1,720,958 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
Light-front puzzles
Get PDFLight-front formulations of quantum field theories have many advantages for
computing electroweak matrix elements of strongly interacting systems and other
quantities that are used to study hadronic structure. The theory can be
formulated in Hamiltonian form so non-perturbative calculations of the strongly
interacting initial and final states are in principle reduced to linear
algebra. These states are needed for calculating parton distribution functions
and other types of distribution amplitudes that are used to understand the
structure of hadrons. Light-front boosts are kinematic transformations so the
strongly interacting states can be computed in any frame. This is useful for
computing current matrix elements involving electroweak probes where the
initial and final hadronic states are in different frames related by the
momentum transferred by the probe. Finally in many calculations the vacuum is
trivial so the calculations can be formulated in Fock space.
The advantages of light front-field theory would not be interesting if the
light-front formulation was not equivalent to the covariant or canonical
formulations of quantum field theory. Many of the distinguishing properties of
light-front quantum field theory are difficult to reconcile with canonical or
covariant formulations of quantum field theory.
This paper discusses the resolution of some of the apparent inconsistencies
in canonical, covariant and light-front formulations of quantum field theory.
The puzzles that will be discussed are (1) the problem of inequivalent
representations (2) the problem of the trivial vacuum (3) the problem of
ill-posed initial value problems (4) the problem of rotational covariance (5)
the problem of zero modes and (6) the problem of spontaneously broken
symmetries.Comment: 29 pages, no figures - corrected reference 3
Electromagnetic current operators for phenomenological relativistic models
Get PDFBackground: Phenomenological Poincar\'e invariant quantum mechanical models
can provide an efficient description of the dynamics of strongly interacting
particles that is consistent with spectral and scattering observables. These
models are representation dependent and in order to apply them to reactions
with electromagnetic probes it is necessary to have a consistent
electromagnetic current operator.
Purpose: The purpose of this work is to use local gauge invariance to
construct consistent strong current operators.
Method: Current operators are constructed from a model Hamiltonian by
replacing momentum operators in the Weyl representation by gauge covariant
derivatives.
Results: The construction provides a systematic method to construct explicit
expressions for current operators that are consistent with relativistic models
of strong interaction dynamics.Comment: 31 pages, contribution to 25-th European Conference on Few Body
Problems Physics, Main
Path integrals, complex probabilities and the discrete Weyl representation
Get PDFA discrete formulation of the real-time path integral as the expectation
value of a functional of paths with respect to a complex probability on a
sample space of discrete valued paths is explored. The formulation in terms of
complex probabilities is motivated by a recent reinterpretation of the
real-time path integral as the expectation value of a potential functional with
respect to a complex probability distribution on cylinder sets of paths. The
discrete formulation in this work is based on a discrete version of Weyl
algebra that can be applied to any observable with a finite number of outcomes.
The origin of the complex probability in this work is the completeness
relation. In the discrete formulation the complex probability exactly factors
into products of conditional probabilities and exact unitarity is maintained at
each level of approximation. The approximation of infinite dimensional quantum
systems by discrete systems is discussed. Applications to scattering theory and
quantum field theory are illustrated.Comment: 56 pages, 14 figures, expanded - revised text, minor typos correcte
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
Unitarity of the Bencze--Redish--Sloan Equations
No full textIt is shown that the N-particle scattering equations of Bencze, Redish and Sloan satisfy a proper unitarity relation. The proof uses a recently proposed form of these equations given by Benoist-Gueutal, L'Huillier, Redish and Tandy
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