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Nuclear Theory·nucl-th

Wednesday·March 29, 2017

10 papers—6 primary·4 cross-listed

All10Primary6Cross-lists4
  1. 07

    [Submitted on 26 Mar 2017] (cross-list from hep-th)

    Relativistic magnetohydrodynamics

    Juan Hernandez🇨🇦 · Pavel Kovtun🇨🇦

    We present the equations of relativistic hydrodynamics coupled to dynamical electromagnetic fields, including the effects of polarization, electric fields, and the derivative expansion. We enumerate the transport coefficients at leading order in derivatives, including electrical conductivities, viscosities, and thermodynamic coefficients. We find the constraints on transport coefficients due to the positivity of entropy production, and derive the corresponding Kubo formulas. For the neutral state in a magnetic field, small fluctuations include Alfven waves, magnetosonic waves, and the dissipative modes. For the state with a non-zero dynamical charge density in a magnetic field, plasma oscillations gap out all propagating modes, except for Alfven-like waves with a quadratic dispersion relation. We relate the transport coefficients in the "conventional" magnetohydrodynamics (formulated using Maxwell's equations in matter) to those in the "dual" version of magnetohydrodynamics (formulated using the conserved magnetic flux).

    Comments:
    42 pages
    Subjects:
    High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1703.08757 [pdf]
    JHEP(2017)·170 citations
  2. 08

    [Submitted on 27 Mar 2017] (cross-list from hep-lat)

    Light baryons below and above the deconfinement transition: medium effects and parity doubling

    Gert Aarts🇬🇧 · Chris Allton🇬🇧 · Davide De Boni🇬🇧 · Simon Hands🇬🇧 · Benjamin Jäger🇬🇧 · Chrisanthi Praki🇬🇧 · Jon-Ivar Skullerud🇮🇪

    We study what happens to the Nucleon, Delta and Omega baryons in the hadronic gas and the quark-gluon plasma, with particular interest in parity doubling and its emergence as the plasma is heated. This is done using simulations of lattice QCD, employing the FASTSUM anisotropic Nf=2+1 ensembles, with four temperatures below and four above the deconfinement transition temperature. Below Tc we find that the positive-parity groundstate masses are largely temperature independent, whereas the negative-parity ones are reduced considerably as the temperature increases. This may be of interest for heavy-ion phenomenology. Close to the transition, the masses are nearly degenerate, in line with the expectation from chiral symmetry restoration. Above Tc we find a clear signal of parity doubling in all three channels, with the effect of the heavier s quark visible.

    Comments:
    33 pages, several figures; additional evidence on the absence of light baryonic bound states in the QGP provided, references added, to appear in JHEP
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1703.09246 [pdf]
    JHEP(2017)·135 citations
  3. 09

    [Submitted on 27 Mar 2017] (cross-list from hep-ph)

    Probing subnucleon scale fluctuations in ultraperipheral heavy ion collisions

    Heikki Mäntysaari🇺🇸 · Björn Schenke🇺🇸

    We show that introducing subnucleon scale fluctuations constrained by HERA diffractive production data significantly affects the incoherent diffractive production cross section in ultraperipheral heavy ion collisions. We find that the inclusion of the additional fluctuations increases the ratio of the incoherent to the coherent cross section approximately by a factor of , and modifies the transverse momentum spectra of the produced at momenta larger than the scale that corresponds to the distance scale of the subnucleonic fluctuations. We present predictions for production in ultraperipheral heavy ion collisions at at the LHC and at RHIC.

    Comments:
    9 pages, 8 figures. v2: small clarifications to the text, matches the published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1703.09256 [pdf]
    PLB(2017)·120 citations
  4. 10

    [Submitted on 28 Mar 2017] (cross-list from hep-th)

    Paths to equilibrium in non-conformal collisions

    Maximilian Attems🇪🇸 · Jorge Casalderrey-Solana🇬🇧 · David Mateos🇪🇸 · Daniel Santos-Oliván🇪🇸 · Carlos F. Sopuerta🇪🇸 · Miquel Triana🇪🇸 · Miguel Zilhão🇪🇸

    We extend our previous analysis of holographic heavy ion collisions in non-conformal theories. We provide a detailed description of our numerical code. We study collisions at different energies in gauge theories with different degrees of non-conformality. We compare four relaxation times: the hydrodynamization time (when hydrodynamics becomes applicable), the EoSization time (when the average pressure approaches its equilibrium value), the isotropization time (when the longitudinal and transverse pressures approach each other) and the condensate relaxation time (when the expectation value of a scalar operator approaches its equilibrium value). We find that these processes can occur in several different orderings. In particular, the condensate can remain far from equilibrium even long after the plasma has hydrodynamized and EoSized. We also explore the rapidity distribution of the energy density at hydrodynamization. This is far from boost-invariant and its width decreases as the non-conformality increases. Nevertheless, the velocity field at hydrodynamization is almost exactly boost-invariant regardless of the non-conformality. This result may be used to constrain the initialization of hydrodynamic fields in heavy ion collisions.

    Comments:
    45 pages, 17 figures. Expanded some sections. Matches published version in JHEP
    Subjects:
    High Energy Physics — Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1703.09681 [pdf]
    JHEP(2017)·70 citations

Affiliations

first authorsco-authorsvia INSPIRE