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Nuclear Theory·nucl-th

Tuesday·June 25, 2024

10 papers—6 primary·4 cross-listed

All10Primary6Cross-lists4
  1. 01

    [Submitted on 21 Jun 2024]

    Stochastic fluctuations and the relaxation time in transient relativistic fluids

    Gabriel S. Denicol🇧🇷 · Jorge Noronha🇺🇸

    We argue that the ratio between the shear viscosity and the shear relaxation time, , should be defined as a thermodynamic quantity obtained from the equal-time symmetric correlator of the shear-stress tensor. In kinetic theory, we show that this ratio does not depend on the type of interaction. Similarly, an exact expression for this ratio is obtained for holographic gauge theories. We also determine how stochastic fluctuations change in transient relativistic hydrodynamics and show that thermal fluctuations do not spoil causality and stability.

    Comments:
    13 pages (including Appendix)
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th)
    arXiv:
    2406.15569 [pdf]
    PLB(2025)·3 citations
  2. 02

    [Submitted on 23 Jun 2024]

    Impact of reactor neutrino uncertainties on coherent scattering's discovery potential

    Leendert Hayen🇫🇷

    Nuclear power reactors are the most intense man-made source of antineutrino's and have long been recognized as promising sources for coherent elastic neutrino-nucleus scattering (CENS) studies. Its observation and the spectral shape of the associated recoil spectrum is sensitive to a variety of exotic new physics scenarios and many experimental efforts are underway. Within the context of the reactor antineutrino anomaly, which initially indicated eV-scale sterile neutrino's, the modeling of the reactor antineutrino spectrum has seen a significant evolution in the last decade. Even so, uncertainties remain due to a variety of nuclear structure effects, incomplete information in nuclear databases and fission dynamics complexities. Here, we investigate the effects of these uncertainties on one's ability to accurately distinguish new physics signals. For the scenarios discussed here, we find that reactor spectral uncertainties are similar in magnitude to the projected sensitivities pointing towards a need for spectroscopy measurements below the inverse decay threshold.

    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2406.16081 [pdf]
    J.Phys.G(2025)·3 citations
  3. 03

    [Submitted on 23 Jun 2024]

    Multipole modes of excitation in tetrahedrally deformed neutron-rich Zr isotopes

    Jie Zhao

    The multipole modes of excitation for tetrahedrally deformed neutron-rich Zr isotopes are investigated using the quasiparticle finite amplitude method based on the covariant density functional theories. By employing the density-dependent point-coupling covariant density functional theory with the parameter set DD-PC1 in the particle-hole channel and a separable pairing interaction of finite range, it is observed that a distinct peak emerges at MeV in the isoscalar quadrupole strength when distortion is considered for Zr. This peak is absent when the deformation is limited to axially symmetric octuple or spherical case. It also does not appears in neighboring axially quadrople or octupole deformed nuclei, thus can be viewed as an indicator for the tetrahedral shape.

    Comments:
    6 pages, 5 figures, accepted for publication in Phys. Rev. C
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2406.16100 [pdf]
    PRC(2024)·4 citations
  4. 04

    [Submitted on 23 Jun 2024]

    Short-Range Correlations and Urca Process in Neutron Stars

    Armen Sedrakian

    Recent measurements of high-momentum correlated neutron-proton pairs at JLab suggest that the dense nucleonic component of the compact stars contains a fraction of high-momentum neutron-proton pairs that is not accounted for in the familiar Fermi-liquid theory of the neutron-proton fluid mixture. We compute the rate of the Urca process in compact stars taking into account the non-Fermi liquid contributions to the proton's spectral widths induced by short-range correlations. The Urca rate differs strongly from the Fermi-liquid prediction at low temperatures, in particular, the high threshold on the proton fraction precluding the Urca process in neutron stars is replaced by a smooth increase with the proton fraction. This observation may have a profound impact on the theories of cooling of compact stars.

    Comments:
    v3: added references and fixed typos. Matches the published version, 6 pages, 2 figures. v2: Typos fixed; v1: 5 pages, 2 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
    arXiv:
    2406.16183 [pdf]
    PRL(2024)·26 citations
  5. 05

    [Submitted on 23 Jun 2024]

    Monopole Excitation and Nuclear Compressibility: Present and Future Perspectives

    J. C. Zamora · S. Giraud

    Isoscalar giant resonances are nuclear collective excitations associated with the oscillation in phase of protons and neutrons according to a certain multipolarity . In particular, the isoscalar giant monopole resonance () is the strongest nuclear compression mode, and its excitation energy is directly related to the compression modulus for finite nuclei. Typically, microscopic calculations are utilized to establish a relationship between the experimental compression modulus and the nuclear incompressibility that is a crucial parameter of the equation of state for nuclear matter. The incompressibility of nuclear matter has been determined with an accuracy of 10 to 20\% using relativistic and non-relativistic microscopic models for describing the monopole distributions in Pb and Zr isotopes. However, the same theoretical models are not able to describe data for open-shell nuclei, such as those of tin and cadmium isotopes. In fact, only effective interactions with a softer nuclear-matter incompressibility are able to predict the centroid energy of monopole distributions for open-shell nuclei. An unified description of the monopole resonance in Pb and other open-shell nuclei remains unsolved from the theory side. Most of this uncertainty is due to our poor knowledge of the symmetry energy, which is another essential component of the equation of state of nuclear matter. Therefore, new experimental data along isotopic chains covering a wide range in ratios, including neutron-deficient and neutron-rich nuclei, are of paramount importance for determining both the nuclear-matter incompressibility and the symmetry energy more precisely.

    Comments:
    In Oxford Research Encyclopedia of Physics
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
    arXiv:
    2406.16217 [pdf]
    2 citations
  6. 06

    [Submitted on 24 Jun 2024]

    Revisiting the nuclear magnetic octupole moment

    Stavros Bofos · Theo J. Mertzimekis

    The nuclear magnetic octupole moment is revisited as a potentially useful observable for nuclear structure studies. The magnetic octupole moment, , is examined in terms of the nuclear collective model including weak and strong coupling. Single-particle formulation is additionally considered in the overall comparison of theoretical predictions with available experimental data. Mirror nuclei symmetry is examined in terms of the magnetic octupole moment isoscalar and isovector terms. A full list of predictions for of odd-proton and odd-neutron nuclei in medium-heavy mass regimes of the nuclear chart is produced aiming at providing starting values for future experimental endeavors.

    Comments:
    Accepted for publication in Atomic Data Nuclear Data Tables (27 pages, 2 figures, 5 tables)
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2406.16429 [pdf]
    Atom.Data Nucl.Data Tabl.(2024)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE