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Nuclear Theory·nucl-th

Friday·April 7, 2017

6 papers—4 primary·2 cross-listed

All6Primary4Cross-lists2
  1. 01

    [Submitted on 5 Apr 2017]

    Quantum phase transitions and collective enhancement of level density in odd-A and odd-odd nuclei

    S. Karampagia · A. Renzaglia · V. Zelevinsky

    The nuclear shell model assumes an effective mean-field plus interaction Hamiltonian in a specific configuration space. We want to understand how various interaction matrix elements affect the observables, the collectivity in nuclei and the nuclear level density for odd-A and odd-odd nuclei. Using the sd and pf shells, we vary specific groups of matrix elements and study the evolution of energy levels, transition rates and the level density. In all cases studied, a transition between a "normal" and a collective phase is induced, accompanied by an enhancement of the level density in the collective phase. In distinction to neighboring even-even nuclei, the enhancement of the level density is observed already at the transition point. The collective phase is reached when the single-particle transfer matrix elements are dominant in the shell model Hamiltonian, providing a sign of their fundamental role.

    Comments:
    28 pages, 8 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1704.01601 [pdf]
    NPA(2017)·11 citations
  2. 02

    [Submitted on 6 Apr 2017]

    First-principles results for electromagnetic properties of shell nuclei

    Archana Saxena · Praveen C. Srivastava

    In this work we present shell-model calculations for electric quadrupole moments and magnetic dipole moments of shell nuclei using valence-space Hamiltonians derived with two approaches: the in-medium similarity renormalization group (IM-SRG) and the coupled-cluster effective interaction (CCEI). Results are in a reasonable agreement with the available experimental data as well as with the results from the phenomenological USDB effective interaction. This work will add more information to the available results for the spectroscopy of shell nuclei.

    Comments:
    13 pages, 3 figures, 3 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1704.01798 [pdf]
    PRC(2017)·22 citations
  3. 03

    [Submitted on 6 Apr 2017]

    Steady state of isolated systems versus microcanonical ensemble in cell model of particle creation and annihilation

    M. Gazdzicki · M. I. Gorenstein · A. Fronczak · P. Fronczak · M. Mackowiak-Pawlowska

    A simple model of particle creation and annihilation in an isolated assembly of particles with conserved energy and fixed volume, the Cell Model, is formulated. With increasing time, particle number distribution, obtained by averaging over many systems, approaches a time-independent, steady state distribution. Dependence of the steady state distribution on creation and annihilation conditional reaction probabilities is studied. The results obtained for the steady state are compared with predictions of statistical mechanics within the microcanonical ensemble. In general, the predictions of both models are different. They agree only if the creation and annihilation conditional probabilities are equal. This condition also results in the detailed balance in the steady state.

    Comments:
    25 pages, 5 figures, replaced by the published version
    Subjects:
    Nuclear Theory (nucl-th); Statistical Mechanics (cond-mat.stat-mech)
    arXiv:
    1704.01878 [pdf]
    IJMPE(2017)·3 citations
  4. 04

    [Submitted on 6 Apr 2017]

    Low energy meson spectrum from a QCD approach based on many-body methods

    D. A. Amor-Quiroz🇲🇽 · T. Yépez-Martínez🇦🇷 · P. O. Hess🇲🇽 · O. Civitarese🇦🇷 · A. Weber🇲🇽

    The TDA and RPA many-body methods are applied to a QCD motivated Hamiltonian in the Coulomb gauge. The gluon effects in the low energy domain are accounted for by the Instantaneous color-Coulomb Interaction between color-charge densities, approximated by the sum of a Coulomb and a confining linear potentials. We use the eigenfunctions of the harmonic oscillator as a basis for the quantization of the quark fields, and discuss how suitable this basis is in various steps of the calculation. We show that the TDA results already reproduce the gross-structure of the light flavored meson states. The pion-like state in the RPA description, which is a highly collective state, is in a better agreement with the experimental value. The results are related to other nonperturbative treatments and compared to experimental data. We discuss the advantages of the present approach.

    Comments:
    23 pages, 3 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1704.01947 [pdf]
    IJMPE(2017)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE