Chiral Condensate in Two Dimensional Models

We investigate two different models. In one of them massive fermions interact with a massive scalar field and in the other the fermion field is in an electrical field (QED2). The chiral condensates are calculated in one-loop approximation. We found that the chiral condensate in the case of the Yukawa interaction the fermions and scalar field does not vanish if the mass of the fermion field tends to zero. The chiral condensate disappears in QED2, if the fermion mass is zero.