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Nuclear Theory·nucl-th

Wednesday·June 3, 2015

9 papers—5 primary·4 cross-listed

All9Primary5Cross-lists4
  1. 06

    [Submitted on 1 Jun 2015] (cross-list from hep-ph)

    Real time evolution of non-Gaussian cumulants in the QCD critical regime

    Swagato Mukherjee🇺🇸 · Raju Venugopalan🇺🇸 · Yi Yin🇺🇸

    We derive a coupled set of equations that describe the non-equilibrium evolution of cumulants of critical fluctuations for space-time trajectories on the cross-over side of the QCD phase diagram. In particular, novel expressions are obtained for the non-equilibrium evolution of non-Gaussian Skewness and Kurtosis cumulants. Utilizing a simple model of the space-time evolution of a heavy- ion collision, we demonstrate that, depending on the relaxation rate of critical fluctuations, Skewness and Kurtosis can differ significantly in magnitude as well as in sign from equilibrium expectations. Memory effects are important and shown to persist even for trajectories that skirt the edge of the critical regime. We use phenomenologically motivated parameterizations of freeze-out curves, and of the beam energy dependence of the net baryon chemical potential, to explore the implications of our model study for the critical point search in heavy-ion collisions.

    Comments:
    16 pages, 9 figures, accepted version in Phys.Rev. C
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1506.00645 [pdf]
    PRC(2015)·170 citations
  2. 07

    [Submitted on 1 Jun 2015] (cross-list from hep-ph)

    Perturbative Renormalization of Neutron-Antineutron Operators

    Michael I. Buchoff🇺🇸 · Michael Wagman🇺🇸

    Two-loop anomalous dimensions and one-loop renormalization scheme matching factors are calculated for six-quark operators responsible for neutron-antineutron transitions. When combined with lattice QCD determinations of the matrix elements of these operators, our results can be used to reliably predict the neutron-antineutron vacuum transition time, , in terms of basic parameters of baryon-number violating beyond-the-Standard-Model theories. The operators are classified by their chiral transformation properties, and a basis in which there is no operator mixing due to strong interactions is identified. Operator projectors that are required for non-perturbative renormalization of the corresponding lattice QCD six-quark operator matrix elements are constructed. A complete calculation of in a particular beyond-the-Standard-Model theory is presented as an example to demonstrate how operator renormalization and results from lattice QCD are combined with experimental bounds on to constrain the scale of new baryon-number violating physics. At the present computationally accessible lattice QCD matching scale of 2 GeV, the next-to-next-to-leading-order effects calculated in this work correct the leading-order plus next-to-leading-order predictions of beyond-the-Standard-Model theories by . Next-to-next-to-next-to-leading-order effects provide additional unknown corrections to predictions of that are estimated to be .

    Comments:
    38 pages, 1 figure. Journal version including erratum (operator normalization corrected, all perturbative renormalization results unchanged)
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1506.00647 [pdf]
    PRD(2016)·50 citations
  3. 08

    [Submitted on 1 Jun 2015] (cross-list from hep-ph)

    Perturbative Vacuum Wavefunctional for Gauge Theories in the Milne Space

    Sangyong Jeon🇨🇦 · Thomas Epelbaum🇨🇦

    The spectrum of vacuum fluctuations in the Milne space (i.e. the tau-eta coordinate system) is an important ingredient in the thermalization studies in relativistic heavy ion collisions. In this paper, the Schrodinger functional for the gauge theory perturbative vacuum is derived for the Milne space. The Wigner-transform of the corresponding vacuum density functional is also found together with the propagators. We finally identify the fluctuation spectrum in vacuum, and show the equivalence between the present approach and the symplectic product based method.

    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1506.00672 [pdf]
    Annals Phys.(2016)·4 citations
  4. 09

    [Submitted on 2 Jun 2015] (cross-list from hep-ph)

    Relativistic Causal Hydrodynamics Derived from Boltzmann Equation: a novel reduction theoretical approach

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

    We derive the second-order hydrodynamic equation and the microscopic formulae of the relaxation times as well as the transport coefficients systematically from the relativistic Boltzmann equation. Our derivation is based on a novel development of the renormalization-group method, a powerful reduction theory of dynamical systems, which has been applied successfully to derive the non-relativistic second-order hydrodynamic equation Our theory nicely gives a compact expression of the deviation of the distribution function in terms of the linearized collision operator, which is different from those used as an ansatz in the conventional fourteen-moment method. It is confirmed that the resultant microscopic expressions of the transport coefficients coincide with those derived in the Chapman-Enskog expansion method. Furthermore, we show that the microscopic expressions of the relaxation times have natural and physically plausible forms. We prove that the propagating velocities of the fluctuations of the hydrodynamical variables do not exceed the light velocity, and hence our seconder-order equation ensures the desired causality. It is also confirmed that the equilibrium state is stable for any perturbation described by our equation.

    Comments:
    25 pages, 1 figure. Detailed calculation of the relaxation equation is added
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Fluid Dynamics (physics.flu-dyn)
    arXiv:
    1506.00846 [pdf]
    PRD(2015)·26 citations

Affiliations

first authorsco-authorsvia INSPIRE