  Two phenomenological models describing an SU(N) quark-gluon plasma are
presented. The first is obtained from high temperature expansions of the free
energy of a massive gluon, while the second is derived by demanding color
neutrality over a certain length scale. Each model has a single free parameter,
exhibits behavior similar to lattice simulations over the range T_d-5T_d, and
has the correct blackbody behavior for large temperatures. The N=2
deconfinement transition is second order in both models, while N=3,4, and 5 are
first order. Both modelsappear to have a smooth large-N limit. In both models,
the confined phase is characterized by a mutual repulsion of Polyakov loop
eigenvalues that makes the Polyakov loop expectation value zero. In the
deconfined phase, the rotation of the eigenvalues in the complex plane towards
1 is responsible for the approach to the blackbody limit over the range
T_d-5T_d. The addition of quarks in SU(3) breaks Z(3) symmetry weakly and
eliminates the deconfining phase transition for sufficiently light quarks.
