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Nuclear Theory·nucl-th

Thursday·June 11, 2020

15 papers—5 primary·10 cross-listed

All15Primary5Cross-lists10
  1. 01

    [Submitted on 8 Jun 2020]

    Fast neutrino cooling of nuclear pasta in neutron stars: molecular dynamics simulations

    Zidu Lin · Matthew E. Caplan · Charles J. Horowitz · Cecilia Lunardini

    The direct URCA process of rapid neutrino emission can occur in nonuniform nuclear pasta phases that are expected in the inner crust of neutron stars. Here, the periodic potential for a nucleon in nuclear pasta allows momentum conservation to be satisfied for direct URCA reactions. We improve on earlier work by modeling a rich variety of pasta phases (gnocchi, waffle, lasagna, and anti-spaghetti) with large-scale molecular dynamics simulations. We find that the neutrino luminosity due to direct URCA reactions in nuclear pasta can be 3 to 4 orders of magnitude larger than that from the modified URCA process in the NS core. Thus neutrino radiation from pasta could dominate radiation from the core and this could significantly impact the cooling of neutron stars

    Comments:
    12 pages, 9 figures, Accepted by PRC, Fig. 9b was given at wrong temperature in earlier version, and the mistake was corrected in this version
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2006.04963 [pdf]
    PRC(2020)·35 citations
  2. 02

    [Submitted on 9 Jun 2020]

    Constraining isovector nuclear interactions with giant resonances within a Bayesian approach

    Jun Xu · Jia Zhou · Zhen Zhang · Wen-Jie Xie · Bao-An Li

    We put a stringent constraint on the isovector nuclear interactions in the Skyrme-Hartree-Fock model from the centroid energy of the isovector giant dipole resonance in Pb as well as its electric polarizability . Using the Bayesian analysis method, and are found to be mostly determined by the nuclear symmetry energy at about fm and the isovector nucleon effective mass at the saturation density. At confidence level, we obtain MeV and .

    Comments:
    5 pages, 5 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2006.05217 [pdf]
    PLB(2020)·27 citations
  3. 03

    [Submitted on 9 Jun 2020]

    The spin-polarized ferromagnetic state of a cold Fermi gas

    J.P.W. Diener · F.G. Scholtz

    The spin-polarized ferromagnetic state of a cold Fermi gas is investigated for interacting and non-interacting charge-neutral and -equilibrated gases. The standard minimal couplings between the magnetic field and the fermions' charges and magnetic dipole moments define the fermions' interaction with the magnetic field. Assuming a variable coupling strength between the magnetic field and the fermion (baryon) dipole moments, it is shown that a ferromagnetized state can be achieved that corresponds to a lower energy spin-polarized state with a magnetic field entirely due to the gas's magnetic response. We find that, depending on the density, a very large increase in the baryon dipole moments is needed to achieve this ferromagnetized state. While the required increase seems unlikely, the induced magnetic field is of the order gauss. Furthermore, while externally magnetized Fermi gases have an anisotropic pressure, the pressure of the ferromagnetized gas is completely isotropic and the thermodynamically preferred magnetized state.

    Comments:
    22 Pages, 7 Figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
    arXiv:
    2006.05247 [pdf]
    PRC(2020)·1 citation
  4. 04

    [Submitted on 10 Jun 2020]

    Constraining nuclear matter parameters from correlation systematics:a mean-field perspective

    B. K. Agrawal🇮🇳 · Tuhin Malik🇮🇳 · J.N. De🇮🇳 · S. K. Samaddar🇮🇳

    The nuclear matter parameters define the nuclear equation of state (EoS), they appear as coefficients of expansion around the saturation density of symmetric and asymmetric nuclear matter. We review their correlations with several properties of finite nuclei and of neutron stars within mean-field frameworks. The lower order nuclear matter parameters such as the binding energy per nucleon, incompressibility and the symmetry energy coefficients are found to be constrained in narrow limits through their strong ties with selective properties of finite nuclei. From the correlations of nuclear matter parameters with neutron star observables, we further review how precision knowledge of the radii and tidal deformability of neutron stars in the mass range may help cast them in narrower bounds. The higher order parameters such as the density slope and the curvature of the symmetry energy or the skewness of the symmetric nuclear matter EoS are, however, plagued with larger uncertainty. From inter-correlation of these higher order nuclear matter parameters with lower order ones, we explore how they can be brought to more harmonious bounds.

    Comments:
    to be appeared in EPJST
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
    arXiv:
    2006.05758 [pdf]
    Eur.Phys.J.ST(2021)·16 citations
  5. 05

    [Submitted on 10 Jun 2020]

    A nuclear model with explicit mesons

    D.V. Fedorov🇩🇰

    A nuclear model is proposed where the nucleons interact by emitting and absorbing mesons, and where the mesons are treated explicitly. A nucleus in this model finds itself in a quantum superposition of states with different number of mesons. Transitions between these states hold the nucleus together. The model---in its simplest incarnation---is applied to the deuteron, where the latter becomes a superposition of a neutron-proton state and a neutron-proton-meson state. Coupling between these states leads to an effective attraction between the nucleons and results in a bound state with negative energy, the deuteron. The model is able to reproduce the accepted values for the binding energy and the charge radius of the deuteron. The model, should it work in practice, has several potential advantages over the existing non-relativistic few-body nuclear models: the reduced number of model parameters, natural inclusion of few-body forces, and natural inclusion of mesonic physics.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2006.05851 [pdf]
    Few Body Syst.(2020)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE