Gross-Neveu model with overlap fermions

Abstract

We investigate the chiral properties of overlap lattice fermion by using two dimensional Gross-Neveu model coupled with a gauge field. Chiral properties of this model are similar to those of QCD$_4$, that is, the chiral symmetry is spontaneously broken in the presence of small but finite fermion mass and also there appears the chiral anomaly because of the coupling with the gauge field. In order to respect Lüscher's extended chiral symmetry we insert overlap Dirac operator even in the interaction terms so that the whole action including them are invariant under the extended chiral transformation at {\em finite lattice spacing}, though the interaction terms become nonlocal. We calculate mass of the quasi-Nambu-Goldstone boson as a function of the bare fermion mass and two parameters in the overlap formalism, and find that the quasi-Nambu-Goldstone boson has desired properties as a result of the extended chiral symmetry. We furthermore examine the PCAC relation and find that it is satisfied at {\em finite lattice spacing}. Relationship between the anomaly term in the PCAC relation and the U(1) problem is also discussed.