Asymmetric nuclear matter: The role of the isovector scalar channel

TLDR

The study aims to isolate qualitative effects of minimally coupling a δ‑isovector‑scalar meson in a phenomenological hadronic field theory. The authors introduce the δ coupling consistently within a relativistic hadronic framework, emphasizing its minimal implementation and theoretical consistency. Results show that adding a δ‑isovector‑scalar meson modifies the equation of state and symmetry energy of asymmetric nuclear matter, producing a more repulsive neutron‑matter EOS at high densities, altering the slope and curvature of the symmetry energy, affecting effective mass splitting, critical properties, and isospin distillation, with largely analytical insights that impact drip‑line nuclei and reactions with radioactive beams.

Abstract

We try to single out some qualitative effects of coupling to a \ensuremath{\delta}-isovector-scalar meson, introduced in a minimal way in a phenomenological hadronic field theory. Results for the equation of state (EOS) and the phase diagram of asymmetric nuclear matter (ANM) are discussed. We stress the consistency of the \ensuremath{\delta}-coupling introduction in a relativistic approach. Contributions to the slope and curvature of the symmetry energy and to the neutron-proton effective mass splitting appear particularly interesting. A more repulsive EOS for neutron matter at high baryon densities is expected. Effects on the critical properties of warm ANM, mixing mechanical and chemical instabilities and isospin distillation, are also presented. The \ensuremath{\delta} influence is mostly on the isovectorlike collective response. The results are largely analytical, and this makes the physical meaning quite transparent. Implications for nuclear structure properties of drip-line nuclei and for reaction dynamics with radioactive beams are finally pointed out.