Axial Correlation Functions in the epsilon-Regime: a Numerical Study with Overlap Fermions

We present simulation results employing overlap fermions for the axialcorrelation functions in the epsilon-regime of chiral perturbation theory. Inthis regime, finite size effects and topology play a dominant role. Theirdescription by quenched chiral perturbation theory is compared to our numericalresults in quenched QCD. We show that lattices with a linear extent L > 1.1 fmare necessary to interpret the numerical data obtained in distinct topologicalsectors in terms of the epsilon-expansion. Such lattices are, however, stillsubstantially smaller than the ones needed in standard chiral perturbationtheory. However, we also observe severe difficulties at very low values of thequark mass, in particular in the topologically trivial sector.Comment: 15 pages, 6 figures, final version published in JHE