Order Parameters for Confinement

Abstract

There are certain observables whose behavior indicates that a gauge system is, or is not, in a phase of magnetic disorder. These are the Wilson loop, the Polyakov loop, the ‘t Hooft loop, and the vortex free energy. The Wilson loop has been discussed already, to some extent. The Polyakov loop is a Wilson loop which winds around a finite, periodic lattice in the time direction; it is a crucial probe of center symmetry and the high temperature deconfinement phase transition, in which center symmetry is spontaneously broken. The ‘t Hooft loop is an operator which creates an object known as a center vortex. The center vortex scenario for confinement will be discussed in some detail in Chaps. 6 and 7.