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Nuclear Theory·nucl-th

Monday·April 18, 2016

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 05

    [Submitted on 6 Apr 2016] (cross-list from cond-mat.mes-hall)

    Quantum Wigner molecules in semiconductor quantum dots and cold-atom optical traps and their mathematical symmetries

    Constantine Yannouleas · Uzi Landman

    Strong repelling interactions between a few fermions or bosons confined in two-dimensional circular traps lead to particle localization and formation of quantum Wigner molecules (QWMs) possessing definite point-group space symmetries. These point-group symmetries are "hidden" (or emergent), namely they cannot be traced in the circular single-particle densities (SPDs) associated with the exact many-body wave functions, but they are manifested as characteristic signatures in the ro-vibrational spectra. An example, among many, are the few-body QWM states under a high magnetic field or at fast rotation, which are precursor states for the fractional quantum Hall effect. The hidden geometric symmetries can be directly revealed by using spin-resolved conditional probability distributions, which are extracted from configuration-interaction (CI), exact-diagonalization wave functions. The hidden symmetries can also be revealed in the CI SPDs by reducing the symmetry of the trap (from circular to elliptic to quasi-linear). In addition the hidden symmetries are directly connected to the explicitly broken-symmetry (BS) solutions of mean-field approaches, such as unrestricted Hartree-Fock (UHF). A companion step of restoration of the broken symmetries via projection operators applied on the BS-UHF solutions produces wave functions directly comparable to the CI ones, and sheds further light into the role played by the emergence of hidden symmetries in the exact many-body wave functions. Illustrative examples of the importance of hidden symmetries in the many-body problem of few electrons in semiconductor quantum dots and of few ultracold atoms in optical traps (where unprecedented control of the interparticle interaction has been experimentally achieved recently) will be presented.

    Comments:
    11 pages with 4 color figures. Invited extended abstract for the Proceedings of the 16th International Conference on Computational and Mathematical Methods in Science and Engineering, CMMSE 2016, Rota, Cadiz, Spain, 4-8 July, 2016
    Subjects:
    Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    1604.01749 [pdf]
    0 citations
  2. 06

    [Submitted on 14 Apr 2016] (cross-list from hep-ph)

    Cumulative production of pions by heavy baryonic resonances in proton-nucleus collisions

    A. Motornenko🇺🇦 · M. I. Gorenstein🇺🇦

    Pion production in proton-nucleus (p+A) collisions outside the kinematical boundary of proton-nucleon (p+N) reactions, the so-called cumulative effect, is studied. Restrictions from energy-momentum conservation on the energy of pions emitted in the backward direction in the target rest frame are analyzed. It is assumed that the cumulative pions are produced in p+A reactions by heavy baryonic resonances. The baryonic resonances are first created in p+N reactions. Due to successive collisions with nuclear nucleons the masses of these resonances may then increase and, simultaneously, their longitudinal velocities decrease. We also use the Ultra relativistic Quantum Molecular Dynamics model to reveal the key role of successive collisions of baryonic resonances with nuclear nucleons for cumulative pion production in p+A reactions. Further experimental studies of cumulative hadron production in p+A reactions at high collision energies are needed to search for heavy hadron-like objects and investigate their properties.

    Comments:
    21 pages, 36 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1604.04308 [pdf]
    J.Phys.G(2017)·13 citations
  3. 07

    [Submitted on 15 Apr 2016] (cross-list from hep-ph)

    Classical Electromagnetic Fields from Quantum Sources in Heavy-Ion Collisions

    Robert Holliday🇺🇸 · Ryan McCarty🇺🇸 · Balthazar Peroutka🇺🇸 · Kirill Tuchin🇺🇸

    Electromagnetic fields are generated in high energy nuclear collisions by spectator valence protons. These fields are traditionally computed by integrating the Maxwell equations with point sources. One might expect that such an approach is valid at distances much larger than the proton size and thus such a classical approach should work well for almost the entire interaction region in the case of heavy nuclei. We argue that, in fact, the contrary is true: due to the quantum diffusion of the proton wave function, the classical approximation breaks down at distances of the order of the system size. We compute the electromagnetic field created by a charged particle described initially as a Gaussian wave packet of width 1 fm and evolving in vacuum according to the Klein-Gordon equation. We completely neglect the medium effects. We show that the dynamics, magnitude and even sign of the electromagnetic field created by classical and quantum sources are different.

    Comments:
    12 pages, 4 figures. V2: a numerical error corrected, figures improved, other minor improvements
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1604.04572 [pdf]
    NPA(2017)·28 citations

Affiliations

first authorsco-authorsvia INSPIRE