Spatial correlation of the topological charge in pure SU(3) gauge theory and in QCD

We study the spatial correlator of the topological charge density operator in pure SU(3) gauge theory and in two flavor QCD. We show that the data for distances up to about 1 fm is consistent with a vacuum consisting of individual instantons and closely bound pairs. The percentage of paired objects is twice as large on the dynamical configurations than on the pure gauge ones, implying increased molecule formations due to fermionic interactions.