1,720,962 research outputs found
Dynamical mean-field theory approach for ultracold atomic gases
No full textIn this thesis we have studied the physics of different ultracold Bose-Fermi mixtures in optical lattices, as well as spin 1=2 fermions in a harmonic trap. To study these systems we generalized dynamical mean-field theory for a mixture of fermions and bosons, as well as for an inhomogeneous environment. Generalized dynamical mean-field theory (GDMFT) is a method that describes a mixture of fermions and bosons. This method consists of Gutzwiller mean-field for the bosons, and dynamical mean-field theory for the fermions, which are coupled on-site by the Bose-Fermi density-density interaction and possibly a Feshbach term which converts a pair of up and down fermions into a molecule, i.e. a boson. We derived the self-consistency equations and showed that this method is well-controlled in the limit of high lattice coordination number z. We develop real-space dynamical mean-field theory for studying systems in an inhomogeneous environment, e.g. in a harmonic trap. The crucial difference compared to standard DMFT is that we are taking into account that different sites are not equivalent to each other and thus take into account the inhomogeneity of the system. Different sites are coupled by the real-space Dyson equation. ...Durch eindrucksvollen experimentellen Fortschritt innerhalb der letzten Dekade rückte das Gebiet der ultrakalten Atome in den Blickpunkt der Erforschung stark korrelierter Vielteilchensysteme. Die Fähigkeit Atome in optische Gitter, die durch stehende Wellen aus Laserlicht erzeugt werden, zu laden und darin zu manipulieren, macht es möglich, verschiedene Modell-Hamiltonoperatoren der Festkörperphysik zu realisieren. Dadurch können neue Einblicke in bekanntermaßen schwierigen Probleme [1–3] gewonnen werden. Darüberhinaus können Systeme realisiert werden, die keine Analoga in der Festkörperphysik besitzen. Im Besonderen können innerhalb des Gebietes der ultrakalten Atome Mischungen aus Bosonen und Fermionen erzeugt werden [4–19]. Diese Mischungen stellen physikalisch reichhaltige Systeme dar, die bisher noch wenig verstanden sind. Bose-Fermi-Mischungen haben einige Ähnlichkeit zu den wohlbekannten zweikomponentigen Fermi-Fermi-Mischungen, jedoch besitzen sie eine reichhaltigere Physik. Indem man eine Spinkomponente durch ein Boson ersetzt, bewahrt man die Instabilität der Ladungsdichtewelle halbgefüllter fermionischer Systeme. Aus historischen Gründen wird diese Terminologie beibehalten, obwohl die betrachteten fermionischen Atome keine Ladung tragen. Zusätzlich können sich die Bosonen in der superfluiden Phase befinden, woraus sich die Möglichkeit supersoliden (SS) Verhaltens ergibt, welches gekennzeichnet ist durch koexistierende diagonale Ladungsdichtewellen und nichtdiagonale, langreichweitige Superfluidität. Zahlreiche theoretische Arbeiten haben Bose-Fermi-Mischungen in optischen Gittern als Forschungsgegenstand [20–45]. Zur Untersuchung stark korrelierter Bose-Fermi-Mischungen in optischen Gittern wurden verschiedene numerische und analytische Methoden benutzt. In einer Dimension beinhaltet dies den Bethe-Ansatz [25], Bosonisierung [26, 28], Dichtematrix-Renormierungsgruppe [32, 35] und Quanten-Monte-Carlo [23, 36–40]. Jedoch sind nicht-perturbative Methoden in höheren Dimensionen rar. In zwei Dimensionen wurde die Renormierungsgruppenmethode verwendet [24, 31]. Obwohl diese Methode nicht-perturbative Effekte beschreiben kann, ist sie auf schwache Kopplungen beschränkt . Eine weitere Methode, das Ausintegrieren der Fermionen, wurde in zwei [29] und kürzlich in drei Dimensionen [33, 34] angewendet. Darin wird eine langreichweitige, retardierte Wechselwirkung zwischen den Bosonen erzeugt. Dies wiederum bedeutet, dass das resultierende bosonische Problem schwer zu lösen ist. Mit dieser Methode wurde ein wichtiger Fortschritt im Auffinden der Phasengrenzen zwischen Mott-Isolator und Superfluid erzielt. Weiterhin wurde ein Ansatz zusammengesetzter Fermionen verwendet, um qualitativ die möglichen Quantenphasen von Bose-Fermi-Mischungen zu beschreiben [30]. ..
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
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
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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