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Nuclear Theory·nucl-th

Friday·August 19, 2016

10 papers—7 primary·3 cross-listed

All10Primary7Cross-lists3
  1. 08

    [Submitted on 17 Aug 2016] (cross-list from cond-mat.quant-gas)

    A generalized Theory of Diffusion based on Kinetic Theory

    Thomas Schaefer (North Carolina State University)

    We propose to use spin hydrodynamics, a two-fluid model of spin propagation, as a generalization of the diffusion equation. We show that in the dense limit spin hydrodynamics reduces to Fick's law and the diffusion equation. In the opposite limit spin hydrodynamics is equivalent to a collisionless Boltzmann treatment of spin propagation. Spin hydrodynamics avoids unphysical effects that arise when the diffusion equation is used to describe to a strongly interacting gas with a dilute corona. We apply spin hydrodynamics to the problem of spin diffusion in a trapped atomic gas. We find that the observed spin relaxation rate in the high temperature limit [Sommer et al., Nature 472, 201 (2011)] is consistent with the diffusion constant predicted by kinetic theory.

    Comments:
    26 pages, 9 figures; revised version (one figure added), to appear in Phys Rev A
    Subjects:
    Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Fluid Dynamics (physics.flu-dyn)
    arXiv:
    1608.05083 [pdf]
    PRA(2016)·5 citations
  2. 09

    [Submitted on 18 Aug 2016] (cross-list from hep-ph)

    Thermal Electromagnetic Radiation in Heavy-Ion Collisions

    R. Rapp🇺🇸 · H. van Hees🇩🇪

    We review the potential of precise measurements of electromagnetic probes in relativistic heavy-ion collisions for the theoretical understanding of strongly interacting matter. The penetrating nature of photons and dileptons implies that they can carry undistorted information about the hot and dense regions of the fireballs formed in these reactions and thus provide a unique opportunity to measure the electromagnetic spectral function of QCD matter as a function of both invariant mass and momentum. In particular we report on recent progress on how the medium modifications of the (dominant) isovector part of the vector current correlator ( channel) can shed light on the mechanism of chiral symmetry restoration in the hot and/or dense environment. In addition, thermal dilepton radiation enables novel access to (a) the fireball lifetime through the dilepton yield in the low invariant-mass window , and (b) the early temperatures of the fireball through the slope of the invariant-mass spectrum in the intermediate-mass region (). The investigation of the pertinent excitation function suggests that the beam energies provided by the NICA and FAIR projects are in a promising range for a potential discovery of the onset of a first order phase transition, as signaled by a non-monotonous behavior of both low-mass yields and temperature slopes.

    Comments:
    5 pages, 4 figures; contribution to the NICA White Paper (EPJA topical issue)
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1608.05279 [pdf]
    EPJA(2016)·34 citations
  3. 10

    [Submitted on 18 Aug 2016] (cross-list from hep-ph)

    Mott dissociation of pions and kaons in hot, dense quark matter

    A. Dubinin🇵🇱 · A. Radzhabov🇵🇱 · D. Blaschke🇷🇺 · A. Wergieluk🇺🇸

    We describe the Mott dissociation of pions and kaons within a Beth-Uhlenbeck approach based on the PNJL model, which allows for a unified description of bound, resonant and scattering states. Within this model we evaluate the temperature and chemical potential dependent modification of the phase shifts both in the pseudoscalar and scalar isovector meson channels for quark flavors. We show that the character change of the pseudoscalar bound states to resonances in the continuum at the Mott transition temperature is signaled by a jump of the phase shift at the threshold from to zero, in accordance with the Levinson theorem. In particular, we demonstrate the importance of accounting for the scattering continuum states, which ensures that the total phase shift in each of the meson channels vanishes at high energies, thus eliminating mesonic correlations from the thermodynamics at high temperatures. In this way, we prove that the present approach provides a unified description of the transition from a meson gas to a quark-gluon plasma. We discuss the occurrence of an anomalous mode for mesons composed of quarks with unequal masses which is particularly pronounced for and states at finite densities a a possible mechanism to explain the "horn" effect for the ratio in heavy-ion collisions.

    Comments:
    11 pages, 9 figures, discussion of K+/pi+ and references added
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1608.05383 [pdf]
    PRD(2017)·32 citations

Affiliations

first authorsco-authorsvia INSPIRE