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Nuclear Theory·nucl-th

Thursday·February 18, 2016

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 01

    Di-neutrons in neutron matter within Brueckner-Hartree-Fock approach

    F. Isaule · H. F. Arellano · A. Rios

    We investigate the appearance of di-neutron bound states in pure neutron matter within the Brueckner-Hartree-Fock approach at zero temperature. We consider Argonne and Paris bare interactions as well as chiral two- and three-nucleon forces. Self-consistent single-particle potentials are calculated controlling explicitly singularities in the matrix associated with bound states. Di-neutrons are loosely bound, with binding energies below MeV, but are unambiguously present for Fermi momenta below fm for all interactions. Within the same framework we are able to calculate and characterize di-neutron bound states, obtaining mean radii as high as fm. The resulting equations of state and mass-radius relations for pure neutron stars are analyzed including di-neutron contributions.

    nucl-thPRC(2016)·27 citations
  2. 02

    Microscopic study of Ca+Ni fusion reactions

    D. Bourgin🇫🇷 · C. Simenel🇦🇺 · S. Courtin🇫🇷 · F. Haas🇫🇷

    Background: Heavy-ion fusion reactions at energies near the Coulomb barrier are influenced by couplings between the relative motion and nuclear intrinsic degrees of freedom of the colliding nuclei. The time-dependent Hartree-Fock (TDHF) theory, incorporating the couplings at the mean-field level, as well as the coupled-channels (CC) method are standard approaches to describe low energy nuclear reactions. Purpose: To investigate the effect of couplings to inelastic and transfer channels on the fusion cross sections for the reactions Ca+Ni and Ca+Ni. Methods: Fusion cross sections around and below the Coulomb barrier have been obtained from coupled-channels (CC) calculations, using the bare nucleus-nucleus potential calculated with the frozen Hartree-Fock method and coupling parameters taken from known nuclear structure data. The fusion thresholds and neutron transfer probabilities have been calculated with the TDHF method. Results: For Ca+Ni, the TDHF fusion threshold is in agreement with the most probable barrier obtained in the CC calculations including the couplings to the low-lying octupole state for Ca and to the low-lying quadrupole state for Ni. This indicates that the octupole and quadrupole states are the dominant excitations while neutron transfer is shown to be weak. For Ca+Ni, the TDHF barrier is lower than predicted by the CC calculations including the same inelastic couplings as those for Ca+Ni. TDHF calculations show large neutron transfer probabilities in Ca+Ni which could result in a lowering of the fusion threshold. Conclusions: Inelastic channels play an important role in Ca+Ni and Ca+Ni reactions. The role of neutron transfer channels has been highlighted in Ca+Ni.

    nucl-thPRC(2016)·24 citations
  3. 03

    Weak and strong coupling limits of the Boltzmann equation in the relaxation-time approximation

    Amaresh Jaiswal🇩🇪 · Bengt Friman🇩🇪 · Krzysztof Redlich🇵🇱

    We consider a momentum dependent relaxation time for the Boltzmann equation in the relaxation time approximation. We employ a power law parametrization for the momentum dependence of the relaxation time, and calculate the shear and bulk viscosity, as well as, the charge and heat conductivity. We show, that for the two popular parametrizations, referred to as the linear and quadratic ansatz, one can obtain transport coefficients which corresponds to the weak and strong coupling regimes, respectively. We also show that, for a system of massless particles with vanishing chemical potential, the off-equilibrium corrections to the phase-space distribution function calculated with the quadratic ansatz are identical with those of the Grad's 14-moment method.

    nucl-thhep-ph11 citations
  4. 04

    Investigating the QCD phase diagram with hadron multiplicities at NICA

    F. Becattini (U. Florence, Italy)🇮🇹 · R. Stock (U. Franfkurt, Germany)🇩🇪

    We discuss the potential of the experimental programme at NICA to investigate the QCD phase diagram and particularly the position of the critical line at large baryon-chemical potential with accurate measurements of particle multiplicities. We briefly review the present status and we outline the tasks to be accomplished both theoretically and the experimentally to make hadronic abundances a sensitive probe.

    nucl-thEPJA(2016)·3 citations

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