1,720,955 research outputs found
The quantum E(2) group
Full text linkHet onderwerp van deze doctoraatsthesis situeert zich in de theorie van lokaal compacte kwantumgroepen. Dit is een niet-commutatieve veralgemening van de welbekende theorie van lokaal compacte groepen. De lokaal compacte groepen vormen dan ook de basisvoorbeelden van lokaal compacte kwantumgroepen. Elke gekende eigenschap over lokaal compacte groepen geeft aanleiding tot een studie van de overeenkomstige eigenschap voor kwantumgroepen.De theorie van kwantumgroepen is vrij recent. In zijn huidige vorm kennen we deze theorie sinds 1999. Maar reeds eerder (ongeveer vanaf 1961) hebben tal van onderzoekers bijdragen geleverd die tot de huidige theorie geleid hebben.Het waren uiteindelijk J. Kustermans en S. Vaes die er als eersten in gelukt zijn om een bevredigende definitie te geven van wat een `lokaal compacte kwantumgroep' nu precies is. Ze gaven hun definitie in 1999 en bouwden daarna een hele theorie uit. Zij steunden hierbij op heel wat resultaten van andere onderzoekers (Van Daele, Woronowicz, Baaj, Skandalis,...).Ondertussen is de theorie van Kustermans en Vaes wijd verspreid en verder ontwikkeld. We beschikken momenteel over een zeer uitgewerkte theorie.Het is uiteraard nodig om interessante voorbeelden te hebben. Er is immers geen enkele theorie die kan overleven zonder voorbeelden. Het blijkt echter niet eenvoudig om een nieuwe kwantumgroep te vinden en om dan zijn typische kenmerken te beschrijven. Er is dan ook al heel wat tijd ingestoken om nieuwe voorbeelden te construeren en uit te werken. Het is vooral S.L. Woronowicz die hieromtrent belangrijke bijdragen heeft geleverd.In de thesis bestuderen we de `kwantum E(2) groep'. Dit is een belangrijk en zeer verfijnd voorbeeld van een niet-compacte kwantumgroep. De nodige fundamenten voor de constructie van dit voorbeeld zijn reeds in 1991 gelegd door Woronowicz. Ook S. Baaj leverde een heel belangrijke bijdrage door bestaan en uniciteit van de Haargewichten te bewijzen. Dit gebeurde in 1992.Het eerste hoofdstuk van de thesis behandelt de algemene theorie. In het bijzonder richten we hierin onze aandacht op de wereld van (modulaire) multiplicatieve unitairen. We introduceren een nieuwe techniek voor het bestuderen van invariante gewichten binnen deze structuur.In Hoofdstuk 2 tonen we dat deze nieuwe techniek een elegante manier levert om te bewijzen dat de kwantum E(2) groep past in de Kustermans-Vaes theorie. We maken bovendien van de gelegenheid gebruik om de gekende resultaten te hernieuwen en te vereenvoudigen.We bestuderen verder ook enkele algemene kenmerken van de kwantum E(2) groep. Hierbij passeren vooral de amenability eigenschappen (Hoofdstuk 3) en de representatietheorie (Hoofdstuk 4) de revue. Op deze manier krijgen we een volledig uitgewerkt voorbeeld van een niet-compacte kwantumgroep.status: Publishe
Galois coacties voor algebraïsche en lokaal compacte kwantumgroepen.
Full text linkIn this thesis, we develop a theory of Galois objects in the setting of algebraic and locally compact quantum groups. Quantum groups, in some form or another, have been around for at least 5 0 years, but only recently, in 2000, a very elegant and powerful definit ion of locally compact quantum groups was introduced by Kustermans and V aes. Algebraically, this theory was much inspired by the theory of algeb raic quantum groups, developed by A. Van Daele in the nineties. These in turn were generalisations of the more well-known Hopf algebras In Hopf algebra theory, an important role is played by Galois coactions, which are to be seen as quantum equivalents of (a weak notion of) princ ipal fiber bundles. For algebraic quantum groups, these coactions were s tudied by Van Daele and Zhang. In our thesis, we also introduce this not ion on the level of locally compact quantum groups. Although implicitly, they appear in the work of Vaes, we give some more details concerning t heir structure. The main emphasis of the thesis however is on the notion of Galois objec ts: these are Galois coactions with trivial space of coinvariants. Class ically interpreted, this would correspond to fiber bundles over a point, a quite trivial notion. Luckily, the quantum situation is richer. We sh ow that Galois objects (for either algebraic or locally compact quantum groups) are always a non-symmetric part of a bigger symmetric structure, called a bi-Galois object. Namely, from a Galois object, one can constr uct a (possibly new) quantum group and an action of this quantum group o n the Galois object, such that this action commutes with the original ac tion. This reconstruction process is at the core of our thesis, and is q uite involved in the analytic setting. However, by this general theory, we were able to solve an open problem in the theory of locally compact q uantum groups, by proving that (unitary) two-cocycle twists of locally c ompact quantum groups are again locally compact (i.e. have integrals). Apart from this reconstruction process, we also spend some time on devel oping a theory of projective representations for locally compact quantum groups. Just as for ordinary groups, the theory of projective represent ations is closely connected to the notions `2-cocycles' and `2-cohomolog y', we show that in our setting of projective representations for quantu m groups, the natural role is played by the Galois objects. One peculiar result in this aspect is that it is now possible for compact quantum gr oups to have infinite-dimensional irreducible projective representations (which is impossible in the classical case). This has as a corollary th at if one applies the reconstruction process for the associated Galois o bject (which will be a Galois object for the dual, discrete quantum grou p), one obtains that the newly constructed locally compact quantum group is no longer discrete. This is in sharp contrast with the case of algeb raic quantum groups, where we show that the notion of discreteness is pr eserved under this process.status: Publishe
Hopf C*-algebras
Full text linkIn this paper we introduce the notion of a Hopf C*-algebra and construct the
counit and antipode. A Hopf C*-algebra is a C*-algebra with comultiplication
satisfying some extra condition which makes possible the construction of the
counit and antipode. The leading example is of course the C*-algebra of
continuous, vanishing at infinity functions on a locally compact group. Also
locally compact quantum groups will be examples. We include several formulas
for the counit and antipode which are familiar from Hopf algebra theory.status: Publishe
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
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