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Nuclear Theory·nucl-th

Monday·April 28, 2025

8 papers—4 primary·4 cross-listed

All8Primary4Cross-lists4
  1. 01

    [Submitted on 25 Apr 2025]

    Study of Gamow-Teller strength and associated weak-rates on odd-A nuclei in stellar matter

    Muhammad Majid · Jameel-Un Nabi · Muhammad Riaz

    In a recent study by Cole et al., it was concluded that QRPA calculations show larger deviations and overestimate the total experimental Gamow-Teller (GT) strength. It was also concluded that QRPA calculated electron capture rates exhibit larger deviation than those derived from the measured GT strength distributions. The main purpose of this study is to probe the findings of the Cole et al. paper. This study gives useful information on the performance of QRPA-based nuclear models. As per simulation results, the capturing of electrons that occur on medium heavy isotopes have a significant role in decreasing the ratio of electron-to-baryon content of the stellar interior during the late stages of core evolution. We report the calculation of allowed charge-changing transitions strength for odd-A fp-shell nuclei (45Sc and 55Mn) by employing the deformed pn-QRPA approach. The computed GT transition strength is compared with previous theoretical calculations and measured data. For stellar applications the corresponding electron capture rates are computed and compared with rates using previously calculated and measured Gamow-Teller values. Our finding show that our calculated results are in decent accordance with measured data. At higher stellar temperature our calculated electron capture rates are larger than those calculated by Independent Particle Model (IPM) and shell model. It was further concluded that at low temperature and high density regions the positron emission weak-rates from 45Sc and 55Mn may be neglected in simulation codes.

    Comments:
    21 Pages, 3 Tables, 6 Figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2504.18199 [pdf]
    IJMPE(2018)·4 citations
  2. 02

    [Submitted on 25 Apr 2025]

    Continuum quasiparticle random-phase approximation for reactions on neutron-rich nuclei: collectivity and resonances in low-energy cross section

    Teruyuki Saito · Masayuki Matsuo

    We formulate a microscopic theory to calculate cross section of the radiative neutron capture on neutron-rich nuclei using the continuum quasiparticle random-phase approximation. This formulation is designed to be applied to neutron-rich nuclei around the -process path, for which the compound nuclear model may not be appropriate. It takes into account effects of various excitation modes such as the soft dipole excitation, the giant resonances, and the quasiparticle resonance in addition to the surface vibrations such as quadrupole and octupole modes. We perform numerical calculations to demonstrate new features of the present theory, employing reactions and with transitions populating the ground state, collective and states in and . With these examples, we discuss enhanced resonance contributions in the reaction at low energy, which originate from the quasiparticle resonance and the pygmy quadrupole resonance located just above the one neutron separation energy, and from combination with the low-lying octupole vibrational state.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2504.18239 [pdf]
    PRC(2026)·0 citations
  3. 03

    [Submitted on 25 Apr 2025]

    Equation of state and Fermi liquid properties of dense matter based on chiral effective field theory interactions

    Faruk Alp🇩🇪 · Yannick Dietz🇩🇪 · Kai Hebeler🇩🇪 · Achim Schwenk🇩🇪

    We present results for the equation of state of symmetric nuclear matter and pure neutron matter obtained in many-body-perturbation theory (MBPT) up to third order, based on various chiral two- and three-nucleon interactions used in ab initio calculations of nuclei. We extract equation of state properties, such as the incompressibility and the symmetry energy, and discuss estimates of the theoretical uncertainties due to neglected higher-order contributions in the MBPT expansion as well as the chiral effective field theory expansion. In addition, we discuss the Fermi liquid approach to nuclear matter. We calculate all two- and three-nucleon contributions to the quasiparticle interaction up to second order in MBPT and present results for the Landau parameters, effective mass, and speed of sound for pure neutron matter.

    Comments:
    16 pages, 12 figures, published version
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
    arXiv:
    2504.18259 [pdf]
    PRC(2025)·24 citations
  4. 04

    [Submitted on 25 Apr 2025]

    Investigation of Gamow Teller Transition Properties in 56-64Ni Isotopes Using QRPA Methods

    Sadiye Cakmak · Jameel-Un Nabi · Tahsin Babacan

    Weak rates in nickel isotopes play an integral role in the dynamics of supernovae. Electron capture and -decay of nickel isotopes, dictated by Gamow-Teller transitions, significantly alter the lepton fraction of the stellar matter. In this paper we calculate Gamow-Teller (GT) transitions for isotopes of nickel, Ni, using QRPA methods. The GT strength distributions were calculated using four different QRPA models. Our results are also compared with previous theoretical calculations and measured strength distributions wherever available. Our investigation concluded that amongst all RPA models, the pn-QRPA(C) model best described the measured GT distributions (including total GT strength and centroid placement). It is hoped that the current investigation of GT properties would prove handy and may lead to a better understanding of the presupernova evolution of massive stars.

    Comments:
    33 Pages, 12 Figures, 7 Tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2504.18282 [pdf]
    NPA(2018)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE