1,720,965 research outputs found
Hydrodynamic theory of quantum fluctuating superconductivity
No full textNon UBCUnreviewedAuthor affiliation: Stanford U & APC, CNRS ParisPostdoctora
Black hole solutions to Einstein's equations in the presence of matter and modifications of gravitation in extra dimensions
No full textDans cette thèse, nous nous intéressons aux solutions de trou noir dans des théories de gravitation modifiées, inspirées par la Cosmologie ou la Théorie des Cordes. Les théories Einstein-Maxwell-Dilaton (EMD) comprennent des champs scalaires et de jauge additionnels, ainsi qu'un potentiel de Liouville en exponentielle. Dans les théories Einstein-Gauss-Bonnet, l'espace-temps est étendu plus de quatre dimensions. Nous commençons par passer en revue et classer les solutions des tthéories EMD. L'un des principaux résultats est obtenu dans le cas o l'horizon est planaire, lorsqu'une équation maîtresse permet d'intégrer totalement le système d'équations, au prix d'une contrainte sur les constantes de couplage. Dans le cas des théories Einstein-Gauss-Bonnet six dimensions, le tenseur de Weyl de l'horizon intervient dans les équations par l'action de la constante de couplage du terme de Gauss-Bonnet : cela a pour effet de restreindre grandement la topologie de l'horizon. Par la suite, nous étudions les propriétés thermodynamiques des trous noirs en Relativité Générale et en théories EMD. Pour ces dernières, nous montrons que des transitions de phases similaires celles en Relativité Générale existent dans l'ensemble canonique. Plus généralement, ces propriétés dépendent de manière cruciale des constantes de couplage de la théorie. Pour finir, nous donnons une interprétation holographique aux trous noirs des théories EMD, en tant que bonnes approximations l'Infra-Rouge. Nous calculons également les conductivités en courant continu et alternatif dans le cadre d'une application la Matière Condensée, et trouvons certaines caractéristiques typiques des métaux étranges.In this thesis, we wish to examine the black-hole solutions of modi_fied gravity theories inspired by String Theory or Cosmology. Namely, these modifi_cations will take the guise of additional gauge and scalar fi_elds for the so-called Einstein-Maxwell-Dilaton (EMD) theories with an exponential Liouville potential; and of extra spatial dimensions for Einstein-Gauss-Bonnet theories. The black-hole solutions of EMD theories as well as their integrability are reviewed and classified. One of the main results is that a master equation is obtained in the case of planar horizon topology, which allows to completely integrate the problem for a special relationship between the couplings. We move on with the study of six-dimensional Gauss-Bonnet black holes. The Gauss-Bonnet coupling then exposes the Weyl tensor of the horizon to the dynamics, severely restricting the Einstein spaces admissible and e_ffectively lifting some of the degeneracy on the horizon topology. We continue with the study of the thermodynamic properties of black holes, in General Relativity as well as in EMD theories. For the latter, phase transitions may be found in the canonical ensemble, which resemble those in General Relativity. Generically, we _find that the thermodynamic properties (stability, order of phase transitions) depend crucially on the values of the EMD coupling constants. Finally, we interpret our planar EMD solutions holographically as Infra-Red geometries through the AdS/CFT correspondence, taking into account various validity constraints. We also compute AC and DC conductivities as applications to Condensed Matter Systems, and _find some properties characteristic of strange metal behaviour.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF
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
- …
