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Nuclear Theory·nucl-th

Tuesday·November 17, 2020

6 papers—4 primary·2 cross-listed

All6Primary4Cross-lists2
  1. 01

    [Submitted on 14 Nov 2020]

    Cluster effective field theory and nuclear reactions

    Shung-Ichi Ando (Sunmoon U.)🇰🇷

    An effective field theory (EFT) for a nuclear reaction at low energies is studied. The astrophysical -factor of radiative capture on C at the Gamow-peak energy, MeV, is a fundamental quantity in nuclear-astrophysics, and we construct an EFT for the reaction. To fix parameters appearing in the effective Lagrangian, the EFT is applied to the study for three reactions: elastic -C scattering at low energies, transition of radiative capture on C, and delayed emission from N. We report an estimate of the -factor of the reaction through the transition at by employing the EFT. We also discuss applications of EFTs to nuclear reactions at low energies.

    Comments:
    19 pages, 9 figures, version accepted for publication in EPJA
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2011.07207 [pdf]
    EPJA(2021)·15 citations
  2. 02

    [Submitted on 14 Nov 2020]

    Microscopic shell-model counterpart of the Bohr-Mottelson model

    H. G. Ganev

    In the present paper we demonstrate that there exists a fully microscopic shell-model counterpart of the Bohr-Mottelson model by embedding the latter in the microscopic shell-model theory of atomic nucleus within the framework of the recently proposed fully microscopic proton-neutron symplectic model (PNSM). For this purpose, another shell-model coupling scheme of the PNSM is considered in which the basis states are classified by the algebraic structure . It is shown that the configuration space of the PNSM contains a six-dimensional subspace that is closely related to the configuration space of the generalized quadrupole-monopole Bohr-Mottelson model and its dynamics splits into radial and orbital motions. The group acting in this space, in contrast, e.g., to popular IBM, contains an subgroup which allows to introduce microscopic shell-model counterparts of the exactly solvable limits of the Bohr-Mottelson model that closely parallel the relationship of the original Wilets-Jean and rotor models. The Wilets-Jean-type dynamics in the present approach, in contrast to the original collective model formulation, is governed by the microscopic shell-model intrinsic structure of the symplectic bandhead which defines the relevant Pauli allowed , and hence , subrepresentations. The original Wilets-Jean dynamics of the generalized Bohr-Mottelson model is recovered for the case of closed-shell nuclei, for which the symplectic bandhead structure is trivially reduced to the scalar or equivalent to it irreducible representation.

    Comments:
    12 pages, no figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2011.07373 [pdf]
    EPJA(2021)·8 citations
  3. 03

    [Submitted on 15 Nov 2020]

    Creation of radiocarbon C-14 at thunderstorms

    V.I. Lyashuk

    The synthesis of isotopes is possible under conditions of power electric discharge in the atmosphere. Knowledge of the radioactive 14C yield under flash conditions (as additional channel of 14C production relative to the main - cosmogenic one) is important for radiocarbon analysis. It is proposed the gross model for evaluation of the upper limit of the 14C yield, which creation was simulated for the altitudes up to 15 km. It is presented the results for yield of radioactive isotope 41Ar which synthesis goes along with 14C creation under thunderstorm conditions. It was obtained that the possible thunderstorm mechanisms of 14C creation cannot compete with cosmogenic production.

    Comments:
    8 pages, 8 figures, 15 refererences
    Subjects:
    Nuclear Theory (nucl-th); physics.ao-ph (physics.ao-ph)
    arXiv:
    2011.07417 [pdf]
    0 citations
  4. 04

    [Submitted on 16 Nov 2020]

    Skyrme-Hartree-Fock-Bogoliubov mass models on a 3D Mesh: Effect of triaxial shape

    Guillaume Scamps🇧🇪 · Stephane Goriely🇧🇪 · Erik Olsen🇧🇪 · Michael Bender🇫🇷 · Wouter Ryssens🇧🇪

    The modeling of nuclear reactions and radioactive decays in astrophysical or earth-based conditions requires detailed knowledge of the masses of essentially all nuclei. Microscopic mass models based on nuclear energy density functionals (EDFs) can be descriptive and used to provide this information. The concept of intrinsic symmetry breaking is central to the predictive power of EDF approaches, yet is generally not exploited to the utmost by mass models because of the computational demands of adjusting up to about two dozen parameters to thousands of nuclear masses. We report on a first step to bridge the gap between what is presently feasible for studies of individual nuclei and large-scale models: we present a new Skyrme-EDF-based model that was adjusted using a three-dimensional coordinate-space representation, for the first time allowing for both axial and triaxial deformations during the adjustment process. To compensate for the substantial increase in computational cost brought by the latter, we have employed a committee of multilayer neural networks to model the objective function in parameter space and guide us towards the overall best fit. The resulting mass model BSkG1 is computed with the EDF model independently of the neural network. It yields a root mean square (rms) deviation on the 2457 known masses of 741 keV and an rms deviation on the 884 measured charge radii of 0.024 fm.

    Comments:
    25 pages, 15 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2011.07904 [pdf]
    EPJA(2021)·57 citations

Affiliations

first authorsco-authorsvia INSPIRE