Infrared singularities in the null-plane bound-state equation when going to 1+1 dimensions
Abstract
In this paper we first consider the null-plane bound-state equation for a q q pair in 1+3 dimensions and in the lowest-order Tamm-Dancoff approximation. Light-cone gauge is chosen with a causal prescription for the gauge pole in the propagator. Then we show that this equation, when dimensionally reduced to 1+1 dimensions, becomes 't Hooft's bound-state equation, which is characterized by an x+-instantaneous interaction. The deep reasons for this coincidence are carefully discussed.
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