1,721,009 research outputs found
HQET form factors for decays beyond leading order
Full text linkWe compute semi-leptonic decay form factors using Heavy Quark Effective Theory on the lattice. To obtain good control of the expansion, one has to take into account not only the leading static order but also the terms arising at : kinetic, spin and current insertions. We show results for these terms calculated through the ratio method, using our prior results for the static order. After combining them with non-perturbative HQET parameters they can be continuum-extrapolated to give the QCD form factor correct up to corrections and without corrections
Extraction of bare form factors for Bs →Kℓν decays in nonperturbative HQET
No full textWe discuss the extraction of the ground state matrix elements from Euclidean lattice correlation functions. The emphasis is on the elimination of excited state contributions. Two typical gauge-field ensembles with lattice spacings fm and pion masses MeV are used from the O()- improved CLS 2-flavour simulations and the final state momentum is . The b-quark is treated in HQET including the corrections. Fits to two-point and three-point correlation functions and suitable ratios including summed ratios are used, yielding consistent results with precision of around 2% which is limited by the corrections but by the dominating static form factors. Excited state contributions are under reasonable control but are the bottleneck towards precision. We do not yet include a specific investigation of multi-hadron contaminations, a gap in the literature which ought to be filled soon
Continuum limit of the leading order HQET form factor in decays
No full textWe discuss the computation of form factors for semi-leptonic decays of -, - mesons in lattice QCD. Considering in particular the example of the static form factors we demonstrate that after non-perturbative renormalization the continuum limit can be taken with confidence. The resulting precision is of interest for extractions of . The size of the corrections of order is just estimated at present but it is expected that their inclusion does not pose significant difficulties
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
a comparison between the Chroma software system and the Domain-Decomposition-Hybrid-Monte-Carlo software
Full text linkDie vorliegende Arbeit untersucht zwei "Open Source" Projekte für die Gitter-Quanten-Chromo-Dynamik (Gitter-QCD), und zwar das "Chroma Software Projekt" und die "Domain-Decomposition-Hybrid-Monte-Carlo (DD-HMC) Software". Ziel war, Informationen für die Anwendung der Programme aus der Sicht eines neuen Benutzers zu erhalten. Chroma kann für unterschiedliche Anwendungen der Gitter-QCD benutzt werden und ist somit sehr umfangreich. Sowohl Simulationen als auch Messungen können mit verschiedene Algorithmen durchgeführt werden. Um die Software zu benutzen, reicht es aus, den Umgang mit XML-Dateien zur Programmsteuerung zu erlernen. Das Verst"andnis von Details des Quellcodes kann jedoch eine umfassende Aufgabe sein. Um die Richtigkeit der Simulation und Messung von Chroma zu prüfen, wurde die effektive Pionmasse für einen bestimmten Parametersatz ermittelt. Das Ergebniskonnte mit anderen Messungen verglichen werden. Die Funktionalität der DD-HMC Software beschränkt sich auf die Produktion von Eichfeldkonfigurationen. Dafür wird der Hybrid-Monte-Carlo (HMC) Algorithmus mit der Methode der "Domain-Decomposition" benutzt. Das DD-HMC Programm bietet im Vergleich zu Chroma weniger Möglichkeiten. Somit ist der Quellcode nicht so umfangreich und weitestgehend verständlich. Um die Effizienz von Chroma zu analysieren, wurde die Laufzeit des Wilson-Dirac Operators getestet. In einer Simulation mit dynamischen Fermionen ist diese Anwendung die rechenaufwendigste. Daher hängt die Laufzeit der ganzen Simulation von dieser Anwendung ab. Zur Analyse wurde ein theoretisches Modell, sowohl für die Benutzung eines Prozessors als auch für die Benutzung eines Computers mit mehreren Prozessoren, diskutiert.This thesis analyses two Open Source software projects for Lattice Quantum Chromo Dynamics (LQCD), in fact the Chroma software system and the Domain Decomposition Hybrid Monte-Carlo (DD-HMC) software. The goal was to obtain information about the usage of the software and its libraries from the point of view of a new user. Chroma is a comprehensive software project which can be used for several applications for LQCD like simulation and measurement with different algorithms. To use the software it is sufficient to learn how to deal with XML input files whereas the understanding of the source code in detail can be a difficult task. The correctness of the simulation and measurement with Chroma could be proved for a sample calculation. For it, the effective mass of a pion was determined for a certain set of parameters. This result was compared with other computations. DD-HMC is a software for the generation of gauge configurations by means of the Hybrid Monte-Carlo (HMC) algorithm used with domain decomposition methods. Methods for measurements are not provided by the software. Therefore, the possibilities of DD-HMC are lesser in comparison to the Chroma software system. Thus, the source code of DD-HMC is not as comprehensive as the code of the Chroma and is fairly understandable. To analyse the efficiency of the Chroma software system the application of the Wilson-Dirac operator was benchmarked. Since it is the most computationally intensive task of a simulation with dynamical fermions, the execution time of the whole simulation can depend on the efficiency of this application. For the analysis a theoretical model was discussed for single processors as well as for parallel machines
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
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