  We consider large N zero-coupling d-dimensional U(N) gauge theories, with N_f
matter fields in the fundamental representation on a compact spatial manifold
S^{d-1} x time, with N_f/N finite. The Gauss' law constraint induces
interactions among the fields, in spite of the zero-coupling. This class of
theories undergo a 3rd order deconfinement phase transition at a temperature
T_c proportional to the inverse length scale of the compact manifold.
  The low-temperature phase has a free-energy of {\cal O} (N^2_f), interpreted
as that of a gas of (color singlet) mesons and glueballs. The high-temperature
(deconfinement) phase has a free energy of order N^2 f (N_f/N, T), which is
interpreted as that of a gas of gluons and of fundamental and anti-fundamental
matter states. This suggests the existence of a dual string theory, and a
transition to a black hole at high temperature.
