128 research outputs found
Bjorken hydrodynamics and gradual freeze out
The freeze out of the expanding systems, created in relativistic heavy ion collisions, is discussed. We combine kinetic freeze out equations with Bjorken type system expansion into a unified model. The important feature of the proposed scenario is that physical freeze out is completely finished in a finite time, which can be varied from 0 (freeze out hypersurface) to infinit. The dependence of the post freeze out distribution function on the freeze out time will be studied. Model allows analytical analyses for the simplest systems such as pion gas. We shall see that the basic freeze out features, pointed out in the earlier works, are not smeared out by the expansion of the system. The entropy evolution in such a scenario is also studied
Effect of temperature-dependent eta/s on flow anisotropies
We investigate the effects of a temperature-dependent shear viscosity over
entropy density ratio eta/s on the flow anisotropy coefficients v_2 and v_4 in
ultrarelativistic heavy-ion collisions at RHIC and LHC. We find that v_4 is
more sensitive to the viscosity at low temperatures than v_2. At RHIC v_2 is
mostly affected by the viscosity around the phase transition, but the larger
the collision energy, the more the quark-gluon plasma viscosity affects v_2.Comment: 6 pages, 11 figures, parallel talk in Strangeness in Quark Matter
conference, Cracow, Sept 201
Freeze Out Process with In-Medium Nucleon Mass
We investigate the kinetic freeze out scenario of a nucleon gas through a
finite layer. The in-medium mass modification of nucleons and it's impact on
the freeze out process is studied. A considerable modification of the
thermodynamical parameters temperature, flow-velocity, energy density and
particle density has been found in comparison with evaluations which use a
constant vacuum nucleon mass.Comment: 6 pages, 4 figures, Proceeding of the Conference "Quark Matter 2005",
4th - 9th August 2005, Budapest/Hungar
Shakhov-type extension of the relaxation time approximation in relativistic kinetic theory and second-order fluid dynamics
We present a relativistic Shakhov-type generalization of the Anderson-Witting
relaxation time model for the Boltzmann collision integral to modify the ratio
of momentum diffusivity to thermal diffusivity. This is achieved by modifying
the path on which the single particle distribution function f_{\bk}
approaches local equilibrium f_{0\bk} by constructing an intermediate
Shakhov-type distribution f_{{\rm S} \bk} similar to the 14-moment
approximation of Israel and Stewart. We illustrate the effectiveness of this
model in case of the Bjorken expansion of an ideal gas of massive particles and
the damping of longitudinal waves through an ultrarelativistic ideal gas.Comment: 7 pages + 3 pages SM; 2 figure
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