\texttt{NuHamil}: A numerical code to generate nuclear two- and three-body matrix elements from chiral effective field theory

TL;DR

NuHamil is a modern Fortran code that efficiently generates nuclear two- and three-body matrix elements from chiral effective field theory, facilitating ab initio nuclear structure calculations.

Contribution

The paper introduces NuHamil, a new numerical tool that simplifies and accelerates the generation of nuclear interaction matrix elements for many-body calculations.

Findings

Successfully generates NN and 3N matrix elements in a harmonic-oscillator basis.

Enables calculations of ground-state energies for doubly closed shell nuclei.

Utilizes hybrid parallelization for efficient computation.

Abstract

The applicability of nuclear {\it ab initio} calculations has rapidly extended over the past decades. However, starting research projects is still challenging due to the required numerical expertise in the generation of underlying nuclear interaction matrix elements and many-body calculations. To ease the first issue, in this paper we introduce the numerical code \texttt{NuHamil} to generate the nucleon-nucleon (NN) and three-nucleon (3N) matrix elements expressed in a spherical harmonic-oscillator basis, inputs of many-body calculations. The ground-state energies for the selected doubly closed shell nuclei are calculated with the no-core shell-model (NCSM) and in-medium similarity renormalization group (IMSRG). The code is written in modern Fortran, and OpenMP+MPI hybrid parallelization is available for the 3N matrix-element calculations.