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Nuclear Theory·nucl-th

Friday·July 10, 2015

6 papers—3 primary·3 cross-listed

All6Primary3Cross-lists3
  1. 01

    [Submitted on 9 Jul 2015]

    General transformation of alpha cluster model wave function to jj-coupling shell model in various 4N nuclei

    N. Itagaki · H. Matsuno · T. Suhara

    The antisymmetrized quasi-cluster model (AQCM) is a method to describe a transition from the alpha-cluster wave function to the jj-coupling shell model wave function. In this model, the cluster-shell transition is characterized by only two parameters; R representing the distance between alpha clusters and Lambda describing the breaking of alpha clusters, and the contribution of the spin-orbit interaction, very important in the jj-coupling shell model, can be taken into account starting with the alpha cluster model wave function. In this article we show the generality of AQCM by extending the application to heavier region; various 4N nuclei from 4He to 52Fe. We show and compare the energy curves for the alpha+40Ca cluster configuration calculated with and without alpha breaking effect in 44Ti.

    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1507.02400 [pdf]
    PTEP(2016)·21 citations
  2. 02

    [Submitted on 9 Jul 2015]

    The BCS pairing gap in the on-shell limit of the Similarity Renormalization Group

    E. Ruiz Arriola · S. Szpigel · V.S. Timoteo

    The pairing gap plays a fundamental role in the nuclear many-body problem and many large scale and accurate mass formula fits suggest the smooth nuclear mass dependence in the liquid drop model which lacks a theoretical motivation. Within the BCS theory we analyze the impact of phase equivalent interactions on the pairing gap for a translational invariant many-fermion system such as nuclear and neutron matter. To that end we use explicitly the Similarity Renormalization Group (SRG) transformations. We show that in the on-shell and continuum limits the pairing gap vanishes. For finite size systems the pairing gap can be computed directly from the scattering phase-shifts by the formula where is the Fermi momentum and the level spacing at the Fermi energy which for the harmonic oscillator shell model becomes , so that The comparison with double differences from binding energies of stable nuclei is satisfactory and the discrepancy with the large scale analysis may be attributed to the lack of three-body forces. Nevertheless, the on-shell two-body interaction provides a basis for the dependency and accounts for 75\% of the coefficient .

    Comments:
    10 pages, 4 figures. Major changes, References added
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1507.02475 [pdf]
    2 citations
  3. 03

    [Submitted on 9 Jul 2015]

    Beyond the mean field in the particle-vibration coupling scheme

    M. Baldo (1) · P.F. Bortignon (2,3) · G. Colo' (2,3) · D. Rizzo (2) · L. Sciacchitano (2) ((1) INFN, Sezione di Catania, via S. Sofia 64, I-95123, Catania, Italy, (2) Dipartimento di Fisica, Universita' degli Studi di Milano, via Celoria 16, I-20133 Milano, Italy, (3) INFN, sezione di Milano, via Celoria 16, via Celoria 16, I-20133 Milano, Italy)

    The Energy Density Functional theory is one of the most used methods developed in nuclear structure. It is based on the assumption that the energy of the ground state is a functional only of the density profile. The method is extremely successful within the effective force approach, noticeably the Skyrme or Gogny forces, in reproducing the nuclear binding energies and other bulk properties along the whole mass table. Although the Density Functional is in this case represented formally as the Hartree-Fock mean field of an effective force, the corresponding single-particle states in general do not reproduce the phenomenology particularly well. To overcome this difficulty, a strategy has been developed where the effective force is adjusted to reproduce directly the single particle energies, trying to keep the ground state energy sufficiently well reproduced. An alternative route, that has been developed along several years, for solving this problem is to introduce the mean field fluctuations, as represented by the collective vibrations of the nuclear system, and their influence on the single particle dynamics and structure. This is the basis of the particle-vibration coupling model. In this paper we present a formal theory of the particle-vibration coupling model based on the Green' s function method. The theory extends to realistic effective forces the macroscopic particle-vibration coupling models and the (microscopic) Nuclear Field Theory. It is formalized within the functional derivative approach to many-body theory. An expansion in diagrams is devised for the single particle self-energy and the phonon propagator. Critical aspects of the particle-vibration coupling model are analysed in general. Applications at the lowest order of the expansion are presented and discussed.

    Comments:
    J. Phys. G (in press)
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1507.02516 [pdf]
    J.Phys.G(2015)·25 citations
  4. 04

    [Submitted on 9 Jul 2015] (cross-list from hep-ph)

    Photon emission in neutral current interactions at the T2K experiment

    E. Wang🇨🇳 · L. Alvarez-Ruso🇪🇸 · Y. Hayato🇯🇵 · K. Mahn🇺🇸 · J. Nieves🇪🇸

    We have applied a microscopic model for single photon emission in neutral current interactions on nucleons and nuclei to determine the number and distributions of such events at the Super-Kamiokande detector, for the flux and beam exposure of the T2K experiment in neutrino mode. These reactions represent an irreducible background in electron-(anti)neutrino appearance measurements aimed at a precise measurement of mixing angle and the violating phase. We have obtained a total number of photon events that is twice larger than the one from the NEUT event generator (version 5.1.4.2) used in the analysis of T2K data. Detailed comparisons of energy and angular distributions for the and fluxes have also been performed.

    Comments:
    9 pages, 6 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    1507.02446 [pdf]
    PRD(2015)·26 citations
  5. 05

    [Submitted on 9 Jul 2015] (cross-list from hep-th)

    Constructing higher-order hydrodynamics: The third order

    Sašo Grozdanov🇳🇱 · Nikolaos Kaplis🇳🇱

    Hydrodynamics can be formulated as the gradient expansion of conserved currents in terms of the fundamental fields describing the near-equilibrium fluid flow. In the relativistic case, the Navier-Stokes equations follow from the conservation of the stress-energy tensor to first order in derivatives. In this paper, we go beyond the presently understood second-order hydrodynamics and discuss the systematisation of obtaining the hydrodynamic expansion to an arbitrarily high order. As an example of the algorithm that we present, we fully classify the gradient expansion at third order for neutral fluids in four dimensions, thus finding the most general next-to-leading-order corrections to the relativistic Navier-Stokes equations in curved space-time. In doing so, we list new transport coefficient candidates in the conformal and in the non-conformal case. As we do not consider any constraints that could potentially arise from the local entropy current analysis, this is the maximal possible set of neutral third-order transport coefficients. To investigate the physical implications of these new transport coefficients, we obtain the third-order corrections to the linear dispersion relations that describe the propagation of diffusion and sound waves in relativistic fluids. We also compute the corrections to the scalar (spin-) two-point correlation function of the third-order stress-energy tensor. Furthermore, as an example of a non-linear hydrodynamic flow, we calculate the third-order corrections to the energy density of a boost-invariant Bjorken flow. Finally, we apply our field theoretic results to the supersymmetric Yang-Mills fluid at infinite 't Hooft coupling and infinite number of colours to find the values of five new linear combinations of the conformal transport coefficients.

    Comments:
    V5: 33 pages. Typos fixed in Eqs. (5), (118) and (126). As a result, the value of the transport coefficient has been corrected
    Subjects:
    High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Fluid Dynamics (physics.flu-dyn)
    arXiv:
    1507.02461 [pdf]
    PRD(2016)·109 citations
  6. 06

    [Submitted on 9 Jul 2015] (cross-list from hep-th)

    Universal hydrodynamic flow in holographic planar shock collisions

    Paul M. Chesler🇺🇸 · Niki Kilbertus🇩🇪 · Wilke van der Schee🇺🇸

    We study the collision of planar shock waves in AdS as a function of shock profile. In the dual field theory the shock waves describe planar sheets of energy whose collision results in the formation of a plasma which behaves hydrodynamically at late times. We find that the post-collision stress tensor near the light cone exhibits transient non-universal behavior which depends on both the shock width and the precise functional form of the shock profile. However, over a large range of shock widths, including those which yield qualitative different behavior near the future light cone, and for different shock profiles, we find universal behavior in the subsequent hydrodynamic evolution. Additionally, we compute the rapidity distribution of produced particles and find it to be well described by a Gaussian.

    Comments:
    23 pages, 15 figures, published version
    Subjects:
    High Energy Physics — Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1507.02548 [pdf]
    JHEP(2015)·43 citations

Affiliations

first authorsco-authorsvia INSPIRE