Deep inelastic processes and the equations of motion

We show that the Politzer theorem on the equations of motion implies approximate constraints on the quark correlator. These, in turn, restrict considerably, for sufficiently large Q 2 , the number of independent distribution functions that characterize the internal structure of the nucleon, and of independent fragmentation functions. This result leads us to suggesting an alternative method for determining transversity. Moreover, our approach implies predictions on the Q 2 -dependence of some azimuthal asymmetries, like Sivers, Qiu-Sterman and Collins asymmetry. Lastly, we discuss some implications on the Burkhardt-Cottingham sum rule.