625 research outputs found
Thermalization and plasma instabilities
I review recent analytical and numerical advances in the study of
non-equilibrium quark-gluon plasma physics. I concentrate on studies of the
dynamics of plasmas which are locally anisotropic in momentum space. In
contrast to locally isotropic plasmas such anisotropic plasmas have a spectrum
of soft unstable modes which are characterized by exponential growth of
transverse (chromo)-magnetic fields at short times. Parametrically the
instabilities provide the fastest method for generation of soft background
fields and dominate the short-time dynamics of the system.Comment: 8 pages, 3 figures; Contribution to the proceedings of the
International Conference on Strong & Electroweak Matter 2006, Brookhaven
National Laboratory, Upton, NY, May 200
Viscosity Information from Relativistic Nuclear Collisions: How Perfect is the Fluid Observed at RHIC?
Relativistic viscous hydrodynamic fits to RHIC data on the centrality
dependence of multiplicity, transverse and elliptic flow for sqrt{s}=200 GeV
Au+Au collisions are presented. For Glauber-type initial conditions, while data
on integrated v_2 is consistent with a ratio of viscosity over entropy density
up to eta/s=0.16, data on minimum bias v_2 seems to favor a much smaller
viscosity over entropy ratio, below the bound from the AdS/CFT conjecture. Some
caveats on this result are discussed.Comment: 4 pages, 5 figures; v2: matches published version, title changed by
journa
A Weibel Instability in the Melting Color Glass Condensate
Based on hep-ph/0510121, we discuss further the numerical study of classical
SU(2) 3+1-D Yang-Mills equations for matter produced in a high energy heavy ion
collision. The growth of the amplitude of fluctuations as (where is a scale arising from the saturation of
gluons in the nuclear wavefunction) is shown to be robust over a wide range of
initial amplitudes that violate boost invariance. We argue that this growth is
due to a non-Abelian Weibel instability, the scale of which is set by a
dynamically generated plasmon mass. We find good agreement when we relate
to the prediction from kinetic theory.Comment: 8 pages, invited talk at Workshop on Quark Gluon Plasma
Thermalization, Vienna, August 10th-12th, 200
Do nuclear collisions create a locally equilibrated quark-gluon plasma?
Experimental results on azimuthal correlations in high energy nuclear
collisions (nucleus-nucleus, proton-nucleus and proton-proton) seem to be well
described by viscous hydrodynamics. It is often argued that this agreement
implies either local thermal equilibrium or at least local isotropy. In this
note, I present arguments why this is not the case. Neither local
near-equilibrium nor near-isotropy are required in order for hydrodynamics to
offer a successful and accurate description of experimental results. However, I
predict the breakdown of hydrodynamics at momenta of order seven times the
temperature, corresponding to a smallest possible QCD liquid drop size of 0.15
fm.Comment: 14 pages, 6 figures; v2: references added, major changes in section
VI, qualitative conclusions unchanged; v3: minor typos fixed, matches
published versio
Cold deconfined matter EOS through an HTL quasi-particle model
Using quasi-particle models, lattice data can be mapped to finite chemical
potential. By comparing a simple and an HTL quasi-particle model, we derive the
general trend that a full inclusion of the plasmon effect will give.Comment: 5 pages, 6 figures, contribution to the conference Strong and
Electroweak Matter (SEWM2002), Heidelberg, Germany, October 2-5, 2002; v2:
plots and references update
Relativistic Hydrodynamic Attractors with Broken Symmetries: Non-Conformal and Non-Homogeneous
Standard textbooks will state that hydrodynamics requires near-equilibrium to
be applicable. Recently, however, out-of-equilibrium attractor solutions for
hydrodynamics have been found in kinetic theory and holography in systems with
a high degree of symmetry, suggesting the possibility of a genuine
out-of-equilibrium formulation of hydrodynamics. This work demonstrates that
attractor solutions also occur in non-conformal kinetic theory and spatially
non-homogeneous systems, potentially having important implications for the
interpretation of experimental data in heavy-ion and proton-proton collisions
and relativistic fluid dynamics as a whole.Comment: 13 pages, 2 figures; v2: minor changes (typos, etc.); v3: matches
published versio
Azimuthal Anisotropies at High Momentum from Purely Non-Hydrodynamic Transport
In the limit of short mean free path, relativistic kinetic theory gives rise
to hydrodynamics through a systematically improvable gradient expansion. In the
present work, a systematically improvable expansion in the opposite limit of
large mean free path is considered, describing the dynamics of particles which
are almost, but not quite, non-interacting. This non-hydrodynamic "eremitic"
expansion does not break down for large gradients, and may be useful in
situations where a hydrodynamic treatment is not applicable. As applications,
azimuthal anisotropies at high transverse momentum in Pb+Pb and p+Pb collisions
at TeV are calculated from the first order eremitic expansion
of kinetic theory in the relaxation time approximation.Comment: 26 pages, 5 figures; v2: reference to Borghini and Gombeaud added who
discussed same setup in 2010, typos corrected; v3: minor changes, matches
published versio
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