Symmetry Relations for Deep-Inelastic Processes

Relations between structure functions conventionally obtained from quark-parton or light-cone models are shown to follow from model-independent symmetry assumptions common in hadron scattering. Exotic $t$-channel exchanges are forbidden. No strong-interaction symmetry beyond isospin is assumed, and SU(3) is used only for vertices involving currents. Relations originally derived for nucleon targets hold for any isospin mirror pair and apply to complex targets appearing in the Mueller formalism for inclusive processes in the target fragmentation region. New relations are derived.