  We discuss an effective theory for QCD at finite chemical potential and
non-zero temperature, where QCD is reduced to its center degrees of freedom.
The effective action can be mapped to a flux representation, where the complex
phase problem is solved and the theory accessible to Monte Carlo techniques. In
this work, we use a generalized Prokof'ev-Svistunov worm algorithm to perform
the simulations and determine the phase diagram as a function of temperature,
quark mass and chemical potential. It turns out that the transition is
qualitatively as expected for QCD.
