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Nuclear Theory·nucl-th

Thursday·February 13, 2020

6 papers—2 primary·4 cross-listed

All6Primary2Cross-lists4
  1. 03

    [Submitted on 11 Feb 2020] (cross-list from hep-th)

    Conformal Bjorken flow in the general frame and its attractor: Similarities and discrepancies with the Müller-Israel-Stewart formalism

    M. Shokri🇮🇷 · F. Taghinavaz🇮🇷

    We investigate the implications of the general frame approach for conformal Bjorken flow beyond the earlier studies. We show that the power series solution at late times is not unique and is accompanied by an exact solution of the form , which becomes unphysical if taken on shell. In contrast to the Müller-Israel-Stewart formalism, a matching between results and the hydro expansion is only possible up to the first order, which gives rise to . Matching the results to the next order gives rise to causality/stability-violating values. Furthermore, we show that the pressure anisotropy in the general frame cannot capture the hydrodynamization, and we introduce an alternative measure to find the attractor. Using slow-roll expansion, we find an analytical approximation form for the attractor. We also show that the early-time behavior of attractors is related to stability and causality conditions. The attractor solutions outside the stable and causal regime give rise to reheating and negative longitudinal pressures in early times, in contrast to the stable and causal ones. We also comment on the violation of the second law of thermodynamics by the off-shell parameters. We show that for the stable and causal choice of parameters, the off-shell canonical entropy of the attractors, which is not a physical quantity, has a negative divergence in early times before tending to its on-shell limit. On the other hand, the unstable and acausal attractors have non-negative entropy divergence. We speculate that the violation of the second law by stable and causal off-shell parameters is required for stability of the first-order hydrodynamics. We investigate the analytical structure of the Borel-transformed series and find the proper relation between the poles and nonhydro modes.

    Comments:
    14 double-column pages, 7 figures. Version accepted for publication in Physical Review D
    Subjects:
    High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Fluid Dynamics (physics.flu-dyn)
    arXiv:
    2002.04719 [pdf]
    PRD(2020)·23 citations
  2. 04

    [Submitted on 17 Jan 2020] (cross-list from hep-th)

    Light-front quantum mechanics and quantum field theory

    Wayne N. Polyzou🇺🇸

    Contribution to Light Cone 2019: This contribution discusses some of the advantages and unique properties of relativistic quantum theories with kinematic light-front symmetries.

    Comments:
    4 pages, Contribution to Light Cone 2019 - QCD on the light cone: from hadrons to heavy ions, 16-20 September 2019, L'École Polytechnique, Palaiseau, France
    Subjects:
    High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2002.04981 [pdf]
    PoS(2020)·4 citations
  3. 05

    [Submitted on 12 Feb 2020] (cross-list from hep-ph)

    Electromagnetic field of ultrarelativistic charge in topologically random nuclear matter

    Kirill Tuchin🇺🇸

    Electromagnetic field of a fast electric charge in nuclear matter with spatially uniform but random topological charge density is derived. A useful approximation is developed for the relativistic heavy-ion collisions.

    Comments:
    12 pages, 4 figures; V2: a few minor changes + typos
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2002.05047 [pdf]
    NPA(2020)·5 citations
  4. 06

    [Submitted on 12 Feb 2020] (cross-list from hep-ph)

    Multiplicity Dependence of Shear Viscosity, Isothermal Compressibility and Speed of Sound in collisions at = 7 TeV

    Dushmanta Sahu🇮🇳 · Sushanta Tripathy🇮🇳 · Raghunath Sahoo🇮🇳 · Archita Rani Dash🇮🇳

    In order to understand the detailed dynamics of systems produced in collisions, it is essential to know about the Equation of State (EoS) and various thermodynamic properties. In this work, we study the shear viscosity to entropy density ratio, isothermal compressibility and speed of sound of the system by considering a differential freeze-out scenario. We have used a thermodynamically consistent Tsallis non-extensive statistics to have a better explanation for the dynamics of collision systems. While the shear viscosity to entropy density ratio provides information about the measure of fluidity of a system formed in high energy collisions, the isothermal compressibility gives a clear idea about the deviation of the system from a perfect fluid. The speed of sound in the system as a function of gives us a vivid picture of the dynamics of the system. The results show quite an intuitive perspective on high multiplicity collisions and give us a limit of (10 - 20), after which a change in the dynamics of the system may be observed.

    Comments:
    Same as the published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2002.05054 [pdf]
    EPJA(2020)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE