Abstract
Background: Recent developments in ab initio nuclear theory demonstrate promising results in medium-to heavy-mass nuclei. A particular challenge for many of the many-body methodologies, however, is an accurate treatment of the electric-quadrupole, E2, strength associated with collectivity. Purpose: The valence-space in-medium similarity renormalization group (VS-IMSRG) is a particularly powerful method for accessing medium-and high-mass nuclei but has been found to underpredict E2 strengths. The purpose of this work is to evaluate the isospin dependence of this underprediction. Methods: We perform a systematic comparison of VS-IMSRG calculations with available literature. We make use of isoscalar and isovector contributions to the E2 matrix elements to assess isoscalar and isovector contributions to the missing strength. Results: It is found that the E2 strength is consistent throughout Tz=|12|, Tz=|1|, Tz=|32|, and Tz=2 pairs within the sd shell. Furthermore, no isovector contribution to the deficiency is identified. Conclusions: A comparison with toy-models and coupled-cluster calculations is used to discuss potential origins of the missing strength, which arises from missing many-particle, many-hole excitations out of the model space. The absence of any significant isovector contribution to the missing E2 strength indicates that the E2 strength discrepancy, and therefore any correction, is largely independent of the isospin of the nuclei in question.
| Original language | English |
|---|---|
| Article number | 034333 |
| Journal | Physical Review C |
| Volume | 105 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 2022 |
Funding
This work has been supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), The Canada Foundation for Innovation and the British Columbia Knowledge Development Fund. TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada. Computations were performed with an allocation of computing resources on Cedar at WestGrid and Compute Canada, and on the Oak Cluster at TRIUMF managed by the University of British Columbia department of Advanced Research Computing (ARC). Work at LLNL was performed under Contract No. DE-AC52-07NA27344. This work was supported by the Office of Nuclear Physics, U.S. Department of Energy, under Grant no. desc0018223 (NUCLEI SciDAC-4 collaboration) and by the Field Work Proposal No. ERKBP72 at Oak Ridge National Laboratory (ORNL). S.R.S. was supported by the U.S. Department of Energy office of Science, Office of Nuclear Physics, under Contract Nos. DE-FG02-97ER41014 and DEAC02-06CH11357. J.H. is supported at the University of Surrey under UKRI Future Leaders Fellowship Grant No. MR/T022264/1. The codes imsrg and nutbar used in this work make use of the Armadillo library .