Efficient calculation of chiral three-nucleon forces up to N3LO for ab initio studies

TL;DR

This paper introduces an efficient framework for calculating chiral three-nucleon forces in momentum space, enabling advanced ab initio nuclear studies with higher-order forces and detailed force contributions.

Contribution

A novel, computationally efficient method for decomposing three-nucleon forces in momentum space, facilitating higher-order calculations in nuclear physics.

Findings

New framework significantly reduces computational cost.

Sub-leading force terms are important for nonlocal regulators.

Matrix elements are stored in a flexible, user-friendly format.

Abstract

We present a novel framework to decompose three-nucleon forces in a momentum space partial-wave basis. The new approach is computationally much more efficient than previous methods and opens the way to ab initio studies of few-nucleon scattering processes, nuclei and nuclear matter based on higher-order chiral 3N forces. We use the new framework to calculate matrix elements of chiral three-nucleon forces at N2LO and N3LO in large basis spaces and carry out benchmark calculations for neutron matter and symmetric nuclear matter. We also study the size of the individual three-nucleon force contributions for $^3$H. For nonlocal regulators, we find that the sub-leading terms, which have been neglected in most calculations so far, provide important contributions. All matrix elements are calculated and stored in a user-friendly way, such that values of low-energy constants as well as the form of regulator functions can be chosen freely.