Constraints on the Quark Correlation Matrix from Equations of Motion

We show that the Politzer theorem on the equations of motion implies strong constraints on the quark correlation matrix, restricting the number of independent distribution functions that characterize the internal structure of the nucleon. Then we draw some important consequences from this result. First of all, we suggest an alternative method for determining transversity. Secondly, we predict the Q^2-dependence of some azimuthal asymmetries. Lastly, we illustrate the origin of the main contributions to some twist-3 distribution functions.