1,720,970 research outputs found
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
Inflation and Effective Shift Symmetries
No full textCosmic inflation not only sets the initial conditions for the evolution of the universe but also provides the origin of structure formation. It is hence both from a theoretical and observational point of view a highly successful paradigm. Precision measurements of the cosmic microwave background constrain inflation to be effectively driven by a single scalar field whose potential maintains an approximate and continuous shift symmetry V ∼ const. sufficiently far from its minimum. In effective field theory, such a shift symmetry amounts to tuning an essentially infinite number of coefficients of all higher dimensional operators involved. Here, we study different realisations of shift-symmetric inflaton potentials to examine if the amount of fine tuning can be reduced. We begin by considering a UV example and find that underlying parameters do not evade tuning as the intrinsic suppressions do not suffice. Continuing to study non-canonical dynamics, we formulate a condition on the non-canonical kinetic term equivalent to the potential shift symmetry and provide expressions for universal corrections and phenomenological imprints resulting from a broken shift symmetry. Studying modified gravity, we derive allorder expressions for broken shift symmetries that allow for observationally viable inflation to occur. Finally, we study scalar field dynamics non-minimally coupled to gravity. After developing an understanding of the phenomenological implications of different types of shift symmetry breaking, we propose a mechanism that realises a sufficient intermediate shift symmetry for inflation to occur by essentially only tuning one parameter. This parameter sets the spectral index as well as the normalisation of the cosmic microwave background temperature spectrum and is found to satisfy both observational constraints while at the same time pushing all higher order terms sufficiently far away in field space
The Power Spectrum of Inflationary Attractors
No full textInflationary attractors predict the spectral index and tensor-to-scalar ratio to take specific values that are consistent with Planck. Moreover, in this letter we demonstrate that they also give rise to a specific relation between the amplitude of the power spectrum and the number of e-folds. We investigate this relation in the context of the universal attractor for models with a generalised non-minimal coupling, leading to Starobinsky inflation. The length and height of the inflationary plateau are related via the non-minimal coupling: in a wide variety of examples, the observed power normalisation leads to at least 55 flat e-foldings. Prior to this phase, the inflationary predictions vary and can account for the observational indications for power loss at large angular scales
UV inspired f(R)
No full textMotivated by UV realisations of Starobinsky-like inflation models, we study generic exponential plateau-like potentials to understand whether an exact f(R)-formulation may still be obtained when the asymptotic shift-symmetry of the potential is broken for larger field values. Potentials which break the shift symmetry with rising exponentials at large field values only allow for corresponding f(R)-descriptions with a leading order term Rn with 1<n<2, regardless of whether the duality is exact or approximate. The R2-term survives as part of a series expansion of the function f(R) and thus cannot maintain a plateau for all field values. We further find a lean and instructive way to obtain a function f(R) describing m2ϕ2-inflation which breaks the shift symmetry with a monomial, and corresponds to effectively logarithmic corrections to an R+R2 model. These examples emphasise that higher order terms in f(R)-theory may not be neglected if they are present at all. Additionally, we relate the function f(R) corresponding to chaotic inflation to a more general Jordan frame set-up. In addition, we consider f(R)-duals of two given UV examples, both from supergravity and string theory. Finally, we outline the CMB phenomenology of these models which show effects of power suppression at low-ℓ
Starobinsky-Type Inflation
No full textBoth WMAP and PLANCK have hinted at a slight suppression of power in the CMB temperature spectrum at large angular scales. Yet this power loss is usually unaccounted for by models that are claimed to provide a best fit to the data at first order, such as the Starobinsky f(R) model. In a first step, we demonstrate how to obtain a viable observational signature in f(R) theory by explicitly constructing higher order terms to the Starobinsky model. In a second step, we outline a new inflationary scenario deriving from higher derivative corrections in String theory giving rise to a similar observational fingerprint
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