485 research outputs found
Density functional theory of phase coexistence in weakly polydisperse fluids
The recently proposed universal relations between the moments of the
polydispersity distributions of a phase-separated weakly polydisperse system
are analyzed in detail using the numerical results obtained by solving a simple
density functional theory of a polydisperse fluid. It is shown that universal
properties are the exception rather than the rule.Comment: 10 pages, 2 figures, to appear in PR
Geometric Integration of Hamiltonian Systems Perturbed by Rayleigh Damping
Explicit and semi-explicit geometric integration schemes for dissipative
perturbations of Hamiltonian systems are analyzed. The dissipation is
characterized by a small parameter , and the schemes under study
preserve the symplectic structure in the case . In the case
the energy dissipation rate is shown to be asymptotically
correct by backward error analysis. Theoretical results on monotone decrease of
the modified Hamiltonian function for small enough step sizes are given.
Further, an analysis proving near conservation of relative equilibria for small
enough step sizes is conducted.
Numerical examples, verifying the analyses, are given for a planar pendulum
and an elastic 3--D pendulum. The results are superior in comparison with a
conventional explicit Runge-Kutta method of the same order
Light propagation in statistically homogeneous and isotropic universes with general matter content
We derive the relationship of the redshift and the angular diameter distance
to the average expansion rate for universes which are statistically homogeneous
and isotropic and where the distribution evolves slowly, but which have
otherwise arbitrary geometry and matter content. The relevant average expansion
rate is selected by the observable redshift and the assumed symmetry properties
of the spacetime. We show why light deflection and shear remain small. We write
down the evolution equations for the average expansion rate and discuss the
validity of the dust approximation.Comment: 42 pages, no figures. v2: Corrected one detail about the angular
diameter distance and two typos. No change in result
Some Consequences of Thermosolutal Convection: The Grain Structure of Castings
The essential principles of thermosolutal convection are outlined, and how convection provides a transport mechanism between the mushy region of a casting and the open bulk liquid is illustrated. The convective flow patterns which develop assist in heat exchange and macroscopic solute segregation during solidification; they also provide a mechanism for the transport of dendritic fragments from the mushy region into the bulk liquid. Surviving fragments become nuclei for equiaxed grains and so lead to blocking of the parental columnar, dendritic growth front from which they originated. The physical steps in such a sequence are considered and some experimental data are provided to support the argument
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at TeV
The elliptic, , triangular, , and quadrangular, , azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range at different collision centralities and as a
function of transverse momentum, , out to GeV/.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for GeV/. The small dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to GeV/. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
GeV/ indicating that the particle type dependence persists out
to high .Comment: 16 pages, 5 captioned figures, authors from page 11, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
Measurement of charm production at central rapidity in proton-proton collisions at TeV
The -differential production cross sections of the prompt (B
feed-down subtracted) charmed mesons D, D, and D in the rapidity
range , and for transverse momentum GeV/, were
measured in proton-proton collisions at TeV with the ALICE
detector at the Large Hadron Collider. The analysis exploited the hadronic
decays DK, DK, DD, and their charge conjugates, and was performed on a
nb event sample collected in 2011 with a
minimum-bias trigger. The total charm production cross section at TeV and at 7 TeV was evaluated by extrapolating to the full phase space
the -differential production cross sections at TeV
and our previous measurements at TeV. The results were compared
to existing measurements and to perturbative-QCD calculations. The fraction of
cdbar D mesons produced in a vector state was also determined.Comment: 20 pages, 5 captioned figures, 4 tables, authors from page 15,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/307
Modeling body size evolution in Felidae under alternative phylogenetic hypotheses
The use of phylogenetic comparative methods in ecological research has advanced during the last twenty years, mainly due to accurate phylogenetic reconstructions based on molecular data and computational and statistical advances. We used phylogenetic correlograms and phylogenetic eigenvector regression (PVR) to model body size evolution in 35 worldwide Felidae (Mammalia, Carnivora) species using two alternative phylogenies and published body size data. The purpose was not to contrast the phylogenetic hypotheses but to evaluate how analyses of body size evolution patterns can be affected by the phylogeny used for comparative analyses (CA). Both phylogenies produced a strong phylogenetic pattern, with closely related species having similar body sizes and the similarity decreasing with increasing distances in time. The PVR explained 65% to 67% of body size variation and all Moran's I values for the PVR residuals were non-significant, indicating that both these models explained phylogenetic structures in trait variation. Even though our results did not suggest that any phylogeny can be used for CA with the same power, or that “good” phylogenies are unnecessary for the correct interpretation of the evolutionary dynamics of ecological, biogeographical, physiological or behavioral patterns, it does suggest that developments in CA can, and indeed should, proceed without waiting for perfect and fully resolved phylogenies
Particle-yield modification in jet-like azimuthal di-hadron correlations in Pb-Pb collisions at = 2.76 TeV
The yield of charged particles associated with high- trigger
particles ( GeV/) is measured with the ALICE detector in
Pb-Pb collisions at = 2.76 TeV relative to proton-proton
collisions at the same energy. The conditional per-trigger yields are extracted
from the narrow jet-like correlation peaks in azimuthal di-hadron correlations.
In the 5% most central collisions, we observe that the yield of associated
charged particles with transverse momenta GeV/ on the
away-side drops to about 60% of that observed in pp collisions, while on the
near-side a moderate enhancement of 20-30% is found.Comment: 15 pages, 2 captioned figures, 1 table, authors from page 10,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/350
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