6,576 research outputs found
A hyperbolic conservation law and particle systems
In these notes we consider two particle systems: the totally asymmetric simple
exclusion process and the totally asymmetric zero-range process. We introduce the
notion of hydrodynamic limit and describe the partial differential equation that governs
the evolution of the conserved quantity – the density of particles p(t,.). This equation is
a hyperbolic conservation law of type ətp(p, u) + vF(p(t, u)) = 0, where the flux F is a
concave function. Taking these systems evolving on the Euler time scale tN, a central
limit theorem for the empirical measure holds and the temporal evolution of the limit
density field is deterministic. By taking the system in a reference frame with constant
velocity, the limit density field does not evolve in time. In order to have a non-trivial
limit, time needs to be speeded up and for time scales smaller than tN 4=3, there is still
no temporal evolution. As a consequence, the current across a characteristic vanishes
up to this longer time scale.Fundação para a Ciência e a Tecnologia (FCT) - bolsa SFRH/BPD/39991/2007Fundação Calouste Gulbenkian - projecto "Hydrodynamic limit of particle systems
Strong curvature singularities in quasispherical asymptotically de Sitter dust collapse
We study the occurrence, visibility, and curvature strength of singularities
in dust-containing Szekeres spacetimes (which possess no Killing vectors) with
a positive cosmological constant. We find that such singularities can be
locally naked, Tipler strong, and develop from a non-zero-measure set of
regular initial data. When examined along timelike geodesics, the singularity's
curvature strength is found to be independent of the initial data.Comment: 16 pages, LaTeX, uses IOP package, 2 eps figures; accepted for
publication in Class. Quantum Gra
Different faces of the phantom
The SNe type Ia data admit that the Universe today may be dominated by some
exotic matter with negative pressure violating all energy conditions. Such
exotic matter is called {\it phantom matter} due to the anomalies connected
with violation of the energy conditions. If a phantom matter dominates the
matter content of the universe, it can develop a singularity in a finite future
proper time. Here we show that, under certain conditions, the evolution of
perturbations of this matter may lead to avoidance of this future singularity
(the Big Rip). At the same time, we show that local concentrations of a phantom
field may form, among other regular configurations, black holes with
asymptotically flat static regions, separated by an event horizon from an
expanding, singularity-free, asymptotically de Sitter universe.Comment: 6 pages, presented at IRGAC 2006, Barcelona, 11-15 July 200
Scaling limits of a tagged particle in the exclusion process with variable diffusion coefficient
We prove a law of large numbers and a central limit theorem for a tagged
particle in a symmetric simple exclusion process in the one-dimensional lattice
with variable diffusion coefficient. The scaling limits are obtained from a
similar result for the current through -1/2 for a zero-range process with bond
disorder. For the CLT, we prove convergence to a fractional Brownian motion of
Hurst exponent 1/4.Comment: 9 page
Análise da expressão de sequências de genes tipo RGA em espécies de Coffea resistentes e susceptÃveis ao nematóide Meloidogyne exigua.
Flexor digitorum brevis tendon transfer to the flexor digitorum longus tendon according to Valtin in posttraumatic flexible claw toe deformity due to extrinsic toe flexor shortening
AbstractClaw toe deformity after posterior leg compartment syndrome is rare but incapacitating. When the mechanism is flexor digitorum longus (FDL) shortening due to ischemic contracture of the muscle after posterior leg syndrome, a good treatment option is the Valtin procedure in which the flexor digitorum brevis (FDB) is transferred to the FDL after FDL tenotomy. The Valtin procedure reduces the deformity by lengthening and reactivating the FDL. Here, we report the outcomes of FDB to FDL transfer according to Valtin in 10Â patients with posttraumatic claw toe deformity treated a mean of 34Â months after the injury. Toe flexion was restored in all 10Â patients, with no claw toe deformity even during dorsiflexion of the ankle
The anisotropic XY model on the inhomogeneous periodic chain
The static and dynamic properties of the anisotropic XY-model on
the inhomogeneous periodic chain, composed of cells with different
exchange interactions and magnetic moments, in a transverse field are
determined exactly at arbitrary temperatures. The properties are obtained by
introducing the Jordan-Wigner fermionization and by reducing the problem to a
diagonalization of a finite matrix of order. The quantum transitions are
determined exactly by analyzing, as a function of the field, the induced
magnetization 1/n\sum_{m=1}^{n}\mu_{m}\left ( denotes
the cell, the site within the cell, the magnetic moment at site
within the cell) and the spontaneous magnetization which is obtained from the correlations for large spin separations. These results,
which are obtained for infinite chains, correspond to an extension of the ones
obtained by Tong and Zhong(\textit{Physica B} \textbf{304,}91 (2001)). The
dynamic correlations, , and the dynamic
susceptibility, are also obtained at arbitrary
temperatures. Explicit results are presented in the limit T=0, where the
critical behaviour occurs, for the static susceptibility as
a function of the transverse field , and for the frequency dependency of
dynamic susceptibility .Comment: 33 pages, 13 figures, 01 table. Revised version (minor corrections)
accepted for publiction in Phys. Rev.
Crossover to the KPZ equation
We characterize the crossover regime to the KPZ equation for a class of
one-dimensional weakly asymmetric exclusion processes. The crossover depends on
the strength asymmetry () and it occurs at
. We show that the density field is a solution of an
Ornstein-Uhlenbeck equation if , while for it is
an energy solution of the KPZ equation. The corresponding crossover for the
current of particles is readily obtained.Comment: Published by Annales Henri Poincare Volume 13, Number 4 (2012),
813-82
Caracterização térmica da borracha natural de clones IAC da série 400 da cidade de Jaú em São Paulo.
Propriedades tecnológicas da borracha natural de clones IAC da série 400 da cidade de Mococa em São Paulo.
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