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Nuclear Theory·nucl-th

Friday·January 15, 2016

11 papers—5 primary·6 cross-listed

All11Primary5Cross-lists6
  1. 01

    [Submitted on 14 Jan 2016]

    Solitonic modulation and Lifshitz point in an external magnetic field within Nambu--Jona-Lasinio model

    Gaoqing Cao🇨🇳 · Anping Huang🇨🇳

    We study the inhomogeneous solitonic modulation of a chiral condensate within the effective Nambu--Jona-Lasinio model when a constant external magnetic field is present. The self-consistent Pauli-Villars regularization scheme is adopted to manipulate the ultraviolet divergence encountered in the thermodynamic quantities. In order to determine the chiral restoration lines efficiently, a new kind of Ginzburg-Landau expansion approach is proposed here. At zero temperature, we find that both the upper and lower boundaries of the solitonic modulation oscillate with the magnetic field in the -- phase diagram which is actually the de Hass-van Alphan (dHvA) oscillation. It is very interesting to find out how the tricritical Lifshitz point evolves with the magnetic field: There are also dHvA oscillations in the -- and -- curves, though the tricritical temperature increases monotonically with the magnetic field.

    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
    arXiv:
    1601.03493 [pdf]
    PRD(2016)·17 citations
  2. 02

    [Submitted on 14 Jan 2016]

    No-core configuration-interaction model for the isospin- and angular-momentum-projected states

    W. Satula · P. Baczyk · J. Dobaczewski · M. Konieczka

    [Background] Single-reference density functional theory is very successful in reproducing bulk nuclear properties like binding energies, radii, or quadrupole moments throughout the entire periodic table. Its extension to the multi-reference level allows for restoring symmetries and, in turn, for calculating transition rates. [Purpose] We propose a new no-core-configuration-interaction (NCCI) model treating properly isospin and rotational symmetries. The model is applicable to any nucleus irrespective of its mass and neutron- and proton-number parity. It properly includes polarization effects caused by an interplay between the long- and short-range forces acting in the atomic nucleus. [Methods] The method is based on solving the Hill-Wheeler-Griffin equation within a model space built of linearly-dependent states having good angular momentum and properly treated isobaric spin. The states are generated by means of the isospin and angular-momentum projection applied to a set of low-lying (multi)particle-(multi)hole deformed Slater determinants calculated using the self-consistent Skyrme-Hartree-Fock approach. [Results] The theory is applied to calculate energy spectra in N~Z nuclei that are relevant from the point of view of a study of superallowed Fermi beta-decays. In particular, a new set of the isospin-symmetry-breaking corrections to these decays is given. [Conclusions] It is demonstrated that the NCCI model is capable to capture main features of low-lying energy spectra in light and medium-mass nuclei using relatively small model space and without any local readjustment of its low-energy coupling constants. Its flexibility and a range of applicability makes it an interesting alternative to the conventional nuclear shell model.

    Comments:
    13 pages, 10 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1601.03593 [pdf]
    PRC(2016)·40 citations
  3. 03

    [Submitted on 14 Jan 2016]

    Harmonic Oscillator Trap and the Phase-Shift Approximation

    H. S. Köhler

    The energy-spectrum of two point-like particles interacting in a 3-D isotropic Harmonic Oscillator (H.O.) trap is related to the free scattering phase-shifts of the particles by a formula first published by Busch et al. It is here used to find an expression for the \it shift \rm of the energy levels, caused by the interaction, rather than the perturbed spectrum itself. In the limit of high energy (large quantum number of the H.O.) this shift is shown to be given by , also valid in the limit of infinite as well as zero scattering length at all H.O. energies. Numerical investigation shows that the shifts differ from the exact result of Busch et al, by less than except for when it can be as large as . This approximation for the energy-shift is well known from another exactly solvable model, namely that of two particles interacting in a spherical infinite square-well trap (or box) of radius in the limit , and/or in the limit of large energy. It is in this context referred to as the \it phase-shift approximation \rm. It can be (and has been) used in (infinite) nuclear matter calculations to calculate the two-body effective interaction in situations where in-medium effects can be neglected. It has also been used in expressing the energy of free electrons in a metal.

    Comments:
    arXiv admin note: text overlap with arXiv:1110.0039
    Subjects:
    Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); Mathematical Physics (math-ph); math.MP (math.MP); Quantum Physics (quant-ph)
    arXiv:
    1601.03692 [pdf]
    Physics(2014)·1 citation
  4. 04

    [Submitted on 14 Jan 2016]

    Hartree-Fock Many-Body Perturbation Theory for Nuclear Ground-States

    Alexander Tichai · Joachim Langhammer · Sven Binder · Robert Roth

    We investigate the order-by-order convergence behavior of many-body perturbation theory (MBPT) as a simple and efficient tool to approximate the ground-state energy of closed-shell nuclei. To address the convergence properties directly, we explore perturbative corrections up to 30th order and highlight the role of the partitioning for convergence. The use of a simple Hartree-Fock solution to construct the unperturbed basis leads to a convergent MBPT series for soft interactions, in contrast to, e.g., a harmonic oscillator basis. For larger model spaces and heavier nuclei, where a direct high-order MBPT calculation in not feasible, we perform third-order calculation and compare to advanced ab initio coupled-cluster calculations for the same interactions and model spaces. We demonstrate that third-order MBPT provides ground-state energies for nuclei up into tin isotopic chain that are in excellent agreement with the best available coupled-cluster results at a fraction of the computational cost.

    Comments:
    6 pages, 5 figures, 1 table
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1601.03703 [pdf]
    PLB(2016)·92 citations
  5. 05

    [Submitted on 14 Jan 2016]

    Sensitivity of the COSY Dibaryon Candidate to np Elastic Scattering Measurements

    R.L. Workman🇺🇸 · W.J. Briscoe🇺🇸 · I.I. Strakovsky (GWU)🇺🇸

    The case for a dibaryon resonance, appearing in np scattering, has support from a WASA-at-COSY measurement of the polarization quantity A_y over a center-of-mass energy region suggested by structures seen earlier in two-pion production experiments. Here we compare fits with and without an associated pole in order to clarify the impact of these COSY data. We then consider what further np scattering measurements would most clearly distinguish between the pole and non-pole fit results.

    Comments:
    7 pages, 7 figures, 1 table; added 1 figure and made small text polishing
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1601.03706 [pdf]
    PRC(2016)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE