Low fermionic eigenmode dominance in QCD on the lattice

The utility of a spectral approximation to the quark propagator will be demonstrated, using low-lying eigenmodes of the hermitian Wilson-Dirac matrix, Q = γ 5 M . The investigation is based on a total of 400 full QCD vacuum configurations, with two degenerate flavors of dynamical Wilson fermions at β = 5 .6, at two different sea quark masses. The spectral approach is successful in accessing both the topological charge and disconnected diagrams, as they appear in the η' correlation function. A suitable partial summation technique is proposed that provides sufficient saturation for Tr Q -1 , which is a quantity directly related to the topological charge. In the effective mass plot of the η' meson a consistent early plateau formation is achieved, by ground state projecting the connected piece of the propagator.