0 30 70 69 v 1 1 7 Ju l 2 00 3 Relativistic nuclear model with point - couplings constrained by QCD and chiral symmetry ⋆

We derive a microscopic relativistic point-coupling model of nuclear many-body dynamics constrained by in-medium QCD sum rules and chiral symmetry. The effective Lagrangian is characterized by density dependent coupling strengths, determined by chiral oneand two-pion exchange and by QCD sum rule constraints for the large isoscalar nucleon self-energies that arise through changes of the quark condensate and the quark density at finite baryon density. This approach is tested in the analysis of the equations of state for symmetric and asymmetric nuclear matter, and of bulk and single-nucleon properties of finite nuclei. In comparison with purely phenomenological mean-field approaches, the built-in QCD constraints and the explicit treatment of pion exchange drastically reduce the freedom in adjusting parameters and functional forms of density dependent couplings. It is shown that nuclear binding and saturation are almost completely generated by chiral (two-pion exchange) fluctuations, 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. The results achieved are at a level of accuracy comparable to the best phenomenological relativistic mean-field calculations.