Coupling constant and quark-loop expansion for corrections to the valence approximation - art. no. 094508

For full QCD vacuum expectation values we construct an expansion in quark-l oop count and in powers of a coupling constant. The leading term in this ex pansion is the valence (quenched) approximation vacuum expectation value. H igher terms give corrections to the valence approximation. A test of the ex pansion is presented for moderately heavy quarks on a small lattice. We con sider briefly an application of the expansion to quarkonium-glueball mixing . [S0556-2821(99)07209-4].