nucleon) are actually bound not because of confining forces, but mainly due to the instanton-induced forces. Quite different effective interactions in various mesonic and baryonic channels can be explained in this way. Moreover, many hadronic parameters and even the point-to-point correlation functions are quantitatively reproduced by the simplest possible ensemble of instantons, the so-called “Random Instanton Liquid Model” (RILM). Recent lattice works have confirmed it, essentially deriving the “instanton vacuum” from lattice configuration by their “cooling”. At non-zero temperatures the (quark-induced) interaction between instantons becomes much stronger, and at the critical temperature T = T c the chiral symmetry becomes restored, due to “pairing” of the instantons and the anti-instantons into a kind of “ / ̄ II molecules”.