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Nuclear Theory·nucl-th

Wednesday·May 20, 2020

7 papers—3 primary·4 cross-listed

All7Primary3Cross-lists4
  1. 01

    [Submitted on 19 May 2020]

    The thermal conductivity of "pastas" in neutron star matter

    Claudio Dorso · Jonathan Dunn · Alejandro Strachan · Guillermo Frank

    This investigation explores the phononic thermal conductivity of nuclear star matter as it undergoes the "topological" transition to the "pasta" regime, and further down to the solid-liquid phase transition. The study was carried out using molecular dynamics simulations with nuclear potentials embedded in an effective (i.e. Thomas-Fermi) Coulomb potential. The thermal conductivity experiences a dramatic change within a narrow temperature interval around T=1 MeV. This change accomplishes the "pasta" breakdown during a heating process. The thermal conductivity by flipping protons' or neutrons' velocity further shows a decoupling for asymmetric nuclear star matter.

    Comments:
    11 pages, 20 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2005.09142 [pdf]
    NPA(2020)·13 citations
  2. 02

    [Submitted on 19 May 2020]

    Cross-shell excitations in doubly magic 132Sn and its nearest neighbours

    Sangeeta Das · M. Saha Sarkar

    Large scale shell model calculations have been performed to study the excitation spectra of 132Sn and its nearest neighbours with a new cross-shell interaction constructed from two widely used interactions, sn100pn and CWG, of this mass region. A few of the two-body matrix elements have been tuned to reproduce the low-lying multiplet states of 132Sn. This is the first full scale shell model study of 132Sn energy spectra as well as transition probabilities. The excitation spectra for other nearest neighbours are reproduced reasonably well. The most important observable calculated are the E1 transition probabilities, which were so far beyond the scope of calculations with the existing interactions.

    Comments:
    13 Pages, 12 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2005.09411 [pdf]
    NPA(2021)·4 citations
  3. 03

    [Submitted on 19 May 2020]

    Transport in neutron star mergers

    Steven P. Harris🇺🇸

    After an introduction to the QCD phase diagram, the nuclear equations of state, and neutron star mergers, I discuss three projects related to transport and nuclear matter in neutron star mergers. The first is the nature of beta equilibrium in the portion of a merger that is transparent to neutrinos. We calculate the weak interaction (Urca) rates and find that the beta equilibrium condition needs to be modified by adding an additional chemical potential, which changes slightly the particle content in neutrino-transparent beta equilibrium. Secondly, we calculate the bulk viscosity in neutrino-transparent nuclear matter in conditions encountered in neutron star mergers. Bulk viscosity arises from a phase lag between the pressure and density in the nuclear matter, which is due to the finite rate of beta equilibration. When bulk viscosity is sufficiently strong, which happens when the equilibration rate nearly matches the frequency of the density oscillation, it can noticeably dampen the oscillation. We find that in certain thermodynamic conditions likely encountered in mergers, oscillations in nuclear matter can be damped on timescales on the order of 10 milliseconds, so we conclude that bulk viscosity should be included in merger simulations. Finally, we study thermal transport due to axions in neutron star mergers. We conclude that axions are never trapped in mergers, but instead escape, carrying energy away from the merger. We calculate the cooling time due to the energy carried away by axions and find that within current constraints on the axion-nucleon coupling, axions could cool fluid elements in mergers on timescales which could affect the dynamics of the merger.

    Comments:
    Thesis, based on the works: arXiv:1705.09880, arXiv:1803.00662, arXiv:1907.03795, and arXiv:2003.09768
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2005.09618 [pdf]
    ProQuest Dissertations Publishing, 2020. …·8 citations

Affiliations

first authorsco-authorsvia INSPIRE