If the expression of the topological charge density operator, suggested by fermions obeying the Ginsparg--Wilson relation, is employed, it is possible to prove on the lattice the validity of the Witten--Veneziano formula for the η′ mass. Recent numerical results from simulations with overlap fermions in 2 (abelian Schwinger model) and 4 (QCD) dimensions give values for the mass of the lightest pseudo-scalar flavour-singlet state that agree with theoretical expectations and/or experimental data.
@article{arxiv.hep-lat/0110036,
title = {The $U_A(1)$ Problem on the Lattice},
author = {L. Giusti and G. C. Rossi and M. Testa and G. Veneziano},
journal= {arXiv preprint arXiv:hep-lat/0110036},
year = {2016}
}
Comments
3 pages, talk presented by G.C. Rossi at Lattice2001(theorydevelop)