Fluctuating parts of nuclear ground state correlation energies

TL;DR

This paper examines how higher order correlation effects influence nuclear binding energies, using Skyrme interactions and advanced many-body methods to analyze fluctuations and improve nuclear models.

Contribution

It introduces a method to evaluate fluctuation parts of correlation energies in nuclei and investigates their impact using QRPA and MBPT2 with a cut-off scheme.

Findings

Correlation energy fluctuations vary across isotopic chains.

Higher order effects can be explicitly summed with the improved interaction.

Refitting interaction parameters is necessary for quantitative accuracy.

Abstract

Background: Heavy atomic nuclei are often described using the Hartree-Fock-Bogoliubov (HFB) method. In principle, this approach takes into account Pauli effects and pairing correlations while other correlation effects are mimicked through the use of effective density-dependent interactions. Purpose: Investigate the influence of higher order correlation effects on nuclear binding energies using Skyrme's effective interaction. Methods: A cut-off in relative momenta is introduced in order to remove ultraviolet divergences caused by the zero-range character of the interaction. Corrections to binding energies are then calculated using the quasiparticle-random-phase approximation (QRPA) and second order many-body perturbation theory (MBPT2). Result: Contributions to the correlation energies are evaluated for several isotopic chains and an attempt is made to disentangle which parts give rise to fluctuations that may be difficult to incorporate on the HFB level. The dependence of the results on the cut-off is also investigated. Conclusions: The improved interaction allows explicit summations of perturbation series which is useful for the description of some nuclear observables. However, refits of the interaction parameters are needed to obtain more quantitative results.