1,720,992 research outputs found
Vers une interprétation galoisienne de la théorie de l'homotopie
Full text linkInternational audienceGiven any pointed CW complex (X,x), it is well known that the fondamental group of X pointed at x is naturally isomorphic to the automorphism group of the functor which associates to a locally constant sheaf on X its fibre at x. The purpose of this work is to generalize this fact to higher homotopy. For this we introduce the (infinite) category of locally constant stacks on X, and we prove that the loop-space of endomorphisms of its fibre functor at x is naturally equivalent to the loop space of X based at x
Generalized local jacobians and commutative group stacks
Full text linkIn [CS01, Page 109] Grothendieck sketches the construction of a complex J_*(X) or commutative pro-algebraic groups, associated to a smooth variety X, and for which each J_i(X) is a product of local factors called the local generalized jacobians. The purpose of this note is to recast this construction in the setting of higher algebraic group stacks for the fppf topology. For this, we introduce a notion of algebraic homology associated to a scheme which is a universal object computing fppf cohomology with coefficients in group schemes. We endow this algebraic homology with a filtration by dimension of supports, and prove that, when X is smooth, J_*(X) appears as the E1-page of the corresponding spectral sequence. In a final part we partially extends our constructions and results over arbitrary bases.28 pages. Small changes in the exposition by removing some unnecessary unipotency conditions in the main definition. Results remain essentially the sam
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
Homotopical and Higher Categorical Structures in Algebraic Geometry
No full textHabilitation thesis, 93 pages. Some misprints corrected and remarks addedThis a slightly expended version of my habilitation thesis, which is an overview of my research activities during the last 4 years, written in a rather informal style
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
CLASSES CARACTÉRISTIQUES DES SCHÉMAS FEUILLETÉS
No full textDans ce travail, nousétudions la notion de feuilletages dérivés sur des schémas et schémas dérivés généraux et de caractéristiques quelconques. Nous introduisons la filtration de Hodge associéeà un feuilletage dérivé, qui filtre de manière fonctorielle la cohomologie de de Rham dérivée. Nous utilisons cette filtration pourétudier les propriétés d'annulation des classes caractéristiques de complexes parfaits munis de connexion le long de feuilletages dérivés. En guise d'application, nous démontrons des extensionsà la caractéristique positive, età valeurs dans la cohomologie cristalline, du théorème d'annulation de Bott (voir [Bot70]) et d'existence de résidus pour les feuilletages avec singularités (voir [BB72])
Simplicial presheaves and derived algebraic geometry.
No full textInternational audienceThis text is an introduction to derived algebraic geometry based on model categories of simplicial presheaves
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
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