1,720,992 research outputs found
Probing the Universe: A Geometrical View for Observers of Spacetime Physics
No full textThis book provides a fresh perspective on the relationships between gravitation, electrodynamics, and quantum physics. Designed for graduate students and postdoctoral researchers with a background in mathematical physics, it organizes key ideas into a series of paradigms inspired by the history of scientific discoveries, from Aristotle and Euclid to modern physics. Framed within the language of modern differential geometry, these paradigms rely on essential concepts such as fiber bundles and manifolds, which are introduced in the text. Although the primary focus is on Einstein’s theory of gravitation, the discussion is set within a broader mathematical framework that includes arbitrary dimensional manifolds with linear connections, metric tensor fields (with any signature), torsion, and metric gradients. A chapter introduces the concept of Frenet-Serret frames along curves in various arbitrary-dimensional manifolds with metric tensor fields of arbitrary signature and provides examples relevant to spacetime physics. The book makes precise the concept of an “ideal spacetime observer” and a “standard clock in spacetime”, highlighting the inevitable role of quantum wave-particle duality in interpreting local measurement processes.
The text offers a variational approach to deriving generalized theories of gravitation interacting with matter using the exterior calculus of differential forms. This provides an efficient calculus for deriving stress-energy-momentum tensors and leads to a detailed analysis of the Einstein-Maxwell paradigm in spacetime. Killing vector and Killing tensor fields are employed in analyzing the geodesics of Schwarzschild, Reissner-Nordstrom and Kerr spacetimes. Throughout the book emphasis is placed upon distinguishing between geometric and co-ordinate singularities, and is illustrated using charts constructed by Painleve-Gullstrand and Kruskal-Szekeres, leading to a discussion of the properties of black hole spacetimes. A geometrical framework is provided for analyzing the Tolman-Oppenheimer-Volkoff theory for stellar interiors and a chapter examines the “Oppenheimer-Schiff Debate” about the electromagnetic fields generated by rotating charged shells, clarifying key points in the literature. A chapter introduces chiral pulse models in Maxwell electrodynamics, Bopp-Lande-Podolsky electrodynamics and linearised Einstein gravitation. Spinor fields are introduced as sections of a Clifford algebra bundle and used to discuss spinor pulse fields in Minkowski spacetime. Several appendices complement the main text. They include a guide to notations, detailed proofs of mathematical identities, a table of physical dimensions for quantities discussed, and a primer on set and measure theory. For readers interested in further exploration, additional appendices outline the mathematical foundations of quantum mechanics, providing a stepping stone to future paradigms in modern physics
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
Walton, Timothy L.;Experimenting with Qohelet: A Text Linguistic Approach to Reading Qohelet as Discourse
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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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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