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/$N_f$ 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/$N_f$, and do not satisfy the ‘‘scaling relations.’’