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 $\exp{(\Gamma \sqrt{g^2\mu \tau})}$ (where $g^2\mu$ 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 $\Gamma$ to the prediction from kinetic theory.Comment: 8 pages, invited talk at Workshop on Quark Gluon Plasma Thermalization, Vienna, August 10th-12th, 200

Particle spectra and HBT radii for simulated central nuclear collisions of C+C, Al+Al, Cu+Cu, Au+Au, and Pb+Pb from Sqrt(s)=62.4-2760 GeV

We study the temperature profile, pion spectra and HBT radii in central symmetric and boost-invariant nuclear collisions using a super hybrid model for heavy-ion collisions (SONIC) combining pre-equilibrium flow with viscous hydrodynamics and late-stage hadronic rescatterings. In particular, we simulate Pb+Pb collisions at Sqrt(s)=2.76 TeV, Au+Au, Cu+Cu, Al+Al, and C+C collisions at Sqrt(s)=200 GeV and Au+Au, Cu+Cu collisions at Sqrt(s)=62.4 GeV. We find that SONIC provides a good match to the pion spectra and HBT radii for all collision systems and energies, confirming earlier work that a combination of pre-equilibrium flow, viscosity and QCD equation of state can resolve the so-called HBT puzzle. For reference, we also show p+p collisions at Sqrt(s)=7 TeV. We make tabulated data for the 2+1 dimensional temperature evolution of all systems publicly available for the use in future jet energy loss or similar studies.Comment: 9 pages, 5 figures, 2 tables; v2: fixed typos, updated figures; v3: minor changes, matches published versio

Collective non-Abelian instabilities in a melting Color Glass Condensate

We present first results for 3+1-D simulations of SU(2) Yang-Mills equations for matter expanding into the vacuum after a heavy ion collision. Violations of boost invariance cause a Weibel instability leading soft modes to grow with proper time $\tau$ as $\exp(\Gamma \sqrt{g^2\mu \tau})$, where $g^2\mu$ is a scale arising from the saturation of gluons in the nuclear wavefunction. The scale for the growth rate $\Gamma$ is set by a plasmon mass, defined as $\omega_{\rm pl}= \kappa_0 \sqrt{\frac{g^2\mu}{\tau}}$, generated dynamically in the collision. We compare the numerical ratio $\Gamma/\kappa_0$ to the corresponding value predicted by the Hard Thermal Loop formalism for anisotropic plasmas.Comment: 4 pages, 4 figures, revtex4; v2: typos corrected, discussion on growth rate in expanding system added, accepted for publication in PR

Tsunamis, Viscosity and the HBT Puzzle

The equation of state and bulk and shear viscosities are shown to be able to affect the transverse dynamics of a central heavy ion collision. The net entropy, along with the femtoscopic radii are shown to be affected at the 10-20% level by both shear and bulk viscosity. The degree to which these effects help build a tsunami-like pulse is also discussed.Comment: Contribution to SQM 2007 in Levoca, Slovaki

A fully relativistic lattice Boltzmann algorithm

Starting from the Maxwell-Juettner equilibrium distribution, we develop a relativistic lattice Boltzmann (LB) algorithm capable of handling ultrarelativistic systems with flat, but expanding, spacetimes. The algorithm is validated through simulations of quark-gluon plasma, yielding excellent agreement with hydrodynamic simulations. The present scheme opens the possibility of transferring the recognized computational advantages of lattice kinetic theory to the context of both weakly and ultra-relativistic systems.Comment: 12 pages, 8 figure

Bjorken Flow, Plasma Instabilities, and Thermalization

At asymptotically high energies, thermalization in heavy ion collisions can be described via weak-coupling QCD. We present a complete treatment of how thermalization proceeds, at the parametric weak-coupling level. We show that plasma instabilities dominate the dynamics, from immediately after the collision until well after the plasma becomes nearly in equilibrium. Initially they drive the system close to isotropy, but Bjorken expansion and increasing diluteness makes the system again become more anisotropic. At time \tau ~ \alpha^(-12/5) Q^(-1) the dynamics become dominated by a nearly-thermal bath; and at time \tau ~ \alpha^(-5/2) Q^(-1)$ the bath comes to dominate the energy density, completing thermalization. After this time there is a nearly isotropic and thermal Quark-Gluon Plasma.Comment: 22 pages, 5 figure

Collective modes of an Anisotropic Quark-Gluon Plasma II

We continue our exploration of the collective modes of an anisotropic quark gluon plasma by extending our previous analysis to arbitrary Riemann sheets. We demonstrate that in the presence of momentum-space anisotropies in the parton distribution functions there are new relevant singularities on the neighboring unphysical sheets. We then show that for sufficiently strong anisotropies that these singularities move into the region of spacelike momentum and their effect can extend down to the physical sheet. In order to demonstrate this explicitly we consider the polarization tensor for gluons propagating parallel to the anisotropy direction. We derive analytic expressions for the gluon structure functions in this case and then analytically continue them to unphysical Riemann sheets. Using the resulting analytic continuations we numerically determine the position of the unphysical singularities. We then show that in the limit of infinite contraction of the distribution function along the anisotropy direction that the unphysical singularities move onto the physical sheet and result in real spacelike modes at large momenta for all "out-of-plane" angles of propagation.Comment: 13 pages, 8 figure

Nonspherically Symmetric Collapse in Asymptotically AdS Spacetimes

We numerically simulate gravitational collapse in asymptotically anti-de Sitter spacetimes away from spherical symmetry. Starting from initial data sourced by a massless real scalar field, we solve the Einstein equations with a negative cosmological constant in five spacetime dimensions and obtain a family of non-spherically symmetric solutions, including those that form two distinct black holes on the axis. We find that these configurations collapse faster than spherically symmetric ones of the same mass and radial compactness. Similarly, they require less mass to collapse within a fixed time

Comment on and Erratum to "Pressure of Hot QCD at Large N_f"

We repeat and correct the recent calculation of the thermodynamic potential of hot QCD in the limit of large number N_f of fermions. The new result for the thermal pressure turns out to agree significantly better with results obtained from perturbation theory at small coupling. For large coupling, a nonmonotonic behaviour is reproduced, but the pressure of the strongly coupled theory does not exceed the free pressure as long as the Landau pole ambiguity remains negligible numerically.Comment: 9 pages, 3 figures, JHEP3; v2: version accepted for publication in JHEP (title changed, 1 footnote added, 1 reference updated, content otherwise unchanged