PaperPanorama
FAQ

Nuclear Theory·nucl-th

Monday·June 12, 2017

6 papers—4 primary·2 cross-listed

All6Primary4Cross-lists2
  1. 01

    [Submitted on 8 Jun 2017]

    Higher-order symmetry energy and neutron star core-crust transition with Gogny forces

    C. Gonzalez-Boquera · M. Centelles · X. Viñas · A. Rios

    We study the symmetry energy and the core-crust transition in neutron stars using the finite-range Gogny nuclear interaction and examine the deduced crustal thickness and crustal moment of inertia. We start by analyzing the second-, fourth- and sixth-order coefficients of the Taylor expansion of the energy per particle in powers of the isospin asymmetry for Gogny forces. These coefficients provide information about the departure of the symmetry energy from the widely used parabolic law. The neutron star core-crust transition is evaluated by looking at the onset of thermodynamical instability of the liquid core. The calculation is performed with the exact (i.e., without Taylor expansion) Gogny EoS for the core, and also with its Taylor expansion in order to assess the influence of isospin expansions on locating the inner edge of neutron star crusts. It is found that the properties of the core-crust transition derived from the exact EoS differ from the predictions of the Taylor expansion even when the expansion is carried through sixth order in the isospin asymmetry. Gogny forces, using the exact EoS, predict the ranges for the transition density and for the transition pressure. The transition densities show an anticorrelation with the slope parameter of the symmetry energy. The transition pressures are not found to correlate with . Neutron stars obtained with Gogny forces have maximum masses below and relatively small moments of inertia. The crustal mass and moment of inertia are evaluated and comparisons are made with the constraints from observed glitches in pulsars.

    Comments:
    24 pages, 15 figures, discussions and bibliography updated, to appear in Physical Review C
    Subjects:
    Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
    arXiv:
    1706.02736 [pdf]
    PRC(2017)·79 citations
  2. 02

    [Submitted on 9 Jun 2017]

    Partial correlation analysis method in ultra-relativistic heavy-ion collisions

    Adam Olszewski🇵🇱 · Wojciech Broniowski🇵🇱

    We argue that statistical data analysis of two-particle longitudinal correlations in ultra-relativistic heavy-ion collisions may be efficiently carried out with the technique of partial covariance. In this method, the spurious event-by-event fluctuations due to imprecise centrality determination are eliminated via projecting out the component of the covariance influenced by the centrality fluctuations. We bring up the relationship of the partial covariance to the conditional covariance. Importantly, in the superposition approach, where hadrons are produced independently from a collection of sources, the framework allows us to impose centrality constraints on the number of sources rather than hadrons, that way unfolding of the trivial fluctuations from statistical hadronization and focusing better on the initial-state physics. We show, using simulated data from hydrodynamics followed with statistical hadronization, that the technique is practical and very simple to use, giving insight into the correlations generated in the initial stage. We also discuss the issues related to separation of the short- and long-range components of the correlation functions, and show that in our example the short-range component from the resonance decays is largely reduced by considering pions of the same sign. We demonstrate the method explicitly on the cases where centrality is determined with a single central control bin, or with two peripheral control bins.

    Comments:
    13 pages, 6 figures, Mistakes in Eqs. (10-12) corrected
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1706.02862 [pdf]
    PRC(2017)·17 citations
  3. 03

    [Submitted on 9 Jun 2017]

    A new temperature dependent hyperonic equation of state: application to rotating neutron star models and I-Q-relations

    Miguel Marques🇫🇷 · Micaela Oertel🇫🇷 · Matthias Hempel🇨🇭 · Jérôme Novak🇫🇷

    In this work we present a newly constructed equation of state (EoS) --applicable to stellar core collapse and neutron star mergers--, including the entire baryon octet. Our EoS is compatible with the main constraints from nuclear physics and, in particular, with a maximum mass for cold beta-equilibrated neutron stars of 2 solar masses in agreement with recent observations. As an application of our new EoS, we compute numerical stationary models for rapidly (rigidly) rotating hot neutron stars. We consider maximum masses of hot stars, such as proto-neutron stars or hypermassive neutron stars in the post-merger phase of binary neutron star coalescence. The universality of I-Q-relations at nonzero temperature for fast rotating models, comparing a purely nuclear EoS with its counterparts containing Lambda-hyperons or the entire baryon octet, respectively, is discussed, too. We find that the I-Q universality is broken when thermal effects become important, whatever the value of entropy gradients in our models. Thus, the use of I-Q relations for the analysis of proto-neutron stars or merger remnant data, including gravitational wave signals from the last stages of binary neutron star mergers, should be regarded with care.

    Comments:
    20 pages, 13 figures, v2: additional discussion of EoS properties and I-Q fit, some references added, accepted for publication in PRC
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
    arXiv:
    1706.02913 [pdf]
    PRC(2017)·114 citations
  4. 04

    [Submitted on 9 Jun 2017]

    Optical properties of an anisotropic hot QCD medium

    M. Yousuf Jamal · Sukanya Mitra · Vinod Chandra

    The present investigation involves explorations on the chromo-dielectric properties of the hot QCD medium produced in relativistic heavy-ion collisions in terms of refractive index. The isotropic/equilibrium modelling is done within an effective quasi-particle model of hot QCD medium. The possibilities of negative refraction in the medium are also explored in terms of the Depine-Lakhtakia index. The anisotropic aspects of the hot QCD medium are incorporated by introducing the anisotropy in a particular direction. That makes the medium quite similar to uniaxial crystals, and hence we observe phenomenon of birefringence ( two distinct refractive indices in the anisotropic case). Interestingly, both anisotropy and medium effects play significant roles in deciding the optical properties of the hot QCD/Quark-Gluon-Plasma (QGP) medium.

    Comments:
    12 pages, 6 figures, two column
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1706.02995 [pdf]
    1 citation
  5. 05

    [Submitted on 9 Jun 2017] (cross-list from hep-lat)

    The nucleon spin and momentum decomposition using lattice QCD simulations

    C. Alexandrou (Univ. of Cyprus & Cyprus Inst.)🇨🇾 · M. Constantinou (Temple Univ.)🇺🇸 · K. Hadjiyiannakou (Cyprus Inst.)🇨🇾 · K. Jansen (DESY-Zeuthen)🇩🇪 · C. Kallidonis (Cyprus Inst.)🇨🇾 · G. Koutsou (Cyprus Inst.)🇨🇾 · A. Vaquero Avilés-Casco (Univ. of Utah)🇺🇸 · C. Wiese (DESY-Zeuthen)🇩🇪

    We determine within lattice QCD, the nucleon spin carried by valence and sea quarks, and gluons. The calculation is performed using an ensemble of gauge configurations with two degenerate light quarks with mass fixed to approximately reproduce the physical pion mass. We find that the total angular momentum carried by the quarks in the nucleon is and the gluon contribution is giving a total of consistent with the spin sum. For the quark intrinsic spin contribution we obtain . All quantities are given in the scheme at 2~GeV. The quark and gluon momentum fractions are also computed and add up to satisfying the momentum sum.

    Comments:
    Version published in PRL
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1706.02973 [pdf]
    PRL(2017)·172 citations
  6. 06

    [Submitted on 9 Jun 2017] (cross-list from hep-ph)

    Waves in magnetized quark matter

    D. A. Fogaça🇧🇷 · S. M. Sanches Jr.🇧🇷 · F. S. Navarra🇧🇷

    We study wave propagation in a non-relativistic cold quark-gluon plasma immersed in a constant magnetic field. Starting from the Euler equation we derive linear wave equations and investigate their stability and causality. We use a generic form for the equation of state, the EOS derived from the MIT bag model and also a variant of the this model which includes gluon degrees of freedom. The results of this analysis may be relevant for perturbations propagating through the quark matter phase in the core of compact stars and also for perturbations propagating in the low temperature quark-gluon plasma formed in low energy heavy ion collisions, to be carried out at FAIR and NICA.

    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1706.02991 [pdf]
    NPA(2018)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE