1,720,979 research outputs found
Gromov-Witten/Pairs correspondence for the quintic 3-fold
No full textWe use the Gromov-Witten/Pairs (GW/P) descendent correspondence for toric 3-folds and degeneration arguments to establish the GW/P correspondence for several compact Calabi-Yau (CY) 3-folds (including all CY complete intersections in products of projective spaces). A crucial aspect of the proof is the study of the GW/P correspondence for descendents in relative geometries. Projective bundles over surfaces relative to a section play a special role. The GW/P correspondence for Calabi-Yau complete intersections provides a structure result for the Gromov-Witten invariants in a fixed curve class. After a change of variables, the Gromov-Witten series is a rational function in the variable -q=e[superscript iu] invariant under q ↔ q[subscript -1]
The tautological ring of the moduli space of curves
No full textThe tautological ring of the moduli space of curves M_g is a subring R^*(M_g) of the Chow ring A^*(M_g). The tautological ring can also be defined for other moduli spaces of curves, such as the moduli space of curves of compact type M^c_g or the moduli space of Deligne-Mumford stable pointed curves Mbar_{g,n}. We conjecture and prove various results about the structure of the tautological ring.
In particular, we give two proofs of the Faber-Zagier relations, a large family of relations between the kappa classes in R^*(M_g) that contains all known relations. The first proof (joint work with R. Pandharipande) uses the virtual geometry of the moduli space of stable quotients developed by Marian, Oprea, and Pandharipande. The second proof (joint work with R. Pandharipande and D. Zvonkine) uses Witten's class on the moduli space of 3-spin curves and the classification of semisimple cohomological field theories by Givental and Teleman. The second proof has the disadvantage that it only proves the image of the Faber-Zagier relations in cohomology, but the advantage that it also proves an extension of the relations to Mbar_{g,n} that was conjectured by the author. These relations on Mbar_{g,n} and their restrictions to smaller moduli spaces of curves seem to describe all known relations in the tautological ring.
We also prove several combinatorial results about the structure of the Gorenstein quotient rings of R^*(M_g) and R^*(M^c_g). This includes several new families of relations that are similar to the Faber-Zagier relations, as well as joint work with F. Janda giving formulas for ranks of restricted socle pairings in R^*(M^c_g).
The appendix presents data obtained by computer calculations of the tautological relations on Mbar_{g,n} and their restrictions to M^c_{g,n} and M^{rt}_{g,n} for small values of g and n. The data suggests several new locations in which the tautological ring might not be a Gorenstein ring
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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