1,721,056 research outputs found
Multiset Constraints and P Systems
No full textCALUDE C.S.; PAUN GH.; ROZEMBERG G. EDS. (a cura di) Multiset Processing 2235, BERLIN: Springer-Verlag, (2001) 103- 121, ISBN:3-540-43063-
Every Computably Enumerable Random Real Is Provably Computably Enumerable Random
No full textWe prove that every computably enumerable (c.e.) random real is provable in
Peano Arithmetic (PA) to be c.e. random, a statement communicated to one author
by B. Solovay. A major step in the proof is to show that the theorem stating that “a
real is c.e. and random iff it is the halting probability of a universal prefix-free Turing
machine" can be proven in PA. Our proof, which is simpler than the standard one, can
also be used for the original theorem.
The result that every c.e. random real is provably c.e. random is in contrast with
the case of computable functions, where not every computable function is provably
computable. It is even more interesting to compare this result with the fact that – in general – random finite strings are not provably random.
The paper also includes a sharper form of the Kraft-Chaitin Theorem, as well as an
automatic proof of this theorem written with the interactive theorem prover Isabelle
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
Real Numbers: From Computable to Random
No full textA real is computable if it is the limit of a computable, increasing, computably converging sequence
of rationals. Omitting the restriction that the sequence converges computably we arrive at the notion
of computably enumerable (c.e.) real, that is, the limit of a computable, increasing, converging
sequence of rationals. A real is random if its binary expansion is a random sequence (equivalently,
if its expansion in base b ≥ 2 is random). The aim of this paper is to review some recent results on
computable, c.e. and random reals. In particular, we will present a complete characterization of the
class of c.e. and random reals in terms of halting probabilities of universal Chaitin machines, and we
will show that every c.e. and random real is the halting probability of some Solovay machine, that is,
a universal Chaitin machine for which ZFC (if sound) cannot determine more than its initial block
of 1 bits. A few open problems will be also discussed
A Glimpse into Algorithmic Information Theory
No full textThis paper is a subjective, short overview of algorithmic information theory. We
critically discuss various equivalent algorithmical models of randomness motivating
a "randomness hypothesis". Finally some recent results on computably enumerable
random reals are reviewed
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
De-Quantising the Solution of Deutsch's Prolem
No full textProbably the simplest and most frequently used way to illustrate the power of quantum
computing is to solve the so-called Deutsch’s problem. Consider a Boolean function f :
{0,1}→{0,1} and suppose that we have a (classical) black box to compute it. The problem
asks whether f is constant (that is, f (0) = f (1)) or balanced ( f (0) ≠ f (1)). Classically, to
solve the problem seems to require the computation of f (0) and f (1), and then the comparison
of results. Is it possible to solve the problem with only one query on f ? In a famous paper
published in 1985, Deutsch posed the problem and obtained a “quantum” partial affirmative
answer. In 1998 a complete, probability-one solution was presented by Cleve, Ekert, Macchiavello,
and Mosca. Here we will show that the quantum solution can be de-quantised to a
deterministic simpler solution which is as efficient as the quantum one. The use of “superposition”,
a key ingredient of quantum algorithm, is—in this specific case—classically available
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