88,591 research outputs found
Description of Charged Particle Pseudorapidity Distributions in Pb+Pb Collisions with Tsallis Thermodynamics
The centrality dependence of pseudorapidity distributions for charged
particles produced in Au+Au collisions at GeV and 200 GeV
at RHIC, and in Pb+Pb collisions at TeV at LHC are
investigated in the fireball model, assuming that the rapidity axis is
populated with fireballs following one distribution function. We assume that
the particles in the fireball fulfill the Tsallis distribution. The theoretical
results are compared with the experimental measurements and a good agreement is
found. Using these results, the pseudorapidity distributions of charged
particles produced in Pb+Pb central collisions at TeV and
10 TeV are predicted.Comment: 9 pages, 8 figure
On the Mass-to-Light Ratio of Large Scale Structure
We examine the dependence of the mass-to-light (M/L) ratio of large-scale
structure on cosmological parameters, in models that are constrained to match
observations of the projected galaxy correlation function w(rp). For a sequence
of cosmological models with a fixed P(k) shape and increasing normalization
\sig8, we find parameters of the galaxy halo occupation distribution (HOD) that
reproduce SDSS measurements of w(rp) as a function of luminosity. Using these
HOD models we calculate mean M/L ratios as a function of halo mass and populate
halos of N-body simulations to compute M/L in larger scale environments,
including cluster infall regions. For all cosmological models, the M/L ratio in
high mass halos or high density regions is approximately independent of halo
mass or smoothing scale. However, the "plateau" value of M/L depends on \sig8
as well as \Omega_m, and it represents the universal mass-to-light ratio
only for models in which the galaxy correlation function is approximately
unbiased, i.e., with \sig8 ~ \sig8_gal. Our results for cluster mass halos
follow the trend M/L = 577(\Omega_m/0.3)(\sig8/0.9)^{1.7} h Msun/Lsun. Combined
with Carlberg et al.'s (1996) mean M/L ratio of CNOC galaxy clusters, this
relation implies (\sig8/0.9)(\Omega_m/0.3)^{0.6} = 0.75 +/- 0.06. M/L ratios of
clusters from the SDSS and CAIRNS surveys yield similar results. This
constraint is inconsistent with parameter values \Omega_m ~ 0.3, \sig8 ~ 0.9
favored by recent joint analyses of CMB measurements and other large-scale
structure data. We discuss possible resolutions, none of which seems entirely
satisfactory. Appendices present an improved formula for halo bias factors and
an improved analytic technique for calculating the galaxy correlation function
from a given cosmological model and HOD. (Abridged)Comment: Accepted to ApJ (v 630, no 2). Replaced with accepted versio
Self Interference of Single Electrodynamic Particle in Double Slit
It is by the long established fact in experiment and theory that
electromagnetic waves, here as one component of an IED particle, passing a
double slit will undergo self inference each, producing at a detector plane
fringed intensities. The wave generating point charge of a zero rest mass, as
the other component of the particle, is maintained a constant energy and speed
by a repeated radiation reabsorption/reemission scheme, and in turn steered in
direction in its linear motion by the reflected radiation field, and will
thereby travel to the detector along (one of) the optical path(s) of the waves
leading to a bright interference fringe. We elucidate the process formally
based on first principles solutions for the IED particle and known principles
for wave-matter interaction.Comment: Presentation at The 6th Int. Symp. Quantum Theory and Symmetries,
Univ. Kent, 2009
Viscous effects on a vortex wake in ground effect
Wake vortex trajectories and strengths are altered radically by interactions with the ground plane. Prediction of vortex strength and location is especially important in the vicinity of airports. Simple potential flow methods have been found to yield reasonable estimates of vortex descent rates in an otherwise quiescent ambient background, but those techniques cannot be adjusted for more realistic ambient conditions and they fail to provide satisfactory estimates of ground-coupled behavior. The authors have been involved in a systematic study concerned with including viscous effects in a wake-vortex system which is near the ground plane. The study has employed numerical solutions to the Navier-Stokes equations, as well as perturbation techniques to study ground coupling with a descending vortex pair. Results of a two-dimensional, unsteady numerical-theoretical study are presented in this paper. A time-based perturbation procedure has been developed which permits the use of analytical solutions to an inner and outer flow domain for the initial flow field. Predictions have been compared with previously reported laminar experimental results. In addition, the influence of stratification and turbulence on vortex behavior near the ground plane has been studied
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