1,720,970 research outputs found
Orientifolds in Dimer Models: General Aspects and Applications.
Get PDFIn this thesis we study orientifolds and D-branes at toric Calabi-Yau singularities using dimer model techniques. We present new general results concerning orientifold projections and we apply them, constructing the first example of fully stable dynamical supersymmetry breaking model.
The thesis is divided into three parts.
In the first part we present mostly background material. We start with a short review of the Gauge/Gravity duality and generalizations. In particular we consider D3-branes at the tip of singular toric Calabi-Yau threefolds, introducing the idea of quiver theory and its natural generalization, dimer models. We then present known results obtained using this tool to explore orientifold projections. Finally, we review two dynamical supersymmetry breaking models, that are the simplest ones that can be engineered on D3-branes in this framework and which will play a prominent role in the last part of the thesis.
The second part focuses on orientifolds. We present two new results: the first one links the geometry of the Calabi-Yau variety and the chiral anomaly of the orientifolded theory, in particular we will provide a criterium to determine whether an orientifold projection can be safely performed, i.e. without introducing uncancelled anomalies. The second concerns a new kind of orientifold projection related to glide involutions of the dimer model. This construction has the property to preserve superconformal invariance in the projected theory.
In the third and last part of this thesis, we investigate dynamical supersymmetry breaking vacua obtained by D-branes at Calabi-Yau singularities. We first review known models and we show that all those theories have instabilities along Coulomb branches. We then show that this instability can be overcome, with suitable generalizations of the models presented in the first part. Finally, using the results of the second part, we will show how to constrain the possible geometries able to host dynamical supersymmetry breaking models free of any instabilities. This will select a singular Calabi-Yau, that we dubbed the Octagon, which furnishes the first instance of a model able to host a fully stable dynamical supersymmetry breaking model within the Gauge/String correspondence
Dimers, Orientifolds and Stability of Supersymmetry Breaking Vacua
Get PDFInternational audienceWe study (orientifolded) toric Calabi-Yau singularities in search for D-brane configurations which lead to dynamical supersymmetry breaking at low energy. By exploiting dimer techniques we are able to determine that while most realizations lead to a Coulomb branch instability, a rather specific construction admits a fully stable supersymmetry breaking vacuum. We describe the geometric structure that a singularity should have in order to host such a construction, and present its simplest example, the Octagon
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
- …
