  We construct the phase diagram of the chiral and diquark condensates at
finite temperature and density in the 1+1 dimensional (2D) two flavor massless
Gross Neveu model. The resultant phase diagram shows (I) the chiral condensed
phase at low temperature and density, (II) the diquark condensed phase at low
temperature and high density, and (III) the chiral and diquark coexisting phase
at low temperature and intermediate density. This phase structure is also seen
in the 3D Gross Neveu model and the 4D Nambu Jona-Lasinio (NJL) model. Thus the
phase diagrams of the chiral and diquark condensates in the NJL-type models do
not change qualitatively in 2D, 3D and 4D.
