Ivan da Costa Marques

On complexity properties of recursively enumerable sets

An important goal of complexity theory, as we see it, is to characterize those partial recursive functions and recursively enumerable sets having some given complexity properties, and to do so in terms which do not involve the notion of complexity. As a contribution to this goal, we provide characterizations of the effectively speedable, speedable and levelable [2] sets in purely recursive theoretic terms. We introduce the notion of subcreativeness and show that every program for computing a partial recursive function f can be effectively speeded up on infinitely many integers if and only if the graph of f is subcreative. In addition, in order to cast some light on the concepts of effectively speedable, speedable and levelable sets we show that all maximal sets are levelable (and hence speedable) but not effectively speedable and we exhibit a set which is not levelable in a very strong sense but yet is effectively speedable.

Mathematical Metaphors and Politics of Presence/Absence

Of course the global and the local come together. And so do the universal and the particular. We know that, as well as including the local, whatever the global is it ‘is more than one but less than many’. But what is one? And where can the global one be found, and by whom? One can be studied only in its tensioned relation with the other. The suggestion is that the global and the local, and the large and the small, are effects of modes of ordering; that between them there is no more than ephemeral effects of scale, or effects of ever-changing contingent differences of relative quantities or positions (densities). But, then, how does the global end up being global or the large become large? I will explore this question by focusing on performances of mathematical discourses. How do mathematical discourses intermingle with heterogeneous networks conveying, shaping, and mobilizing intentional but nonsubjective strategies of framing the global as one? And how do heterogeneous networks always locally (partially) escape mathematical capture and constantly overflow often renewed mathematizing framings?

Minicomputadores brasileiros nos anos 1970: uma reserva de mercado democrática em meio ao autoritarismo

This article offers readers a new understanding of success and failure of the so-called computer market reserve policy, calling their attention to nets, as well as social and technical interruptions and interference. Three models of freedom have been used in order to approach the principles of political organization within liberal and democratic tradition. Three social and technical developmental models stand out during the 1970s and 1980s: the specific characteristics of Brazilian professionals in computer science in the 1970s, the intervention of political police force during the dictatorship and microcomputers themselves. As the result of the combination of these elements, the present analysis has divided the period into two different phases. The first phase shows a strong relation - not always taken into account - between liberal democratic practice and the possibility of successful industrial and technological policies that simultaneously sought economic development and science and technology development in Brazil.

Conhecimentos e redes: produção e apropriação de C&T

The changes that accompany the formation of increasingly globalized collectives and the concomitant development of information and communication technologies are strategic elements in the transformation of these collectives’ conditions to produce knowledge and information. Due to the importance given to the networks of knowledge production, dissemination and appropriation, it has become strategic to consider those networks, as well as the possibilities and implications that they bring to the forms of economic, social and cultural life, especially to the possibilities of interdisciplinary, transdisciplinary and sectorial activities. The purpose here is to present a series of debates on this subject, which refers to the relationship between the production of science, technology, innovation and living conditions, and the need for an extension of the social debate on technoscience, its construction, uses, and the possibilities for the inclusion of new actors in this debate.

A Knowledge-Construction Perspective on Human Computing, Collaborative Behavior and New Trends in System Interactions

This article presents an analysis of collaborative behavior within the historical process of the construction of scientific thought. We start from evidence that the origin of computing was immersed in a conceptual background heavily dominated by structuring thought, resulting in a mode of thinking organized around a centralized unit, strengthening categorization, disciplinarity and a predominant dichotomous logic. However, the new settings in which computer systems are involved, such as collaborative behavior and human computation, reveal a mode of thought and organization within an acentered model of realization. Sociology of knowledge helps us to understand this dynamic, allowing us to verify that the rhizomatic model of realization embraces not only what is traditionally viewed as the setting of computer systems, but also extends to the way of thinking, organization and operation of collective relations around computer systems.

History of Computing in Latin America [Guest editors' introduction]

The collection of articles on the history of computing in Latin America reflects a growing body of work looking at the influences and effects of computer technology in the region. The articles here cover a broad range of topics, including the degree of dissemination of computer machinery, the availability of local expertise, the regulation of the computer markets, the quantity and quality of local activities involving computers, the role played by the state, and the relations between the computer and telecommunication sectors.

Brazil's Computer Market Reserve: Democracy, Authoritarianism, and Ruptures

Since its demise in 1990, the technological-industrial policy for manufacturing computers in Brazil during the 1970s and 1980s has generally been regarded as a capital sin. People see the policy as having emerged from a spurious alliance between leftist and nationalist academics, bureaucrats, and the military and believe it provided nothing other than business opportunities for shrewd entrepreneurs. This article departs from this simplistic view and provides a new perspective on Brazils computer market reserve policy.

Brazil and its unenlightened despots: 1979/1980

I juxtapose testimony and research to take notice and illustrate the kind of intervention in the Politica Nacional de Informatica (P.N.I.) carried out in 1979 by a group of military officials who were members of the Servico Nacional de Informacoes (S.N.I.) - the political police of the military dictatorship that ruled Brazil from 1964 to 1986. Very specifically, I focus on an episode: that group of military officials of the political police of the dictatorship prohibited the exhibition of a slide show about “a story of Indians.” I also specially aim at stimulating the reader to watch this slide show that can be accessed today in a video format that can be downloaded from http://dl.dropbox.com/u/23492126/Video_Indio.mpg.