Magnetic catalysis in a P-even, chiral-invariant three-dimensional model   with four-fermion interaction
  The influence of an external constant and homogeneous magnetic field H on the phase structure of the P-symmetric, chiral invariant 3-dimensional field theory model with two four-fermion interaction structures is considered. An arbitrary small (nonzero) magnetic field is shown to induce spontaneous violation of the initial symmetry (magnetic catalysis). Moreover, vacuum of the model at H>0 can be either P-symmetric or chiral invariant, depending on the values of the coupling constants. 
V. Ch. Zhukovsky, K. G. Klimenko, V. V. Khudyakov