Tests of Light-Cone Commutators: Fixed-Mass Sum Rules

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Abstract
By use of light-cone commutators, corrected versions of six infinite-momentum sum rules are derived. The light-cone commutators are given by bilocal operators whose matrix elements are shown to be Fourier transforms of deep-inelastic-scattering structure functions. A modification of the Bég sum rule is found, and a sum rule for the axial-vector coupling constant in terms of a nucleon (spin-flip) structure function is presented. The latter is related to an old result of Bjorken. We deal with the full spin-dependent forward Compton amplitude and discuss in detail the form-factor decomposition of the bilocal operators which give the fermion-quark-model light-cone commutators. The model dependence of the present results is discussed, and boson-model commutators are given for comparison.