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Nuclear Theory·nucl-th

Wednesday·May 19, 2021

6 papers—2 primary·4 cross-listed

All6Primary2Cross-lists4
  1. 01

    [Submitted on 17 May 2021]

    -like quartetting in the excited states of proton-neutron pairing Hamiltonians

    M. Sambataro🇮🇹 · N. Sandulescu🇷🇴

    Previous studies have shown that the ground state of systems of nucleons composed by an equal number of protons and neutrons interacting via proton-neutron pairing forces can be described accurately by a condensate of -like quartets. Here we extend these studies to the low-lowing excited states of these systems and show that these states can be accurately described by breaking a quartet from the ground state condensate and replacing it with an "excited" quartet. This approach, which is analogous to the one-broken-pair approximation employed for like-particle pairing, is analysed for various isovector and isovector-isoscalar pairing

    Comments:
    14 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2105.08136 [pdf]
    PLB(2021)·10 citations
  2. 02

    [Submitted on 18 May 2021]

    Constructing approximate shell-model wavefunctions by eigenvector continuation

    Sota Yoshida🇯🇵 · Noritaka Shimizu🇯🇵

    Shell-model calculations play a key role in elucidating various properties of nuclei. In general, those studies require a huge number of calculations to be repeated for parameter calibration and quantifying uncertainties. To reduce the computational burden, we propose a new workflow of shell-model calculations using a method called eigenvector continuation (EC). It enables us to efficiently approximate the eigenpairs under a given Hamiltonian by previously sampled eigenvectors. We demonstrate the validity of EC as an emulator of the valence shell-model, including first application of EC to electromagnetic transition matrix elements. Furthermore, we propose a new usage of EC: preprocessing, in which we start the Lanczos iterations from the approximate eigenvectors, and demonstrate that this can accelerate subsequent research cycles. With the aid of the EC, the eigenvectors obtained during the parameter optimization are not necessarily to be discarded, even if their eigenvalues are far from the experimental data. Those eigenvectors can become accumulated knowledge.

    Comments:
    18 pages, title changed from v1, accepted for publication in PTEP
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2105.08256 [pdf]
    PTEP(2022)·33 citations

Affiliations

first authorsco-authorsvia INSPIRE