Connecting Relativistic Density Functional Theory to Microscopic Calculations

TL;DR

This paper explores how extending relativistic mean-field models can improve nuclear density functional theories by aligning them more closely with microscopic chiral EFT calculations, especially for properties like charge radii and neutron skins.

Contribution

It demonstrates the impact of nonlinear RMF model extensions fitted to chiral EFT predictions, highlighting improvements and limitations in describing nuclear properties.

Findings

RMF model extensions improve agreement with chiral EFT for charge radii.

Extensions capture physics of neutron skins in closed-shell nuclei.

Additional effects remain unmodeled within the current RMF framework.

Abstract

The development of systematic effective field theories (EFTs) for nuclear forces and advances in solving the nuclear many-body problem have greatly improved our understanding of dense nuclear matter and the structure of finite nuclei. For global nuclear calculations, density functional theories (DFTs) have been developed to reduce the complexity and computational cost required in describing nuclear systems. However, DFT often makes approximations and assumptions about terms included in the functional, which may introduce systematic uncertainties compared to microscopic calculations using EFTs. In this work, we investigate possible avenues of improving nuclear DFT using nonlinear relativistic mean-field (RMF) theory. We explore the impact of RMF model extensions by fitting the nonlinear RMF model to predictions of nuclear matter and selected closed-shell nuclei using four successful chiral EFT Hamiltonians. We find that these model extensions are impactful and important in capturing the physics present within chiral Hamiltonians, particularly for charge radii and neutron skins of closed-shell nuclei. However, there are additional effects that are not captured within the RMF model, particularly within the isoscalar sector of RMF theory. Additional model extensions and the reliability of the nonlinear RMF model are discussed.