2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/210997A 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.17 pages, 3 figures, new appendix, revised conclusionsNuclear Theorytext