193 research outputs found
Coarse graining scale and effectiveness of hydrodynamic modeling
Some basic questions about the hydrodynamical approach to relativistic heavy
ion collisions are discussed aiming to clarify how far we can go with such an
approach to extract useful information on the properties and dynamics of the
QCD matter created. We emphasize the importance of the coarse-graining scale
required for the hydrodynamic modeling which determines the space-time
resolution and the associated limitations of collective flow observables. We
show that certain kinds of observables can indicate the degree of inhomogeneity
of the initial condition under less stringent condition than the local thermal
equilibrium subjected to the coarse-graining scale compatible to the scenario.Comment: 12 pages, 4 figures, Quark Matter 201
Bulk viscosity effects on elliptic flow
The effects of bulk viscosity on the elliptic flow are studied using
realistic equation of state and realistic transport coefficients. We find that
thebulk viscosity acts in a non trivial manner on . At low , the
reduction of is even more effective compared to the case of shear
viscosity, whereas at high , an enhancement of compared to the
ideal case is observed. We argue that this is caused by the competition of the
critical behavior of the equation of state and the transport coefficients.Comment: 4 pages, 3 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse
Effect of bulk viscosity on Elliptic Flow near QCD phase transition
Effects of the bulk viscosity on the elliptic flow are studied. To introduce
a realistic equation of state and transport coefficients, we apply the results
of the lattice QCD and hadron resonance gas calculations for these quantities.
We found that the bulk viscosity acts in a non trivial manner on the elliptic
flow . The reduction of is more effective at low
compared to the case of shear viscosity, whereas at high , the situation
is reversed, leading to enhancement. We argue that this is caused by
the competition of the critical behaviors of the equation of state and the
transport coefficients. We further found that Grad's method with the 14 moments
approximation is not applicable to estimate the viscous effects for the
one-particle distribution function at the freeze out.Comment: 14 pages, 12 figure
Fusion excitation function revisited
We report on a comprehensive systematics of fusion-evaporation and/or
fusion-fission cross sections for a very large variety of systems over an
energy range 4-155 A.MeV. Scaled by the reaction cross sections, fusion cross
sections do not show a universal behavior valid for all systems although a high
degree of correlation is present when data are ordered by the system mass
asymmetry.For the rather light and close to mass-symmetric systems the main
characteristics of the complete and incomplete fusion excitation functions can
be precisely determined. Despite an evident lack of data above 15A.MeV for all
heavy systems the available data suggests that geometrical effects could
explain the persistence of incomplete fusion at incident energies as high as
155A.MeV.Comment: 8 pages, 5 figures, contribution to the NN2012 Proceeding
A dynamical description of neutron star crusts
Neutron Stars are natural laboratories where fundamental properties of matter
under extreme conditions can be explored. Modern nuclear physics input as well
as many-body theories are valuable tools which may allow us to improve our
understanding of the physics of those compact objects.
In this work the occurrence of exotic structures in the outermost layers of
neutron stars is investigated within the framework of a microscopic model. In
this approach the nucleonic dynamics is described by a time-dependent mean
field approach at around zero temperature. Starting from an initial crystalline
lattice of nuclei at subnuclear densities the system evolves toward a manifold
of self-organized structures with different shapes and similar energies. These
structures are studied in terms of a phase diagram in density and the
corresponding sensitivity to the isospin-dependent part of the equation of
state and to the isotopic composition is investigated.Comment: 8 pages, 5 figures, conference NN201
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
Unraveling the Landau's consistence criterion and the meaning of interpenetration in the "Two-Fluid" Model
In this letter we show that it is possible to unravel both the physical
origin of the Landau's consistence criterion and the specific and subtle
meaning of interpenetration of the "two fluids" if one takes into account that
in the hydrodynamic regime one needs a coarse-graining in time to bring the
system into local equilibrium. That is, the fuzziness in time is relevant for
the phenomenological Landau's consistency criterion and the meaning of
interpenetration. Note also that we are not questioning the validity of the
"Two-Fluid" Model.Comment: 8 pages, affiliation added, typos corrected, final version published
in Eur. Phys. J.
Chameleonic Generalized Brans--Dicke model and late-time acceleration
In this paper we consider Chameleonic Generalized Brans--Dicke Cosmology in
the framework of FRW universes. The bouncing solution and phantom crossing is
investigated for the model. Two independent cosmological tests: Cosmological
Redshift Drift (CRD) and distance modulus are applied to test the model with
the observation.Comment: 20 pages, 15 figures, to be published in Astrophys. Space Sci. (2011
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