QCD in a finite box: Numerical test studies in the three Leutwyler-Smilga regimes

The Leutwyler-Smilga prediction regarding the (ir)relevance of the global topological charge for QCD in a finite box is subject to a test. To this end the lattice version of a suitably chosen analogue (massive 2-flavour Schwinger model) is analyzed in the small ($V\Sigma m \ll 1$), intermediate ($V\Sigma m \simeq 1$) and large ($V\Sigma m \gg 1$) Leutwyler-Smilga regimes. The predictions for the small and large regimes are confirmed and illustrated. New results about the role of the functional determinant in all three regimes and about the sensitivity of physical observables on the topological charge in the intermediate regime are presented.