DIMENSIONAL REDUCTION AND DYNAMICAL CHIRAL-SYMMETRY BREAKING BY A MAGNETIC-FIELD IN 3+1 DIMENSIONS

It is shown that in 3 + 1 dimensions, a constant magnetic field is a c atalyst of dynamical chiral symmetry breaking, leading to the generati on of a fermion mass even at the weakest attractive interaction betwee n fermions. The essence of this effect is the dimensional reduction D --> D - 2(3 + 1 --> 1 + 1) in the dynamics of fermion pairing in a mag netic field. The effect is illustrated in the Nambu-Jona-Lasinio model . Possible applications of this effect are briefly discussed.