Thermodynamics of (2+1)-dimensional four-fermion models

The thermodynamics of the (2+1)-dimensional Gross-Neveu model is analyzed. The model is not renormalizable in the weak-coupling expansion but becomes renormalizable in the 1/Nf expansion. We calculate the critical temperature and find the phase structure. The critical exponents {α}, {α}', {β}, {γ}, {γ}', {δ}, {η}, {ν}, and {ν}' are calculated to leading order in 1/Nf, and do not satisfy the ``scaling relations.''