Why does the quark?gluon plasma at RHIC behave as a nearly ideal fluid?

Abstract

The lecture is a brief review of the following topics: (i) collective flow phenomena in heavy ion collisions. The data from RHIC indicate robust collective flows, well described by hydrodynamics with expected Equation of State. The transport properties turned out to be unexpected, with very small viscosity; (ii) physics of highly excited matter produced in heavy ion collisions at T c < T < 4T c is different from weakly coupled quark-gluon plasma because of relatively strong coupling generating bound states of quasiparticles; (iii) wider discussion of other "strongly coupled systems" including strongly coupled supersymmetric theories studied via Maldacena duality, as well as recent progress in trapped atoms with very large scattering length.

Far-from-equilibrium dynamics of a strongly coupled non-Abelian plasma with non-zero charge density or external magnetic field

“…11 Setting to zero the variation of the action with respect to the metric gives the Einstein equation, 19) while varying the bulk gauge field (with…”

CMS Physics Technical Design Report: Addendum on High Density QCD with Heavy Ions

“…The robust collective flow generated in the first instants of the reaction, the fast (local) thermalisation times, and the good agreement of the data with ideal relativistic hydrodynamic models which assume a fluid evolution with zero viscosity (i.e. with negligible internal shear stress), have been presented as evidence that the matter formed at RHIC is a strongly interacting QGP (sQGP) [83][84][85][86][87]. This new state of matter with liquid-like properties, challenges the anticipated paradigm [8,9] of a weakly interacting gas of relativistic partons, lending support to the application of strongly-coupled-gauge/weakly-coupled-gravity duality techniques [33][34][35][36][37] to compute relevant sQGP parameters (see Section 1.1).…”

Thermalisation properties of various field theories

“…Our results are presented on graph 5. Tsallis f (x) = ax n (1 + (q − 1) l x) 1 1−q and Boltzmann g(x) = Ax N e −Bx fits are applied to the numeric data. The time-like size of the lattice were N t = 2 and the space-like was N 3 s = 50 3 .…”

“…It is well-known from experiments, that the matter formed in relativistic heavy-ion collisions behave as a nearly ideal liquid and the shear-viscosity (η) over entropy-density (s) ratio is extremely small [1]. In a liquid-like matter where information is spread by diffusion and the transport coefficient so small, interactions can no longer be neglected.…”