Flavor-singlet axial charge of the nucleon and anomalous Ward identity

A Goldberger-Treiman relation is derived for the flavor singlet gA0 using the same approach which resolves the U(1) problem. We show that there are two components which are identified as the valence quark and vacuum-polarization contributions. They also reflect the two different ways that an η' couples to the nucleon. It is shown that the relation has the expected chiral, non-relativistic, and large Nc limits. (orig.)