387 research outputs found
Viscous Effects on Elliptic Flow and Shock Waves
Fast thermalization and a strong buildup of elliptic flow of QCD matter as
found at RHIC are understood as the consequence of perturbative QCD (pQCD)
interactions within the 3+1 dimensional parton cascade BAMPS. The main
contributions stem from pQCD bremsstrahlung processes.
By comparing to Au+Au data of the flow parameter as a function of
participation number the shear viscosity to entropy ratio is dynamically
extracted, which lies in the range of 0.08 and 0.2, depending on the chosen
coupling constant and freeze out condition. Furthermore, first simulations on
the temporal propagation of dissipative shock waves are given. The cascade can
either simulate true ideal shocks as well as initially diluted, truely viscous
shocks, depending on the employed cross sections or mean free path,
respectively.Comment: 7 pages, 8 figures, to appear in the proceedings of the 2008 Erice
School on Nuclear Physics, Sicil
Collective Flow and Energy Loss with parton transport
Quenching of gluonic jets and heavy quark production in Au+Au collisions at
RHIC can be understood within the pQCD based 3+1 dimensional parton transport
model BAMPS including pQCD bremsstrahlung processes.
Furthermore, the development of conical structures induced by gluonic jets is
investigated in a static box for the regimes of small and large dissipation.Comment: typos corrected, figure labels enlarged; Talk given by C. Greiner; to
appear in the proceedings of WISH201
Collective Flow and Mach Cones with Parton Transport
Fast thermalization and a strong build up of elliptic flow of QCD matter were
investigated within the pQCD based 3+1 dimensional parton transport model BAMPS
including bremsstrahlung processes. Within the same
framework quenching of gluonic jets in Au+Au collisions at RHIC can be
understood. The development of conical structure by gluonic jets is
investigated in a static box for the regimes of small and large dissipation.
Furthermore we demonstrate two different approaches to extract the shear
viscosity coefficient from a microscopical picture.Comment: 7 pages, 8 figures, 1 table; to appear in the proceedings of Hot and
Cold Baryonic Matter -- HCBM 201
Investigation of shock waves in the relativistic Riemann problem: A comparison of viscous fluid dynamics to kinetic theory
We solve the relativistic Riemann problem in viscous matter using the
relativistic Boltzmann equation and the relativistic causal dissipative
fluid-dynamical approach of Israel and Stewart. Comparisons between these two
approaches clarify and point out the regime of validity of second-order fluid
dynamics in relativistic shock phenomena. The transition from ideal to viscous
shocks is demonstrated by varying the shear viscosity to entropy density ratio
. We also find that a good agreement between these two approaches
requires a Knudsen number .Comment: Version as published in PRC 82, 024910 (2010); 16 pages, 16 figures,
typos correcte
Derivation of fluid dynamics from kinetic theory with the 14--moment approximation
We review the traditional derivation of the fluid-dynamical equations from
kinetic theory according to Israel and Stewart. We show that their procedure to
close the fluid-dynamical equations of motion is not unique. Their approach
contains two approximations, the first being the so-called 14-moment
approximation to truncate the single-particle distribution function. The second
consists in the choice of equations of motion for the dissipative currents.
Israel and Stewart used the second moment of the Boltzmann equation, but this
is not the only possible choice. In fact, there are infinitely many moments of
the Boltzmann equation which can serve as equations of motion for the
dissipative currents. All resulting equations of motion have the same form, but
the transport coefficients are different in each case.Comment: 15 pages, 3 figures, typos fixed and discussions added; EPJA: Topical
issue on "Relativistic Hydro- and Thermodynamics
Response to the discussion on “An improved k – ω turbulence model for the simulations of the wind turbine wakes in a neutral atmospheric boundary layer flow” by Y Yang
Mach Cones in Viscous Matter
Employing a microscopic transport model we investigate the evolution of high
energetic jets moving through a viscous medium. For the scenario of an
unstoppable jet we observe a clearly strong collective behavior for a low
dissipative system , leading to the observation of
cone-like structures. Increasing the dissipation of the system to the Mach Cone structure vanishes. Furthermore, we investigate
jet-associated particle correlations. A double-peak structure, as observed in
experimental data, is even for low-dissipative systems not supported, because
of the large influence of the head shock.Comment: 4 pages, 3 figures, to appear in the conference proceedings of Hot
Quarks 201
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