Testing the density matrix expansion against ab initio calculations of trapped neutron drops

TL;DR

This paper evaluates various density matrix expansion strategies for neutron drops in harmonic traps by comparing them to Hartree-Fock and ab initio calculations, highlighting improvements with a new DME implementation.

Contribution

The study introduces a new DME approach with exact Hartree treatment and demonstrates its effectiveness in matching ab initio results for neutron drops.

Findings

New DME with exact Hartree best reproduces HF results.

Supplementing DME with Skyrme-like contact terms improves agreement with NCFC.

Systematic comparison of DME strategies against ab initio calculations.

Abstract

Microscopic input to a universal nuclear energy density functional can be provided through the density matrix expansion (DME), which has recently been revived and improved. Several DME implementation strategies are tested for neutron drop systems in harmonic traps by comparing to Hartree-Fock (HF) and ab initio no-core full configuration (NCFC) calculations with a model interaction (Minnesota potential). The new DME with exact treatment of Hartree contributions is found to best reproduce HF results and supplementing the functional with fit Skyrme-like contact terms shows systematic improvement toward the full NCFC results.