A Time Dependent Local Isospin Density Approximation Study of Asymmetric Nuclear Matter

TL;DR

This paper investigates the dynamic response of asymmetric nuclear matter using a time-dependent density approximation based on a functional derived from Monte Carlo calculations, revealing various excited states and instabilities.

Contribution

It introduces a novel TDLIDA approach with a density functional from AFDMC calculations to analyze asymmetric nuclear matter's excitations and stability.

Findings

Identification of collective, quasi-particle, and unstable states.

Derivation of an analytical compressibility expression.

Discovery of neutron matter instability at specific densities.

Abstract

The dynamic response of asymmetric nuclear matter is studied by using a Time-Dependent Local Isospin Density (TDLIDA) approximation approach. Calculations are based on a local density energy functional derived by an Auxiliary Field Diffusion Monte Carlo (AFDMC) calculation of bulk nuclear matter. Three types of excited states emerge: collective states, a continuum of quasi-particle-quasi-hole excitations and unstable solutions. These states are analyzed and discussed for different values of the nuclear density $\rho$ and isospin asymmetry $\xi=(N-Z)/A$. An analytical expression of the compressibility as a function of $\rho$ and $\xi$ is derived which show explicitly an instability of the neutron matter around $\rho\simeq 0.09 fm^{-3}$ when a small fraction of protons is added to the system.