1,720,959 research outputs found
Gluing theory for slc surfaces and threefolds in positive characteristic
Get PDFWe develop a gluing theory in the sense of Koll\'{a}r for slc surfaces and
threefolds in positive characteristic. For surfaces we are able to deal with
every positive characteristic , while for threefolds we assume that .
Along the way we study nodes in characteristic and establish a theory of
sources and springs \`a la Koll\'{a}r for threefolds. We also give applications
to the topology of lc centers on slc threefolds, and to the projectivity of the
moduli space of stable surfaces in characteristic .Comment: v2: minor corrections. To appear in Annali SN
Positivity Of The Cm Line Bundle For K-Stable Log Fanos
No full textWe prove the bigness of the Chow-Mumford line bundle associated to a Q-Gorenstein family of log Fano varieties of maximal variation with uniformly K-stable general geometric fibers. This result generalizes a theorem of Codogni and Patakfalvi to the logarithmic setting
On the singularities of quotients by 1-foliations
Get PDFWe study the singularities of varieties obtained as infinitesimal quotients
by -foliations in positive characteristic. (1) We show that quotients by
(log) canonical -foliations preserve the (log) singularities of the MMP. (2)
We prove that quotients by multiplicative derivations preserve many properties,
amongst which most -singularities. (3) We formulate a notion of families of
-foliations, and investigate the corresponding families of quotients.Comment: v2: 33 pages, comments welcome. The results have been slightly
expanded, and the material on resolution of 1-foliations will appear on a
separate preprint. The title and the abstract have been changed accordingl
Gluing for stable families of surfaces in mixed characteristic
Get PDFWe study the normalizations of non-normal stable families of slc surfaces
over an excellent DVR. In mixed characteristic, we establish a gluing statement
that is relevant for the properness of the moduli space of such surfaces. We
also study the fibers of such glued families, in mixed and equi-characteristic,
and provide an essential result for slc adjunction in residue characteristic
>5.Comment: 25 pages. Comments welcome at anytime. (v4: Final version, to appear
in Algebraic Geometry. Abstract has been changed, minor corrections.
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
Normality of minimal log canonical centers of threefolds in mixed and positive characteristic
Get PDFWe prove the normality of minimal log canonical centers on threefold pairs
which residue fields are perfect of residue characteristics and
. We also show that the union of all log canonical centers on threefold
pairs with standard coefficients are seminormal provided that the residue
characteristic is large enough. We provide an example of a non-seminormal log
canonical center on a threefold in characteristic , and give sufficient
conditions to construct similar examples.Comment: 20 pages. Comments are welcom
On the projectivity of some moduli spaces of varieties
No full textThis thesis is constituted of one article and three preprints that I wrote during my PhD thesis. Their common theme is the moduli theory of algebraic varieties. In the first article I study the Chow--Mumford line bundle for families of uniformly K-stable Fano pairs, and I show it is ample when the family has maximal variation. The three preprints deal with a generalization to positive characteristic of Kollár's gluing theory for stable varieties. I generalize this theory to surfaces and threefolds. Then I apply it to study the abundance conjecture for surfaces, the topology of lc centers on threefolds, existence of semi-resolutions for surfaces, and gluing theory for families of surfaces in mixed characteristic.CA
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
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