Two-Component Description for Relativistic Fermions

<正> We propose a two-component form to describe massive relativistic fermions in gauge theories. Relationsbetween the Green's functions in this form and those in the conventional four-component form are derived. It is shownthat the S-matrix elements in both forms are exactly the same. The description of the fermion in the new form simplifiessignificantly the γ-matrix algebra in the four-component form. In particular, in perturbative calculations the propagatorof the fermion is a scalar function. As examples, we use this form to reproduce the relativistic spectrum of hydrodronatom, the S-matrix of e+e-→μ+μ- and QED one-loop vacuum polarization of photon.