# Benchmark calculations of pure neutron matter with realistic nucleon-nucleon interactions

## TL;DR

This paper presents benchmark calculations of pure neutron matter energy using three advanced many-body methods and various realistic nucleon-nucleon potentials, showing improved agreement and reduced uncertainties.

## Contribution

It provides the first comprehensive benchmark comparison of neutron matter energies with multiple methods and modern potentials, including technical improvements in the methods.

## Key findings

- Methods show some divergence at higher densities but with improved agreement.
- Potentials fitted to higher-energy scattering data yield smaller energy spread.
- Results enhance understanding of neutron matter properties with realistic interactions.

## Abstract

We report benchmark calculations of the energy per particle of pure neutron matter as a function of the baryon density using three independent many-body methods: Brueckner-Bethe-Goldstone, Fermi hypernetted chain/single-operator chain, and auxiliary-field diffusion Monte Carlo. Significant technical improvements are implemented in the latter two methods. The calculations are made for two distinct families of realistic coordinate-space nucleon-nucleon potentials fit to scattering data, including the standard Argonne $v_{18}$ interaction and two of its simplified versions, and four of the new Norfolk $\Delta$-full chiral effective field theory potentials. The results up to twice nuclear matter saturation density show some divergence among the methods, but improved agreement compared to earlier work. We find that the potentials fit to higher-energy nucleon-nucleon scattering data exhibit a much smaller spread of energies.