Lorentz invariance relations between parton distributions and the Wandzura-Wilczek approximation

Abstract

The violation of the so-called Lorentz invariance relations between parton distribution functions is considered in a model independent way. It is shown that these relations are not violated in a generalized Wandzura-Wilczek approximation, indicating that numerically their violation may be small.

Comments: 13 pages, added references, minor changes, to appear in Phys. Lett. B