1,721,038 research outputs found
Boundedness of Fourier integral operators on Hardy spaces
No full textFor 0\ltp\le1, let denote the local Hardy space. Let be a Fourier integral operator defined by the oscillatory integral
where is a non-degenerate real phase function, and is a symbol of order and type , \sfrac12\lt\rho\le1, vanishing for outside a compact set of . We show that when and then initially defined on Schwartz functions in extends to a bounded operator . The range of and is sharp. This result extends to the local Hardy spaces the seminal result of Seeger \et for the spaces. As immediate applications we prove the boundedness of smooth Radon transforms on hypersurfaces with non-vanishing Gaussian curvature on the local Hardy spaces.
Finally, we prove a local version for the boundedness of Fourier integral operators on local Hardy spaces on smooth Riemannian manifolds of bounded geometry
- boundedness of analytic families of fractional integrals
No full textWe consider a double analytic family of fractional integrals S(z)(gamma,alpha) along the curve t -> | t|^(alpha), introduced in the particular case alpha = 2 by L. Grafakos in 1993, depending on two complex parameters z, alpha and defined
in a suitable way .
We determine the characteristic set of this family, that is,
set of all (1/p, 1/q, Re z) such that S(z)(gamma,alpha) maps L(p)(R(2)) to L(q)(R(2)) boundedly, and we prove that is does not depend on alpha. Our proof is based on product-type kernel arguments. More precisely, we prove that
at the height Re z=-1
the convolution kernel is a product kernel on R^2, adapted to the curve t -> |t|^(alpha); as a consequence, we show that the corresponding operator is bounded on L(p)(R(2)) for 1 < p < infinity
Product structures and fractional integration along curves
No full textWe establish L^p boundedness for a double analytic family of fractional integrals. Our proof is based on product-type kernels arguments. We prove in particular that the convolution kernel is
a product kernel adapted to a polynomial curve in R^3
Local Riesz transforms characterization of local Hardy spaces
No full textFor 0 0 be an integer and suppose (n-1)/(n + M -1) 0 such that for all ε with 0 < ε ≤ 1 we have ΣM≤|α|≤M+1∥r α(f)*Ψε∥LP(Rn) ≤ A Here, Ψε(x) = ε-nΨ(x/ε), α = (α0,..., αn)ε Nn+1, rα, as usual, denotes the composition r0α0 O...O r nαn. This result extends to the local Hardy spaces the analogous characterization of the classical Hardy spaces H p(Rn) (see e.g. [9, Chapter III.5.16])
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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