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Nuclear Theory·nucl-th

Monday·July 20, 2015

10 papers—4 primary·6 cross-listed

All10Primary4Cross-lists6
  1. 05

    [Submitted on 1 Jul 2015] (cross-list from cond-mat.quant-gas)

    Simulation of Time-dependent Heisenberg Models in 1D

    A. G. Volosniev · H.-W. Hammer · N. T. Zinner

    In this paper, we provide a theoretical analysis of strongly interacting quantum systems confined by a time-dependent external potential in one spatial dimension. We show that such systems can be used to simulate spin chains described by Heisenberg Hamiltonians in which the exchange coupling constants can be manipulated by time-dependent driving of the shape of the external confinement. As illustrative examples, we consider a harmonic trapping potential with a variable frequency and an infinite square well potential with a time-dependent barrier in the middle.

    Comments:
    Version accepted for publication in PRB
    Subjects:
    Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
    arXiv:
    1507.00186 [pdf]
    PRB(2016)·16 citations
  2. 06

    [Submitted on 16 Jul 2015] (cross-list from astro-ph.SR)

    Some properties of convection in hybrid stars

    A.V. Yudin · M. Hempel · D.K. Nadyozhin · T.L. Razinkova

    It is shown that the unusual thermodynamic properties of matter within the region of two-phase coexistence in hybrid stars result in a change of the standard condition for beginning of convection. In particular, the thermal flux transported by convection may be directed towards the stellar center. We discuss favorable circumstances leading to such an effect of "inverse convection" and its possible influence on the thermal evolution of hybrid stars.

    Comments:
    13 pages, 3 figures. The discussion is extended according to referees suggestions. New references added. Accepted to MNRAS
    Subjects:
    Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    1507.04598 [pdf]
    MNRAS(2016)·7 citations
  3. 07

    [Submitted on 16 Jul 2015] (cross-list from hep-ph)

    Critical versus spurious fluctuations in the search for the QCD critical point

    Maurício Hippert🇧🇷 · Eduardo S. Fraga🇧🇷 · Edivaldo M. Santos🇧🇷

    The neighborhood of the QCD chiral critical point is characterized by intense fluctuations of the chiral field which could, in principle, generate pronounced experimental signatures. However, experimental uncertainties which are inherent to heavy ion collisions, as well as the modest size and duration of the formed plasma, will severely attenuate these signatures. Using Monte Carlo techniques, we study second-order event-by-event moments of pions as a prototype for signatures of the chiral critical point based on the enhancement of the correlation length and event-by-event analysis. We test their viability against some realistic ingredients, similar to the ones found in the RHIC Beam Energy Scan program.

    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1507.04764 [pdf]
    PRD(2016)·18 citations
  4. 08

    [Submitted on 17 Jul 2015] (cross-list from hep-ph)

    Derivation of second-order relativistic hydrodynamics for reactive multi-component systems

    Yuta Kikuchi🇯🇵 · Kyosuke Tsumura🇯🇵 · Teiji Kunihiro🇯🇵

    We derive the second-order hydrodynamic equation for reactive multi-component systems from the relativistic Boltzmann equation. In the reactive system, particles can change their species under the restriction of the imposed conservation laws during the collision process. Our derivation is based on the renormalization group (RG) method, in which the Boltzmann equation is solved in an organized perturbation method as faithfully as possible and possible secular terms are resummed away by a suitable setting of the initial value of the distribution function. The microscopic formulae of the relaxation times and the lengths are explicitly given as well as those of the transport coefficients for the reactive multi-component system. The resultant hydrodynamic equation with these formulae has nice properties that it satisfies the positivity of the entropy production rate and the Onsager's reciprocal theorem, which ensure the validity of our derivation.

    Comments:
    18 pages, 2 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Fluid Dynamics (physics.flu-dyn)
    arXiv:
    1507.04894 [pdf]
    PRC(2015)·21 citations
  5. 09

    [Submitted on 17 Jul 2015] (cross-list from hep-lat)

    Nucleon and pion structure with lattice QCD simulations at physical value of the pion mass

    A. Abdel-Rehim (Cyprus Inst.)🇨🇾 · C. Alexandrou (Cyprus Inst. & Univ. of Cyprus)🇨🇾 · M. Constantinou (Cyprus Inst. & Univ. of Cyprus)🇨🇾 · P. Dimopoulos (Fermi Center & Rome Tor Vergata)🇮🇹 · R. Frezzotti (INFN & Rome Tor Vergata)🇮🇹 · K. Hadjiyiannakou (Univ. of Cyprus & Cyprus Inst.)🇨🇾 · K. Jansen (DESY)🇩🇪 · Ch. Kallidonis (Cyprus Inst.)🇨🇾 · B. Kostrzewa (Humboldt Univ. & DESY)🇩🇪 · G. Koutsou (Cyprus Inst.)🇨🇾 · M. Mangin-Brinet (Grenoble)🇫🇷 · M. Oehm (Bonn Univ.)🇩🇪 and 3 other authors

    We present results on the nucleon scalar, axial and tensor charges as well as on the momentum fraction, and the helicity and transversity moments. The pion momentum fraction is also presented. The computation of these key observables is carried out using lattice QCD simulations at a physical value of the pion mass. The evaluation is based on gauge configurations generated with two degenerate sea quarks of twisted mass fermions with a clover term. We investigate excited states contributions with the nucleon quantum numbers by analyzing three sink-source time separations. We find that, for the scalar charge, excited states contribute significantly and to a less degree to the nucleon momentum fraction and helicity moment. Our analysis yields a value for the nucleon axial charge agrees with the experimental value and we predict a value of 1.027(62) in the scheme at 2 GeV for the isovector nucleon tensor charge directly at the physical point. The pion momentum fraction is found to be in the at 2 GeV.

    Comments:
    The experimental value of the helicity plotted in Fig.17 is corrected. ETM Collaboration. 25 pages, 19 figures. Version accepted for PRD (volume 92, eid 114513)
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1507.04936 [pdf]
    PRD(2015)·175 citations
  6. 10

    [Submitted on 17 Jul 2015] (cross-list from hep-ph)

    Tetraquarks from the Bethe-Salpeter equation

    Gernot Eichmann🇩🇪 · Christian S. Fischer🇩🇪 · Walter Heupel🇩🇪

    We present a numerical solution of the four-quark Bethe-Salpeter equation for a scalar tetraquark. We find that the four-body equation dynamically generates pseudoscalar poles in the Bethe-Salpeter amplitude. The sensitivity to the pion poles leads to a light isoscalar tetraquark mass M ~ 400 MeV, which is comparable to that of the sigma/f0(500). The masses of its multiplet partners kappa and a0/f0 follow a similar pattern, thereby providing support for the tetraquark interpretation of the light scalar nonet.

    Comments:
    7 pages, 4 figures. Proceedings of the workshop "Excited QCD 2015", Tatranska Lomnica, Slovakia, March 8-14, 2015. To be published in Acta Physica Polonica B Proc. Suppl
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1507.05022 [pdf]
    Acta Phys.Polon.Supp.(2015)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE