168 research outputs found
Initial condition for hydrodynamics, partonic free streaming, and the uniform description of soft observables at RHIC
We investigate the role of the initial condition used for the hydrodynamic
evolution of the system formed in ultra-relativistic heavy-ion collisions and
find that an appropriate choice motivated by the models of early-stage
dynamics, specifically a simple two-dimensional Gaussian profile, leads to a
uniform description of soft observables measured in the Relativistic Heavy-Ion
Collider (RHIC). In particular, the transverse-momentum spectra, the
elliptic-flow, and the Hanbury-Brown--Twiss correlation radii, including the
ratio R_out/R_side as well as the dependence of the radii on the azimuthal
angle (azHBT), are properly described. We use the perfect-fluid hydrodynamics
with a realistic equation of state based on lattice calculations and the
hadronic gas at high and low temperatures, respectively. We also show that the
inclusion of the partonic free-streaming in the early stage allows to delay the
start of the hydrodynamical description to comfortable times of the order of 1
fm/c. Free streaming broadens the initial energy-density profile, but generates
the initial transverse and elliptic flow. The data may be described equally
well when the hydrodynamics is started early, or with a delay due to partonic
free-streaming.Comment: 4 pages, 4 figure
On cosine families close to scalar cosine families
We prove that if two normed-algebra-valued cosine families indexed by a
single Abelian group, of which one is bounded and comprised solely of scalar
elements of the underlying algebra, differ in norm by less than uniformly
in the parametrising index, then these families coincide.Comment: Updated the bibliograph
General formulation of transverse hydrodynamics
General formulation of hydrodynamics describing transversally thermalized
matter created at the early stages of ultra-relativistic heavy-ion collisions
is presented. Similarities and differences with the standard
three-dimensionally thermalized relativistic hydrodynamics are discussed. The
role of the conservation laws as well as the thermodynamic consistency of
two-dimensional thermodynamic variables characterizing transversally
thermalized matter is emphasized
The realistic QCD equation of state in relativistic heavy-ion collisions and the early Universe
The realistic equation of state of strongly interacting matter, that has been
successfully applied in the recent hydrodynamic studies of hadron production in
relativistic heavy-ion collisions at RHIC, is used in the Friedmann equation to
determine the precise time evolution of thermodynamic parameters in the early
Universe. A comparison with the results obtained with simple ideal-gas
equations of state is made. The realistic equation of state describes a
crossover rather than the first-order phase transition between the quark-gluon
plasma and hadronic matter. Our numerical calculations show that small
inhomogeneities of strongly interacting matter in the early Universe are
moderately damped during such crossover
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