Orientador: Ricardo de Oliveira Anido / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-16T15:08:23Z (GMT). No. of bitstreams: 1 Amorim_VicenteJosePeixotode_M.pdf: 4964887 bytes, checksum: bfab031069f938f7f502f1bc4f0d5d13 (MD5) Previous issue date: 2010 / Resumo: O estudo crítico apresentado discute o problema de ordenação de mensagens, típico da área de sistemas distribuídos, contextualizado em um ambiente de comunicação Bluetooth. Por ainda serem poucos os trabalhos com tal foco na bibliografia atual, este provê uma visão geral do comportamento de uma classe específica de protocolos distribuídos, quando executados no ambiente citado. Partindo desse contexto, o trabalho utiliza uma análise comparativa de alguns dos diversos algoritmos existentes, como forma de se obter informações sobre determinadas variáveis, e se caracterizar o melhor a ser utilizado em um ambiente de comunicação sem-fio com restrições de tempo real (real time). Ao se demonstrar a viabilidade de utilização deste(s) dentro de um ambiente de comunicação Bluetooth (com características real time), automaticamente surgem novas oportunidades de aplicações, principalmente para redes móveis onde a topologia predominante é ad- hoc, ou ainda, qualquer outro tipo de aplicação em que seja necessário se garantir a entrega em ordem das informações compartilhadas dentro de um limite de tempo. Como resultado desta análise, propõe-se um protocolo para o problema de ordenação total de mensagens aplicado a redes Bluetooth, onde se garante que, no ambiente de comunicação, todas as informações trocadas pelos nós (sites) serão enviadas e recebidas na mesma ordem. / Abstract: The presented work discuss the messages ordering problem, a common subject associated to distributed systems area which was here contextualized against Bluetooth network environment. The main target of this work is focused on distributed algorithms not so commonly considered until now, specially when they are applied to this related environment. As a way to obtain enough information about some systems variables and behavior, a comparative analysis was made between the already proposed protocols and algorithms. It generates a large set of information that makes possible to identify the better approach to be aplied at real time environments. Once the protocol viability is demonstrated, a large set of new applications can arise, specifically to this case: mobile applications using Bluetooth networks. This is mainly due to the mobile ad-hoc network topology which allows the use of distributed applications. However, it can also bring another class of problems as message ordering, which must ensure that all network shared data will keep a local and global sending order. / Mestrado / Computação Distribuída / Mestre em Ciência da Computação

Les travaux récents en fondements de la théorie quantique (des champs) et en information quantique relativiste tentent de mieux comprendre les effets des contraintes de causalité imposées aux opérations physiques sur la structure des corrélations quantiques. Le premier chapitre de cette thèse est consacré à l'étude des implications conceptuelles de la non-localité quantique, notion qui englobe celle d'intrication dans un sens précis. Nous détaillons comment les récentes approches informationnelles tentent de saisir la structure des corrélations non-locales, ainsi que les questions que ces dernières soulèvent concernant la capacité d'un observateur localisé à isoler un système de son environnement. Le second chapitre détaille les effets de l'invariance de Poincaré sur la détection et la quantification de l'intrication. Cette invariance impose que tous les systèmes soient modélisés en dernière instance dans le cadre de la théorie des champs, ce qui implique qu'aucun système à énergie finie ne puisse être localisé, ainsi que la divergence de toute mesure d'intrication pour des observateurs localisés. Nous fournissons une solution à ces deux problèmes en démontrant l'équivalence générique qui existe entre une résolution spatiale finie des appareils de mesure et l'exclusion des degrés de liberté de haute énergie de la définition du système observé. Cette équivalence permet une interprétation épistémique du formalisme quantique standard décrivant les systèmes localisés non-relativistes et leurs corrélations, clarifiant ainsi l'origine des mesures finies d'intrication pour de tels systèmes. Le dernier chapitre explore un cadre théorique récemment introduit qui prédit l'existence de corrélations quantiques sans ordre causal défini. Procédant par analogie avec le cas des corrélations non-locales, nous présentons quelques principes informationnels contraignant la structure de ces corrélations dans le but de mieux en comprendre l'origine physique. / Recent works in foundations of quantum (field) theory and relativistic quantum information try to better grasp the interplay between the structure of quantum correlations and the constraints imposed by causality on physical operations. Chapter 1 is dedicated to the study of the conceptual implications of quantum nonlocality, a concept that subsumes that of entanglement in a certain way. We detail the recent information-theoretic approaches to understanding the structure of nonlocal correlations, and the issues the latter raise concerning the ability of local observers to isolate a system from its environment. Chapter 2 reviews in what sense imposing Poincaré invariance affects entanglement detection and quantification procedures. This invariance ultimately forces a description of all quantum systems within the framework of quantum field theory, which leads to the impossibility of localized finite-energy states and to the divergence of all entanglement measures for local observers. We provide a solution to these two problems by showing that there exists a generic equivalence between a finite spatial resolution of the measurement apparatus and the exclusion of high-energy degrees of freedom from the definition of the observed system. This equivalence allows for an epistemic interpretation of the standard quantum formalism describing nonrelativistic localized systems and their correlations, hence a clarification of the origin of the finite measures of entanglement between such systems. Chapter 3 presents a recent theoretical framework that predicts the existence of correlations with indefinite causal order. In analogy to the information-theoretic approaches to nonlocal correlations, we introduce some principles that constrain the structure of such correlations, which is a first step toward a clear understanding of their physical origin.