Prestigious Houses or Provisional Homes? The \u3ci\u3eghar\u3c/i\u3e as a Symbol of Kathmandu Valley Peri-Urbanism

Compared to the uniform brick architecture and contiguous courtyard structure of houses in the urban core of Kathmandu Valley cities, the houses of the growing urban periphery appear fragmented, disorganized, and unplanned. While critics attribute this haphazard growth to a site-then-services (house first, then infrastructure) approach of rural migrants, in this paper I consider it a result of an alternative formulation of planning generated by three-plus decades of economic and governmental liberalization. The practices of new homeowners in the periphery must be understood within the greater context of peri-urbanism controlled by a complex negotiation of brokers, contractors, housing companies, and neighborhood associations. I draw from the multiple expressions of what ‘ghar’ (house/ home) means to make sense of everyday life in a new neighborhood on the western edge of Kathmandu Valley. While ghar references the singular focus on building a prestigious house, it also indexes aspirations of neighborly cooperation and collective action to develop neighborhoods. Based on an ethnographic account of one family’s struggles to build a ghar, I track how such aspirations can unravel into debt, shame, and alienation, which ultimately produce a provisional sense of place in the city

On the Early Evolution of Forming Jovian Planets I: Initial Conditions, Systematics and Qualitative Comparisons to Theory

(abridged) We analyze the formation and migration of a proto-Jovian companion in a circumstellar disk in 2d, during the period in which the companion makes its transition from `Type I' to `Type II' migration, using a PPM code. Spiral waves are generated by the gravitational torque of the planet on the disk. Their effects are to cause the planet to migrate inward and the disk to form a deep (low surface density) gap. Until a transition to slower Type II migration, the migration rate of the planet is of order 1 AU/10$^3$ yr, and varies by less than a factor of two with a factor twenty change in planet mass, but depends near linearly on the disk mass. Although the disk is stable to self gravitating perturbations (Toomre $Q>5$ everywhere), migration is faster by a factor of two or more when self gravity is suppressed. Migration is equally sensitive to the disk's mass distribution within 1--2 Hill radii of the planet, as demonstrated by our simulations' sensitivity to the planet's assumed gravitational softening parameter. Rapid migration can continue after gap formation. Gaps are typically several AU in width and display the \mplan$^{2/3}$ proportionality predicted by theory. Beginning from an initially unperturbed 0.05\msun disk, planets of mass $M_{\rm pl}> 0.3$\mj can open a gap deep and wide enough to complete the transition to slower \ttwo migration. Lower mass objects continue to migrate rapidly, eventually impacting the inner boundary of our grid. This transition mass is much larger than that predicted as the `Shiva mass' discussed in Ward and Hahn (2000), making the survival of forming planets even more precarious than they would predict.Comment: 39 pages incl 13 figures. High resolution color figures at http://www.maths.ed.ac.uk/~andy/publications.htm

Dynamics of Circumstellar Disks III: The case of GG Tau A

(abridged) We present 2-dimensional hydrodynamic simulations using the Smoothed Particle Hydrodynamic (SPH) code, VINE, to model a self-gravitating binary system similar to the GG Tau A system. We simulate systems configured with semi-major axes of either $a=62$~AU (`wide') or $a=32$~AU (`close'), and with eccentricity of either $e=0$ or $e=0.3$. Strong spiral structures are generated with large material streams extending inwards. A small fraction accretes onto the circumstellar disks, with most returning to the torus. Structures also propagate outwards, generating net outwards mass flow and eventually losing coherence at large distances. The torus becomes significantly eccentric in shape. Accretion onto the stars occurs at a rate of a few $\times10^{-8}$\msun/yr implying disk lifetimes shorter than $\sim10^4$~yr, without replenishment. Only wide configurations retain disks by virtue of robust accretion. In eccentric configurations, accretion is episodic, occurs preferentially onto the secondary at wrates peaked near binary periapse. We conclude that the \ggtaua\ torus is strongly self gravitating and that a major contribution to its thermal energy is shock dissipation. We interpret its observed features as manifestations of spiral structures and the low density material surrounding it as an excretion disk created by outward mass flux. We interpret GG Tau A as a coplanar system with an eccentric torus, and account for its supposed mutual inclination as due to degeneracy between the interpretation of inclination and eccentricity. Although the disks persist for long enough to permit planet formation, the environment remains unfavorable due to high temperatures. We conclude that the GG Tau A system is in an eccentric, $a\sim62$~AU orbit.Comment: Accepted for publication in the Astrophysical Journa

Agglomeration Index Towards a New Measure of Urban Concentration

A common challenge in analyzing urbanization is the data. The United Nations (UN) compiles information on urbanization (urban population and its share of total national population) that is reported by various countries but there is no standardized definition of ‘urban’, resulting in inconsistencies. This situation is particularly troublesome if one wishes to conduct a cross-country analysis or determine the aggregate urbanization status of the regions (such as Asia or Latin America) and the world. This paper proposes an alternative to the UN measure of urban concentration that we call an agglomeration index. It is based on three factors: Population density, The population of a ‘large’ city centre and Travel time to that large city centre. The main objective in constructing this new measure is to provide a globally consistent definition of settlement concentration in order to conduct cross-country comparative and aggregated analyses. As an accessible measure of economic density, the agglomeration index lends itself to the study of concepts such as agglomeration rents in urban areas, the ‘thickness’ of a market, and the travel distance to such a market with many workers and consumers. With anticipated advances in remote sensing technology and geo-coded data analysis tools, the agglomeration index can be further refined to address some of the caveats currently associated with it.agglomeration index, urbanization, accessibility map, cost surface