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Nuclear Theory·nucl-th

Monday·August 28, 2023

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 01

    [Submitted on 25 Aug 2023]

    Composite octet baryons in a relativistic mean field description of nuclear and neutron star matter

    Kaito Noro🇯🇵 · Wolfgang Bentz🇯🇵 · Ian C. Cloët🇺🇸 · Teruyuki Kitabayashi🇯🇵

    We examine the properties of composite octet baryons in the nuclear medium and neutron star matter. The internal quark-diquark structure of the octet baryons and the equations of state of nuclear matter and neutron star matter in the mean field approximation are described by using the three-flavor Nambu--Jona-Lasinio (NJL) model as an effective quark theory of QCD. After introducing our model, we first discuss the properties of single baryons and their effective meson exchange interactions in symmetric nuclear matter by using concepts of Fermi liquid theory. Several model independent implications of this description are derived, and illustrated by numerical results obtained in our model. Second, we extend the model description to high baryon densities, and investigate the equation of state of neutron star matter and the resulting star masses. We find that the so called hyperon puzzle persists also for the case of composite hadrons. To get more information on this point, we also investigate the role of 6-fermi and 8-fermi interactions, in addition to the standard 4-fermi interactions. The strengths of those higher order fermi interactions is determined so as not to spoil the saturation properties of nuclear matter. Among them, an interaction characterized by a product of four quark current operators plays a special role to stabilize the stars over a large region of central baryon densities, although it has little effect on the maximum star masses.

    Comments:
    22 pages, 11 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2308.13179 [pdf]
    PRC(2024)·6 citations
  2. 02

    [Submitted on 25 Aug 2023]

    An extension of the generator coordinate method with basis optimization

    Moemi Matsumoto · Yusuke Tanimura · Kouichi Hagino

    The generator coordinate method (GCM) has been a well-known method to describe nuclear collective motions. In this method, one specifies {\it a priori} the relevant collective degrees of freedom as input of the method, based on empirical and/or phenomenological assumptions. We here propose a new extension of the GCM, in which both the basis Slater determinants and weight factors are optimized according to the variational principle. Applying this method to O and Si nuclei with the Skyrme functional, we demonstrate that the optimized bases correspond to excited states along a collective path, unlike the conventional GCM which superposes only the local ground states. This implies that a collective coordinate for large amplitude collective motions is determined in a much more complex way than what has been assumed so far.

    Comments:
    5 pages, 3 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2308.13233 [pdf]
    PRC(2023)·11 citations
  3. 03

    [Submitted on 25 Aug 2023]

    Relativistic constraints on 3N contact interactions

    Alessia Nasoni🇮🇹 · Elena Filandri🇮🇹 · Luca Girlanda🇮🇹

    In this paper we analyze the relativistic corrections to the leading order three-nucleon (3N) contact interactions. These boost corrections are derived first from the nonrelativistic reduction of covariant Lagrangians and later from the Poincaré algebra constraints on nonrelativistic theories. We show that in order to describe the 3N potential in reference frames other than the center-of-mass frame, the inclusion of five additional terms with fixed coefficients is required. These terms will be relevant in systems with mass number A>3. How they will affect EFT calculations of binding energies and scattering observables in these systems should be investigated.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2308.13341 [pdf]
    EPJA(2023)·7 citations
  4. 04

    [Submitted on 25 Aug 2023]

    Coupling between collective modes in the deformed Zr nucleus: Insights from consistent HFB+QRPA calculations with the Gogny interaction

    E. V. Chimanski · E. J. In · S. Péru · A. Thapa · W. Younes · J. E. Escher

    The Zirconium isotopes exhibit structural properties that present multiple challenges to nuclear theory. Investigations of the coupling present within isoscalar modes and within isovector modes are scarce but important for advancing our understanding of the microscopic picture of nuclei. To explore some of these underlying coupling features, and to test the predictive power of a state-of-the-art nuclear structure approach, we provide a detailed analysis of the properties of Zr. This region includes a benchmarking case and offers insights into nuclear deformation phenomena. To investigate the coupling between collective modes in deformed nuclei, we focused our analysis on the ground and excited-state properties of these isotopes, employing a consistent approach with the axially-symmetric deformed Hartree-Fock-Bogoliubov (HFB) and the Quasiparticle Random Phase Approximation (QRPA) framework, both using the Gogny D1M force. This approach effectively describes both low-lying and giant-resonance states. We devoted special attention to the deformed Zr nucleus, where we confirm the existence of coupling between monopole and quadrupole excitations through the QRPA components and demonstrate an analogous dipole-octupole coupling through the and components. Intrinsic transition densities and associated radial projections illustrate the coupling. Our work complements and extends earlier studies carried out using density-functional-based methods and notably, we included the complete Coulomb interaction also in the pairing fields, i.e. we treat terms exactly that are approximated in typical calculations that use the Gogny D1 and D2 interaction families.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2308.13374 [pdf]
    PRC(2025)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE