Pions in Lattice QCD with the Overlap Fermions at Strong Gauge Coupling

Abstract

In the previous paper we developed a strong-coupling expansion for the lattice QCD with the overlap fermions and showed that L\"usher's "extended" chiral symmetry is spontaneously broken in some parameter region of the overlap fermions. In this paper, we obtain a low-energy effective action and show that there exist quasi-Nambu-Goldsone bosons which are identified as the pions. The pion field is a {\em nonlocal} composite field of quark and anti-quark even at the strong-coupling limit because of the nonlocality of the overlap fermion formalism and L\"usher's chiral symmetry. The pions become massless in the limit of the vanishing bare-quark mass as it is desired.