Why is the nuclear symmetry energy so uncertain at supra-saturation densities?

TL;DR

This paper investigates the causes of large uncertainties in the nuclear symmetry energy at densities above nuclear saturation, focusing on in-medium interactions and short-range forces within an interacting Fermi gas model.

Contribution

It provides a transparent analysis of how three-body interactions, tensor forces, and nucleon correlations influence the high-density behavior of the symmetry energy.

Findings

In-medium three-body interactions significantly affect symmetry energy.

Short-range tensor forces due to rho meson exchange impact high-density behavior.

Nucleon correlations contribute to the uncertainty in symmetry energy at supra-saturation densities.

Abstract

Within the interacting Fermi gas model for isospin asymmetric nuclear matter, effects of the in-medium three-body interaction and the two-body short-range tensor force due to the $\rho$ meson exchange as well as the short-range nucleon correlation on the high-density behavior of the nuclear symmetry energy are demonstrated respectively in a transparent way. Possible physics origins of the extremely uncertain nuclear symmetry energy at supra-saturation densities are discussed.