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Nuclear Theory·nucl-th

Wednesday·February 20, 2019

8 papers—5 primary·3 cross-listed

All8Primary5Cross-lists3
  1. 01

    [Submitted on 18 Feb 2019]

    Absence of Landau-Peierls Instability in the Magnetic Dual Chiral Density Wave Phase of Dense QCD

    Efrain J Ferrer🇺🇸 · Vivian de la Incera🇺🇸

    We investigate the stability of the Magnetic Dual Chiral Density Wave (MDCDW) phase of cold and dense QCD against collective low-energy fluctuations of the order parameter. The appearance of additional structures in the system free-energy due to the explicit breaking of the rotational and isospin symmetries by the external magnetic field and the field-induced asymmetry of the lowest Landau level modes play a crucial role in the analysis. The new structures not only affect the condensate minimum equations, but also the spectrum of the thermal fluctuations, which lacks the transverse soft modes that typically affect single-modulated inhomogeneous phases in the absence of a magnetic field. Consequently, the long-range order of the MDCDW phase is preserved at finite temperature. The lack of Landau-Peierls instabilities in the MDCDW phase makes this inhomogeneous phase of dense quark matter particularly relevant for the physics of neutron stars.

    Comments:
    Typos corrected, new discussions added
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1902.06810 [pdf]
    PRD(2020)·28 citations
  2. 02

    [Submitted on 18 Feb 2019]

    Nuclear electromagnetic currents to fourth order in chiral effective field theory

    H. Krebs🇩🇪 · E. Epelbaum🇩🇪 · U.-G. Meißner🇩🇪

    Recently, we have shown that the continuity equation for the nuclear vector and axial current operators acquires additional terms if the latter depend on the energy transfer. We analyze in detail the electromagnetic single-nucleon four-current operators and verify the validity of the modified continuity equation for all one- and two-nucleon contributions up to fourth order in the chiral expansion. We also derive, for the first time, the leading contribution to the three-nucleon charge operator which appears at this order. Our study completes the derivation of the electroweak nuclear currents to fourth order in the chiral expansion.

    Comments:
    18 pages, 3 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1902.06839 [pdf]
    Few Body Syst.(2019)·53 citations
  3. 03

    [Submitted on 19 Feb 2019]

    Bayesian analysis of the crust-core transition with a compressible liquid-drop model

    Thomas Carreau🇫🇷 · Francesca Gulminelli🇫🇷 · Jérôme Margueron🇫🇷

    The crust-core phase transition of neutron stars is quantitatively studied within a unified meta-modelling of the nuclear Equation of State (EoS). The variational equations in the crust are solved within a Compressible Liquid Drop (CLD) approach, with surface parameters consistently optimized for each EoS set on experimental nuclear mass data. When EoS parameters are taken from known Skyrme or RMF functionals, the transition point of those models is nicely reproduced. A model-independent probability distribution of EoS parameters and of the transition density and pressure is determined with a Bayesian analysis, where the prior is given by an uncorrelated distribution of parameters within the present empirical uncertainties, and constraints are applied both from neutron star physics and ab-initio modelling. We show that the characteristics of the transition point are largely independent of the high density properties of the EoS, while ab-initio EoS calculations of neutron and symmetric matter are far more constraining. The most influential parameter for the determination of the transition point governs the surface properties of extremely neutron rich matter, and it is strongly unconstrained. This explains the large dispersion of existing predictions of the transition point. Only if the surface tension is fixed to a reasonable but somewhat arbitrary value, strong correlations with isovector parameters ( and ) are recovered. Within the present experimental and theoretical uncertainties on those parameters, we estimate the transition density as fm and the transition pressure as MeV fm.

    Comments:
    14 pages, 12 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1902.07032 [pdf]
    EPJA(2019)·96 citations
  4. 04

    [Submitted on 19 Feb 2019]

    Quadrupole collectivity and shell closure in neutron-rich nuclei around

    X. Y. Wu · J. M. Yao

    We present a comprehensive study on the low-lying states of neutron-rich Er, Yb, Hf, and W isotopes across the shell with a multi-reference covariant density functional theory. Beyond mean-field effects from shape mixing and symmetry restoration on the observables that are relevant for understanding quadrupole collectivity and underlying shell structure are investigated. The general features of low-lying states in closed-shell nuclei are retained in these four isotopes around , even though the shell gap is overall quenched by about 30\% with the beyond mean-field effects. These effects are consistent with the previous generator-coordinate calculations based on Gogny forces, but much smaller than that predicted by the collective Hamiltonian calculation. It implies that the beyond mean-field effects on the -process abundances before the third peak at might be more moderate than that found in A. Arcones and G. F. Bertsch, Phys. Rev. Lett. 108, 151101 (2012).

    Comments:
    12 pages with 13 figures and 1 table
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1902.07077 [pdf]
    PRC(2019)·9 citations
  5. 05

    [Submitted on 19 Feb 2019]

    New paradigm for fluctuations in heavy-ion collisions

    Giuliano Giacalone🇫🇷 · Pablo Guerrero-Rodríguez🇪🇸 · Matthew Luzum🇧🇷 · Cyrille Marquet🇫🇷 · Jean-Yves Ollitrault🇫🇷

    Since their discovery, fluctuations in the initial state of heavy-ion collisions have been understood as originating mostly from the random positions of nucleons within the colliding nuclei. We consider an alternative approach where all the focus is on fluctuations generated by QCD interactions, that we evaluate at leading logarithmic accuracy in the color glass condensate effective theory. We validate our approach using BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) data on anisotropic flow. In particular, we show that, compared to standard Glauber-inspired calculations, our formalism provides a better description of the centrality dependence of the ratio of elliptic flow and triangular flow. It also naturally explains the evolution of elliptic flow fluctuations between RHIC and LHC energies.

    Comments:
    v1: 7 pages, 2 figures. v2: 10 pages, 6 figures; Extensive revision of the paper. We now use ATLAS data. More observables investigated in Figs 3 and 4. Detailed justification of formulas in Appendix A. Validity of formalism assessed in Appendix B
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1902.07168 [pdf]
    PRC(2019)·35 citations

Affiliations

first authorsco-authorsvia INSPIRE