  The phase structure of hot gauge theories with dynamical matter fields is
reexamined in the canonical ensemble with respect to triality. Since this
ensemble implies a projection to the zero triality sector of the theory we
introduce a proper quantity which is able to reveal a critical behaviour of the
theory with fundamental quarks. We discuss the properties of both the
chromoelectric and chromomagnetic sectors of the theory and show while electric
charges carrying a unit of Z(N) charge are screened at high temperatures by
dynamical matter loops, this is not the case for the Z(N) magnetic flux. An
order parameter is constructed to probe the realization of local discrete Z(N)
symmetry in the magnetic sector. We argue it can be used to detect a
deconfinement phase being defined in terms of the screening mechanism as a
phase of unscreened Z(N) flux. It may be detectable at long range via the
Aharonov-Bohm effect. We discuss the possible phase structure of QCD in this
approach.
