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A survey on hyperbolicity of projective hypersurfaces
No full textA survey on hyperbolicity of projective hypersurface
A note on Lang's conjecture for quotients of bounded domains
Full text linkIt was conjectured by Lang that a complex projective manifold is Kobayashi
hyperbolic if and only if it is of general type together with all of its
subvarieties. We verify this conjecture for projective manifolds whose
universal cover carries a bounded, strictly plurisubharmonic function. This
includes in particular compact free quotients of bounded domains.Comment: 10 pages, no figures, comments are welcome. v3: following suggestions
made by the referee, the exposition has been improved all along the paper, we
added a variant of Theorem A which includes manifolds whose universal cover
admits a bounded psh function which is strictly psh just at one point, and we
added a section of examples. Final version, to appear on \'Epijournal G\'eom.
Alg\'ebriqu
Hyperbolicity of projective hypersurfaces
Full text linkThis book presents recent advances on Kobayashi hyperbolicity in complex geometry, especially in connection with projective hypersurfaces. This is a very active field, not least because of the fascinating relations with complex algebraic and arithmetic geometry. Foundational works of Serge Lang and Paul A. Vojta, among others, resulted in precise conjectures regarding the interplay of these research fields (e.g. existence of Zariski dense entire curves should correspond to the (potential) density of rational points). Perhaps one of the conjectures which generated most activity in Kobayashi hyperbolicity theory is the one formed by Kobayashi himself in 1970 which predicts that a very general projective hypersurface of degree large enough does not contain any (non-constant) entire curves. Since the seminal work of Green and Griffiths in 1979, later refined by J.-P. Demailly, J. Noguchi, Y.-T. Siu and others, it became clear that a possible general strategy to attack this problem was to look at particular algebraic differential equations (jet differentials) that every entire curve must satisfy. This has led to some several spectacular results. Describing the state of the art around this conjecture is the main goal of this work
The geometry of the Bismut Connection
Full text linkThis thesis concerns the study of special metrics in Hermitian and almost-Hermitian geometry, characterized by classical constraints on the curvature of their Bismut, Chern, or Gauduchon connection. More precisely, we intend to study the analogs in Hermitian and almost-Hermitian geometry of constant scalar curvature metrics, Einstein metrics, and metrics whose curvature tensor satisfies some positivity notion. We study the existence of metrics with constant scalar curvature with respect to the Gauduchon connection, which can be interpreted as a Yamabe-type problem. We then analyze the geometry of 4-dimensional compact almost-complex manifolds that carry a second-Chern–Einstein metric and we produce new examples of such spaces. With the aim of investigating the geometry of the Bismut connection, we describe the Calabi–Yau with torsion metrics of submersion type on toric bundles over Hermitian manifolds. Moreover, we analyze the cohomological properties of compact complex manifolds equipped with a Bismut flat metric. This leads to a better understanding of the evolution of the pluriclosed flow on Bismut flat manifolds. Finally, we consider a new notion of positivity for Hermitian manifolds which involves the Bismut curvature tensor, and we investigate its behavior under the action of the Hermitian curvature flows
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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