We derive the two-point spectral correlation function of the Dirac operator with a specific external source in the ϵ-regime of QCD. This correlation function has a unique and strong dependence on Fπ, and thus provides an novel way to extract Fπ from lattice simulations. We test the method in a quenched lattice simulation with staggered fermions.
@article{arxiv.hep-lat/0508029,
title = {A New Method for Determining $F_\pi$ on the Lattice},
author = {P. H. Damgaard and Urs M. Heller and K. Splittorff and B. Svetitsky},
journal= {arXiv preprint arXiv:hep-lat/0508029},
year = {2009}
}