Neutron matter from chiral effective field theory interactions

TLDR

The neutron‑matter equation of state, which spans a wide density range, can be systematically studied with chiral EFT, where all many‑body forces among neutrons are predicted to next‑to‑next‑to‑next‑to‑leading order (N³LO). The study presents the first complete N³LO calculation of neutron‑matter energy—including subleading three‑nucleon and leading four‑nucleon forces—and discusses its astrophysical implications for the supernova equation of state, symmetry energy, and neutron‑star structure. The calculation employs chiral EFT at N³LO, incorporating subleading three‑nucleon and leading four‑nucleon forces to compute the neutron‑matter energy with quantified theoretical uncertainties. The results estimate that N³LO many‑body contributions to symmetric nuclear matter energy are sizable, underscoring their importance for nuclear‑structure calculations.

Abstract

The neutron-matter equation of state constrains the properties of many physical systems over a wide density range and can be studied systematically using chiral effective field theory (EFT). In chiral EFT, all many-body forces among neutrons are predicted to next-to-next-to-next-to-leading order (N${}^{3}$LO). We present details and additional results of the first complete N${}^{3}$LO calculation of the neutron-matter energy, which includes the subleading three-nucleon as well as the leading four-nucleon forces, and provides theoretical uncertainties. In addition, we discuss the impact of our results for astrophysics: for the supernova equation of state, the symmetry energy and its density derivative, and for the structure of neutron stars. Finally, we give a first estimate for the size of the N${}^{3}$LO many-body contributions to the energy of symmetric nuclear matter, which shows that their inclusion will be important in nuclear structure calculations.