Social exclusion and transportation in Peachtree City, Georgia

This paper will discuss how, in a small American city, Peachtree City (43km south of Atlanta), the flexibility and relative affordability of electric golf carts, as a viablealternative to the automobile, means that the level at which families and individuals are disadvantaged through their lack of access to public/private transport is effectively lowered. Economic access to golf carts, in of itself, would not be sufficient if it were not for the extensive, highly penetrative and 'ringy' spatial structure of the cart path system, a mostly-segregated, 150 kilometre network. A spatial analysis of this dual transportation system is presented and its implications discussed. The conclusion of this paper is that the duality of the effective spatial structure of the cart path networkand the relative low cost and inherent flexibility of the golf carts combine to reduce transportation-linked social exclusion in Peachtree City. This argument is substantiated, in the final section of the paper, through the evidence of a questionnairedistributed to a random sampling of 1,038 property owners and renters in the city

Is Eta Carinae a fast rotator, and how much does the companion influence the inner wind structure?

We analyze interferometric measurements of the Luminous Blue Variable Eta Carinae with the goal of constraining the rotational velocity of the primary star and probing the influence of the companion. Using 2-D radiative transfer models of latitude-dependent stellar winds, we find that prolate wind models with a ratio of the rotational velocity (vrot) to the critical velocity (vcrit) of W=0.77-0.92, inclination angle of i=60-90 degrees, and position angle PA=108-142 degrees reproduce simultaneously K-band continuum visibilities from VLTI/VINCI and closure phase measurements from VLTI/AMBER. Interestingly, oblate models with W=0.73-0.90 and i=80-90 degrees produce similar fits to the interferometric data, but require PA=210-230 degrees. Therefore, both prolate and oblate models suggest that the rotation axis of the primary star is not aligned with the Homunculus polar axis. We also compute radiative transfer models of the primary star allowing for the presence of a cavity and dense wind-wind interaction region created by the companion star. We find that the wind-wind interaction has a significant effect on the K-band image mainly via free-free emission from the compressed walls and, for reasonable model parameters, can reproduce the VLTI/VINCI visibilities taken at phase 0.92-0.93. We conclude that the density structure of the primary wind can be sufficiently disturbed by the companion, thus mimicking the effects of fast rotation in the interferometric observables. Therefore, fast rotation may not be the only explanation for the interferometric observations. Intense temporal monitoring and 3-D modeling are needed to resolve these issues.Comment: 6 pages, 4 color figures, accepted for publication in ApJ Letter

On the Importance of the Interclump Medium for Superionization: O VI Formation in the Wind of Zeta Pup

We have studied superionization and X-ray line formation in the spectra of Zeta Pup using our new stellar atmosphere code (XCMFGEN) that can be used to simultaneously analyze optical, UV, and X-ray observations. Here, we present results on the formation of the O VI ll1032, 1038 doublet. Our simulations, supported by simple theoretical calculations, show that clumped wind models that assume void in the interclump space cannot reproduce the observed O VI profiles. However, enough O VI can be produced if the voids are filled by a low density gas. The recombination of O VI is very efficient in the dense material but in the tenuous interclump region an observable amount of O VI can be maintained. We also find that different UV resonance lines are sensitive to different density regimes in Zeta Pup : C IV is almost exclusively formed within the densest regions, while the majority of O VI resides between clumps. N V is an intermediate case, with contributions from both the tenuous gas and clumps.Comment: Accepted for publication in ApJL, 4 pages with 3 figure

The knowledge that shapes the city:the human city beneath the social city

In the Atlanta Symposium (Hillier, 2001, 2003a) a theory of the social constructionof the city was presented. In this paper it is proposed that underlying the variouskinds of social city there is a deeper, more generic human city, which arises from thepervasive intervention of the human cognitive subject in the shaping and workingof the city. This intervention is explored at two critical stages in the forming of thecity: in the 'vertical' form-creating process by which the accumulation of built formscreates an emergent spatial pattern; and in the 'lateral' form-function process bywhich the emergent spatial pattern shapes movement and sets off the process bywhich an aggregate of buildings becomes a living city. The nature of these cognitiveinterventions is investigated by asking a question: how do human beings 'synchronise'diachronically acquired (and diachronically created) spatial information into asynchronic picture of ambient urban spatial patterns, since it is such synchronicpictures which seem to mediate both interventions? A possible answer is sought bydeveloping the concept of 'description retrieval', originally proposed in 'The SocialLogic of Space' as the means by which human beings retrieve abstract informationfrom patterns of relations in the real world. Our ability to retrieve such descriptionhappens, it is argued, at more than one level, and can includes the high-level notionsof the grid which seems to plays a key role in cognitive intervention in the city.Finally we ask what the ubiquity of the human cognitive subject in the formation ofthe city implies for how we should see cities as complex systems. It is argued that,as with language, there is a 'objective subject' at the heart of the processes by whichcities come into existence, and that this provides us both with the need and themeans to mediate between the social physics paradigm of the city, with its focus onthe mathematics of the generation of the physical city and phenomenologicalparadigm with its - too often anti-mathematical - focus on the human experience ofthe city. Since the intervention of the cognitive subject involves formal ideas andhas formal consequences for the structure of the city, we cannot, it is argued, explaineither without the other

What do we need to add to a social network to get a society? answer: something like what we have to add to a spatial network to get a city

Recent years have seen great advances in social network analysis. Yet, with a few exceptions, the field of network analysis remains remote from social theory. As a result, much social network research, while technically accomplished and theoretically suggestive, is essentially descriptive. How then can social networks be linked to social theory ? Here we pose the question in its simplest form: what must we add to a social network to get a society ? We begin by showing that one reason for the disconnection between network theory and society theory is that because it exists in spacetime, the concept of social network raises the issue of space in a way that is problematical for social theory. Here we turn the problem on its head and make the problem of space in social network theory explicit by proposing a surprising analogy with the question: what do you have to add to an urban space network to get a city. We show first that by treating a city as a naïve spatial network in the first instance and allowing it to acquire two formal properties we call reflexivity and nonlocality, both mediated through a mechanism we call description retrieval, we can build a picture of the dynamics processes by which collections of the buildings become living cities. We then show that by describing societies initially as social networks in space-time and adding similar properties, we can construct a plausible ontology of a simple human society

Studying cities to learn about minds: some possible implications of space syntax for spatial cognition

What can we learn of the human mind by examining its products? The city is a case in point. Since the beginning of cities human ideas about them have been dominated by geometric ideas, and the real history of cities has always oscillated between the geometric and the ‘organic’. Set in the context of the suggestion from cognitive neuroscience that we impose more geometric order on the world than it actually possesses, and intriguing question arises: what is the role of the geometric intuition in how we understand cities and how we create them? Here I argue, drawing on space syntax research which has sought to link the detailed spatial morphology of cities to observable functional regularities, that all cities, the organic as well as the geometric, are pervasively ordered by geometric intuition, so that neither the forms of the cities nor their functioning can be understood without insight into their distinctive and pervasive emergent geometrical forms. The city is often said to be the creation of economic and social processes, but here it is argued that these processes operate within an envelope of geometric possibility defined by the human mind in its interaction with spatial laws that govern the relations between objects and spaces in the ambient world

The architectures of seeing and going:or, are cities shaped by bodies or minds? And is there a syntax ofspatial cognition?

In my first paper to this Symposium, it was argued that the human cognitive subjectplayed a key part the shaping and working of the city. The key mechanism was thesynchronisation of diachronically experienced (and usually diachronically created)information into higher order pictures of spatial relations, the guiding form for whichwas an abstracted notion of a grid formed by linearised spaces. This notion wasargued to be both perceptual and conceptual, serving at once as an abstractedrepresentation of the space of the city and as a means of solving problems, such asnavigational problems. In this paper, the question addressed is where the notion ofthe ideal grid comes from, why it has the properties it does, and what it has to dowith the real grids of cities, which are commonly of the 'deformed' or 'interrupted'rather than 'ideal' kinds (Hillier, 1996). The answer, it is proposed, lies in the verynature of complex spaces, defining these as spaces in which objects are placed so asto partially block seeing and going, and, in particular, in certain divergences in thelogics of metric and visual accessibility in such spaces. The real grid, deformed orinterrupted, is, it is argued the practical resolution of these divergent logics, and theideal grid its abstract resolution. In both resolutions, however, the resolution is moreon the terms of the visual than the metric, suggesting that cognitive factors are morepowerful than metric factors in shaping the space of the city. The question is thanraised: do people have or acquire the concept of the grid, perhaps as some kind ofperceptual-conceptual invariance of spatial experience in complex spaces, and dothey use it as a model to interact with complex spatial patterns of the urban kind?This possibility is examined against the background of current opinion in the cognitivesciences

Between social physics and phenomenology

In recent years, both phenomenology and social physics, which might be thought of asoccupying the humanistic and scientific poles of urban discourse, have taken an interestin space syntax as a means of furthering their academic aims. Here we suggest that thiscould presage a far deeper theoretical integration of the multi-disciplinary study of citiesthan either currently envisage