P. Bernardos

On the sufficient conditions for the pseudospin symmetry in relativistic models

Abstract The reliability of the sufficient conditions for the pseudospin symmetry proposed for atomic nuclei has been analyzed, at a quantitative level, in the framework of the relativistic Hartree approximation (some effects of the exchange terms are also investigated). The contribution to the single-particle energy of the different terms appearing in the equation for the small component F of the Dirac spinor is calculated for the neutron pseudospin doublet states in the 40Ca and 208Pb nuclei. The F wave function is numerically calculated for the hypothetical case in which the symmetry is supposed to be exact.

Magnetic properties of strongly asymmetric nuclear matter in a Dirac-Hartree-Fock approach

Abstract The magnetic susceptibility of strongly asymmetric nuclear matter, at relevant densities in neutron stars, is studied in the framework of a relativistic σ + ω + π + ϱ Hartree-Fock approach. The presence of protons, through their interaction with neutrons, means that formation of spontaneous magnetized matter occurs at lower densities than in pure neutron matter. A possible ferromagnetic transition is predicted at about four times the nuclear matter saturation density.

On the relativistic origin of the kink effect in the chain of Pb isotopes

Abstract We investigate the origin of the kink effect (KE) in the relativistic mean field theory by transforming the single-particle Dirac equation into a Schrodinger-like equation. It is found that relativistic self-consistent effects as well as contributions coming from the ρ meson determine the actual structure of the KE. However, the spin–orbit force generated by the ρ meson has no significant influence on the KE.

A density-dependent effective interaction for relativistic Hartree-Fock calculations

Abstract We present a general method to derive density-dependent effective interactions to be used in the relativistic Hartree-Fock approximation. In the non-relativistic limit (i.e. at low density), this method is identical to the usual variational ansatz with a two-body correlation function whose range is used as a variational parameter. At normal nuclear matter density, it provides a useful prescription to fit relativistic Brueckner-Hartree-Fock calculations. It provides in particular a physical way to deal with the zero-range pieces of π and ϱ interactions in the medium. We apply our method to infinite symmetric nuclear matter. This effective interaction is also particularly well suited for calculations in finite nuclei.

Investigation of a chiral model in a relativistic Hartree - Fock approximation to asymmetric nuclear matter

A relativistic HF approximation is developed for a globally chiral invariant model including mesons and the axial meson a. Some bulk properties of asymmetric nuclear matter are investigated in this framework and compared with the approximate version of the model where the axial meson is omitted and the meson is taken into account in a conventional way.

The Pseudospin Symmetry in Finite Nuclei: Dirac Phenomenology

In the framework of the Dirac phenomenology it is shown that the pseudo-spin symmetry breaking term is not perturbative. The self-consistent effects are important for generating the total pseudo spin-orbit splitting (PSOS). The total PSOS is determined by the general structure of the Dirac equation through a delicate compensation of different contributions to the single-particle energy.

NUCLEAR MATTER CALCULATIONS WITH A PSEUDOSCALAR-PSEUDOVECTOR CHIRAL MODEL

A mixed pseudoscalar-pseudovector N coupling relativistic Lagrangian is obtained from a pure pseudoscalar chiral one, by transforming the nucleon field according to a generalized Weinberg transformation, which depends on a mixing parameter. The interaction is generated by the , and meson exchanges. Within the Hartree-Fock context, pion polarization effects, including the isobar, are considered in the random phase approximation in nuclear matter. These effects are interpreted, in a non-relativistic framework, as a modification of the range and intensity of a Yukawa-type potential by means of a simple function which takes into account the nucleon-hole and -hole excitations. Results show stability of relativistic nuclear matter against pion condensation. Compression modulus is diminished by the combined effects of the nucleon and polarization towards the usually accepted experimental values. The N interaction strength used in this paper is less than the conventional one to ensure the viability of the model. The fitting parameters of the model are the scalar meson mass and the -N coupling constant .