1,720,969 research outputs found
Dynamics of (4+1)-Dihedrally Symmetric Nearly Parallel Vortex Filaments
Get PDFWe give a detailed analytical and numerical description of the global dynamics of 4+1 points interacting through the singular logarithmic potential and subject to the following symmetry constraint: at each instant 4 of them form an orbit of the Klein group D 2 of order 4. The main device in order to achieve our results is to use a McGehee-like transformation introduced in (Paparella and Portaluri in Global dynamics of the dihedral singular logarithmic potential and nearly parallel vortex filaments, 2011) for a problem analogous to the present one.
After performing this transformation in order to regularize the total collision, we study the rest-points of the flow, the invariant (stable and unstable) manifolds and we derive some interesting information about the global dynamics
Geometry of Stationary Solutions for a System Of Vortex Filaments: A Dynamical Approach.
Get PDFWe give a detailed analytical description of the global dynamics
of N points interacting through the singular logarithmic potential and subject
to the following symmetry constraint: at each instant they form an orbit of
the dihedral group Dl of order 2l. The main device in order to achieve our
results is a technique very popular in Celestial Mechanics, usually referred to
as McGehee transformation. After performing this change of coordinates that
regularizes the total collision, we study the rest-points of the flow, the invariant
manifolds and, with the help of a computer algebra system, we derive inter-
esting information about the global dynamics for l = 2. We observe that our
problem is equivalent to studying the geometry of stationary configurations of
nearly-parallel vortex filaments in three dimensions in the LIA approximation
Singular dynamics under a weak potential on a sphere
Get PDFWe give a detailed analytical description of the global dynamics of a point mass moving on a sphere under the action of a logarithmic potential. We perform a McGehee-type blow-up in order to cope with the singularity of the potential when the point mass goes through the singularity. In addition we investigate the rest-points of the flow, the invariant (stable and unstable) manifolds and we give a complete dynamical description of the motion
The homology of path spaces and Floer homology with conormal boundary conditions
No full textWe define the Floer complex for Hamiltonian orbits on the cotangent bundle of a compact manifold which satisfy non-local conormal boundary conditions. We prove that the homology of this chain complex is isomorphic to the singular homology of the natural path space associated to the boundary conditions
Workshop on Variational methods in N-body and Vortex Dynamics May 28 - June 8, 2012 Department of Mathematics and Physics "Ennio De Giorgi" Università del Salento
No full textThe aim of this workshop is to understand the relationship between three important singular dynamical problems: the N-body problem of celestial mechanics, and the N-vortex and N-filament problems of ideal fluid mechanics. Of all the techniques and devices used in order to tackle these problems, variational methods are an important source of new ideas and results.
A crucial point for a complete understanding of the dynamic and chaotic properties of these singular systems is the description of the dynamics near collisions. In this respect it is natural and useful both from theoretical and numerical viewpoint to know, for instance, if some regularization techniques of the Celestial Mechanics could be generalized to the other two problems.
Other interesting questions are related to the study of the linear stability by using symplectic techniques and in particular the Maslov index, as well as to provide some index theorems both for the ode's and for the pde's that govern the dynamics, particularly in the case of colliding solutions. We close by mentioning a challenging problem to tackle, consisting in developing a Morse theory. In this respect, due to the lack of compactness, the understanding of the asymptotic behavior of the collision solutions is fundamental.
We hope that the workshop could be a starting point in order to provide an effective way to treat these milestone dynamical problems
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
- …
