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The omega rule is \Pi^1_1-complete in the lambda-calculus
No full textWe give a many-one reduction of the set of true \Pi^1_1 sentences to the set of consequences of the lambda-calculus with the omega-rule. This solves in the affirmative a long-standing problem of H. Barendregt (1975). © Springer-Verlag Berlin Heidelberg 2007
Some results on extensionality in lambda calculus
No full textIn this paper we consider the problem (due to A. Cantini) of the existence of a λ-theory T such that:
–T is recursive enumerable;
–the ω-rule holds in T (that is: if two terms M, N are such that for every closed term Q, MQ=NQ holds in T, then M=N holds in T).
We solve affirmatively this problem.
Some related questions are also discussed
THE OMEGA RULE IS Pi(1)(1)-COMPLETE IN THE lambda beta-CALCULUS
No full textIn a functional calculus, the so called omega-rule states that if two terms P and Q applied to any closed term N return the same value (i.e. PN = QN), then they are equal (i.e. P = Q holds). As it is well known, in the lambda beta-calculus the omega-rule does not hold, even when the eta-rule (weak extensionality) is added to the calculus. A long-standing problem of H. Barendregt (1975) concerns the determination of the logical power of the omega-rule when added to the lambda beta-calculus. In this paper we solve the problem, by showing that the resulting theory is Pi(1)(1)-Complete
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
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