Hedgehog loops and finite-temperature transition in Yang-Mills theory

The dynamics of non-Abelian gauge theory can be described not only in terms of local gauge fields but also in terms of nonlocal gauge-invariant variables known as Wilson loops. In Wilson loop space, specific trajectories (defects) are considered on which Wilson loop operators take values in the center of the underlying gauge group. It is shown that, at finite temperature, the density of static (thermal) defects in the Euclidean formulation of Yang-Mills theory is sensitive to the thermodynamic phase transition: numerical calculations reveal that, in contrast to the gluon-plasma phase, where the defect density is high, the density of static defects is very low in the confining phase.