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Contributions to the positive models theory
No full textLa première étude systématique de la théorie des modèles positive était faite par Ben Yaacov qui a proposé une approche uniforme aux travaux précurseurs accomplis indépendamment par Robinson, Shelah, Hrushovski et Pillay avec un souci croissant d'incorporer les techniques modernes de la théorie des modèles dans le contexte des logiques réduites. Ben Yaacov et Poizat dans leur travail intitulé Fondements de la logique positive ont défini un nouveau cadre pour la théorie des modèles positive, qui détermine le contexte de cette thèse. Dans le premier chapitre nous rappelons les outils de la théorie des modèle positive et nous développons des notions et des outils qui nous seront utiles dans le reste des chapitres. Parmi ceux-ci, il convient de souligner les extensions universelles. Elles caractérisent les bases d'amalgamation dans le deuxième chapitre, et sont cruciales dans la construction des domaines universels positifs. Dans le deuxième chapitre nous étudions la notion d'amalgamation qui s'avère centrale dans la théorie des modèles positive. Elle nous permettra d'étudier la conservation de la séparation topologique entre les extensions élémentaires positives, et de caractériser les théories de Robinson et l'élimination des quanteurs dans certaines classes des structures. Dans le troisième chapitre, nous continuons l'étude de la stabilité positive déjà entamée par Ben Yaacov, et nous en proposons une nouvelle caractérisation par une notion d'ordre propre à la théorie des modèles positiveThe first systematic study of positive model theory was introduced by Ben Yaacov, where he proposed a uniform approach to works accomplished independently by Robinson, Shelah, Hrushovski and Pillay, our aim is to incorporate modern technics of model theory in the context of positive logic. The work of Ben Yaacov and Poizat entitled foundations of positive logic defined a new framework of the positive model theory, which determines the context of this thesis. In the first chapter we review the tools of the theory of positive model and we develop concepts and tools that we will be useful in the remaining chapters. One of these concepts is the universal extensions, they characterize the bases amalgamation in the second chapter, and it's crucial in the construction of the positive universal domains. In the second chapter we study the notion of amalgamation which is central in the positive models theory. It will allow us to study the conservation of topologic separation between the positives elementary extensions, and characterize the theories of Robinson and quantifier elimination in some classes of structures. In the third chapter, we continue the study of positive stability which is already initiated by Ben Yaacov, and we propose a new characterization of order property which is specific to the positive models theor
A model-theoretical study of the tannakian formalism
No full textNous définissons et étudions dans cette thèse un formalisme permettant de traiter de questions tannakiennes pour des groupes définis sur des anneaux différentiels généralisés, qui généralisent à la fois les anneaux différentiels et les anneaux de différence. Nous définissons une notion de catégorie tannakienne différentielle de manière similaire au formalisme tannakien usuel, en ajoutant une structure supplémentaire permettant de décrire la structure induite par la différentielle généralisée. Nous étudions ensuite les propriétés modèle-théoriques des catégories qui en résultent, réalisant le groupe tannakien associé à la catégorie comme un groupe de liaison modèle-théorique. Dans le dernier chapitre, nous étudions la notion d'univers d'une structure du premier ordre, et introduisons une topologie dans ce contexte qui est réminiscente de la topologie des espaces de types en Théorie des Modèles du premier ordre. Nous étudions également la notion de groupoïde de liaison du point de vue des universIn this thesis, we define and study a formalism which allows one to work on Tannakian questions for groups defined over generalized differential rings, which generalize both differential rings and difference rings. We define a notion of differential Tanakian category which is similar to the usual Tannakian formalism, adding a structure which permits to describe the differential structure induced by the generalized differential. We then study the model-theoretical properties of the resulting categories, realizing the Tannakian group associated to a category as a model-theoretical binding group. In the last chapter, we study the notion of universe associated to a first-order structure, and we introduce a topology in this context, which is reminiscent of the topology on the spaces of types in first-order Model Theory. We also study the notion of binding groupoid from the point of view of universe
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
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