Gauge fields on the null plane

The theory of gauge fields interacting with fermions is quantized on the null plane. The singularities of the gauge field propagator are related to the infrared divergences of the theory and cancel in the gauge-invariant sector. Ultraviolet divergences are due only to the high-transverse-momentum behavior and in the gauge-invariant sector are eliminated by coupling-constant renormalization. Equivalence to the covariant-gauge formulation is proved by explicitly performing the gauge transformation. Gauge-invariant ultraviolet and infrared cutoffs which preserve unitarity are used wherever necessary. Gauge-variant amplitudes are infrared divergent and non-Lorentz-invariant.