1,721,052 research outputs found
Vacuum oscillations of quasi degenerate solar neutrinos
No full textThe atmospheric neutrino oscillations and the vacuum oscillation solution of the solar neutrino problem can be consistently described by a doubly or triply degenerate neutrino spectrum as long as the high level of degeneracy required is not spoiled by radiative corrections. We show that this is the case for neutrino mass matrices generated by symmetries. This imposes a strong constraint on the mixing angles and requires the mixing should be close to bi-maximal. We briefly discuss the relevance of our results for the measurability of the neutrino spectrum
Solar neutrino oscillation from large extra dimensions
No full textA plausible explanation for the existence of additional light sterile neutrinos is that they correspond to modulini, fermionic partners of moduli, which propagate in new large dimensions. We discuss the phenomenological implications of such states and show that solar neutrino oscillation is well described by small angle MSW oscillation to the tower of Kaluza Klein states associated with the modulini. In the optimal case the recoil electron energy spectrum agrees precisely with the measured one, in contrast to the single sterile neutrino case which is disfavoured. We also consider how all oscillation phenomena can be explained in a model including bulk neutrino states. In particular, we show that a naturally maximal mixing for atmospheric neutrinos can be easily obtained
Brane-bulk neutrino oscillations
No full textA plausible explanation for the existence of additional light sterile neutrinos is that they correspond to modulini, fermionic partners of moduli, which propagate in new large dimensions. We discuss the phenomenological implications of such states and show that solar neutrino oscillation is well described by small angle MSW oscillation to the tower of Kaluza Klein states associated with the modulini. We also consider how all oscillation phenomena can be explained in a model including bulk neutrino states
Neutrino masses and mixing in brane-world theories
No full textWe present a comprehensive study of five-dimensional brane-world models for neutrino physics based on flat compactifications. Particular emphasis is put on the inclusion of bulk mass terms. We derive a number of general results for such brane-world models with bulk mass terms. In particular, in the limit of small brane-bulk couplings, the electroweak eigenstates are predominantly given as a superposition of three light states with non-trivial small admixtures of bulk states. As a consequence, neutrinos can undergo standard oscillations as well as oscillation into bulk Kaluza-Klein states. We use this structure to construct a specific model based on ℤ2 orbifolding and bulk Majorana masses which is compatible with all observed oscillation phenomena. The solar neutrino deficit is explained by oscillations into sterile bulk states while the atmospheric neutrino deficit is due to νμ - ντ oscillations with naturally maximal mixing. In addition, the model can accommodate the LSND result and a significant neutrino dark matter component. We also analyze the constraints from supernova energy loss on neutrino brane-world theories and show that our specific model is consistent with these constraints
Precision test of a Fermion mass texture
No full textTexture zeros in the quark Yukawa matrices generally lead to precise and simple expressions for CKM matrix elements in terms of ratios of quark masses. Using the new data on b-decays we test a particularly promising texture zero solution and show that it is at best approximate. We analyse the approximate texture zero structure and show it is consistent with experiment. We investigate the implications for the CKM unitarity triangle, measurements at BaBar and BELLE as well as for the theories which invoke family symmetries. © 2001 Elsevier Science B.V
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
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