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Nuclear Theory·nucl-th

Thursday·November 26, 2020

5 papers—3 primary·2 cross-listed

All5Primary3Cross-lists2
  1. 01

    Hadron-quark phase transition in the SU(3) local Nambu-Jona-Lasinio (NJL) model with vector interaction

    Grigor Alaverdyan🇦🇲

    We study the hadron-quark hybrid equation of state (EOS) of compact-star matter. The Nambu-Jona-Lasinio (NJL) local SU(3) model with vector-type interaction is used to describe the quark matter phase, while the relativistic mean field (RMF) theory with scalar-isovector -meson effective field adopted to describe the hadronic matter phase. It is shown that the larger the vector coupling constant , the lower the threshold density for the appearance of strange quarks. For a sufficiently small value of the vector coupling constant, the functions of the mass dependence on the baryonic chemical potential have regions of ambiguity which leads to a phase transition in non-strange quark matter with an abrupt change in the baryon number density. We show that within the framework of the NJL model, the hypothesis on the absolute stability of strange quark matter is not realized. In order to describe the phase transition from hadronic matter to quark matter, the Maxwell's construction is applied. It is shown that the greater the vector coupling, the greater the stiffness of the EOS for quark matter and the phase transition pressure. Our results indicate that the infinitesimal core of the quark phase, formed in the center of the neutron star, is stable.

    nucl-thSymmetry(2021)·18 citations
  2. 02

    Consistent description for cluster dynamics and single-particle correlation

    Naoyuki Itagaki · Tomoya Naito

    Cluster dynamics and single-particle correlation are simultaneously treated for the description of the ground state of . The recent development of the antisymmetrized quasi cluster model (AQCM) makes it possible to generate -coupling shell-model wave functions from clusters models. The cluster dynamics and the competition with the -coupling shell-model structure can be estimated rather easily. In the present study, we further include the effect of single-particle excitation; the mixing of the two-particle-two-hole excited states is considered. The single-particle excitation is not always taken into account in the standard cluster model analyses, and the two-particle-two-hole states are found to strongly contribute to the lowering of the ground state owing to the pairing-like correlations. By extending AQCM, all of the basis states are prepared on the same footing, and they are superposed based on the framework of the generator coordinate method (GCM).

    nucl-thnucl-exPRC(2021)·9 citations
  3. 03

    Shell-model based study of the direct capture in neutron-rich nuclei

    K. Sieja🇫🇷 · S. Goriely🇧🇪

    The radiative neutron capture rates for isotopes of astrophysical interest are commonly calculated within the statistical Hauser-Feshbach reaction model. Such an approach, assuming a high level density in the compound system, can be questioned in light and neutron-rich nuclei for which only a few or no resonant states are available. Therefore, in this work we focus on the direct neutron-capture process. We employ a shell-model approach in several model spaces with well-established effective interactions to calculate spectra and spectroscopic factors in a set of 50 neutron-rich target nuclei in different mass regions, including doubly-, semi-magic and deformed ones. Those theoretical energies and spectroscopic factors are used to evaluate direct neutron capture rates and to test global theoretical models using average spectroscopic factors and level densities based on the Hartree-Fock-Bogoliubov plus combinatorial method. The comparison of shell-model and global model results reveals several discrepancies that can be related to problems in level densities. All the results show however that the direct capture is non-negligible with respect to the by-default Hauser-Feshbach predictions and can be even 100 times more important for the most neutron-rich nuclei close to the neutron drip line.

    nucl-thEPJA(2021)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE