We propose a new version of SU(N) Yang-Mills theory reformulated in terms of new field variables which are obtained by a nonlinear change of variables from the original Yang-Mills gauge field. The reformulated Yang-Mills theory enables us to study the low-energy dynamics by explicitly extracting the topological degrees of freedom such as magnetic monopoles and vortices to clarify the mechanism for quark confinement. The dual superconductivity in Yang-Mills theory is understood in a gauge-invariant manner, as demonstrated recently by a non-Abelian Stokes theorem for the Wilson loop operator, although the basic idea of this reformulation is based on the Cho-Faddeev-Niemi decomposition of the gauge potential. §1. Introduction The original Yang-Mills theory 1) is formulated in terms of the Yang-Mills gauge field. This formulation is suitable for studying the high-energy dynamics of YangMills theory. For instance, it is well known that the perturbation theory in the coupling constant developed in terms of the Yang-Mills field is very powerful in the ultraviolet region due to its asymptotic freedom. In the low-energy region, however, we encounter the strong coupling problem, and its description in terms of the YangMills gauge field is no longer valid. In studying the low-energy dynamics of YangMills theory and quantum chromodynamics (QCD), it is important to specify the most relevant degrees of freedom for the phenomenon in question. Quark confinement as a typical phenomenon in the low-energy dynamics caused by strong interactions is believed to be explained by topological defects including magnetic monopoles, vortices and merons. This motivates us to devise another formulation of Yang-Mills theory in terms of new variables reflecting the topological degrees of freedom.
Read full abstract