Hartree-Fock Many-Body Perturbation Theory for Nuclear Ground-States

TL;DR

This paper studies the convergence of many-body perturbation theory for nuclear ground-states, showing that third-order MBPT with a Hartree-Fock basis yields accurate energies comparable to coupled-cluster methods at lower computational cost.

Contribution

It demonstrates that third-order MBPT with a Hartree-Fock basis is an efficient and accurate method for calculating nuclear ground-state energies, extending to heavy nuclei like tin.

Findings

Third-order MBPT agrees well with coupled-cluster results.

Convergence is improved using a Hartree-Fock basis.

MBPT provides a computationally cheaper alternative for heavy nuclei.

Abstract

We investigate the order-by-order convergence behavior of many-body perturbation theory (MBPT) as a simple and efficient tool to approximate the ground-state energy of closed-shell nuclei. To address the convergence properties directly, we explore perturbative corrections up to 30th order and highlight the role of the partitioning for convergence. The use of a simple Hartree-Fock solution to construct the unperturbed basis leads to a convergent MBPT series for soft interactions, in contrast to, e.g., a harmonic oscillator basis. For larger model spaces and heavier nuclei, where a direct high-order MBPT calculation in not feasible, we perform third-order calculation and compare to advanced ab initio coupled-cluster calculations for the same interactions and model spaces. We demonstrate that third-order MBPT provides ground-state energies for nuclei up into tin isotopic chain that are in excellent agreement with the best available coupled-cluster results at a fraction of the computational cost.