12,069 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
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
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
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
Imagens digitais aplicadas para determinação de áreas agrícolas através do classificador Bayes.
Através da classificação das imagens digitais é possível construir painéis amostrais por área, particularmente na estratificação de grandes áreas, e, dependendo da resolução espacial, até mesmo na identificação e delineamento dos seus limites físicos. Este trabalho teve por objetivo desenvolver um algoritmo para um classificador de áreas agrícolas para região que compreende parte da região Leste de Goiás. Através dos resultados obtidos no presente trabalho concluiu-se que a técnica utilizada demonstrou ser eficaz na determinação de áreas agrícolas (pivôs centrais). Também foi possível classificar e estimar as áreas agrícolas sobre a refletância dos alvos na cena de estudo
Ab-initio molecular dynamics simulation of hydrogen diffusion in -iron
First-principles atomistic molecular dynamics simulation in the
micro-canonical and canonical ensembles has been used to study the diffusion of
interstitial hydrogen in -iron. Hydrogen to Iron ratios between
2 \times 2 \times 2$ supercell. We find that
the average optimum absorption site and the barrier for diffusion depend on the
concentration of interestitials. Iron Debye temperature decreases monotonically
for increasing concentration of interstitial hydrogen, proving that iron-iron
interatomic potential is significantly weakened in the presence of a large
number of diffusing hydrogen atoms
Gravitation and Duality Symmetry
By generalizing the Hodge dual operator to the case of soldered bundles, and
working in the context of the teleparallel equivalent of general relativity, an
analysis of the duality symmetry in gravitation is performed. Although the
basic conclusion is that, at least in the general case, gravitation is not dual
symmetric, there is a particular theory in which this symmetry shows up. It is
a self dual (or anti-self dual) teleparallel gravity in which, due to the fact
that it does not contribute to the interaction of fermions with gravitation,
the purely tensor part of torsion is assumed to vanish. The ensuing fermionic
gravitational interaction is found to be chiral. Since duality is intimately
related to renormalizability, this theory may eventually be more amenable to
renormalization than teleparallel gravity or general relativity.Comment: 7 pages, no figures. Version 2: minor presentation changes,
references added. Accepted for publication in Int. J. Mod. Phys.
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