Universality in fermionic field theories at finite temperature

We discuss the critical properties of the three-dimensional NJL model at nonzero temperature. We show that the Z(2)-symmetric model undergoes a second order phase transition with 2d Ising exponents and its critical region is suppressed by a factor 1/N^{-0.5}. We also provide numerical evidence that the U(1)-symmetric model undergoes a BKT transition in accordance with the dimensional reduction scenario.