1,720,974 research outputs found
Stable Postulation and Stable Ideal Generation: Conjectures for Fat Points in the Plane
No full textIt is an open problem to determine the Hilbert function and graded Betti
numbers for the ideal of a fat point subscheme supported at general points
of the projective plane. In fact, there is not yet even a general explicit conjecture
for the graded Betti numbers. Here we formulate explicit asymptotic
conjectures for both problems. We work over an algebraically closed field K
of arbitrary characteristic
ON plane rational curves and the splitting of the tangent bundle
Get PDFGiven a rational plane curve, we give new approaches to determining the splitting of the pullback of the cotangent bundle. We give applications to determining the minimal resolution for ideals of fat points in the plane
Star Configurations in P^n
No full textStar configurations are certain unions of linear subspaces of
projective space. They have appeared in several different contexts: the study of extremal Hilbert functions for fat point schemes in the plane; the study of secant varieties of some classical algebraic varieties; the study of the resurgence of projective schemes. In this paper we study some algebraic properties of the ideals defining star configurations, including getting partial results about Hilbert functions, generators and minimal free resolutions of the ideals and their symbolic powers. We also show that their symbolic powers define arithmetically Cohen–Macaulay subschemes and we obtain
results about the primary decompositions of the powers of the
ideals. As an application, we compute the resurgence for the ideal of the codimension n −1 star configuration in Pn in the monomial case (i.e., when the number of hyperplanes
is n +1)
On the discriminant of spanned line bundles
No full textLet X be an irreducible smooth complex projective variety of dimension n, L a nontrivial spanned line bundle on X, V \subseteq H^0(X,L) a vector subspace od global sections spanning L with dim(V)=N+1.
The discriminant variety D(X,V) parameterizes the singular elements of |V|. By Bertini's theorem one can write dim(D(X,V))=N-1-k with k a non-negative integer. An upper bound on k in terms of N, n, and the dimension of the fibers of the map defined by V is established. Moreover, triplets (X,L,V) for which k is near the maximum are classified
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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