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Nuclear Theory·nucl-th

Thursday·October 15, 2015

8 papers—2 primary·6 cross-listed

All8Primary2Cross-lists6
  1. 01

    [Submitted on 14 Oct 2015]

    Shedding Light on the EOS-Gravity Degeneracy and Constraining the Nuclear Symmetry Energy from the Gravitational Binding Energy of Neutron Stars

    Xiao-Tao He · F. J. Fattoyev · Bao-An Li · W. G. Newton

    A thorough understanding of properties of neutron stars requires both a reliable knowledge of the equation of state (EOS) of super-dense nuclear matter and the strong-field gravity theories simultaneously. To provide information that may help break this EOS-gravity degeneracy, we investigate effects of nuclear symmetry energy on the gravitational binding energy of neutron stars within GR and the scalar-tensor subset of alternative gravity models. We focus on effects of the slope of nuclear symmetry energy at saturation density and the high-density behavior of nuclear symmetry energy. We find that the variation of either the density slope or the high-density behavior of nuclear symmetry energy leads to large changes in the binding energy of neutron stars. The difference in predictions using the GR and the scalar-tensor theory appears only for massive neutron stars, and even then is significantly smaller than the difference resulting from variations in the symmetry energy.

    Comments:
    To appear in the Proceedings of the 13th international symposium on Origin of Matter and Evolution of Galaxies (OMEG2015) , June 24-27, 2015, Beijing, China
    Subjects:
    Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc); Nuclear Experiment (nucl-ex)
    arXiv:
    1510.03969 [pdf]
    EPJ Web Conf.(2016)·0 citations
  2. 02

    [Submitted on 14 Oct 2015]

    Chiral symmetry restoration versus deconfinement in heavy-ion collisions at high baryon density

    W. Cassing🇩🇪 · A. Palmese🇩🇪 · P. Moreau🇩🇪 · E. L. Bratkovskaya🇩🇪

    We study the production of strange hadrons in nucleus-nucleus collisions from 4 to 160 A GeV within the Parton-Hadron-String Dynamics (PHSD) transport approach that is extended to incorporate essentials aspects of chiral symmetry restoration (CSR) in the hadronic sector (via the Schwinger mechanism) on top of the deconfinement phase transition as implemented in PHSD. Especially the and the ratios in central Au+Au collisions are found to provide information on the relative importance of both transitions. The modelling of chiral symmetry restoration is driven by the pion-nucleon -term in the computation of the quark scalar condensate that serves as an order parameter for CSR and also scales approximately with the effective quark masses and . Furthermore, the nucleon scalar density , which also enters the computation of , is evaluated within the nonlinear model which is constraint by Dirac-Brueckner calculations and low energy heavy-ion reactions. The Schwinger mechanism (for string decay) fixes the ratio of strange to light quark production in the hadronic medium. We find that above 80 A GeV the reaction dynamics of heavy nuclei is dominantly driven by partonic degrees-of-freedom such that traces of the chiral symmetry restoration are hard to identify. Our studies support the conjecture of 'quarkyonic matter' in heavy-ion collisions from about 5 to 40 A GeV and provide a microscopic explanation for the maximum in the ratio at about 30 A GeV which only shows up if a transition to partonic degrees-of-freedom is incorporated in the reaction dynamics and is discarded in the traditional hadron-string models.

    Comments:
    12 pages, 7 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1510.04120 [pdf]
    PRC(2016)·80 citations

Affiliations

first authorsco-authorsvia INSPIRE