1,721,059 research outputs found
Higher-dimensional Clifford-Severi equalities
Full text linkLet X be a smooth complex projective variety, a: X → A a morphism to an abelian variety such that pic0(A) injects into pic0(X) and let L be a line bundle on X; denote by ha0(X,L) the minimum of h0(X,LS - a-α) for α Pic0(A). The so-called Clifford-Severi inequalities have been proven in [M. A. Barja, Generalized Clifford-Severi inequality and the volume of irregular varieties, Duke Math. J. 164(3) (2015) 541-568; M. A. Barja, R. Pardini and L. Stoppino, Linear systems on irregular varieties, J. Inst. Math. Jussieu (2019) 1-39; doi:10.1017/S1474748019000069]; in particular, for any L there is a lower bound for the volume given by: vol(L) ≥ n!ha0(X,L), and, if KX - L is pseudoeffective, vol(L) ≥ 2n!ha0(X,L). In this paper, we characterize varieties and line bundles for which the above Clifford-Severi inequalities are equalities
Smoothing semi-smooth stable Godeaux surfaces
Full text linkWe show that all the semi-smooth stable complex Godeaux surfaces, classified in
[M. Franciosi, R. Pardini and S. Rollenske, Ark. Mat. 56 (2018), no. 2, 299–317], are
smoothable and that the moduli stack is smooth of the expected dimension 8 at the
corresponding points
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
Birational geometry of surfaces. Preface
No full textThis volume is an issue of the Bollettino dell’Unione Matematica Italiana connected to the workshop “Birational geometry of surfaces” which took place at the Department of Mathematics of the University of Rome “Tor Vergata”, Italy, in January, 11–15, 2016. We thank the Editors of the Bollettino dell’Unione Matematica Italiana for having accepted to dedicate this issue to this topic.
The workshop was organized by Ciro Ciliberto, Thomas Dedieu, Flaminio Flamini, Rita Pardini with the support of the projects:
Geometria, Algebra e Combinatoria di Spazi di Moduli e Configurazioni—no. PRA-2016-67—of the University of Pisa,
National Research Project (PRIN 2010-11) Geometria delle Varietà Algebriche—no. 2010S47ARA-005—(nodes of Pisa and Roma “Tor Vergata”),
GDRE (CNRS-INdAM) GRIFGA 2012–2015,
Families of subvarieties in complex algebraic varieties; this project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 652782
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
LINEAR SYSTEMS on IRREGULAR VARIETIES
Full text linkLet be a normal complex projective variety, a subvariety of dimension (possibly) and a morphism to an abelian variety such that injects into; let be a line bundle on and a general element.We introduce two new ingredients for the study of linear systems on. First of all, we show the existence of a factorization of the map, called the eventual map of on, which controls the behavior of the linear systems, asymptotically with respect to the pullbacks to the connected étale covers induced by the -th multiplication map of.Second, we define the so-called continuous rank function, where is the pullback of an ample divisor of. This function extends to a continuous function of, which is differentiable except possibly at countably many points; when we compute the left derivative explicitly.As an application, we give quick short proofs of a wide range of new Clifford-Severi inequalities, i.e., geographical bounds of the form where depends on several geometrical properties of, or
I servizi sanitari ed i problemi di igiene urbana: un’analisi sulla organizzazione e sull’efficienza dei servizi erogati in materia di controllo della popolazione felina (L.281/91
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