2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/204369The 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 eps figures, uses PoS.cls; talk presented at XXV International Symposium on Lattice Field Theory, July 30 - August 4 2007, Regensburg, GermanyHigh Energy Physics - Latticetext