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Nuclear Theory·nucl-th

Thursday·December 9, 2021

10 papers—5 primary·5 cross-listed

All10Primary5Cross-lists5
  1. 01

    [Submitted on 7 Dec 2021]

    Natural orbitals for the ab initio no-core configuration interaction approach

    Patrick J. Fasano🇺🇸 · Chrysovalantis Constantinou🇺🇸 · Mark A. Caprio🇺🇸 · Pieter Maris🇺🇸 · James P. Vary🇺🇸

    Ab initio no-core configuration interaction (NCCI) calculations for the nuclear many-body problem have traditionally relied upon an antisymmetrized product (Slater determinant) basis built from harmonic oscillator orbitals. The accuracy of such calculations is limited by the finite dimensions which are computationally feasible for the truncated many-body space. We therefore seek to improve the accuracy obtained for a given basis size by optimizing the choice of single-particle orbitals. Natural orbitals, which diagonalize the one-body density matrix, provide a basis which maximizes the occupation of low-lying orbitals, thus accelerating convergence in a configuration-interaction basis, while also possibly providing physical insight into the single-particle structure of the many-body wave function. We describe the implementation of natural orbitals in the NCCI framework, and examine the nature of the natural orbitals thus obtained, the properties of the resulting many-body wave functions, and the convergence of observables. After taking as an illustrative testbed, we explore aspects of NCCI calculations with natural orbitals for the ground state of the -shell neutron halo nucleus .

    Comments:
    26 pages, 17 figures
    Subjects:
    Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    2112.04027 [pdf]
    PRC(2022)·20 citations
  2. 02

    [Submitted on 8 Dec 2021]

    Symmetry and shape coexistence in 10Be

    M. A. Caprio · A. E. McCoy · P. J. Fasano · T. Dytrych

    Within the low-lying spectrum of 10Be, multiple rotational bands are found, with strikingly different moments of inertia. A proposed interpretation has been that these bands variously represent triaxial rotation and prolate axially-deformed rotation. The bands are well-reproduced in ab initio no-core configuration interaction (NCCI) calculations. We use the calculated wave functions to elucidate the nuclear shapes underlying these bands, by examining the Elliott SU(3) symmetry content of these wave functions. The ab initio results support an interpretation in which the ground-state band, along with an accompanying K=2 side band, represent a triaxial rotor, arising from an SU(3) irreducible representation in the 0 hbar omega space. Then, the lowest excited K=0 band represents a prolate rotor, arising from an SU(3) irreducible representation in the 2 hbar omega space.

    Comments:
    10 pages, 4 figures; contribution to the proceedings of the International Workshop "Shapes and Dynamics of Atomic Nuclei: Contemporary Aspects" (SDANCA-21), Sofia, Bulgaria, September 2021; submitted to Bulg. J. Phys
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2112.04056 [pdf]
    Bulg.J.Phys.(2022)·10 citations
  3. 03

    [Submitted on 8 Dec 2021]

    Translating neutron star observations to nuclear symmetry energy via artificial neural networks

    Plamen G. Krastev (Harvard University)

    One of the most significant challenges involved in efforts to understand the equation of state of dense neutron-rich matter is the uncertain density dependence of the nuclear symmetry energy. Because of its broad impact, pinning down the density dependence of the nuclear symmetry energy has been a longstanding goal of both nuclear physics and astrophysics. Recent observations of neutron stars, in both electromagnetic and gravitational-wave spectra, have already constrained significantly the nuclear symmetry energy at high densities. Training deep neural networks to learn a computationally efficient representation of the mapping between astrophysical observables of neutron stars, such as masses, radii, and tidal deformabilities, and the nuclear symmetry energy allows its density dependence to be determined reliably and accurately. In this work we use a deep learning approach to determine the nuclear symmetry energy as a function of density directly from observational neutron star data. We show for the first time that artificial neural networks can precisely reconstruct the nuclear symmetry energy from a set of available neutron star observables, such as, masses and radii as those measured by, e.g., the NICER mission, or masses and tidal deformabilities as measured by the LIGO/VIRGO/KAGRA gravitational-wave detectors. These results demonstrate the potential of artificial neural networks to reconstruct the symmetry energy, and the equation of state, directly from neutron star observational data, and emphasize the importance of the deep learning approach in the era of Multi-Messenger Astrophysics.

    Comments:
    16 pages, 6 figures. Invited article for Galaxies for the Special Issue "Neutron Stars and Hadrons in the Era of Gravitational Wave Astrophysics". Published version
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
    arXiv:
    2112.04089 [pdf]
    Galaxies(2022)·35 citations
  4. 04

    [Submitted on 8 Dec 2021]

    Thermal properties of hot and dense medium in interacting hadron resonance gas model

    S. Sahoo🇮🇳 · D. K. Mishra🇮🇳 · P. K. Sahu🇮🇳

    The meson exchange interaction based on relativistic mean-field (RMF) theory has been introduced in the hadron resonance gas (HRG) model, called interacting HRG (iHRG) model. This model can be used to explain the experimental data both at finite temperature () with finite chemical potential () and finite temperature at vanishing chemical potential. The nuclear matter equation of state also can be explained at zero temperature with finite baryon density (finite chemical potential) due to the presence of attractive and repulsive interactions between the hadrons in the iHRG model. Similarly, the lattice equation of state is well described at = 0 and finite temperature by the iHRG model. In the present study, we have calculated the thermodynamical quantities as a function of temperature and chemical potential using both HRG and iHRG models. Also, we have presented the isothermal compressibility (), specific heat (), and speed of sound () as a function of , , and center of mass energies. The effect of kinematic acceptance on these quantities are also presented as a function of and . Results from this study on are compared with results from other heavy-ion transport models and experimental data up to LHC energies.

    Comments:
    34 pages, 16 figures, accepted for publication in Nuclear Physics A
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2112.04117 [pdf]
    NPA(2022)·4 citations
  5. 05

    [Submitted on 8 Dec 2021]

    Band-like structures and quartets in deformed N=Z nuclei

    M. Sambataro · N. Sandulescu

    We provide a description of deformed nuclei in a formalism of -like quartets. Quartets are constructed variationally by resorting to the use of proper intrinsic states. Various types of intrinsic states are introduced which generate different sets of quartets for a given nucleus. Energy spectra are generated via configuration-iteraction calculations in the spaces built with these quartets. The approach has been applied to Mg and Si in the shell and to Cr in the shell. In all cases a good description of the low-lying spectra has been achieved. As a peculiarity of the approach, a close correspondence is observed between the various sets of quartets employed and the occurrence of well defined band-like structures in the spectra of the systems under study.

    Comments:
    16 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2112.04370 [pdf]
    PLB(2022)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE