Application of an effective gauge-invariant model to nuclear matter in the relativistic Hartree-Fock approximation

An effective nuclear model describing ω-, ρ- and axial-mesons as gauge fields is applied to nuclear matter in the relativistic Hartree-Fock approximation. The isoscalar two-pion exchange is simulated by a scalar field s similar to that used in the conventional relativistic mean-field approach. Two more scalar fields are essential ingredients of the present treatment: the σ-field, the chiral partner of the pion, and the Σ-field, the Higgs field for the ω-meson. Two versions of the model are used depending on whether the σ-field is considered as a dynamical variable or 'frozen', by taking its mass as infinite. The model contains four free parameters in the first case and three in the second one which are fitted to the nuclear matter saturation conditions. The nucleon and meson effective masses, compressibility modulus and symmetry energy are calculated. The results prove the reliability of the Dirac-Hartree-Fock approach within the linear realization of the chiral symmetry. (author)