17,131 research outputs found
Eccentricity fluctuations in an integrated hybrid approach: Influence on elliptic flow
The effects of initial state fluctuations on elliptic flow are investigated
within a (3+1)d Boltzmann + hydrodynamics transport approach. The spatial
eccentricity ( and ) is calculated for
initial conditions generated by a hadronic transport approach (UrQMD). Elliptic
flow results as a function of impact parameter, beam energy and transverse
momentum for two different equations of state and for averaged initial
conditions or a full event-by-event setup are presented. These investigations
allow the conclusion that in mid-central ( fm) heavy ion collisions the
final elliptic flow is independent of the initial state fluctuations and the
equation of state. Furthermore, it is demonstrated that most of the is
build up during the hydrodynamic stage of the evolution. Therefore, the use of
averaged initial profiles does not contribute to the uncertainties of the
extraction of transport properties of hot and dense QCD matter based on viscous
hydrodynamic calculations.Comment: 7 pages, 7 figures, minor revision of figures and conclusion, as
published in PR
Analytical approach to directed sandpile models on the Apollonian network
We investigate a set of directed sandpile models on the Apollonian network,
which are inspired on the work by Dhar and Ramaswamy (PRL \textbf{63}, 1659
(1989)) for Euclidian lattices. They are characterized by a single parameter
, that restricts the number of neighbors receiving grains from a toppling
node. Due to the geometry of the network, two and three point correlation
functions are amenable to exact treatment, leading to analytical results for
the avalanche distributions in the limit of an infinite system, for .
The exact recurrence expressions for the correlation functions are numerically
iterated to obtain results for finite size systems, when larger values of
are considered. Finally, a detailed description of the local flux properties is
provided by a multifractal scaling analysis.Comment: 7 pages in two-column format, 10 illustrations, 5 figure
Directed flow in ultrarelativistic heavy-ion collisions
We study the generation of directed flow in the hydrodynamic expansion of the
hot matter formed in ultrarelativistic heavy-ion collisions at 200GeV. The
experimentally observed negative directed flow in a wide range of central
pseudorapidities isreproduced assuming that the fireball is tilted away from
the collision axis. The tilt of the source is consistent with a preferential
emission in the forward/backward hemisphere from forward/backward participating
nucleons. The model reproduces the experimentally observed scaling of the
directed flow when going from Au-Au to Cu-Cu systems.Comment: figure adde
The influence of statistical properties of Fourier coefficients on random surfaces
Many examples of natural systems can be described by random Gaussian
surfaces. Much can be learned by analyzing the Fourier expansion of the
surfaces, from which it is possible to determine the corresponding Hurst
exponent and consequently establish the presence of scale invariance. We show
that this symmetry is not affected by the distribution of the modulus of the
Fourier coefficients. Furthermore, we investigate the role of the Fourier
phases of random surfaces. In particular, we show how the surface is affected
by a non-uniform distribution of phases
Importance of Granular Structure in the Initial Conditions for the Elliptic Flow
We show effects of granular structure of the initial conditions (IC) of
hydrodynamic description of high-energy nucleus-nucleus collisions on some
observables, especially on the elliptic-flow parameter v2. Such a structure
enhances production of isotropically distributed high-pT particles, making v2
smaller there. Also, it reduces v2 in the forward and backward regions where
the global matter density is smaller, so where such effects become more
efficacious.Comment: 4 pages, 5 figure
On bare masses in time-symmetric initial-value solutions for two black holes
The Brill-Lindquist time-symmetric initial-value solution for two uncharged
black holes is rederived using the Hamiltonian constraint equation with Dirac
delta distributions as a source for the binary black-hole field. The bare
masses of the Brill-Lindquist black holes are introduced in a way which is
applied, after straightforward modification, to the Misner-Linquist binary
black-hole solution.Comment: LaTeX, 4 page
Fluctuation of the Initial Conditions and Its Consequences on Some Observables
We show effects of the event-by-event fluctuation of the initial conditions
(IC) in hydrodynamic description of high-energy nuclear collisions on some
observables. Such IC produce not only fluctuations in observables but, due to
their bumpy structure, several non-trivial effects appear. They enhance
production of isotropically distributed high-pT particles, making v2 smaller
there. Also, they reduce v2 in the forward and backward regions where the
global matter density is smaller, so where such effects become more
efficacious. They may also produce the so-called ridge effect in the two
large-pT particle correlation.Comment: 6 pages, 6 figures, presented at the IV Workshop on Particle
Correlations and Femtoscopy (WPCF2008), Krakow, Poland, 11-14 Sep 200
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