PUB - Publikationen an der Universität Bielefeld

The nucleon self-energy and its relation to the nucleon axial charge gA arediscussed at large Nc. The energy is compared for the hedgehog, conventional,and recently proposed dichotomous nucleon wavefunctions which give differentvalues for gA. We consider their energies at both perturbative andnon-perturbative levels. In perturbative estimates, we take into account thepion exchanges among quarks up to the third orders of axial charge vertices,including the many-body forces such as the Wess-Zumino terms. It turns out thatthe perturbative pion exchanges among valence quarks give the same leading Nccontributions for three wavefunctions, while their mass differences areO(Lamba_qcd). The signs of splittings flip for different orders of the axialcharge vertices, so it is hard to conclude which one is the most energeticallyfavored. For non-perturbative estimates involving the modification of quarkbases, we use the chiral quark soliton model as an illustration. With thehedgehog quark wavefunctions with gA of O(Nc), we investigate whether solutionswith coherent pions are energetically favored. Again it is hard to givedecisive conclusions, but it is likely that adding the confining effectsdisfavors the solution with the coherent pions, making a pion cloud around anucleon quantum rather than coherent. The nuclear matter at large Nc is alsodiscussed in light of the value of gA.