Collective modes in relativistic cold asymmetric nuclear matter within the covariant Vlasov approach

TL;DR

This paper investigates collective excitations in relativistic asymmetric nuclear matter using a covariant Vlasov approach, analyzing how different nuclear models influence mode propagation and coupling to electron plasmons.

Contribution

It applies a covariant relativistic Vlasov framework to study collective modes in asymmetric nuclear matter across various models and densities, highlighting the impact of the equation of state and symmetry energy.

Findings

Propagation of modes depends on the density dependence of the nuclear matter equation of state.

Stiffer equations favor isoscalar mode propagation at high densities.

Symmetry energy stiffness influences isovector mode behavior below twice saturation density.

Abstract

A covariant relativistic approach based on the Vlasov equation is applied to the study of infinite asymmetric nuclear matter. We use several Walecka-type hadronic models and obtain the dispersion relations for the longitudinal modes. The isovector and isoscalar collective modes are determined for a wide range of densities as a function of isospin asymmetry and momentum transfer within a set of eleven relativistic mean field models with different nuclear matter properties. Special attention is given to beta-equilibrium matter. It is shown that the possible propagation of isoscalar and isovector-like modes depends directly on the density dependence of the symmetric nuclear matter equation of state and of the symmetry energy, with a stiff equation of state favouring the propagation of isoscalar like collective modes at high densities, and a stiff symmetry energy defining the behavior of the isovector like modes which propagate for densities below two times saturation density. The coupling of the nuclear modes to the electron plasmon is also discussed.