Light-front limit in a rest frame

Abstract

Covariant perturbation theory is formulated using a new set of space-time coordinates. This corresponds to a quantization on any flat spacelike surface in Minkowski space. One limit of the theory reproduces the usual instant (equal-time) dynamics, whereas a different limit gives light-front dynamics. Neither the infinite-momentum frame nor infinite momenta are involved. In particular a smooth parametric transformation from the instant to light-front picture is given for a system at rest.