1,721,073 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
Discrete classical vs. continuous quantum data in abstract quantum mechanics
No full text``Quantum'' stands for for the concepts (both operational and formal)
which had to be added to classical physics in order to understand
otherwise unexplainable observed phenomena such as the structure of
the spectral lines in atomic spectra. While the basic part of
classical mechanics deals with the (essentially) reversible
dynamics, quantum required adding the notions of ``measurement'' and
(possibly non-local) ``correlations'' to the discussion. Crucially,
all this comes with a ``probabilistic calculus''. The corresponding
mathematical formalism was considered to have reached maturity in
[von Neumann 1932], but there are some manifest problems with that
formalism:
(i) While measurements are applied to physical systems, application
of their formal counterpart (i.e. a self-adjoint linear operator) to
the vector representing that state of the system in no way reflects
how the state changes during the act of measurement. Analogously,
the composite of two self-adjoint operators has no physical
significance while in practice measurements can be effectuated
sequentially. More generally, the formal types in von Neumann's
formalism do not reflect the nature of the corresponding underlying
concept at all!
(ii) Part of the problem regarding the measurements discussed above
is that in the von Neumann formalism there is no place for storage,
manipulation and exchange of the classical data obtained from
measurements. Protocols such as quantum teleportation involving
these cannot be given a full formal description.
(iii) The behavioral properties of quantum entanglement which for
example enable continuous data exchange using only finitary
communication are hidden in the formalism.
In [Abramsky and Coecke 2004] we addressed all these problems, and in
addition provided a purely categorical axiomatization of quantum
mechanics. The concepts of the abstract quantum mechanics are
formulated relative to a strongly compact closed category with
biproducts (of which the category FdHilb of finite dimensional
Hilbert spaces and linear maps is an example). Preparations,
measurements, either destructive or not, classical data exchange are
all morphisms in that category, and their types fully reflect their
kinds. Correctness properties of standard quantum protocols can be
abstractly proven.
Surprisingly, in this seemingly purely qualitative setting even the
quantitative Born rule arises, that is the rule which tells you how
to calculate the probabilities. Indeed, each such category has as
endomorphism Hom of the tensor unit an abelian semiring of
`scalars', and a special subset of these scalars will play the role
of weights: each scalar induces a natural transformation which
propagates through physical processes, and when a `state' undergoes
a `measurement', the composition of the corresponding morphisms
gives rise to the weight. Hence the probabilistic weights live
within the category of processes.
J. von Neumann. Mathematische Grundlagen der Quantenmechanik.
Springer-Verlag (1932). English translation in Mathematical
Foundations of Quantum Mechanics. Princeton University Press (1955).
S. Abramsky and B. Coecke. A categorical semantics of quantum
protocols. In the proceedings of LiCS'04 (2004). An extended version
is available at arXiv:quant-ph/0402130 A more reader friendly
version entitled `Quantum information flow, concretely, abstractly'
is at http://www.vub.ac.be/CLEA/Bob/Papers/QPL.pd
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
Complete positivity without positivity and without compactness
No full textmaps we exactly obtain completely positive maps as morphisms. This means that mixedness of states and operations, within the categorical quantum axiomatics developed in [AC1, AC2, Sel, CPv, CPq], is a concept which exists independently of the quantum and classical structure. Moreover, since our construction does not require †-compactness, it can be applied to categories which have infinite dimensional Hilbert spaces as objects. Finally, in general Mix(C) is not a †-category, so does not admit a notion of positivity. This means that, in the abstract, the notion of ‘complete positivity ’ can exist independently of a notion of ‘positivity’, which points at a very unfortunately terminology
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
Terminality implies non-signalling
No full textA 'process theory' is any theory of systems and processes which admits sequential and parallel composition. `Terminality' unifies normalisation of pure states, trace-preservation of CP-maps, and adding up to identity of positive operators in quantum theory, and generalises this to arbitrary process theories. We show that terminality and non-signalling coincide in any process theory, provided one makes causal structure explicit. In fact, making causal structure explicit is necessary to even make sense of non-signalling in process theories. We conclude that because of its much simpler mathematical form, terminality should be taken to be a more fundamental notion than non-signalling
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