59,008 research outputs found
Aspects of causal viscous hydrodynamics
We investigate the phenomenology of freely expanding fluids, with different
material properties, evolving through the Israel-Stewart (IS) causal viscous
hydrodynamics, and compare our results with those obtained in the relativistic
Eckart-Landau-Navier-Stokes (ELNS) acausal viscous hydrodynamics. Through the
analysis of scaling invariants we give a definition of thermalization time
which can be self-consistently determined in viscous hydrodynamics. Next we
construct the solutions for one-dimensional boost-invariant flows. Expansion of
viscous fluids is slower than that of one-dimensional ideal fluids, resulting
in entropy production. At late times, these flows are reasonably well
approximated by solutions obtained in ELNS hydrodynamics. Estimates of initial
energy densities from observed final values are strongly dependent on the
dynamics one chooses. For the same material, and the same final state, IS
hydrodynamics gives the smallest initial energy density. We also study
fluctuations about these one-dimensional boost-invariant backgrounds; they are
damped in ELNS hydrodynamics but can become sound waves in IS hydrodynamics.
The difference is obvious in power spectra due to clear signals of
wave-interference in IS hydrodynamics, which is completely absent in ELNS
dynamics.Comment: 27 pages, 17 figures, references added, minor changes, version to
appear in Phys. Rev. (C
Atypical presentation of visceral leishmaniasis from non-endemic region
A case of atypical and acute presentation of visceral leishmaniasis from non-endemic region, characterised by exudative pleural effusion and hepatitis is reporte
Dynamical cluster-decay model for hot and rotating light-mass nuclear systems, applied to low-energy S + Mg Ni reaction
The dynamical cluster-decay model (DCM) is developed further for the decay of
hot and rotating compound nuclei (CN) formed in light heavy-ion reactions. The
model is worked out in terms of only one parameter, namely the neck-length
parameter, which is related to the total kinetic energy TKE(T) or effective
Q-value at temperature T of the hot CN, defined in terms of the
both the light-particles (LP), with 4, Z 2, as well as the
complex intermediate mass fragments (IMF), with , is
considered as the dynamical collective mass motion of preformed clusters
through the barrier. Within the same dynamical model treatment, the LPs are
shown to have different characteristics as compared to the IMFs. The systematic
variation of the LP emission cross section , and IMF emission
cross section , calculated on the present DCM match exactly the
statistical fission model predictions. It is for the first time that a
non-statistical dynamical description is developed for the emission of
light-particles from the hot and rotating CN. The model is applied to the decay
of Ni formed in the S + Mg reaction at two incident
energies E = 51.6 and 60.5 MeV. Both the IMFs and average
spectra are found to compare reasonably nicely with the experimental data,
favoring asymmetric mass distributions. The LPs emission cross section is shown
to depend strongly on the type of emitted particles and their multiplicities
Phases and properties of quark matter
I review recent developments in finite temperature lattice QCD which are
useful for the study of heavy-ion collisions. I pay particular attention to
studies of the equation of state and the light they throw on conformal symmetry
and the large N_c limit, and to the structure of the phase diagram for N_f=2+1.Comment: Plenary talk at Quark Matter 2008, Jaipur, India (8 pages, 5 figures
A faster method of computation of lattice quark number susceptibilities
We compute the quark number susceptibilities in two flavor QCD for staggered
fermions by adding the chemical potential as a Lagrange multiplier for the
point-split number density term. Since lesser number of quark propagators are
required at any order, this method leads to faster computations. We propose a
subtraction procedure to remove the inherent undesired lattice terms and check
that it works well by comparing our results with the existing ones where the
elimination of these terms is analytically guaranteed. We also show that the
ratios of susceptibilities are robust, opening a door for better estimates of
location of the QCD critical point through the computation of the tenth and
twelfth order baryon number susceptibilities without significant additional
computational overload.Comment: 10 pages, 12 figure
Strange freezeout
We argue that known systematics of hadron cross sections may cause different
particles to freeze out of the fireball produced in heavy-ion collisions at
different times. We find that a simple model with two freezeout points is a
better description of data than that with a single freezeout, while still
remaining predictive. The resulting fits seem to present constraints on the
late stage evolution of the fireball, including the tantalizing possibility
that the QCD chiral transition influences the yields at sqrt(S)=2700 GeV and
the QCD critical point those at sqrt(S)=17.3 GeV
Fission and cluster decay of Sr nucleus in the ground-state and formed in heavy-ion reactions
Calculations for fission and cluster decay of are presented for
this nucleus to be in its ground-state or formed as an excited compound system
in heavy-ion reactions. The predicted mass distribution, for the dynamical
collective mass transfer process assumed for fission of , is clearly
asymmetric, favouring -nuclei. Cluster decay is studied within a
preformed cluster model, both for ground-state to ground-state decays and from
excited compound system to the ground-state(s) or excited states(s) of the
fragments.Comment: 14 pages LaTeX, 5 Figures available upon request Submitted to Phys.
Rev.
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