Magnetic Catalysis of Chiral Symmetry Breaking in Gauge Theories

Non-perturbative effect of the formation of a chiral symmetry breaking condensate <\bar\psi\psi> and of a dynamically generated fermion mass in QED in the presence of an external magnetic field is considered. The dynamical mass of a fermion (energy gap in the fermion spectrum) is shown to depend essentially nonanalytically on the renormalized coupling constant \alpha in a strong magnetic field. Possible applications of this effect are discussed.