2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/192689The effects of unquenching on the perturbative improvement coefficients in the Symanzik action are computed within the framework of Lüscher-Weisz on-shell improvement. We find that the effects of quark loops are surprisingly large, and their omission may well explain the scaling violations observed in some unquenched studies.7 pages, 5 figures, uses revtex4; version to appear in Phys.Rev.DHigh Energy Physics - Latticetext