Gauge covariant fermion propagator in the presence of arbitrary external gauge field and its Schwinger-Dyson equation

摘要

Gauge covariance for Green's functions of a gauge theory through a fermion propagator in the presence of arbitrary external gauge field is proven and a formalism of gauge and Lorentz covariant Schwinger-Dyson equation for the fermion propagator with external gauge field is built up within ladder approximation.