Abstract
Ab initio methods aim to solve the nuclear many-body problem with controlled approximations. Virtually exact numerical solutions for realistic interactions can only be obtained for certain special cases such as few-nucleon systems. Here we extend the reach of exact diagonalization methods to handle model spaces with dimension exceeding 1010 on a single compute node. This allows us to perform no-core shell model (NCSM) calculations for Li6 in model spaces up to Nmax=22 and to reveal the He4+d halo structure of this nucleus. Still, the use of a finite harmonic-oscillator basis implies truncations in both infrared (IR) and ultraviolet (UV) length scales. These truncations impose finite-size corrections on observables computed in this basis. We perform IR extrapolations of energies and radii computed in the NCSM and with the coupled-cluster method at several fixed UV cutoffs. It is shown that this strategy enables information gain also from data that is not fully UV converged. IR extrapolations improve the accuracy of relevant bound-state observables for a range of UV cutoffs, thus making them profitable tools. We relate the momentum scale that governs the exponential IR convergence to the threshold energy for the first open decay channel. Using large-scale NCSM calculations we numerically verify this small-momentum scale of finite nuclei.
| Original language | English |
|---|---|
| Article number | 034328 |
| Journal | Physical Review C |
| Volume | 97 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 28 2018 |
Funding
We thank Dean Lee for useful discussions. G.H. and T.P. gratefully acknowledge the hospitality of the Department of Physics at Chalmers during the initial phase of this project. The visit was supported by the Swedish Foundation for International Cooperation in Research and Higher Education (STINT, Grant No. IG2012-5158). This work was also supported by the US Department of Energy, Office of Science, Office of Nuclear Physics under Awards No. DEFG02-96ER40963 (University of Tennessee), No. DE-SC0008499, and No. DE-SC0018223 (SciDAC NUCLEI Collaboration), the Field Work Proposal ERKBP57 at Oak Ridge National Laboratory (ORNL), and under Contract No. DE-AC05-00OR22725 (Oak Ridge National Laboratory). Some of the computations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at C3SE (Chalmers) and NSC (Linköping). This manuscript has been coauthored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). APPENDIX A: