Effective Field Theory for Long Strings

Abstract

In previous work we used magnetic SU(N) gauge theory with adjoint representation Higgs scalars to describe the long distance quark-antiquark interaction in pure Yang-Mills theory, and later to obtain an effective string theory. The empirically determined parameters of the non-Abelian effective theory yielded ZN flux tubes resembling those of the Abelian Higgs model with LandauGinzburg parameter equal to 1/ √ 2, corresponding to a superconductor on the border between type I and type II. However, the physical significance of the differences between the Abelian and the ZN vortices was not elucidated and no principle was found to fix the value of the ’LandauGinzburg parameter’ κ of the non-Abelian theory determining the structure of the ZN vortices. Here we reexamine this point of view. We propose a consistency condition on ZN vortices underlying a confining string. This fixes the value of κ . The transverse distribution of pressure p(r) in the resulting ZN flux tubes provides a physical picture of these vortices which differs essentially from that of the vortices of the Abelian Higgs model. We speculate that this general picture is valid independent of the details of the effective magnetic gauge theory from which it was obtained. Long wavelength fluctuations of the axis of the ZN vortices lead from an effective field theory to an effective string theory with the Nambu-Goto action. This effective string theory depends on a single parameter, the string tension σ . In contrast, the effective field theory has a second parameter, the intrinsic width 1/M of the flux tube, and is applicable at intermediate distances in a range between 0.2 f m and 1 f m, where the contribution of the intrinsic width increases the flux tube width over that predicted by effective string theory.