Phase Transitions in Models with Discrete Symmetry
  We investigate a class of models with a massless fermion and a self-interacting scalar field with the Yukawa interaction between these two fields. The models considered are formulated in two and four spacetime dimensions and possess a discrete symmetry. We calculate the chiral condensates are calculated in the one-loop approximation. We show that the models have a phase transitions as a function of the coupling constants. 
V.G. Ksenzov and A.I. Romanov
hep-ph hep-th