Who Confines Quarks? - On Non-Abelian Monopoles and Dynamics of Confinement

Abstract

The role non-Abelian magnetic monopoles play in the dynamics of confinement is discussed by examining carefully a class of supersymmetric gauge theories as theoretical laboratories. In particular, in the so-called $r$-vacua of softly broken ${N}=2$ supersymmmetric $SU(n_c)$ QCD, the Goddard-Olive-Nuyts-Weinberg monopoles appear as the dominant low-energy effective degrees of freedom. Even more interesting is the physics of confining vacua which are deformations of nontrivial superconformal theories. We argue that in such cases, occurring in the $r= {n_f \over 2}$ vacua of $SU(n_c)$ theories or in all of confining vacua of $USp(2n_c)$ or $SO(n_f)$ theories with massless flavors, a new mechanism of confinement involving strongly interacting non-Abelian magnetic monopoles is at work.