Neutron matter from local chiral effective field theory interactions at large cutoffs

TL;DR

This paper uses large-cutoff local chiral EFT interactions in quantum Monte Carlo calculations to improve the precision of neutron matter equations of state, reducing uncertainties in neutron-star radius predictions.

Contribution

It introduces high-cutoff local chiral EFT interactions for neutron matter, decreasing regulator artifacts and uncertainties in neutron-star property calculations.

Findings

Regulator artifacts decrease with increasing cutoff.

Uncertainty in neutron-star radius predictions is reduced by up to 30%.

Improved neutron matter EOS constrains neutron-star properties.

Abstract

Neutron matter is an important many-body system that provides valuable constraints for the equation of state (EOS) of neutron stars. Neutron-matter calculations employing chiral effective field theory (EFT) interactions have been extensively used for this purpose. Among the various many-body methods, quantum Monte Carlo (QMC) methods stand out due to their nonperturbative nature and the achievable precision. However, QMC methods require local interactions as input, which leads to the appearance of stronger regulator artifacts compared to non-local interactions. To circumvent this, we employ large-cutoff interactions derived within chiral EFT ($400 \mev \leq \Lambda_c \leq 700 \mev$) for studies of pure neutron matter. These interactions have been adjusted to nucleon-nucleon scattering phase shifts, the triton binding energy, as well as the triton $\beta$-decay half-life. We find that regulator artifacts significantly decrease with increasing cutoff, leading to a significant reduction of uncertainties in the neutron-matter EOS. We discuss implications for the symmetry energy and demonstrate how our new calculations lead to a reduction in the theoretical uncertainty of predicted neutron-star radii by up to 30\% for low-mass stars.