Modelling the Quark Determinant in Full QCD Simulations

The computational requirements and dynamics of Monte Carlo simulations of unquenched QCD incorporating the infrared quark eigenmodes (up to $\approx \Lambda_{QCD}$) exactly and UV modes via a loop representation are discussed. The accuracy of such a loop representation is studied for a variety of lattice volumes and quark masses. The method has been successfully applied for lattices up to 10$^3$x20 at $a \simeq$0.17F with improved (clover) action, and allows simulations at or near kappa critical.