We study the spectral gap of the Wilson--Dirac operator in two-flavour lattice QCD as a function of the lattice spacing a, the space-time volume V and the current-quark mass m. It turns out that the median of the probability distribution of the gap scales proportionally to m and that its width is practically equal to a/V. In particular, numerical simulations are safe from accidental zero modes in the large-volume regime of QCD.
@article{arxiv.hep-lat/0512021,
title = {Stability of lattice QCD simulations and the thermodynamic limit},
author = {L. Del Debbio and L. Giusti and M. Lüscher and R. Petronzio and N. Tantalo},
journal= {arXiv preprint arXiv:hep-lat/0512021},
year = {2009}
}