From closed shells to open shells: Coupled-cluster calculations of atomic nuclei

TL;DR

This paper compares various coupled-cluster methods for calculating properties of open-shell atomic nuclei, demonstrating their effectiveness across calcium and nickel isotopes using chiral effective field theory interactions.

Contribution

It provides a comprehensive comparison of coupled-cluster formulations for open-shell nuclei, highlighting their consistency in predicting nuclear properties.

Findings

Different coupled-cluster methods give consistent results for bulk nuclear properties.

The methods accurately predict ground-state energies, two-neutron separation energies, and shell gaps.

Extensions to open-shell nuclei are effective across medium-mass isotopic chains.

Abstract

Coupled-cluster theory is a powerful tool for first-principles calculations of atomic nuclei, enabling accurate predictions of nuclear observables across the Segr\`e chart. While coupled-cluster computations are especially efficient at shell closures, extensions have been developed to tackle open-shell nuclei, by exploiting the equation-of-motion method or by expanding the coupled-cluster wave function on top of a symmetry-breaking (either deformed or superfluid) reference state. In this study, we provide a comprehensive comparison of these different formulations applied to the calcium and nickel isotopes using nuclear two- and three-body interactions from chiral effective field theory. Based on ground-state energies, two-neutron separation energies, and two-neutron shell gaps, different coupled-cluster computations - based on symmetry-broken reference states and equation-of-motion techniques - offer consistent descriptions of bulk properties across medium-mass isotopic chains.