The $U_A(1)$ Problem on the Lattice
arXiv:hep-lat/0110036 · doi:10.1016/S0920-5632(01)01910-7
Abstract
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.
3 pages, talk presented by G.C. Rossi at Lattice2001(theorydevelop)