1,720,975 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
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
Tsirelson's Bound and Beyond: Verifiability and Complexity in Quantum Systems
No full textThis thesis employs operator-algebraic and group-theoretical techniques to study verifiability and complexity in bipartite quantum systems. A bipartite Bell scenario consists of two non-interacting parties, each can make several quantum measurements. If the two parties share an entangled quantum state, their measurement outcomes can be correlated in surprising ways. In general, we do not directly observe the entangled state and measurement operators (which are referred to as a quantum model), only the resulting statistics (which are referred to as a "correlation") --- there are typically many different models achieving a given correlation. Hence it is remarkable that some correlation has a unique quantum model. A correlation with this property is called a self-test. In the first part of this thesis, we give a new definition of self-testing in terms of abstract states on C*-algebras. We show that this operator-algebraic definition of self-testing is equivalent to the standard one and naturally extends to the commuting operator framework for nonlocal correlations.
We also propose an operator-algebraic formulation of robust self-testing. For many nonlocal games of interest, including synchronous games and XOR games, their optimal strategies correspond to tracial states on the associated game algebras. We show that for such nonlocal games, our operator-algebraic definition of robust self-testing is equivalent to the standard one. This, in turn, yields an implication from the uniqueness of tracial states on C*-algebras to robust self-testing for nonlocal games. To address how to compute the robustness function of a self-test explicitly, we provide an enhanced version of a well-known stability result due to Gowers and Hatami and show how it completes a common argument used in self-testing.
Self-testing provides a powerful tool for verifying quantum computations. Given that reliable cloud quantum computers are becoming closer to reality, the concept of verifiability of delegated quantum computations is of central interest. Many models have been proposed, each with specific strengths and weaknesses. In the second part of this thesis, we put forth a new model where the client trusts only its classical processing, makes no computational assumptions, and interacts with a quantum server in a single round. In addition, during a set-up phase, the client specifies the size n of the computation and receives an untrusted, off-the-shelf (OTS) device that is used to report the outcome of a single measurement. We show how to delegate polynomial-time quantum computations in the OTS model. This also yields an interactive proof system for all of QMA, which, furthermore, we show can be accomplished in statistical zero-knowledge. This provides the first relativistic (one-round), two-prover zero-knowledge proof systems for QMA.
Mathematically, bipartite quantum measurement systems can be modeled by the tensor product of free *-algebras. The third part of this thesis studies the complexity of determining positivity of noncommutative polynomials in these algebras. An element of a *-algebra is said to be positive if it is non-negative in all *-representations. In many situations, we'd like to be able to decide whether an element is positive, and if it is, find a certificate of positivity. For noncommutative algebras, it is well known that an element of the free *-algebra is positive if and only if it is a sum of squares. This provides an effective way to determine if a given noncommutative *-polynomial is positive, by searching through sums of squares decompositions. We show that no such procedure exists for the tensor product of two free *-algebras: determining whether a *-polynomial of such an algebra is positive is coRE-hard. We also show that it is coRE-hard to determine whether a noncommutative *-polynomial is trace-positive. Our results hold if free *-algebras are replaced by other algebras that model quantum measurements, such as group algebras of free groups or free products of cyclic groups
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
Entanglement in Non-local Games and the Hyperlinear Profile of Groups
Full text linkWe relate the amount of entanglement required to play linear system non-local games near-optimally to the hyperlinear profile of finitely presented groups. By calculating the hyperlinear profile of a certain group, we give an example of a finite non-local game for which the amount of entanglement required to play ϵ-optimally is at least Ω(1/ϵ^k), f or some k > 0. Since this function approaches infinity as ϵ approaches zero, this provides a quantitative version of a theorem of the first author
Tensors: Entanglement, Geometry, and Combinatorics
Full text linkIn this thesis, we use algebraic-geometric and combinatorial techniques to study tensor decompositions, with applications in quantum information theory, algebraic complexity theory, and algebraic statistics. A tensor is a multilinear map. These objects naturally generalize matrices, and have many useful applications in math and science. They can be used to describe nearly any dataset, and any pure (or even, mixed) quantum state. A decomposition of a tensor v is an expression of v as a linear combination of ``elementary tensors," which are defined according to the application. For a fixed choice of elementary tensors X, the X-rank of v is the minimum number of elementary tensors needed to span a space containing v. The border X-rank of v is the minimum number of elementary tensors needed to approximate v arbitrarily well. The most common choice of elementary tensors X are the product tensors, and we refer to the X-rank and border X-rank under this choice as simply the rank and border rank, respectively.
In quantum information theory, we think of a projective tensor [v] (the projectivization of a tensor v) as a pure quantum state shared by multiple laboratories. Just as matrices are much better understood than multi-way tensors, bipartite entanglement is much better understood than multipartite entanglement. For example, while we know that the most useful state in the bipartite setting under the LOCC paradigm is the canonical maximally entangled state, along with its local unitary equivalents, this question becomes more difficult in the multi-party setting. As a natural recourse, we determine the ``usefulness" of multi-way states for facilitating a particular task: local unambiguous state discrimination. We also study entangled subspaces, entanglement witnesses, and so-called absolutely entangled sets in the multi-way setting. A different set of elementary tensors that are relevant in quantum information are the so-called stabilizer tensors. The stabilizer rank of a pure quantum state [v] represents the computational cost of classically simulating Clifford circuits applied to [v] under the stabilizer formalism. We introduce new techniques from number theory and algebraic geometry for studying the stabilizer rank, and obtain simplified proofs of the best-known lower bounds on stabilizer rank up to a log factor.
In algebraic complexity theory, we think of a tensor v as a multilinear map. In this context, the rank of v is a useful barometer for the computational cost of implementing this multilinear map. We prove new lower bounds on tensor rank.
In algebraic statistics, we think of a tensor v as a probability vector for multiple (observable) random variables. Under an assumption of conditional independence, a decomposition of v into product tensors corresponds to a choice of latent (unobservable) random variable that gives rise to the observable random variables. If v has a unique tensor rank decomposition, this means that there is only one consistent choice of latent random variable (with the smallest number of outcomes) consistent with the probability vector v. We obtain a new sufficient condition for a given decomposition of v to be the unique rank decomposition of v, strengthening a theorem of Joseph Kruskal
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
