Dans cette thèse on s’intéresse à un modèle de faute Byzantins Mobiles. Jusqu’à présent, seulement le problème du Consensus a été résolu en présente de faute Byzantines Mobiles et plusieurs variations de ce modèle de faute ont été proposé. Pour chacun de ces modelés ont été prouvées les bornes inferieures du nombre de processus correct nécessaire et des solutions asymptotiquement optimales ont été proposées. Notre première contribution porte sur les registres repartis dans ce modèle. Les registres repartis sont l’abstraction à la base du stockage reparti. Ces résultats préconisent donc notre deuxième contribution principale, un modèle de faute Byzantine Mobile généralisé. Notre troisième contribution est un ensemble de preuves de nécessité et d’impossibilité pour les registres repartis dans ces modèles. En particulier on prouve qu’il n’est pas possible d’implémenter la spécification plus faible des registres dans un système asynchrone. Par contre, pour les systèmes synchrones, on prouve des bornes inferieures et propose des protocoles asymptotiquement optimaux pour le registrer régulier. Pour conclure, notre dernière contribution porte sur le problème d’accord approximé, une forme affaiblie du consensus. On résout ce problème dans le modèle basé sur ronde, le même du consensus. En outre, il est intéressant de noter qua dans le modèle statique, la borne inferieure sur le nombre de répliques est la même pour le consensus et pour le problème d’accord approximé. Le même invariant s’applique avec les fautes byzantine mobiles. De plus, on accompagne ces bornes inferieures avec une solution asymptotiquement optimale pour le problème d’accord approximé. / In this thesis we consider a model where Byzantine failures are not fixed, we consider the so called Mobile Byzantine failures. So far, only Consensus problem has been solved in presence of Mobile Byzantine failures and interestingly different variations of this failure model have been proposed. For each of them have been proved lower bounds on the number of required processes and have been proposed tight solutions. Our first contribution concerns distributed Registers in such strong model. Distributed Registers are the basic abstraction for Distributed Storages. This advocates our second and main contribution, a general Mobile Byzantine Failure Model. Our main focus is about Distributed Registers, so our third contribution comes, we prove necessities and impossibilities in those models. In particular we prove that is it not possible to solve the weakest register specification in an asynchronous system. On the other side we prove lower bounds for the synchronous system, with respect to the proposed hierarchy models, and tight protocols to solve the Regular Register problem. To conclude, our last contribution is about the Approximate Agreement problem, a weaker form of Consensus. We solve such problem in the same round-based models as Consensus so far. The interesting result is the following, in presence of static Byzantine failures, lower bounds on the number of correct replicas does not change between consensus and approximate agreement. The same invariant still holds in presence of Mobile Byzantine failure. Moreover, along with lower bounds we propose a tight solution to solve approximate agreement.

Materiality and considerations of color in medieval art have been the subject of a growing number of studies in recent years, but have tended to address architecture, monumental works of art such as mosaics, or metalworking. Scholars working on western medieval manuscripts have shown how much can be done with technical art history in this arena, but to date, the study of manuscript materials and their meanings with respect to the Byzantine world have been lacking. This dissertation resituates the understanding of Middle Byzantine (East Medieval Roman) manuscript production from the eleventh and twelfth centuries CE, employing a cross-disciplinary approach that synthesizes traditional codicological analysis with new technologies that identify precise materials and techniques. In particular, this work explores Middle Byzantine manuscript materiality along two perspectives. First, it investigates modes of manufacture, identifying materials and techniques of Middle Byzantine manuscripts themselves, especially in the Lectionary of Katherine Komnena and the Dumbarton Oaks Lectionary. Secondly, it analyzes the meanings and understandings of those materials along liturgical, monastic, and scientific-intellectual contexts in the manuscripts’ specific use in Middle Byzantine milieus. In each case, the focus is Middle Byzantine, Greek-language Gospel Lectionaries traceable to the Rite of Constantinople. These lavishly illuminated books played important roles in Christian liturgical contexts, and provide an opportunity to explore what Byzantines thought about the natural world.This study revises both the methodological approaches of earlier manuscript scholars and interpretations that assign place of production and meaning of materials as solely iconographic or stylistic problems. Byzantine manuscripts — in part due to twentieth-century historiographic traditions — have rarely been considered in terms of their material production, in contrast to their counterparts in western Medieval Europe, which have been explored with modern technology in exciting new ways in recent decades. As a result, this void in Byzantine studies provides a great opportunity for considering the specific contexts of these objects in their production and significance. As this dissertation attends to the material contexts of Byzantine Gospel Lectionaries, it analyzes the manuscripts in terms of their materials and methods of production, and consider the relationships between materials, Byzantine understandings of matter through the field of alchemy, and the production of knowledge about artmaking in Byzantium. This strategy seeks to account for both the interest in Byzantine intellectual works on the nature of matter and the manner in which knowledge about codex creation was passed on. Although this dissertation follows art historical methodologies and not those of the hard sciences, it incorporates scientific data that identifies precise pigments on manuscript pages into my study. In this work, the materials used by the manuscript makers of the studied objects are identified. This involves performing non-destructive analysis, collaborating with conservators, through close observation and the use of x-ray reflectography, which allows for the non-invasive, in situ study of manuscript materials. / Art History

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This thesis investigates the relationship between Christianity and urban monumental space in the late antique Levant. Through the analysis of both textual and archaeological evidence it seeks to clarify both the motives and the stages of the process of Christian takeover of the urban space of Levantine cities from the 4th to the 7th century AD. In doing so Christians were in essence both projecting their growth as the predominant religion and, at the same time, creating an entirely new monumental landscape. The case studies are presented in three separate groups, selected on the basis of the principal strategy that was chosen in the process of Christianisation of urban space. The first section analyses the cases of Gerasa, Jerusalem, Heliopolis, and Petra to illustrate the first of these strategies: the main method for occupying the symbolic space of the city was the construction of a contrast between the surviving ruins of the earlier, Hellenic, temples and the new Christian churches. The second group of case studies includes Scythopolis, Caesarea Maritima, Gaza, and to a certain extent Heliopolis. This section deals with those cities where the main strategy was the physical demolition of all or at least the most pre-eminent Hellenic buildings and their direct replacement with a new, and often grand, church. The third group, and the last, consists of the cities of Bostra, Gadara, Apamea, where rather than having to engage with a major Hellenic monument the main competitor was the secular state whether local or imperial. This is found to have resulted in a search for integration into the landscape rather than active competition.

In 533, Justinian I ordered the conquest of the former Roman provinces of Africa, which had been lost to the Vandals a century earlier. The 'reconquest' has been regarded, by contemporaries and modern scholars alike, as one of the defining successes of the reign. However, despite the evident achievements of the campaign, Roman victory over the Vandals marked little more than the beginning of the Eastern Roman Empire's attempt to consolidate its position in Africa. The unanticipated threat posed by hostilities from the Berber tribes would continue until 548. Roman-Berber relations, unlike other aspects of Justinian's foreign relations, have received comparatively little attention, and this study aims to reassess the establishment of Roman authority in Africa and the Eastern Roman Empire's response to the Berber threat. In particular, it considers whether this response should be seen as a series of ad hoc reactions to immediate circumstances, or whether it is possible to identify a coherent Roman policy vis-à-vis the Berbers. The major conclusions of this study fall in two areas. First, it argues that Roman objectives in Africa were far more limited than has generally been supposed, with the empire's territorial ambitions not extending beyond key coastal positions which offered strategic and commercial advantages, and from which the empire could project its limited authority into the interior. Second, this study concludes that the Eastern Roman Empire's actions with respect to the Berber tribes lacked coherence. Attempts to implement a system of client rulers were unsuccessful, partly as a result of the competition between individual Berber leaders as they sought to establish independent polities within the frontiers of the former Roman Empire; and partly as a result of an increasing lack of resources, as well as the instability caused by constantly changing leadership within the African civil and military administrations, which prevented the development of coherent long term strategies for addressing the Berber threat.

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This thesis explores the archaeology of late antique Sicily from the time of Theodosius I (347–95) to the reign of Constans II (630–68). Analysing published data from urban and rural contexts I aim to define three research subjects that are: 1 – The potential different phases of Sicilian Late Antiquity; 2 – The part played by the Church and the impact of Christianity in this transitional period, and, finally, 3 – The definition of a regional economic pattern. During the centuries here investigated, Sicily went through three main phases named: the fall of the Roman Empire, the Byzantine conquest of the 6th century and the process of Byzantinization of the Sicilian society and culture. The Church played a key role in all these three phases initially negotiating with local elite and cultural background its presence within the urban walls. But after the Byzantine conquest and until the Arab occupation of Sicily, the Church imposed its authority through the building of churches, monasteries and chapels transforming the urban and rural landscape. After the Vandal invasion of North Africa, Sicily became the only food supply for Italy and this deeply impacted the provincial economy increasing production and trade with Italy resulting in a period of economical prosperity and cultural liveliness.

We used a Byzantine Music piece performed by a well recognized chanter in order to derive experimentally the mean frequencies of the first five tones (D – A) of the diatonic scale of Byzantine Music. Then we compared the experimentally derived frequencies with frequencies proposed by two theoretical scales, both representative of traditional Byzantine Music chanting. We found that if a scale is performed by a traditional chanter is very close in frequency to the frequencies proposed theoretically. We then determined an allowed frequency deviation from the mean frequencies for each tone. The concept of allowed deviation is not provided by theory. Comparing our results to the notion of pitch discrimination from psychophysics we further established that the frequency differences are minute. The Attraction Effect was tested for a secondary tone (E) and the effect is quantified for the first time. The concept of the Attraction Effect is not explained in theory in terms of frequencies of tones.

M.A. / The main purpose of this postgraduate study has been to record and investigate the ways in which Byzantine history is presented in the history textbooks of the Hellenic general education. Our attempt has been to demonstrate the ways in which this part of the Hellenic history is presented within the curriculum and syllabi, in order to investigate the various parameters (social, political, cultural, pedagogic and religious) that affect the historic Donsciouness of the Hellenic Primary and Secondary school learners.For research purposes, we contemplated that the study should be separated into two parts. In the first part we examined the theoretical constituents which define History as a subject under the subheadings of "What is history", "Historical event and its elements", "Historical knowledge and validity" as well as "History in general education". We then attempted to sketch out a rough outline of Byzantium and its history through a timeline of the dynasties. In the beginning of each dynasty, we referred to the ruling emperors and then attempted to identify the main factors which, in our opinion, had shaped each period so that the reader can, at least, conceptualize the long, eventful and diverse history of the Byzantine Empire. In the beginning of the second part, we refer to articles and paragraphs of the Hellenic constitution and Hellenic legislation that form the framework within which are defined: the overall purpose of Hellenic education, the structure and function of Primary and Secondary education, the framework for dealing with cross-cultural issues, as well as the general framework and defming directives that are set to promote the development of the European citizen's awareness but also to sustain the national and cultural identity. We, then, proceeded in dealing exclusively with the aforementioned Hellenic general education textbooks.

A querela iconoclasta bizantina do século VIII já foi considerada a maior crise deste período e teve por consequência a legitimação dos ícones enquanto parte da tradição da Igreja. O fenômeno não esteve, no entanto, restrito ao mundo Oriental, tendo desencadeado reações tanto do papado, que se opôs ao iconoclasmo imperial desde seu início, quanto dos carolíngios, que se afirmavam enquanto um novo elemento entre os poderes cristãos. A reunião do concílio de Nicéia II, em 787, quando o culto aos ícones foi definido pela primeira vez como parte da tradição da Igreja, não foi bem recebida pela corte franca, que discordou tanto dos procedimentos quanto das decisões da assembléia, o que deu origem a um tratado, conhecido por libri carolini. Esta obra é sem dúvida um dos mais importantes trabalhos de teologia do governo de Carlos Magno, mas além disso, ele é uma tomada de posição do rei o tratado foi escrito em nome de Carlos Magno que não apenas reivindica a participação na resolução dos assuntos da fé, como se apresenta superior aos gregos, acusados no tratado de arrogância e entendidos como inaptos a interpretar de maneira correta as Escrituras, bem como os testemunhos dos Pais. Os LC são portanto não apenas uma demonstração da teologia de imagens carolíngia, mas um registro do posicionamento do futuro imperador do Ocidente. / The Byzantine Iconoclastic struggle of the eight century has been considered the greatest crisis of this period and had as a consequence the legitimation of icons as part of the churchs traditions. The phenomenon was not restricted to the Oriental world, and unleashed reactions from the papacy, who was opposed to the imperial Iconoclasm from its beginning, as much as from the carolingians, a new element between the Christian powers. The reunion of the second council of Nicaea, in 787, where the cult of icons was established for the first as a Tradition of the church, was not well received by the Frankish court, which disagreed with the procedures and the decisions of the assembly. The Carolingian opposition to the reunion originated a treatise known as libri carolini. This work is with no doubt one of the most important theological writings composed under Charlemagne\'s rule, but also a stand taking of the king who not only revindicates the participation on church matters as presents himself as superior to the Greeks, who are pictured as arrogant and bad interpreters of the Gospels and the Fathers. The LC are, therefore, not only a testimony of the Carolingian theology of images, but a register of the position of the future emperor of the Occident.