The classical pion field in a nucleus

TL;DR

This paper explores how closed G shells in a nucleus generate a classical pion field with a hedgehog shape, significantly affecting nucleon energy levels despite a small amplitude.

Contribution

It introduces a self-consistent symmetry coupling nucleon angular momentum and isospin to produce a classical pion field in nuclei.

Findings

Closed G shells generate a hedgehog-shaped pion field.

The pion field significantly perturbs nucleon energy levels.

The pion field amplitude remains small despite its effects.

Abstract

A self-consistent symmetry arises when the nucleon angular momentum j and the isospin t are coupled to a grand spin G. Closed G shells become sources of a classical pion field with a hedgehog shape. Although the amplitude of the pion field, as measured by the chiral angle, is small, it is found to perturb significantly the energies of the nucleon orbits.