The mechanism of confinement and chiral symmetry breaking in quark nuclearphysics

We review first the dual Ginzburg-Landau (DGL) theory, in which color monop oles and their condensation in the QCD vacuum play the essential role for c onfinement and chiral symmetry breaking. The color monopoles live, however, only in a particular gauge, the maximal abelian gauge. Hence, we discuss n ext the origin of the color monopole, which we conjecture is instanton, the classical solution of the Euclidean Yang-Mills theory. We make one to one correspondence of instanton and color monopole and further of instanton and center vortex. We then study the appearance of monopole condensation due t o large density of instantons in the model QCD vacuum. We conclude that ins tantons are the key objects to provide not only chiral symmetry breaking, b ut also quark confinement. We should further take into account the correlat ions among instantons for quantitative description of confinement.