Absence of Physical Walls in Hot Gauge Theories
  This paper shows that there are no physical walls in the deconfined, high-temperature phase of Z(2) lattice gauge theory. In a Hamiltonian formulation, the interface in the Wilson lines is not physical. The line interface and its energy are interpreted in terms of physical variables. They are associated with a difference between two partition functions. One includes only the configurations with even flux across the interface. The other is restricted to odd flux. 
Joe Kiskis