Quantum Electrodynamics in the Infinite-Momentum Frame

We examine the formal foundations of quantum electrodynamics in the infinite-momentum frame. We interpret the infinite-momentum limit as the change of variables τ=2^-1/1(t+z), Z=2^-1/1(t-z), thus avoiding limiting procedures. Starting from the Feynman rules, we derive a τ-ordered perturbation expansion for the S matrix. We then show how this expansion arises from a canonical formulation of the field theory in the infinite-momentum frame. We feel that this approach should lead to convenient approximation schemes for electrodynamics at high energy.