Chiral Limit of Nuclear Physics

We study nuclear physics in the chiral limit ($m_u$, $m_d=0$) in which the pion mass vanishes. We find that the deuteron mass is changed little, but that P--wave nucleon--nucleon scattering volumes are infinite. This motivates an investigation of the possibilities that there could be a two--nucleon $^3P_0$ bound state, and that the nuclear matter ground state is likely to be a condensed state of nucleons paired to those quantum numbers. However, the short distance repulsion in the nucleon--nucleon potential is not affected by the chiral limit and prevents such new chiral possibilities. Thus the chiral limit physics of nuclei is very similar to that of nature. Using the chiral limit to simplify QCD sum rule calculations of nuclear matter properties seems to be a reasonable approximation.