A quantum field theoretic treatment of the leading light-cone part of the
virtual Compton amplitude is presented. The twist-decomposition of the
operators is performed by a group-theoretic procedure respecting the Lorentz
group O(3,1). The twist-2 contributions to the Compton amplitude are calculated
and it is shown that the electromagnetic current is conserved for these terms.
Relations between the amplitude functions associated to the symmetric and
asymmetric part of the Compton amplitude are derived. These relations
generalize the Callan-Gross and Wandzura-Wilczek relations of forward
scattering for the non-forward Compton amplitude.Comment: 7 pages LATEX, 1 style file, DESY 00-045, Contribution to the
Proceedings of `Loops and Legs in Quantum Field Theory', Bastei, Germany,
April 2000, Nucl. Phys. B (Proc. Suppl.) (2000) to appea
