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Nuclear Theory·nucl-th

Monday·July 11, 2016

7 papers—2 primary·5 cross-listed

All7Primary2Cross-lists5
  1. 03

    [Submitted on 7 Jul 2016] (cross-list from hep-ph)

    Nonthermal Fixed Points in Quantum Field Theory Beyond the Weak-Coupling Limit

    Jürgen Berges🇩🇪 · Benjamin Wallisch🇬🇧

    Quantum systems in extreme conditions can exhibit universal behavior far from equilibrium associated to nonthermal fixed points with a wide range of topical applications from early-universe inflaton dynamics and heavy-ion collisions to strong quenches in ultracold quantum gases. So far, most studies have relied on a mapping of the quantum dynamics onto a classical-statistical theory that can be simulated on a computer. However, the mapping is based on a weak-coupling limit, while phenomenological applications often require moderate interaction strengths. We report on the observation of nonthermal fixed points directly in quantum field theory beyond the weak-coupling limit. For the example of a relativistic scalar O(N)-symmetric quantum field theory, we numerically solve the nonequilibrium dynamics employing a 1/N expansion to next-to-leading order, which does not rely on a small coupling parameter. Starting from two different sets of overoccupied and of strong-field initial conditions, we find that nonthermal fixed points are not restricted to parameter ranges suitable for classical-statistical simulations, but extend also to couplings of order one. While the infrared behavior is found to be insensitive to the differences in the initial conditions, we demonstrate that transport phenomena to higher momenta depend on the presence or absence of a symmetry-breaking field expectation value.

    Comments:
    17 pages, 17 figures; v2: minor changes, matches published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1607.02160 [pdf]
    PRD(2017)·42 citations
  2. 04

    [Submitted on 8 Jul 2016] (cross-list from nucl-ex)

    Has the QCD critical point been observed at RHIC? - A Rebuttal

    Roy A. Lacey (Department of Chemistry, Stony Brook University)🇺🇸

    This note rebuts an old, but recurring claim by Antoniou, Davis and Diakonos [1] that the critical point and associated critical exponents reported in Ref. [2], is based on an erroneous treatment of scaling relations near the critical point.

    Comments:
    1 page, 1 Fig. - Rebuttal to arXiv:1607.01326
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1607.02411 [pdf]
    1 citation
  3. 05

    [Submitted on 8 Jul 2016] (cross-list from hep-ph)

    Janus-Facedness of the Pion: Analytic Instantaneous Bethe-Salpeter Models

    Wolfgang Lucha🇦🇹

    Inversion enables the construction of interaction potentials underlying - under fortunate circumstances even analytic - instantaneous Bethe-Salpeter descriptions of all lightest pseudoscalar mesons as quark-antiquark bound states of Goldstone-boson nature.

    Comments:
    5 pages, 3 figures, contributed to "QCD@Work 2016 - International Workshop on Quantum Chromodynamics: Theory and Experiment" (27 - 30 June 2016, Martina Franca, Italy)
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1607.02426 [pdf]
    EPJ Web Conf.(2016)·5 citations
  4. 06

    [Submitted on 8 Jul 2016] (cross-list from hep-lat)

    The QCD equation of state at finite density from analytical continuation

    J. Gunther · R. Bellwied · S. Borsanyi · Z. Fodor · S. D. Katz · A. Pasztor · C. Ratti

    We determine the equation of state of QCD at finite chemical potential, to order , for a system of 2+1 quark flavors. The simulations are performed at the physical mass for the light and strange quarks on several lattice spacings; the results are continuum extrapolated using lattices of up to temporal resolution. The QCD pressure and interaction measure are calculated along the isentropic trajectories in the plane corresponding to the RHIC Beam Energy Scan collision energies. Their behavior is determined through analytic continuation from imaginary chemical potentials of the baryonic density. We also determine the Taylor expansion coefficients around from the simulations at imaginary chemical potentials. Strangeness neutrality and charge conservation are imposed, to match the experimental conditions.

    Comments:
    5 pages, 4 figures
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1607.02493 [pdf]
    NPA(2017)·148 citations
  5. 07

    [Submitted on 8 Jul 2016] (cross-list from hep-ph)

    Mass ordering of spectra from fragmentation of saturated gluon states in high multiplicity proton-proton collisions

    Bjoern Schenke🇺🇸 · Soeren Schlichting🇺🇸 · Prithwish Tribedy🇺🇸 · Raju Venugopalan🇺🇸

    The mass ordering of mean transverse momentum and of the Fourier harmonic coefficient of azimuthally anisotropic particle distributions in high energy hadron collisions is often interpreted as evidence for the hydrodynamic flow of the matter produced. We investigate an alternative initial state interpretation of this pattern in high multiplicity proton-proton collisions at the LHC. The QCD Yang-Mills equations describing the dynamics of saturated gluons are solved numerically with initial conditions obtained from the Color Glass Condensate based IP-Glasma model. The gluons are subsequently fragmented into various hadron species employing the well established Lund string fragmentation algorithm of the PYTHIA event generator. We find that this ab initio initial state approach reproduces characteristic features of bulk spectra, in particular the particle mass dependence of and .

    Comments:
    7 pages, 6 figures. v2 : 1 new figure and new references added. To be published in PRL
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1607.02496 [pdf]
    PRL(2016)·114 citations

Affiliations

first authorsco-authorsvia INSPIRE