Segregation has been one of the most persistent features of urban life and, accordingly, one of the main subjects of enquiry in urban studies. Stemming from a tradition that can be traced back to the Chicago School in the early twentieth century, social segregation has been seen as the natural consequence of the social division of space. Such naturalized understanding of segregation as ‘territorial segregation' takes space as a surrogate for social distance. We propose a shift in the focus from the static segregation of places—where social distance is assumed rather than fully explained—to how social segregation is reproduced through embodied urban trajectories. We aim to accomplish this by exploring the spatial behaviour of different social groups as networks of movement that constitute opportunities for co‐presence. This alternative view recasts the original idea of segregation as ‘restrictions on interaction' by concentrating on the spatiality of segregation potentially active in the circumstances of social contact and encounters in the city. This approach to segregation as a subtle process that operates ultimately through trajectories of the body is illustrated by an empirical study in a Brazilian city.

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Uma das ideias mais centrais e talvez menos esclarecidas em arquitetura e estudos urbanos-sobretudo desde o trabalho seminal de Jacobs até as recentes ênfases da economia urbana-diz respeito ao papel da forma arquitetônica na "vitalidade urbana", um conjunto de qualidades sociais e microeconômicas de nossas cidades. Entretanto, edifícios podem realmente afetar seus entornos urbanos? Teriam morfologias distintas efeitos também distintos sobre o que ocorre nos espaços públicos? Este artigo investiga a forma construída como condição da copresença e a atividade social e econômica no espaço urbano-dinâmicas locais com implicações de ampla escala na cidade. Propõe uma abordagem para identificar os efeitos da forma arquitetônica, de modo a distingui-los dos efeitos de outros aspectos da estrutura urbana como a acessibilidade, e verificar de fato sua existência e, se confirmada, sua extensão. A abordagem é aplicada em um estudo empírico em 24 áreas no Rio de Janeiro. Finalmente, o artigo lança os fundamentos de uma teoria probabilística dos efeitos da arquitetura que visa contribuir para uma resposta mais precisa a uma questão que captura a imaginação espacial: o quanto a arquitetura importa para a vitalidade urbana? Palavras-chave: Efeitos sociais. Morfologia arquitetônica. Tipologia. Vitalidade urbana.

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Two questions challenge the student of space and society above all others: will new technologies change the spatial basis of society ? And if so, will this have an impact on society itself ? For the urbanist, these two questions crystallise into one: what will the future of cities have to do with their past ? Too often these questions are dealt with as though they were only matters of technology. But they are much more than that. They are deep and difficult questions about the interdependence of technology, space and society that we do not yet have the theoretical apparatus to answer. We know that previous revolutions in technology such as agriculture, urbanism and industrialisation associated radical changes in space with no less radical changes in social institutions. But we do not know how far these linkages were contingent or necessary. We do not, in short, have a theory of society and space adequate to account for where we are now, and therefore we have no reasonable theoretical base for speculating about the future. In this paper, I suggest that a major reason for this theoretical deficit is that most previous attempts to build a theory of society and space have looked at society and tried to find space in its output. The result has been that the constructive role of space in creating and and sustaining society has not been brought to the fore, or if it has, only in a way which is too general to permit the detailed specification of mechanisms. In this paper I try to reverse the normal order of things this by looking first at space and trying the discern society through space: by looking at society through the prism of space. Through this I try to define key mechanisms linking space to society and then use these to suggest how the questions about the future of cities and societies might be better defined. The modern city is losing its external and formal structure. Internally it is in a state of decay while the new community represented by the nation everywhere grows at its expense. The age of the city seems to be at an end. Don Martindale 1958 in his Prefatory Introduction and reviewIn my first paper to this Symposium (Hillier 2001a) it was proposed that the social construction of space in human settlements was mediated by spatial laws. The laws were of two kinds: those by which different ways of placing buildings gave rise to different spatial con-

How can individual acts amount to coherent systems of interaction? In this paper, we attempt to answer this key question by suggesting that there is a place for cities in the way we coordinate seemingly chaotic decisions. We look into the elementary processes of social interaction exploring a particular concept, "social entropy," or how social systems deal with uncertainty and unpredictability in the transition from individual actions to systems of interaction. Examining possibilities that (i) actions rely on informational differences latent in their environments and that (ii) the city itself is an information environment to actions, we propose that (iii) space becomes a form of creating differences in the probabilities of interaction. We investigate this process through simulations of distinct material scenarios, to find that space is a necessary but not sufficient condition for the reduction of entropy. Finally, we suggest that states and fluctuations of entropy are a vital part of social reproduction and reveal a deep connection between social, informational, and spatial systems.

Does the scaling relationship between population sizes of cities with urban metrics like economic output and infrastructure (transversal scaling) mirror the evolution of individual cities in time (longitudinal scaling)? The answer to this question has important policy implications, but the lack of suitable data has so far hindered rigorous empirical tests. In this paper, we advance the debate by looking at the evolution of two urban variables, GDP and water network length, for over 5500 cities in Brazil. We find that longitudinal scaling exponents are city-specific. However, they are distributed around an average value that approaches the transversal scaling exponent provided that the data is decomposed to eliminate external factors, and only for cities with a sufficiently high growth rate. We also introduce a mathematical framework that connects the microscopic level to global behaviour, finding good agreement between theoretical predictions and empirical evidence in all analyzed cases. Our results add complexity to the idea that the longitudinal dynamics is a micro-scaling version of the transversal dynamics of the entire urban system. The longitudinal analysis can reveal differences in scaling behavior related to population size and nature of urban variables. Our approach also makes room for the role of external factors such as public policies and development, and opens up new possibilities in the research of the effects of scaling and contextual factors.

From physics to the social sciences, information is now seen as a fundamental component of reality. However, a form of information seems still underestimated, perhaps precisely because it is so pervasive that we take it for granted: the information encoded in the very environment we live in. We still do not fully understand how information takes the form of cities, and how our minds deal with it in order to learn about the world, make daily decisions, and take part in the complex system of interactions we create as we live together. This paper addresses three related problems that need to be solved if we are to understand the role of environmental information: (1) the physical problem: how can we preserve information in the built environment? (2) The semantic problem: how do we make environmental information meaningful? and (3) the pragmatic problem: how do we use environmental information in our daily lives? Attempting to devise a solution to these problems, we introduce a three-layered model of information in cities, namely environmental information in physical space, environmental information in semantic space, and the information enacted by interacting agents. We propose forms of estimating entropy in these different layers, and apply these measures to emblematic urban cases and simulated scenarios. Our results suggest that ordered spatial structures and diverse land use patterns encode information, and that aspects of physical and semantic information affect coordination in interaction systems.