PaperPanorama
FAQ

Nuclear Theory·nucl-th

Friday·September 20, 2019

5 papers—3 primary·2 cross-listed

All5Primary3Cross-lists2
  1. 01

    [Submitted on 19 Sept 2019]

    From deformed Hartree-Fock to the nucleon-pair approximation

    G. J. Fu · Calvin W. Johnson

    The nucleon-pair approximation (NPA) can be a compact alternative to full configuration-interaction (FCI) diagonalization in nuclear shell-model spaces, but selecting good pairs is a long-standing problem. While seniority-based pairs work well for near-spherical nuclides, they do not work well for deformed nuclides with strong rotational bands. We propose an alternate approach. We show how one can write any Slater determinant for an even number of particles as a general pair condensate, from which one can project out pairs of good angular momentum. We implement this by generating unconstrained Hartree-Fock states in a shell model basis and extracting , , and pairs. The subsequent NPA calculations yield good agreement with FCI results using the same effective interactions.

    Comments:
    7 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1909.08785 [pdf]
    PLB(2020)·21 citations
  2. 02

    [Submitted on 19 Sept 2019]

    Gamow-Teller excitations at finite temperature: Competition between pairing and temperature effects

    E. Yüksel🇹🇷 · N. Paar🇭🇷 · G. Colò🇮🇹 · E. Khan🇫🇷 · Y. F. Niu🇨🇳

    The relativistic and nonrelativistic finite temperature proton-neutron quasiparticle random phase approximation (FT-PNQRPA) methods are developed to study the interplay of the pairing and temperature effects on the Gamow-Teller excitations in open-shell nuclei, as well as to explore the model dependence of the results by using two rather different frameworks for effective nuclear interactions. The Skyrme-type functional SkM* is employed in the nonrelativistic framework, while the density-dependent meson-exchange interaction DD-ME2 is implemented in the relativistic approach. Both the isoscalar and isovector pairing interactions are taken into account within the FT-PNQRPA. Model calculations show that below the critical temperatures the Gamow-Teller excitations display a sensitivity to both the finite temperature and pairing effects, and this demonstrates the necessity for implementing both in the theoretical framework. The established FT-PNQRPA opens perspectives for the future complete and consistent description of astrophysically relevant weak interaction processes in nuclei at finite temperature such as -decays, electron capture, and neutrino-nucleus reactions.

    Comments:
    15 pages, 6 figures, published in Physical Review C
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1909.08930 [pdf]
    PRC(2020)·31 citations
  3. 03

    [Submitted on 19 Sept 2019]

    Enhanced adiabatic index for hot neutron-rich matter from microscopic nuclear forces

    Yeunhwan Lim · Jeremy W. Holt

    We investigate the adiabatic index of hot and dense nuclear matter from chiral effective field theory and find that the results are systematically larger than from typical mean field models. We start by constructing the finite-temperature equation of state from chiral two- and three-nucleon forces, which we then use to fit a class of extended Skyrme energy density functionals. This allows for modeling the thermal index across the full range of densities and temperatures that may be probed in simulations of core-collapse supernovae and neutron star mergers, including the low-density inhomogeneous mixed phase. For uniform matter we compare the results to analytical expressions for based on Fermi liquid theory. The correlation between the thermal index and the effective masses at nuclear saturation density is studied systematically through Bayesian modeling of the nuclear equation of state. We then study the behavior of in both relativistic and non-relativistic mean field models used in the astrophysical simulation community to complement those based on chiral effective field theory constraints from our own study. We derive compact parameterization formulas for across the range of densities and temperatures encountered in core collapse supernovae and binary neutron star mergers, which we suggest may be useful for the numerical simulation community.

    Comments:
    15 pages, 10 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
    arXiv:
    1909.09089 [pdf]
    9 citations

Affiliations

first authorsco-authorsvia INSPIRE