Correlations between Quarks, Monopoles and Instantons

We analyze topological objects in pure QCD in the presence of external quarks by calculating the distributions of instanton and monopole densities around static color sources. We find a suppression of the densities close to external sources and the formation of a flux tube between a static quark--antiquark pair. The similarity in the behavior of instantons and monopoles around static sources might be due to a local correlation between these topological objects. On an $8^{3} \times 4$ lattice at $\beta=5.6$, it turns out that topological quantities are correlated approximately two lattice spacings.