12,195 research outputs found
Free fermionic propagators on a lattice
A method used recently to obtain a formalism for classical fields with
non-local actions preserving chiral symmetry and uniqueness of fermion fields
yields a discrete version of Huygens' principle with free discrete propagators
that recover their continuum forms in certain limit.Comment: LaTex document, 13 pages, 1 figure. Minor changes, two references
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MASS SEGREGATION IN DARK MATTER MODELS.
We use the moments of counts of neighbors as given by the Generalized
Correlation Integrals, to study the clustering properties of Dark Matter Halos
(DH) in Cold Dark Matter (CDM) and Cold+Hot Dark Matter (CHDM) models. We
compare the results with those found in the CfA and SSRS galaxy catalogs. We
show that if we apply the analysis in redshift space, both models reproduce
equally well the observed clustering of galaxies. Mass segregation is also
found in the models: more massive DHs are more clustered compared with less
massive ones. In redshift space, this mass segregation is reduced by a factor
2-3 due to the peculiar velocities. Observational catalogs give an indication
of luminosity and size segregation, which is consistent with the predictions of
the models. Because the mass segregation is smaller in redshift space, it is
suggestive that the real luminosity or size segregation of galaxies could be
significantly larger than what it is found in redshift catalogs.Comment: 13 pages including 9 figures (220 KB) in uuencoded compressed
Postscript format. To appear in The Astrophysical Journal, June 10. Latex
file and figures available at ftp://astrohp.ft.uam.es/pub/preprints/masse
Phenomenology Tools on Cloud Infrastructures using OpenStack
We present a new environment for computations in particle physics
phenomenology employing recent developments in cloud computing. On this
environment users can create and manage "virtual" machines on which the
phenomenology codes/tools can be deployed easily in an automated way. We
analyze the performance of this environment based on "virtual" machines versus
the utilization of "real" physical hardware. In this way we provide a
qualitative result for the influence of the host operating system on the
performance of a representative set of applications for phenomenology
calculations.Comment: 25 pages, 12 figures; information on memory usage included, as well
as minor modifications. Version to appear in EPJ
Unpolarized light in quantum optics
We present a new derivation of the unpolarized quantum states of light, whose
general form was first derived by Prakash and Chandra [Phys. Rev. A 4, 796
(1971)]. Our derivation makes use of some basic group theory, is
straightforward, and offers some new insights.Comment: 3 pages, REVTeX, presented at ICQO'200
Stochastic semiclassical fluctuations in Minkowski spacetime
The semiclassical Einstein-Langevin equations which describe the dynamics of
stochastic perturbations of the metric induced by quantum stress-energy
fluctuations of matter fields in a given state are considered on the background
of the ground state of semiclassical gravity, namely, Minkowski spacetime and a
scalar field in its vacuum state. The relevant equations are explicitly derived
for massless and massive fields arbitrarily coupled to the curvature. In doing
so, some semiclassical results, such as the expectation value of the
stress-energy tensor to linear order in the metric perturbations and particle
creation effects, are obtained. We then solve the equations and compute the
two-point correlation functions for the linearized Einstein tensor and for the
metric perturbations. In the conformal field case, explicit results are
obtained. These results hint that gravitational fluctuations in stochastic
semiclassical gravity have a ``non-perturbative'' behavior in some
characteristic correlation lengths.Comment: 28 pages, RevTeX, no figure
Hot and repulsive traffic flow
We study a message passing model, applicable also to traffic problems. The
model is implemented in a discrete lattice, where particles move towards their
destination, with fluctuations around the minimal distance path. A repulsive
interaction between particles is introduced in order to avoid the appearance of
traffic jam. We have studied the parameter space finding regions of fluid
traffic, and saturated ones, being separated by abrupt changes. The improvement
of the system performance is also explored, by the introduction of a
non-constant potential acting on the particles. Finally, we deal with the
behavior of the system when temporary failures in the transmission occurs.Comment: 22 pages, uuencoded gzipped postscript file. 11 figures include
Adiabatic decaying vacuum model for the universe
We study a model that the entropy per particle in the universe is constant.
The sources for the entropy are the particle creation and a lambda decaying
term. We find exact solutions for the Einstein field equations and show the
compatibilty of the model with respect to the age and the acceleration of the
universe.Comment: 10 pages, 2 figure
Monte Carlo simulation of SU(2) Yang-Mills theory with light gluinos
In a numerical Monte Carlo simulation of SU(2) Yang-Mills theory with light
dynamical gluinos the low energy features of the dynamics as confinement and
bound state mass spectrum are investigated. The motivation is supersymmetry at
vanishing gluino mass. The performance of the applied two-step multi-bosonic
dynamical fermion algorithm is discussed.Comment: latex, 48 pages, 16 figures with epsfi
Introdução ao plone tutorial.
Gerenciamento de conteúdo. Instalação do plone. Criando instância do plone. Criação de usuários. Esquema de workflow de documentos. Alterando a interface do plone. Como realizar backup de instancias do plone.bitstream/CNPTIA/11298/1/doc61.pdfAcesso em: 28 maio 2008
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