Constraining the nuclear equation of state at subsaturation densities

TL;DR

This paper investigates how nuclear observables like giant monopole resonance measurements constrain the nuclear equation of state at densities below saturation, providing more accurate estimates of nuclear matter properties.

Contribution

It demonstrates that nuclear observables constrain the EOS around the crossing density rather than saturation density, refining estimates of key nuclear matter parameters.

Findings

GMR measurements constrain the third derivative M to 1110 ± 70 MeV.

Extrapolation yields incompressibility K∞ = 230 ± 40 MeV.

EOS quantities cross at a density near 0.11 fm⁻³, below saturation.

Abstract

Only one third of the nucleons in $^{208}$Pb occupy the saturation density area. Consequently nuclear observables related to average properties of nuclei, such as masses or radii, constrain the equation of state (EOS) not at saturation density but rather around the so-called crossing density, localised close to the mean value of the density of nuclei: $\rho\simeq$0.11 fm$^{-3}$. This provides an explanation for the empirical fact that several EOS quantities calculated with various functionals cross at a density significantly lower than the saturation one. The third derivative M of the energy at the crossing density is constrained by the giant monopole resonance (GMR) measurements in an isotopic chain rather than the incompressibility at saturation density. The GMR measurements provide M=1110 $\pm$ 70 MeV (6% uncertainty), whose extrapolation gives K$_\infty$=230 $\pm$ 40 MeV (17% uncertainty).