Parton distributions from an operator viewpoint

Spin-dependent quark and gluon distribution functions are derived in terms of light-cone correlation functions. The first moment of the gluon asymmetry Δg is shown to be related to the Chern-Simons current ${\mathit{K}}^{\mathrm{\mu }}$. Renormalization and factorization ambiguities and their implication for the ${\mathit{g}}_1$ problem are discussed.