1,721,006 research outputs found
Supersymmetry breaking in string-derived supergravities
No full textClassical heterotic string solutions with spontaneously broken d = 4, N = 1, 2 or 4 supersymmetry have been recently formulated via coordinate-dependent compactifications. We construct the corresponding low-energy effective lagrangians by means of generalized dimensional reductions à la Scherk-Schwarz. We show that these dimensional reductions of d = 10, N = 1 supergravity + Yang-Mills can be interpreted as special "gaugings" of the resulting d = 4, N = 4 theory, characterized by a positive semidefinite potential. We also describe in detail the properties of the d = 4, N = 1 models obtained from the N = 4 ones by a consistent Z2 × Z2′ truncation. © 1989
Effective super-Higgs and StrM from four-dimensional strings
No full textWe introduce supersymmetry breaking terms into the superpotential of the supergravity theories recently derived as the point field limit of the four-dimensional N = 1 superstrings. The terms we discuss have the special feature of giving mass to the gravitino without inducing one-loop quadratic divergences in the effective theory. It is shown that this property of the effective theory is due to the special geometrical structure shared by the scalar Kähler manifolds of the four-dimensional superstring-induced models. © 1987
Superstrings with spontaneously broken supersymmetry and their effective theories
No full textWe discuss superstring models with spontaneous breaking of N=1, 2 or 4 space-time supersymmetry, via coordinate-dependent compactifications from five to four dimensions. We provide a description of the supersymmetry breaking mechanism in the formulation with complex world-sheet fermions, and we reinterpret it in terms of special deformations of the lorentzian charge lattice. Considering a representative string model with spontaneously broken N=1 supersymmetry and massless chiral fermions, we show that the knowledge of the spectrum of states and of the flat directions completely specifies its low-energy effective lagrangian, which turns out to be a new no-scale supergravity model. We outline the qualitative difference between these models and other scenarios of gaugino (gravitino) condensation or general non-perturbative phenomena. © 1989
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
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