We discuss the usage of continuous external momenta for computing renormalization factors as needed to renormalize operator matrix elements. These kind of external momenta are encoded in special boundary conditions for the fermion fields. The method allows to compute certain renormalization factors on the lattice that would have been very difficult, if not impossible, to compute with standard methods. As a result we give the renormalization group invariant step scaling function for a twist-2 operator corresponding to the average momentum of non-singlet quark densities.
@article{arxiv.hep-lat/0303012,
title = {Continuous external momenta in non-perturbative lattice simulations: a computation of renormalization factors},
author = {M. Guagnelli and K. Jansen and F. Palombi and R. Petronzio and A. Shindler and I. Wetzorke},
journal= {arXiv preprint arXiv:hep-lat/0303012},
year = {2008}
}