Neutron matter from chiral two- and three-nucleon calculations up to N$^3$LO

TL;DR

This paper advances the calculation of neutron matter's equation of state using chiral EFT up to N$^3$LO, incorporating three-nucleon forces in many-body methods to improve astrophysical models.

Contribution

First inclusion of N$^3$LO three-nucleon interactions in MBPT and SCGF for neutron matter, with systematic convergence analysis and finite-temperature extension.

Findings

Enhanced predictions for neutron matter EOS at zero temperature.

Systematic analysis of many-body convergence for different interactions.

Extension of normal-ordering to finite temperatures.

Abstract

Neutron matter is an ideal laboratory for nuclear interactions derived from chiral effective field theory since all contributions are predicted up to next-to-next-to-next-to-leading order (N$^3$LO) in the chiral expansion. By making use of recent advances in the partial-wave decomposition of three- nucleon (3N) forces, we include for the first time N$^3$LO 3N interactions in many-body perturbation theory (MBPT) up to third order and in self-consistent Green's function theory (SCGF). Using these two complementary many-body frameworks we provide improved predictions for the equation of state of neutron matter at zero temperature and also analyze systematically the many-body convergence for different chiral EFT interactions. Furthermore, we present an extension of the normal-ordering framework to finite temperatures. These developments open the way to improved calculations of neutron-rich matter including estimates of theoretical uncertainties for astrophysical applications.