1,720,976 research outputs found
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
Schleifenquantisierung von Supergravitationstheorien
Get PDFThe aim of this thesis is to develop loop quantisation techniques for higher-dimensional supergravities in order to make progress towards comparing loop quantum gravity to superstring theory. The abstract idea for this comparison is to look at loop quantum gravity and string theory as two methods of quantising an underlying gravity theory. While loop quantum gravity circumvents the usual problems associated with standard Fock-type quantisations of gravity theories by starting classically from a different Poisson-*-subalgebra of phase space functions, string theory introduces the string as a fundamental ingredient to cope with the short distance divergences arising in perturbative quantum gravity. The most obvious problem with comparing these two approaches to quantum gravity is that while it was only known how to formulate loop quantum gravity in four (or three) dimensions, including all types of standard model matter couplings, string theory requires a ten-dimensional spacetime with supersymmetry. The possible reductions of string theory to four dimensions on the other hand are highly non-unique, thus it is very hard to compare these approaches at this level. A possible solution to this problem, which is investigated in this thesis, is to extend the techniques of loop quantum gravity to higher-dimensional supergravities, which arise as the low energy limits of string theories. These supergravities have the same low energy particle content and live in the same spacetime dimension as the corresponding string theories and are thus suited to circumvent the above problem. Since this solution does not seem to be overly sophisticated at a first glance, it is important to remark that, prior to recent work on which this thesis is based, it was not even known how to formulate loop quantum gravity for pure higher-dimensional gravity, since the main ingredient at the classical level, the Ashtekar-Barbero connection, is only available in four dimensions. In this thesis, we will first develop a generalisation of this type of connection formulation for higher-dimensional general relativity. We will then show that the quantisation techniques from loop quantum gravity can be mainly carried over to this new formulation, while some new ingredients have to be introduced. Next, we are going to extend this formulation to higher-dimensional supergravities, thus providing a solution for the above problem. On a different route, we provide a partially reduced phase space quantisation of higher-dimensional general relativity conformally coupled to a scalar field based on the constant mean curvature gauge in the fourth part of this thesis. Finally, in the fifth part of this thesis, we will treat isolated horizons as boundaries of the spacetime manifold in order to take first steps to compare string theory and higher-dimensional loop quantum gravity in the presence of a black hole.Es ist das Ziel dieser Arbeit, Methoden zu entwickeln, die die Quantisierung von Supergravitationstheorien mit Hilfe von Techniken aus der Schleifenquantengravitation ermöglichen, um Fortschritte beim Vergleichen der Schleifenquantengravitation mit der Superstringtheorie zu machen. Die abstrakte Idee dieses Vergleichs ist es, sowohl die Schleifenquantengravitation als auch die Superstringtheorie als Quantisierungen einer zugrundeliegenden Gravitationstheorie zu verstehen. Während die Schleifenquantengravitation die üblichen Probleme bei Fock-Typ Quantisierungen von Gravitationstheorien vermeidet, indem sie von einer anderen Poisson-*-Algebra von Phasenraumfunktionen startet, postuliert die Superstringtheorie den String als neuen fundamentalen Baustein um den UV-Divergenzen in der perturbativen Quantengravitation Herr zu werden, welche durch die Betrachtungen von beliebig kleinen Distanzen entstehen. Das offensichtlichste Problem, welches beim Vergleichen dieser beiden Theorien entsteht, ist dass während nur bekannt war, wie man Schleifenquantengravitation in vier (oder drei) Dimensionen formuliert und die Materiefelder des Standardmodells behandelt werden konnten, aber nicht notwendig waren, die Superstringtheorie eine zehndimensionale Raumzeit mit Supersymmetrie braucht. Andererseits sind mögliche Reduktionen der Superstringtheorie auf vier Dimensionen hochgradig nicht-eindeutig und daher ist es sehr schwierig diese Reduktionen mit der Schleifenquantengravitation zu vergleichen. Eine mögliche Lösung dieses Problems, welche in dieser Arbeit untersucht wird, ist es die Techniken der Schleifenquantengravitation auf höherdimensionale Supergravitationen zu erweitern, welche als Niederenergielimites von Superstringtheorien auftreten. Diese Supergravitationen haben das selbe Niederenergieteilchenspektrum und leben in der selben Raumzeitdimension wie die entsprechenden Superstringtheorien und sind deshalb gut geeignet, um das oben beschriebene Problem zu umgehen. Da dieser Lösungsvorschlag auf den ersten Blick nicht sehr tiefsinnig erscheint, muss angemerkt werden, dass es bis vor einigen kürzlich erschienenen Publikationen, welche zu dieser Arbeit geführt haben, nicht einmal bekannt war, wie und ob man höherdimensionale Gravitation mit den Methoden der Schleifenquantengravitation behandeln könnte. Das Problem an dieser Stelle war, dass der Hauptinput in der klassischen Theorie, die Ashtekar-Barbero-Variablen, nur in vier Dimensionen verfügbar sind. In dieser Arbeit wird erst eine Verallgemeinerung dieser Art von Zusammenhangsformulierung auf höherdimensionale allgemeine Relativitätstheorie entwickelt werden. Danach wird gezeigt werden, dass die meisten Quantisierungstechniken der Schleifenquantengravitation auf diese neue Formulierung angewendet werden können, aber auch ein paar neue Techniken gebraucht werden. Als nächstes werden diese Techniken noch auf Supergravitationen erweitert werden, und damit ein Lösungsvorschlag für das obige Problem präsentiert werden. Abseits dieses Hauptthemas wird eine partiell reduzierte Phasenraumquantisierung von höherdimensionaler allgemeiner Relativitätstheorie mit einem konform gekoppeltem Skalarfeld, basierend auf der Konstante-mittlere-Krümmungs-Eichung, im vierten Teil dieser Arbeit vorgestellt werden. Abschließend werden im fünften Teil dieser Arbeit Raumzeiten mit isolierten Horizonten als Rändern betrachtet, um erste Schritte hin zu einem Vergleich der Superstringtheorie mit der höherdimensionalen Schleifenquantengravitation in Raumzeiten mit schwarzen Löchern zu machen
The Living and Dying of Black Holes: About the research of Stephen Hawking and related topics
No full textStephen Hawking war bis zu seinem Tod im März 2018 fasziniert von Schwarzen Löchern und deren Schicksal. Während seiner ganzen Karriere arbeitete er an dafür relevanten Fragen, sein letzter Artikel über das Thema wurde nur wenige Tage vor seinem Tod fertig gestellt und im Oktober 2018 von seinen Koautoren veröffentlicht. Hawking lieferte insbesondere grundlegende Antworten auf die Frage, was mit einem Schwarzen Loch im Laufe seines Lebens geschieht. Genau dieser Fragestellung möchten wir hier nachgehen, dabei Hawkings Beiträge erläutern, und schließlich einen Ausblick darauf wagen, was zukünftig zum Thema gesagt werden könnte.Stephen Hawking was fascinated with black holes and their fate up until his death in March 2018. He worked on related questions during all of his career, his last contribution was finished only days before his passing and published posthumously by his coauthors in October 2018. In particular, Hawking provided fundamental answers to the question of what happens to a black hole during its lifetime. We would like to pursue precisely this question in this article, explain Hawking\u27s contributions, and finally venture to provide an outlook of what may be said about this topic in the future. 
A note on the scalar products in sLQC
No full textSolvable loop quantum cosmology provides a simple model of spatially flat, homogeneous, and isotropic quantum cosmology where the initial singularity is resolved. A close inspection of the literature reveals that there exist two different proposals for a scalar product that are usually assumed to be identical, but agree only in the large volume limit. The small volume limit, and thus the reported difference, turns out to be important for questions such as coarse graining fundamental quantum states in full theory embeddings of these cosmological models
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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