Large-scale exact diagonalizations reveal low-momentum scales of nuclei

Large-scale exact diagonalizations reveal low-momentum scales of nuclei. Forssén, C., Carlsson, B. D., Johansson, H. T., Sääf, D., Bansal, A., Hagen, G., & Papenbrock, T. ArXiv e-prints, 2017.

Paper doi abstract bibtex

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.

@article{forssen_large-scale_2017,
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.},
annote = {From Duplicate 2 (Large-scale exact diagonalizations reveal low-momentum scales of nuclei - Forss{\'{e}}n, C; Carlsson, B D; Johansson, H T; S{\"{a}}{\"{a}}f, D; Bansal, A; Hagen, G; Papenbrock, T)

\_eprint: 1712.09951},
archivePrefix = {arXiv},
arxivId = {1712.09951},
author = {Forss{\'{e}}n, C. and Carlsson, B. D. and Johansson, H. T. and S{\"{a}}{\"{a}}f, D. and Bansal, A. and Hagen, G. and Papenbrock, T.},
doi = {10.1103/PhysRevC.97.034328},
eprint = {1712.09951},
issn = {24699993},
journal = {ArXiv e-prints},
keywords = {Nuclear Theory},
number = {3},
title = {{Large-scale exact diagonalizations reveal low-momentum scales of nuclei}},
url = {https://arxiv.org/abs/1712.09951},
volume = {97},
year = {2017}
}

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