1,720,973 research outputs found
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
Decoherence in Neutrino Oscillations
No full textEven if quantum decoherence in neutrino oscillations was theorized almost 50 years ago, it has yet to be observed, perhaps because there are many effects that can produce similar results. There is not a solid theoretical understanding of such a phenomenon, not even a complete agreement in the community on whether or not this effect is observable at all. These issues does not depends on the details of the interaction: using a QFT approach, we developed a simplified but consistent model to study the decoherence. We present some interesting results we obtained so far: 1. In literature it is often assumed that the neutrino wavepackets must be covariant; we proved that this is not the case since the time evolution will destroy the covariance. 2. Environmental interactions are crucial for decoherence: without them (for example, in vacuum) there is no decoherence due to the spatial separation of the wavepackets
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
Localization and Decoherence in Neutrino Oscillations
No full textThere is still no solid theoretical understanding of the mechanisms behind decohernce in neutrino oscillations: in literature it is possible to find many different approaches, but they all must rely on several strong approximations, often offering contradicting predictions. This could be relevant for the next generations of neutrino experiments: due to their high precision, even a small modification of the oscillation probability could affect the result.
We will present some of the results obtained using a model where all the particles are described by fields, which are evolved dynamically and consistently with Quantum Field Theory.
We have found that environmental interactions are crucial for decoherence, since they localize the moment of production of the neutrino; otherwise the time evolution of the state would be a coherent integral over all the possibilities and there would be no maximal coherent length: this is the case, for example, when neutrinos are produced and detected in vacuum. However this is not the only way to get the decoherence: if the final states are localized as well, the position in time and space of the neutrino production would be constrained by kinematic. We will show that if this is the case, there is a maximal coherence length again, in agreement with the other models available in literature
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