1,721,031 research outputs found
Stochastic cosmological inflation : a replica field-theoretical study
Full text linkKühnel F. Stochastic cosmological inflation : a replica field-theoretical study. Bielefeld (Germany): Bielefeld University; 2009.In dieser Arbeit wenden wir Methoden aus der statistischen Physik auf die stochastische Inflation an. Diese, die Replika-Feldtheorie und die Gauß'sche Variationsmethode sind unseres Wissens nach noch nie zuvor in diesem Kontext angewendet worden und erlauben, das Leistungsspektrum eines skalaren Testfeldes in großer Allgemeinheit zu bestimmen. Diese Methoden stellen einen Rahmen zur Verfügung, in welchem beliebige Quantenfluktuationen behandelt werden können, und könnten ein Startpunkt sein, um Rückwirkungseffekte bezüglich der Geometrie der Raumzeit einzubeziehen.
Einführungen in kosmologische Inflation, kosmologische Störungstheorie und Anisotropien des kosmischen Mikrowellenhintergrundes leiten diese Arbeit ein. Danach erklären wir die Idee der stochastischen Inflation, wobei wir auch einige detaillierte Herleitungen präsentieren, und geben einen Überblick über wichtige Fortschritte in diesem Feld. Es folgt eine Einführung in die Methoden der Replika-Feldtheorie, und zwar in einer Weise, die direkt anwendbar ist auf die stochastische Inflation. Unsere Arbeit wird fortgeführt durch eine explizite Berechnung des Leistungsspektrums eines skalaren Testfeldes in einem Friedmann-Universum. Wir untersuchen den Einfluss von Quantenfluktuationen auf dieses Spektrum und leiten explizite Ausdrücke her, welche die Abhängigkeiten von der Zeit sowie von anderen wichtigen Parametern deutlich machen. Der Effekt von Selbst-Wechselwirkungen und mögliche Auswirkungen auf den kosmischen Mikrowellenhintergrund werden diskutiert. Wir schließen mit einer Zusammenfassung unserer Ergebnisse und geben einen Ausblick.
Ein Teil unserer Hauptresultate wurde in Phys. Rev. D 78, 103501 (2008) publiziert, worin wir zum ersten Mal einen Replika-Feldtheorie-Zugang für die stochastische Inflation präsentieren und das Auftreten des Phänomens der sogenannten dimensionellen Reduktion zeigen. Dieses impliziert, dass unter bestimmten Bedingungen Infrarot-Divergenzen in Korrelationsfunktionen auftreten können. Die genauen Bedingungen hierfür haben wir in der Veröffentlichung Phys. Rev. D 79, 44009 (2009) untersucht, worin wir zeigen konnten, dass für eine große Klasse von Ausgangssituationen diejenigen Bereiche, in denen diese Divergenzen auftreten, exponentiell schnell aus den beobachtbaren Regionen verschoben werden.
Eine weitere Publikation werden wir dem Studium von Selbst-Wechselwirkungen innerhalb des nicht-perturbativen Replika-Feldtheorie-Rahmens widmen. Für eine quartische Selbst-Wechselwirkung finden wir eine Dämpfung auf großen Skalen - ein Aspekt, der in jüngerer Zeit Aufmerksamkeit auf sich gezogen hat. Unsere Resultate sind konsistent mit denen aus der Literatur und könnten dazu beitragen, gewisse Fragestellungen zum kosmischen Mikrowellen-Hintergrund zu beantworten, sowie zu helfen, einige Probleme bezüglich Infrarot-Divergenzen in der inflationären Kosmologie zu klären.In this thesis we apply methods from statistical physics to stochastic inflation. Those methods, the replica field theory and the Gaussian variational methods, have to our knowledge never been applied before in this context, and allow us to compute the power spectrum of a scalar test field in the most general set-up. It provides a framework to perform calculations in regions of arbitrarily large quantum fluctuations and may also serve as a starting point to address the issue of back reaction.
We first give an introduction to cosmological inflation, cosmological perturbation theory and cosmic microwave background anisotropies. Then we explain the idea of stochastic inflation, including some detailed derivations, and give an overview over major progress in this field. This is followed by an introduction to replica field theory, presented in a way directly applicable to stochastic inflation. Our work continues with a detailed calculation of the power spectrum of a scalar test field in a Friedmann Universe. We show the effect of the quantum fluctuations on the spectrum and derive explicit expressions showing its dependence on time and other important parameters. The effect of self-interactions and possible effects on the cosmic microwave background are discussed. We conclude with a summary of our results and give an outlook.
One part of our major results has been published in Phys. Rev. D 78, 103501 (2008), where for the first time we present a replica field-theoretical approach to stochastic inflation in which we find a manifestation of the phenomena of so-called dimensional reduction. It implies under certain conditions inevitable infra-red divergencies of correlation functions on large-scales. These conditions are examined in detail in Phys. Rev. D 79, 44009 (2009), where we find that generically for a wide class of circumstances the divergencies are pushed exponentially fast well beyond observable scales. A subsequent publication is dedicated to the inclusion of self-interaction within our non-perturbative replica framework. For a quartic self-coupling we find a damping of the power spectrum on large scales - an issue which has recently attracted significant attention. Our findings are fully consistent with those in the literature and may provide an explanation of certain features in the cosmic microwave background, and might also help to resolve some long-standing infra-red problems in inflationary cosmology
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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