PaperPanorama

Nuclear Theory·nucl-th

Tuesday·April 15, 2025

23 papers12 primary·11 cross-listed

  1. 01

    [Submitted on 11 Apr 2025]

    Quantifying uncertainty in machine learning on nuclear binding energy

    Mengyao Huang · Kyle A. Wendt · Nicolas F. Schunck · Erika M. Holmbeck

    Techniques from artificial intelligence and machine learning are increasingly employed in nuclear theory, however, the uncertainties that arise from the complex parameter manifold encoded by the neural networks are often overlooked. Epistemic uncertainties arising from training the same network multiple times for an ensemble of initial weight sets offer a first insight into the confidence of machine learning predictions, but they often come with a high computational cost. Instead, we apply a single-model uncertainty quantification method called {\Delta}-UQ that gives epistemic uncertainties with one-time training. We demonstrate our approach on a 2-feature model of nuclear binding energies per nucleon with proton and neutron number pairs as inputs. We show that {\Delta}-UQ can produce reliable and self-consistent epistemic uncertainty estimates and can be used to assess the degree of confidence in predictions made with deep neural networks.

    Comments:
    11 pages, 10 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2504.09013 [pdf]
    PRC(2025)·3 citations
  2. 02

    [Submitted on 12 Apr 2025]

    From spin to pseudospin symmetry: The origin of magic numbers in nuclear structure

    C. R. Ding🇨🇳 · C. C. Wang🇨🇳 · J. M. Yao🇨🇳 · H. Hergert🇺🇸 · H. Z. Liang🇯🇵 · S. Bogner🇺🇸

    Magic numbers lie at the heart of nuclear structure, reflecting enhanced stability in nuclei with closed shells. While the emergence of magic numbers beyond 20 is commonly attributed to strong spin-orbit coupling, the microscopic origin of the spin-orbit potential remains elusive, owing to its dependence on the resolution scale and renormalization scheme of nuclear forces. Here, we investigate the evolution of shell structure with varying momentum resolution in nuclear interactions derived from chiral effective field theory, using the similarity renormalization group to link different scales. We uncover a novel transition from spin symmetry to pseudospin symmetry as the resolution scale decreases, during which magic numbers emerge naturally. A similar pattern is found in calculations using relativistic one-boson-exchange potentials, underscoring the robustness of the phenomenon. This establishes a direct connection between realistic nuclear forces with a high resolution scale and effective nuclear forces at coarse-grained scales, offering a first-principles explanation for the origin of magic numbers and pseudospin symmetry in nuclear shell structure, and new insights into the structure of exotic nuclei far from stability.

    Comments:
    6 pages with 3 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Quantum Physics (quant-ph)
    arXiv:
    2504.09148 [pdf]
    PRL(2026)·8 citations
  3. 03

    [Submitted on 12 Apr 2025]

    Lepton capture rates due to isotopes of vanadium in astrophysical environment

    Ramoona Shehzadi · Jameel-Un Nabi · Fakeha Farooq

    Lepton (electron and positron) capture rates on iron-regime nuclei are an essential element for modeling the late stages in the evolution of massive stars that end as core-collapse and thermonuclear supernovae. Previous simulation studies suggest that lepton capture (LC) rates on isotopes of vanadium have a substantial effect in regulating the electron fraction (Ye) during the final evolutionary phases. The present work involves the calculation of LC rates for 22 isotopes of vanadium using the proton-neutron quasiparticle random phase approximation (pn-QRPA) model. The considered mass range is from A = 43 to 64. The LC rates are computed over stellar densities ranging from 10^1 to 10^11 g/cm^3 and temperatures in the range 10^7 to 3 x 10^10 K. A comparison of our LC rates with those obtained using other models (IPM and LSSM) is also presented. Compared to other models, the pn-QRPA rates at high temperature (3 x 10^10 K) are larger by 1-2 orders of magnitude.

    Comments:
    11 Pages, 2 Figures, 6 Tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2504.09212 [pdf]
    Astrophys.Space Sci.(2020)·3 citations
  4. 04

    [Submitted on 12 Apr 2025]

    Nuclear Structure Properties of even-even Chromium Isotopes and the E ect of Deformation on Calculated Electron Capture Cross Sections

    Jameel-Un Nabi · Mahmut Boyukata · Asim Ullah · Muhammad Riaz

    In this study, we investigate the role of nuclear deformation on the calculated electron capture cross section (ECC) of even-even chromium (Cr) isotopes. We first determined the nuclear structure properties of these nuclei within the interacting boson model-1 (IBM-1). The energy spectra and E2 transition probabilities were calculated by fitting the parameters in the model formalism. The analysis of the potential energy surface was also performed to predict the geometric shape of the Cr nuclei by plotting their contour plot in the plane of (beta, gamma) deformation parameters. Later, we calculated the ECC within the proton-neutron quasiparticle random phase approximation (pn-QRPA) model. In particular, we studied how the calculated ECC changed with different values of the nuclear deformation parameter. The calculated Gamow-Teller (GT) strength distributions were widely spread among the daughter states. The total GT strength decreased with increasing value of the beta parameter. The computed ECC values, however, increased with increasing beta values of the Cr isotopes.

    Comments:
    28 Pages, 7 Figures, 3 Tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2504.09220 [pdf]
    NPA(2020)·4 citations
  5. 05

    [Submitted on 12 Apr 2025]

    Nuclear structure properties and decay rates of molybdenum isotopes

    Jameel-Un Nabi · Tuncay Bayram

    Electron capture and beta-minus decay are the dominant decay processes during the late phases of the evolution of heavy stars. Previous simulation results show that weak rates on isotopes of Molybdenum (Mo) have a meaningful contribution during the development of phases of stars before they go supernova. The relative abundance, coupled with the stellar weak rates on Mo isotopes, may change the lepton-to-baryon content of the core material. Here, we report on the calculation of nuclear structure properties of Mo isotopes from mass number 82 to 138, employing the RMF model. Later, we calculate the weak decay rates of these isotopes using the proton-neutron quasiparticle random phase approximation (pn-QRPA) model. In the first step, the ground-state nuclear properties of Mo isotopes such as binding energy per nucleon, neutron and proton separation energies, charge radii, total electric quadrupole moments, and the deformation parameter of electric quadrupole moments have been calculated using the density-dependent version of the RMF model with DD-PC1 and DD-ME2 functionals. The calculated electric quadrupole deformation parameters have been used in a deformed pn-QRPA calculation in the second phase of this work to calculate half-lives and weak decay rates for these Mo isotopes in stellar matter. We calculate the electron capture and beta-decay rates over an extensive range of temperature (0.01 x 10^9 K to 30 x 10^9 K) and density (10 to 10^11 g/cm^3). Our study can prove useful for simulation of presupernova evolution processes of stars.

    Comments:
    24 Pages, 10 Figures, 4 Tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2504.09266 [pdf]
    Astrophys.Space Sci.(2020)·3 citations
  6. 06

    [Submitted on 13 Apr 2025]

    Unified treatment for in-medium light and heavy clusters with RMF models

    Cheng-Jun Xia🇨🇳

    It was shown that light nuclei such as He, Be, and C can be well described by RMF models, which enables a unified description for nuclei with baryon numbers . In this work, we propose a hybrid treatment for investigating the clustering phenomenon in nuclear medium, where clusters ranging from light nuclei (e.g., H, He, and He) to heavy ones (e.g., C, O, Ca, Ca, and Pb) can be treated in a unified manner. In particular, assuming a spherical Wigner-Seitz cell, the clusters are fixed by solving the Dirac equations imposing the Dirichlet-Neumann boundary condition, while the nuclear medium are treated with Thomas-Fermi approximation and take constant densities. In the presence of nuclear medium, the clusters eventually become unbound as density increases, while the root-mean-square charge radii increase. For clusters with different proton and neutron numbers , their binding energies varies with the proton fraction of nuclear medium, which are less significant for clusters with . The uncertainties of density functionals on the clustering phenomenon are investigated as well adopting 8 different functionals. Based on the obtained results, an analytical formula describing the binding energies of in-medium clusters is then obtained. The results presented in this work should be useful to understand the clustering phenomenon in both heavy-ion collisions and neutron stars.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2504.09386 [pdf]
    PRC(2025)·2 citations
  7. 07

    [Submitted on 13 Apr 2025]

    Time-dependent random phase approximation for particle-number fluctuations and correlations in deep-inelastic collisions of Sm+Sm and Sm+Sm

    Zepeng Gao · Kazuyuki Sekizawa · Long Zhu

    The fluctuation-dissipation mechanism underlying non-equilibrium transport in low-energy heavy-ion reactions remains unclear. Although the time-dependent Hartree-Fock (TDHF) method provides a reasonable description of average reaction outcomes and one-body dissipation, it is known to significantly underestimate fluctuations of observables. The purpose of this work is to investigate deep-inelastic collisions of 144Sm+144Sm and 154Sm+154Sm with microscopic mean-field approaches and to show a predominant role of one-body dissipation as well as one-body fluctuations and correlation in low-energy heavy-ion reactions. Three dimensional TDHF calculations are carried out for 144Sm+144Sm at Ecm=500 MeV and 154Sm+154Sm at Ecm=485 MeV for a range of impact parameters with Skyrme SLy5 energy density functional. Backward time evolutions are performed as well to evaluate fluctuations and correlation in nucleon numbers within time-dependent random phase approximation (TDRPA). With TDRPA we calculate mass- and charge-number fluctuations, as well as the correlation between neutron and proton transfers, for each impact parameter. We demonstrate that TDRPA quantitatively reproduces the experimental \sigma_{AA}^2-TKEL distributions, whereas it systematically underestimates the charge fluctuation, \sigma_{ZZ}. The double-differential cross sections of reaction products are calculated, showing good agreement with the experimental data. We confirm a long-thought characteristic property that the closed-shell structure limits nucleon transfer at small energy losses, based on our microscopic TDHF and TDRPA calculations.

    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2504.09436 [pdf]
    PRC(2025)·8 citations
  8. 08

    [Submitted on 14 Apr 2025]

    Implication of shell quenching in scandium isotopes around N=20

    Rong An · Xiang Jiang · Na Tang · Li-Gang Cao · Feng-Shou Zhang

    Shell closure structures are commonly observed phenomena associated with nuclear charge radii throughout the nuclide chart. Inspired by recent studies demonstrating that the abrupt change can be clearly observed in the charge radii of the scandium isotopic chain across the neutron number , we further review the underlying mechanism of the enlarged charge radii for Sc based on the covariant density functional theory. The pairing correlations are tackled by solving the state-dependent Bardeen-Cooper-Schrieffer equations. Meanwhile, the neutron-proton correlation around the Fermi surface derived from the simultaneously unpaired proton and neutron is appropriately considered in describing the systematic evolution of nuclear charge radii. The calculated results suggest that the abrupt increase in charge radii across the shell closure seems to be improved along the scandium isotopic chain if the strong neutron-proton correlation is properly included.

    Comments:
    10 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2504.09871 [pdf]
    CPC(2025)·2 citations
  9. 09

    [Submitted on 14 Apr 2025]

    Vibrational structure and symmetry in Cd

    A. Leviatan🇮🇱 · J.E. Garcí a-Ramos🇪🇸 · N. Gavrielov🇫🇷 · P. Van Isacker🇫🇷

    We show that a vibrational interpretation and good U(5) symmetry are maintained for the majority of low-lying normal states in Cd isotopes, consistent with the empirical data. The observed deviations from this paradigm are properly treated by an interacting boson model Hamiltonian which breaks the U(5) symmetry in selected non-yrast states, while securing a weak mixing with coexisting SO(6)-like intruder states. The results demonstrate the relevance of the U(5) partial dynamical symmetry notion to this series of isotopes.

    Comments:
    9 pages, 2 figures, 4 Tables, Proceedings of the Zakopane Conference on Nuclear Physics "Extremes of the Nuclear Landscape", Zakopane, Poland, August 25 - September 1, 2024
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2504.10047 [pdf]
    Acta Phys.Polon.Supp.(2025)·0 citations
  10. 10

    [Submitted on 14 Apr 2025]

    Towards nuclear energy density functionals from first principles

    Lars Zurek🇫🇷

    We discuss the GUDE functionals which consist of pion exchanges derived from chiral effective field theory and a Skyrme-like part. Certain pion terms lead to significant improvements in the description of ground-state energies, indicating they might be useful ingredients for true ab initio energy density functionals. In addition, we present estimates of the statistical parameter uncertainties of the GUDE functionals.

    Comments:
    12 pages, 2 figures, proceedings for the 57th Zakopane Conference on Nuclear Physics, "Extremes of the Nuclear Landscape", Zakopane, Poland, 25 August-1 September, 2024
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2504.10164 [pdf]
    Acta Phys.Polon.Supp.(2025)·1 citation
  11. 11

    [Submitted on 14 Apr 2025]

    Quantum three-body problem for nuclear physics

    Emile Meoto

    A brief excursion into the three-body problem in quantum mechanics is presented for graduate students or researchers in nuclear physics. Starting from single-particle coordinates, the three-body Schrödinger equation is systematically transformed into a representation in Jacobi coordinates. Gradient, Laplacian, and kinetic energy operators are explicitly derived using the multivariable chain rule. Faddeev equations are reformulated in hyperspherical coordinates. In all transformations (from single-particle coordinates to Jacobi coordinates, rotation between Jacobi coordinates and from Jacobi coordinates to hyperspherical coordinates) the determinant of the Jacobian matrix is computed to ensure correct transformation of volume elements. The Faddeev equations in hyperspherical coordinates are projected onto a hyperspherical harmonics basis, leading to the coupled hyperradial equations that define the hyperspherical harmonics method.

    Subjects:
    Nuclear Theory (nucl-th); physics.ed-ph (physics.ed-ph)
    arXiv:
    2504.10301 [pdf]
    Eur.J.Phys.(2026)·2 citations
  12. 12

    [Submitted on 14 Apr 2025]

    Role of Coulomb-nuclear breakup of 6,7Li projectiles with heavy deformed 232Th target

    D. Patel · J. Rangel · J. Lubian

    The significance of both Coulomb and nuclear couplings and their interference effects in the breakup processes of 6,7Li with a non-spherical nucleus 232Th has been evaluated. The continuum discretized coupled channel(CDCC) calculations are carried out in a nonstandard way, using short-range imaginary potentials for the fragment-target interaction at energies close to the Coulomb barrier. The present calculations employing short-range imaginary potentials exhibit better agreement with the experimental elastic scattering angular distributions than those using standard systematic value (0.78xWSPP ) used to describe elastic scattering. Including the excitation of the 232Th inelastic shows significant coupling effects on the elastic scattering below the barrier energies compared to higher incident energies. Subsequently, the CDCC framework was used to analyze the nuclear, Coulomb, and total breakup predictions separately. The breakup cross sections for the 6Li+232Th system are greater than those for the 7Li+232Th system across various energies. The present study predicts destructive Coulomb-nuclear interference in the breakup processes involving both 6Li and 7Li projectile nuclei with the deformed 232Th target. Additionally, the breakup reaction cross-sections are compared with experimentally measured fusion cross-sections near the barrier energies for both 6,7Li+232Th systems.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2504.10420 [pdf]
    NPA(2025)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE