We investigate the deconfining phase transition in SU(3) pure gauge theory
and in full QCD with two flavors of staggered fermions by means of a gauge
invariant thermal partition functional. In the pure gauge case our finite size
scaling analysis is in agreement with the well known weak first order phase
transition. In the case of 2 flavors full QCD we find that the phase transition
is consistent with weak first order, contrary to the expectation of a crossover
for not too large quark masses.Comment: 3 pages, 3 figures, Lattice2003(topology