The availability of information about complex networks is severely restrained by issues, such as confidentiality and privacy. This poses a problem when analysing properties of networks that are of...Show moreThe availability of information about complex networks is severely restrained by issues, such as confidentiality and privacy. This poses a problem when analysing properties of networks that are of relevance to the general public. One example is the study of the resilience of banking networks to financial distress. We discuss a random graph model that reconstructs such unavailable networks, based on information that is either node specific or specific to groups of nodes. The procedure is determined by enforcing renormalizability, i.e. consistency when modelling renormalizations of networks. Then we propose a weighted semi-renormalizable extension of this model. Both models are tested on an empirical trade network, by analysing how well they captures properties that are commonly used to characterize networks. Their performances are shown to closely resemble that of the (weighted) fitness-induced Configuration Model.Show less
This work examines the network structure of illicit marketplaces that operate on the darknet. These on-line marketplaces are crawled to obtain data of inter-user communications and this data is...Show moreThis work examines the network structure of illicit marketplaces that operate on the darknet. These on-line marketplaces are crawled to obtain data of inter-user communications and this data is parsed in a network structure and its physical properties are analysed. The Configuration Model is used as a null model to investigate the patterns in these networks to reveal information about their topology. This information is applied to interpret the behaviour of users within these illegal marketplaces.Show less
The aim of this thesis is to suggest the reasons for the collapse of the Romano British polity in the fifth to sixth centuries CE in south-western England via complexity theory. This thesis focused...Show moreThe aim of this thesis is to suggest the reasons for the collapse of the Romano British polity in the fifth to sixth centuries CE in south-western England via complexity theory. This thesis focused on hillforts as a complex network in order to interpret archaeological aspects and material evidence. In Iron Age pre-Roman Britain, a variety of small civitates of Celtic tribes were located in Britain. Julius Caesar witnessed that the Britons were competing to conquer each other when he landed on Kent in 55 BCE. There was not a unified or integrated authority until the Roman troops invaded Britain in the first century CE. In Iron Age Roman Britain, the Roman army started military campaigns to conquer the territory of Britons. The Romans occupied the lowland zone in Britain and built fortresses in Chester, Caerleon, and legion headquarters in York. Even though there were several revolts against the Roman authorities such as that led by Queen Boudicca, the Roman army successfully suppressed them. However, Celtic guerrillas continuously attacked the Roman legions. The Roman authorities ordered to construct defence walls such as Hadrian’s Wall and the Antonine Wall so as to defend their military bases and occupying territory. Unceasing guerrilla attacks caused to increase social entropy. The occupation of Roman troops influenced the culture and customs to Celtic tribes in Britain. It might be a small phenomenon to Roman authorities, but its impact was so huge that changed lowland Roman Britain culturally. It can be defined as the first butterfly effect on culture. As the Western Roman Empire began to decline constantly from the fourth century CE, the migration of the Saxons started. The Roman authorities ordered to withdraw troops from Britain to Gaul in the first half of the fifth century CE. It led whole Britain to small independent communities. When the Roman army withdrew to Gaul, the power balance has been altered. It is identified as the second butterfly effect on culture. In post-Roman Britain after the collapse of the Western Roman Empire, there was civil war between warlords such as Votigern and Ambrosius Aurelianus. Votigern brought the Saxon mercenaries to Britain. The Saxons conquered the realm of Romano-British swiftly. The Saxons started attacking Romano-British hillforts. I presented the distribution of hillforts as a scale-free network in complex networks. There are three components in a scale-free network: hubs, linkers, and edges. The collapse of complex network relies on the number of hubs. Besides, the restoration of a complex network depends on the number of subsisting hubs. The huge hillforts such as Maiden Castle in Dorset, South Cadbury Castle in Somerset, and Tintagel Castle in Cornwall show that they were abandoned between the sixth and seventh centuries CE. As the Saxons expanded their realms westwards, the Romano-British polity collapsed first. They seemed to keep their territory partially. However, they did not succeed to restore their whole areas. Its collapse pattern is semi-nomadic which is classified between that of the nomadic and the sedentary. The reasons for the collapse of Romano-British polity in south-western England in the fifth to sixth centuries CE can be divided into internal and external factors. The former would have been the loss of charismatic military leader, social instability of polity and division of network systems. The latter would have been stated scatterings of continental military league groups in Armorica (Brittany), disconnecting with continental network systems and shift of religious paradigm.Show less
