Relativistic quantum transport theory for electrodynamics

We investigate the relationship between the covariant and the three-dimensional (equal-time) formulations of quantum kinetic theory. We show that the three-dimensional approach can be obtained as the energy average of the covariant formulation. We illustrate this statement in scalar and spinor QED. We especially emphasize the importance of constraint equations in the three-dimensional formulation and explicitly derive via the energy averaging method a complete set of kinetic equations, which contains the BGR equations by Bialynick-Birula er al. as a subset. (C) 1996 Academic Press, Inc.