Year: 1996
Type: preprint
Abstract: We discuss the evaluation of the nucleon isoscalar axial coupling, $g_A^{(0)}$, in the instanton vacuum, using the $1/N_c$ expansion. This approach allows a fully consistent treatment of the $U(1)_A$ anomaly. We compute the nucleon matrix element of the topological charge density, $\langle N | F\widetilde{F} | N \rangle$, and show that it reduces to the matrix element of the divergence of the isoscalar axial quark current. Our arguments show that the usual evaluation of $g_A^{(0)}$ in the chiral quark soliton model is consistent with the $U(1)_A$ anomaly in leading order of $1/N_c$. Such calculations give $g_A^{(0)} = 0.36$, which is in agreement with the recent estimate by Ellis and Karliner.
Source: arXiv (Cornell University)
Author: Weiss, C.
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1556089588