1,721,063 research outputs found
Some remarks on the geometry of the tautological model
No full textS. Brivio has established a linkage between the Theta divisor of a vector bundle E, over a smooth complex curve, and the geometry of the tautological model of E. In this paper we slightly generalize her results by considering other values for the rank and the degree of E
Connected monomial invariants
No full textWe define the monomial invariants of a projective variety Z; they are invariants coming from the generic initial ideal of Z. We prove that, under suitable hypotheses, a variety of codimension at least two has connected monomial invariants; as a corollary, we generalize a result of Cook: if Z is an integral variety of codimension two, satisfying some assumptions on the minimal degree of a hypersurface containing it, then its invariants are connected
Rank 2 vector bundles over P2(C) whose sections vanish on points in general position
No full textIn this paper we address the classification of rank 2 vector bundles E, over P^2(C), such that the zero locus of a general section of E is a set of distinct points in general position. We also discuss the existence of smooth threefolds X = P(E), arising from such bundles
Surfaces in P^4 fibered in cubics
Full text linkAny algebraic surface in Pn(C which is fibered in cubics, so that the generic fibre is a twisted cubic, gives rise to a curve Γ in a suitable compactification X of the space of smooth rational cubics of Pn(C). In this paper the case n = 4 is addressed and the corresponding space X is studied. We apply our results to complete the classification of smooth, rational surfaces in P4(C) ruled in cubics
Key exchange based on three-dimensional Segre products and their projections
Full text linkIn this paper we present a key exchange protocol in which Alice and Bob use a three-dimensional Segre product embedded in a large projective space by mean of the Veronese embedding. Public keys are given by hyperplanes cutting pairs of Segre products containing a common plane. Alice and Bob consider the residual curve which is projectively equivalent to a smooth plane curve of genus 1, whose j-invariant is the exchanged key. When the dimension of the above projective space increases very much, HPC capabilities are required
On connected divisors
No full textA vanishing theorem for numerically connected divisors, first given by Bombieri for surfaces, is established in any dimension. A definition of k-connected divisors is proposed, then such divisors on threefolds are studied
On the lifting problem in codimension two
Full text linkIn this note we prove a special case of a conjecture of Mezzetti [5].<br /
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
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