1,720,965 research outputs found
Phase segregation dynamics for the Blume-Capel model with Kac interaction
No full textWe consider the Glauber and Kawasaki dynamics for the Blume-Capel spin model with weak long-range interaction on the infinite lattice: a ferromagnetic d-dimensional lattice system with the spin variable sigma taking values in {-1, 0, 1} and pair Kac potential gamma(d)(gamma(\ i - j \)), gamma > 0, i,j is an element of Z(d). The Kawasaki dynamics conserves the empirical averages of sigma and sigma(2) corresponding to local magnetization and local concentration. We study the behaviour of the system under the Kawasaki dynamics on the spatial scale gamma(-1) and time scale gamma(-2). We prove that the empirical averages converge in the limit gamma --> 0 to the solutions of two coupled equations, which are in the form of the flux gradient for the energy functional. In the case of the Glauber dynamics we still scale the space as gamma(-1) but look at finite time and prove in the limit of vanishing gamma the law of large number for the empirical fields. The limiting fields are solutions of two coupled nonlocal equations. Finally, we consider a nongradient dynamics which conserves only the magnetization and get a hydrodynamic equation for it in the diffusive limit which is again in the form of the flux gradient for a suitable energy functional. (C) 2000 Elsevier Science B.V. All rights reserved
Large deviations from the macroscopic equation for a particle systems with external random field and Kac type interaction
No full textWe consider a lattice gas in a periodic dimensional lattice of width \g^{-1}, \g>0, interacting via a Kac's
type interaction, with range
\frac 1\g and strength \g^d,
and
under the influence of a random potential given by independent,
bounded, random variables with translational invariant distribution. The system
evolves through a conservative dynamics, i.e. particles jump to nearest neighbor empty
sites, with
rates satisfying detailed balance with respect to the equilibrium measures. In [21] it has been shown
that rescaling space as
\g^{-1} and time as
\g^{-2}, in the limit \g \downarrow 0, for dimensions , the macroscopic density
profile
\r satisfies, a.s. with respect to the random field, a nonlinear integral
partial differential equation, having the diffusion matrix
determined by the statistical properties of the external random
field. Here we show an almost sure
(with respect to the random field) large deviations principle for the
empirical measures of such a process.
The rate function, which depends on the
statistical properties of the external random field, is lower semicontinuous and has compact level sets
Boundary driven Kawasaki process with long range interaction: dynamical large deviations and steady states
No full textA particle system with a single locally-conserved field (density) in a bounded
interval with different densities maintained at the two endpoints of the interval
is under study here. The particles interact in the bulk through a long-range
potential parametrized by β 0 and evolve according to an exclusion rule. It
is shown that the empirical particle density under the diffusive scaling solves
a quasilinear integro-differential evolution equation with Dirichlet boundary
conditions. The associated dynamical large deviation principle is proved.
Furthermore, when β is small enough, it is also demonstrated that the empirical
particle density obeys a law of large numbers with respect to the stationary
measures (hydrostatic). The macroscopic particle density solves a non-local,
stationary, transport equation
Hydrodynamics of a driven lattice gas with open boundaries: the asymmetric simple exclusion.
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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