3 Exploring the Nucleus in the Context of Low-Energy QCD

Abstract

These lecture notes address a central problem of theoretical nuclear physics: how to establish a relationship between low-energy, non-perturbative QCD and nuclear phenomenology which includes both nuclear matter and finite nuclei. We develop a microscopic covariant description of nuclear many-body dynamics constrained by chiral symmetry and in-medium QCD sum rules. A relativistic point-coupling model is derived, based on an effective Lagrangian with density-dependent contact interactions between nucleons. These interactions are constructed from chiral one- and two-pion exchange, combined with the large isoscalar nucleon self-energies that arise through changes in the quark condensate and the quark density at finite baryon density. Nuclear binding and saturation are almost completely generated by chiral (two-pion exchange) fluctuations in combination with Pauli effects, whereas strong scalar and vector fields of about equal magnitude and opposite sign, induced by changes of the QCD vacuum in the presence of baryonic matter, generate the large effective spin-orbit potential in finite nuclei. Promising results are found for the nuclear matter equation of state and for the bulk and single-nucleon properties of finite nuclei.