8 research outputs found
New Formulation of Causal Dissipative Hydrodynamics: Shock wave propagation
The first 3D calculation of shock wave propagation in a homogeneous QGP has
been performed within the new formulation of relativistic dissipative
hydrodynamics which preserves the causality. We found that the relaxation time
plays an important role and also affects the angle of Mach cone.Comment: 4 pages, 1 figure, Proceedings of Quark Matter 200
Relativistic Dissipative Hydrodynamics: A Minimal Causal Theory
We present a new formalism for the theory of relativistic dissipative
hydrodynamics. Here, we look for the minimal structure of such a theory which
satisfies the covariance and causality by introducing the memory effect in
irreversible currents. Our theory has a much simpler structure and thus has
several advantages for practical purposes compared to the Israel-Stewart theory
(IS). It can readily be applied to the full three-dimensional hydrodynamical
calculations. We apply our formalism to the Bjorken model and the results are
shown to be analogous to the IS.Comment: 25 pages, 2 figures, Phys. Rev. C in pres
Hadron production in heavy relativistic systems
We investigate particle production in heavy-ion collisions at RHIC energies
as function of incident energy, and centrality in a three-sources Relativistic
Diffusion Model. Pseudorapidity distributions of produced charged hadrons in Au
+ Au and Cu + Cu collisions at sqrt(s_NN) = 19.6 GeV, 62.4 GeV, 130 GeV and 200
GeV show an almost equilibrated midrapidity source that tends to increase in
size towards higher incident energy, and more central collisions. It may
indicate quark-gluon plasma formation prior to hadronization.Comment: 8 pages, 3 figure
Temperature dependent sound velocity in hydrodynamic equations for relativistic heavy-ion collisions
We analyze the effects of different forms of the sound-velocity function
cs(T) on the hydrodynamic evolution of matter formed in the central region of
relativistic heavy-ion collisions. At high temperatures (above the critical
temperature Tc) the sound velocity is calculated from the recent lattice
simulations of QCD, while in the low temperature region it is obtained from the
hadron gas model. In the intermediate region we use different interpolations
characterized by the values of the sound velocity at the local maximum (at T =
0.4 Tc) and local minimum (at T = Tc). In all considered cases the temperature
dependent sound velocity functions yield the entropy density, which is
consistent with the lattice QCD simulations at high temperature. Our
calculations show that the presence of a distinct minimum of the sound velocity
leads to a very long (about 20 fm/c) evolution time of the system, which is not
compatible with the recent estimates based on the HBT interferometry. Hence, we
conclude that the hydrodynamic description is favored in the case where the
cross-over phase transition renders the smooth sound velocity function with a
possible shallow minimum at Tc.Comment: 6 pages, 3 figures, talk given at SQM'07 Levoca, Slovaki
Nearly Perfect Fluidity: From Cold Atomic Gases to Hot Quark Gluon Plasmas
Shear viscosity is a measure of the amount of dissipation in a simple fluid.
In kinetic theory shear viscosity is related to the rate of momentum transport
by quasi-particles, and the uncertainty relation suggests that the ratio of
shear viscosity eta to entropy density s in units of hbar/k_B is bounded by a
constant. Here, hbar is Planck's constant and k_B is Boltzmann's constant. A
specific bound has been proposed on the basis of string theory where, for a
large class of theories, one can show that eta/s is greater or equal to hbar/(4
pi k_B). We will refer to a fluid that saturates the string theory bound as a
perfect fluid. In this review we summarize theoretical and experimental
information on the properties of the three main classes of quantum fluids that
are known to have values of eta/s that are smaller than hbar/k_B. These fluids
are strongly coupled Bose fluids, in particular liquid helium, strongly
correlated ultracold Fermi gases, and the quark gluon plasma. We discuss the
main theoretical approaches to transport properties of these fluids: kinetic
theory, numerical simulations based on linear response theory, and holographic
dualities. We also summarize the experimental situation, in particular with
regard to the observation of hydrodynamic behavior in ultracold Fermi gases and
the quark gluon plasma.Comment: 76 pages, 11 figures, review article, extensive revision