Composite operators from the operator product expansion: what can go wrong?

Abstract

The operator product expansion is used to compute the matrix elements of composite renormalized operators on the lattice. We study the product of two fundamental fields in the two-dimensional sigma-model and discuss the possible sources of systematic errors. The key problem turns out to be the violation of asymptotic scaling.

Comments: Lattice 99 (Improvement and Renormalization), 3 pages, 3 eps figures