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Nuclear Theory·nucl-th

Wednesday·September 28, 2022

12 papers—4 primary·8 cross-listed

All12Primary4Cross-lists8
  1. 01

    [Submitted on 26 Sept 2022]

    Deformation dependence of 2p-radioactivity half-lives: Probe with a new formula across the mass region with Z<82

    G. Saxena · Mamta Aggarwal · D. Singh · A. Jain · P. K. Sharma · H. L. Yadav

    Effect of deformation on half-life of two-proton (2p) radioactivity is investigated across the periodic chart for nuclei with Z82. 2p-decay half-lives are estimated by employing our newly proposed semi-empirical formula wherein the nuclear deformation has been incorporated in a phenomenological way. Robustness of the formula is demonstrated as it estimates the measured values quite accurately and, hence, reliably applied to predict the other possible 2p-emitters. For many proton rich nuclei for which experimental data on the decay energies are not available, we have used the theoretical values obtained from our calculations using the relativistic mean-field (RMF) approach. The uncertainties in the theoretical decay energy values are minimised by machine learning (ML) technique. Correlation of 2p-radioactivity with 2p-halo and deformation is probed. Our calculations show the phenomenon of shape coexistence in several 2p-emitters, wherein the prolate shape is found to be more predominant for the ground state.

    Comments:
    15 pages, 5 figures, Accepted in J. Phys. G: Nucl. Part. Phys
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2209.12966 [pdf]
    J.Phys.G(2023)·8 citations
  2. 02

    [Submitted on 26 Sept 2022]

    Bayes goes fast: Uncertainty Quantification for a Covariant Energy Density Functional emulated by the Reduced Basis Method

    Pablo Giuliani · Kyle Godbey · Edgard Bonilla · Frederi Viens · Jorge Piekarewicz

    A covariant energy density functional is calibrated using a principled Bayesian statistical framework informed by experimental binding energies and charge radii of several magic and semi-magic nuclei. The Bayesian sampling required for the calibration is enabled by the emulation of the high-fidelity model through the implementation of a reduced basis method (RBM) - a set of dimensionality reduction techniques that can speed up demanding calculations involving partial differential equations by several orders of magnitude. The RBM emulator we build - using only 100 evaluations of the high-fidelity model - is able to accurately reproduce the model calculations in tens of milliseconds on a personal computer, an increase in speed of nearly a factor of 3,300 when compared to the original solver. Besides the analysis of the posterior distribution of parameters, we present predictions with properly estimated uncertainties for observables not included in the fit, specifically the neutron skin thickness of 208Pb and 48Ca, as reported by PREX and CREX collaborations. The straightforward implementation and outstanding performance of the RBM makes it an ideal tool for assisting the nuclear theory community in providing reliable estimates with properly quantified uncertainties of physical observables. Such uncertainty quantification tools will become essential given the expected abundance of data from the recently inaugurated and future experimental and observational facilities.

    Comments:
    23 pages, 7 figures
    Subjects:
    Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
    arXiv:
    2209.13039 [pdf]
    13 citations
  3. 03

    [Submitted on 27 Sept 2022]

    Local position-space two-nucleon potentials from leading to fourth order of chiral effective field theory

    S. K. Saha🇺🇸 · D. R. Entem🇪🇸 · R. Machleidt🇺🇸 · Y. Nosyk🇺🇸

    We present local, position-space chiral NN potentials through four orders of chiral effective field theory ranging from leading order (LO) to next-to-next-to-next-to-leading order (N3LO, fourth order) of the Delta-less version of the theory. The long-range parts of these potentials are fixed by the very accurate pi-N LECs as determined in the Roy-Steiner equations analysis. At the highest order (N3LO), the NN data below 190 MeV laboratory energy are reproduced with the respectable chi^2/datum of 1.45. A comparison of the N3LO potential with the phenomenological Argonne v_18 (AV18) potential reveals substantial agreement between the two potentials in the intermediate range ruled by chiral symmetry, thus, providing a chiral underpinning for the phenomenological AV18 potential. Our chiral NN potentials may serve as a solid basis for systematic ab initio calculations of nuclear structure and reactions that allow for a comprehensive error analysis. In particular, the order by order development of the potentials will make possible a reliable determination of the truncation error at each order. Our new family of local position-space potentials differs from existing potentials of this kind by a weaker tensor force as reflected in relatively low D-state probabilities of the deuteron (P_D less or equal 4.0% for our N3LO potentials) and predictions for the triton binding energy above 8.00 MeV (from two-body forces alone). As a consequence, our potentials may lead to different predictions when applied to light and intermediate-mass nuclei in ab initio calculations and, potentially, help solve some of the outstanding problems in microscopic nuclear structure.

    Comments:
    36 pages, 14 figures. arXiv admin note: text overlap with arXiv:1703.05454. More discussion on contacts and Fierz reordering
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2209.13170 [pdf]
    PRC(2023)·29 citations
  4. 04

    [Submitted on 27 Sept 2022]

    Elastic properties of nuclear pasta in a fully three-dimensional geometry

    Cheng-Jun Xia · Toshiki Maruyama · Nobutoshi Yasutake · Toshitaka Tatsumi · Ying-Xun Zhang

    Realistic estimations on the elastic properties of neutron star matter are carried out with a large strain () in the framework of relativistic-mean-field model with Thomas-Fermi approximation, where various crystalline configurations are considered in a fully three-dimensional geometry with reflection symmetry. Our calculation confirms the validity of assuming Coulomb crystals for the droplet phase above neutron drip density, which nonetheless does not work at large densities since the elastic constants are found to be decreasing after reaching their peaks. Similarly, the analytic formulae derived in the incompressible liquid-drop model give excellent description for the rod phase at small densities, which overestimates the elastic constants at larger densities. For slabs, due to the negligence on the variations of their thicknesses, the analytic formulae from liquid-drop model agree qualitatively but not quantitatively with our numerical estimations. By fitting to the numerical results, these analytic formulae are improved by introducing dampening factors. The impacts of nuclear symmetry energy are examined adopting two parameter sets, corresponding to the slope of symmetry energy and 89.39 MeV. Even with the uncertainties caused by the anisotropy in polycrystallines, the elastic properties of neutron star matter obtained with and 89.39 MeV are distinctively different, results in detectable differences in various neutron star activities.

    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
    arXiv:
    2209.13310 [pdf]
    PLB(2023)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE