We construct the effective potential for a QCD-like theory using the
auxiliary field method. The chiral phase transition exhibited by the model at
finite temperature and the quark chemical potential is studied from the
viewpoint of the shape change of the potential near the critical point. We
further generalize the effective potential so as to have quark number and
scalar quark densities as independent variables near the tri-critical point.Comment: 17 pages, 9 figures, using PTPTeX.cl