1,720,995 research outputs found
Well-posedness of the scale-invariant tetrad formulation of the vacuum Einstein equations
No full textWe show that, with a small modification, the formulation of the Einstein equations of Uggla et al, which uses tetrad variables normalized by the expansion, is a mixed symmetric hyperbolic/parabolic system. Well-posedness of the Cauchy problem follows from a standard theorem
Perturbations of an exact solution for (2+1) -dimensional critical collapse
No full textWe find the perturbation spectrum of a family of spherically symmetric and continuously self-similar (CSS) exact solutions that appear to be relevant for the critical collapse of scalar field matter in 2+1 spacetime dimensions. The rate of exponential growth of the unstable perturbation yields the critical exponent. Our results are compared to the numerical simulations of Pretorius and Choptuik and are inconclusive: We find a CSS solution with exactly one unstable mode, which suggests that it may be the critical solution, but another CSS solution which has three unstable modes fits the numerically found critical solution better.<br/
Existence, uniqueness and other properties of the BCT (minimal strain lapse and shift) gauge
No full textBrady, Creighton and Thorne (BCT) have proposed a choice of the lapse and shift for numerical evolutions in general relativity that extremizes a measure of the rate of change of the 3-metric (BCT gauge). We investigate the existence and uniqueness of this gauge (with Dirichlet boundary conditions), and comment on its use in numerical time evolutions
Angular momentum near the black hole threshold in scalar field collapse
No full textFor the formation of a black hole in the gravitational collapse of a massless scalar field, we calculate a critical exponent that governs the black hole angular momentum for slightly non-spherical initial data near the black hole threshold. We calculate the scaling law by second-order perturbation theory. We then use the numerical results of a previous first-order perturbative analysis to obtain the numerical value ??0.76 for the angular momentum critical exponent. A quasi-periodic fine structure is superimposed on the overall power law
The Books I Wanted to Write
No full textAuthor lists book titles he would have liked to have written and humorous descriptions of them
What Return on Their Investment Can Oakland Students Expect?
No full textData from Payscale Inc. and commentary from author about Oakland University students possible return on their investment in employment field
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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