Gas vs dust radial extent in disks: the importance of their thermal interplay

A key parameter governing the secular evolution of protoplanetary disks is their outer radius. In this paper, the feedback of realistic dust grain size distributions onto the gas emission is investigated. Models predict that the difference of dust and gas extents as traced by CO is primarily caused by differences in the optical depth of lines vs continuum. The main effect of radial drift is the sharp decrease in the intensity profile at the outer edge. The gas radial extent can easily range within a factor of 2 for models with different turbulence. A combination of grain growth and vertical settling leads to thermal de-coupling between gas and dust at intermediate scale-heights. A proper treatment of the gas thermal structure within dust gaps will be fundamental to disentangle surface density gaps from gas temperature gaps.Comment: 8 pages, 6 figures. To appear in the Proceedings of IAU Symposium 332: Astrochemistry VII - Through the Cosmos from Galaxies to Planet

LANDSCAPE AND LAND PROPERTY RIGHT

This article shows how individuals privatise the landscape. It reminds us that landscape was invented by art, and painting in particular. (1). An elite modified the outlook on nature. It made landscape of the countryside. Once individuals give aesthetic value to land, they buy not only the property rights to plant seed or build, but also to look. The demand for landscape thus leads to a supply of development in order to look at it. This means producing viewing points (2) controlling their extension (3) and protecting image rights on property.land, property right, public good and property right

Islam and private property

Cet article soutient que la faiblesse des libertés économiques dans les pays de l'aire musulmane (1) s'explique par l'histoire du droit musulman et plus particulièrement sa conception des droits de propriété. Il montre que la principale résistance à l'avènement de la propriété privée fût le statut de la terre hérité de la domination des premiers califats. Il rappelle, d'une part, les effets des inégalités formelles entre les hommes (homme – femme, homme – esclave, musulman – non musulman) en droit musulman et, d'autre part, des restrictions sur la propriété sur le développement économique (2), mais soutient que le cœur du blocage est le statut juridique de la terre. Ce statut protège la propriété publique et l'étend à l'eau. Il enferme l'économie dans une logique d'enrichissement où les opportunités de profit sont artificiellement créées par les rentes saisies par la classe dirigeante (3). La conclusion est consacrée à l'avenir de la liberté économique dans cette aire (4).développement économique, droit de propriété, Islam et prédation

Trade Liberalization and Industrial Concentration:Evidence from Brazil

This paper applies an endogenous lobby formation model to explain the extent of trade protection granted to Brazilian manufacturing industries during the 1988-1994 trade liberalization episode. Using a panel data set covering this period, we find that even in an environment in which a major regime shift has been introduced,more concentrated sectors have been able to obtain policy advantages, that lead to a reduction in international competition. The importance of industry structure appears to be substantial: In our baseline speci.cation, an increase in concentration by 20% leads to an increase in protection by 5%-7%.lobby formation; tariffs

Wave-like warp propagation in circumbinary discs II. Application to KH 15D

KH 15D is a protostellar binary system that shows a peculiar light curve. In order to model it, a narrow circumbinary precessing disc has been invoked, but a proper dynamical model has never been developed. In this paper, we analytically address the issue of whether such a disc can rigidly precess around KH 15D, and we relate the precessional period to the main parameters of the system. Then, we simulate the disc's dynamics by using a 1D model developed in a companion paper, such that the warp propagates into the disc as a bending wave, which is expected to be the case for protostellar discs. The validity of such an approach has been confirmed by comparing its results with full 3D SPH simulations on extended discs. In the present case, we use this 1D code to model the propagation of the warp in a narrow disc. If the inner truncation radius of the disc is set by the binary tidal torques at {\sim} 1 AU, we find that the disc should extend out to 6-10 AU (depending on the models), and is therefore wider than previously suggested. Our simulations show that such a disc does reach an almost steady state, and then precesses as a rigid body. The disc displays a very small warp, with a tilt inclination that increases with radius in order to keep the disc in equilibrium against the binary torque. However, for such wider discs, the presence of viscosity leads to a secular decay of the tilt on a timescale of {\approx} 3000 ({\alpha}/0.05)^(-1) years, where {\alpha} is the disc viscosity parameter. The presence of a third body (such as a planet), orbiting at roughly 10 AU might simultaneously explain the outer truncation of the disc and the maintenance of the tilt for a prolonged time.Comment: 8 pages, 3 figures, accepted for publication in MNRA

Dual Track Liberalization: With and Without Losers

Dual track liberalization, relying upon the continued enforcement of existing contracts and the simultaneous creation of a free market sector, represents a powerful mechanism in economic reform. If not anticipated, the reform implements an outcome that is both Pareto improving and e±ciency enhancing as compared to the status quo. We show that when the reform is anticipated, intertemporal arbitrage arises potentially undermining these properties. Only when the original policy involves both price setting and quantity restrictions can anticipated dual track liberalization maintain its attractiveness. These conditions correspond well to the circumstances faced by transition economies.http://deepblue.lib.umich.edu/bitstream/2027.42/40047/3/wp661.pd

Decoupled Quantum Walks, models of the Klein-Gordon and wave equations

Decoupling a vectorial PDE consists in solving the system for each component, thereby obtaining scalar PDEs that prescribe the evolution of each component independently. We present a general approach to decoupling of Quantum Walks, again defined as a procedure to obtain an evolution law for each scalar component of the QW, in such a way that it does not depend on the other components. In particular, the method is applied to show the relation between the Dirac (or Weyl) Quantum Walk in three space dimensions with (or without) mass term, and the Klein-Gordon (or wave) equation