Article
The QGP shear viscosity  elusive goal or just around the corner?
Journal of Physics G Nuclear and Particle Physics (Impact Factor: 5.33). 06/2011; 38(12). DOI: 10.1088/09543899/38/12/124045
Source: arXiv

Article: Determining Fundamental Properties of Matter Created in Ultrarelativistic HeavyIon Collisions
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ABSTRACT: Posterior distributions for physical parameters describing relativistic heavyion collisions, such as the viscosity of the quarkgluon plasma, are extracted through a comparison of hydrodynamicbased transport models to experimental results from 100$A$ GeV + 100$A$ GeV Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC). By simultaneously varying six parameters and by evaluating several classes of observables, we are able to explore the complex intertwined dependencies of observables to model parameters. We obtain a full multidimensional posterior distribution for the model output given a large set of experimental observations, the methods developed here provide a range of acceptable values for each parameter, and reveal correlations between them. The breadth of observables and the number of parameters considered here go far beyond previous studies in this field. The statistical tools, which are based upon Gaussian Process emulators, are tested in detail and should be extendable to larger data sets and a higher number of parameters.03/2013; 89(3).  [Show abstract] [Hide abstract]
ABSTRACT: Time evolution of a “little bang” created in heavyion collisions can be divided into two phases, the preequilibrium and hydrodynamic. At what moment does the evolution become hydrodynamic and is there any universality in the hydrodynamic flow? To answer these questions we briefly discuss various versions of hydrodynamics and their applicability conditions. In particular, we elaborate on the idea of “universal” (allorder resumed) hydrodynamics and propose a simple new model for it. The model is motivated by results obtained recently via the Anti–de Sitter and conformal field correspondence. Finally, charged hadron multiplicities in heavyion collisions at the Relativistic Heavy Ion Collider and Large Hadron Collider are discussed. At the freezeout, the multiplicities can be related to total entropy produced in the collision. Assuming the universal hydrodynamics to hold, we calculate the entropy production in the hydro stage of the collision. We end up speculating about a connection between the multiplicity growth and the temperature dependence of the quarkgluon plasma viscosity.Physical Review C 08/2011; 84(6). · 3.72 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: In this talk, we discuss a number of recent calculations aimed at determining the spectral functions corresponding to various components of the energy momentum tensor in hightemperature SU(N) YangMills theory. The computations reviewed include applications of both weak coupling and gauge/gravity techniques, and thus enable one to access different limits of the quantities. The motivation for the work is twofold: On one hand, the results are hoped to aid the eventual nonperturbative extraction of the bulk and shear viscosities from lattice data, while on the other hand they also enable an immediate comparison of the lattice, perturbative and holographic predictions for certain Euclidean correlators.01/2012;
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