Defining housing market areas using commuting and migration algorithms.Catalonia (Spain) as an applied case study.

In the literature on housing market areas, different approaches can be found to defining them, for example, using travel-to-work areas and, more recently, making use of migration data. Here we propose a simple exercise to shed light on which approach performs better. Using regional data from Catalonia, Spain, we have computed housing market areas with both commuting data and migration data. In order to decide which procedure shows superior performance, we have looked at uniformity of prices within areas. The main finding is that commuting algorithms present more homogeneous areas in terms of housing prices.

Dynamical friction in slab geometries and accretion disks

The evolution of planets, stars and even galaxies is driven, to a large extent, by dynamical friction of gravitational origin. There is now a good understanding of the friction produced by extended media, either collisionless of fluid-like. However, the physics of accretion or protoplanetary disks, for instance, is described by slab-like geometries instead, compact in one spatial direction. Here, we find, for the first time, the gravitational wake due to a massive perturber moving through a slab-like medium, describing e.g. accretion disks with sharp transitions. We show that dynamical friction in such environments can be substantially reduced relatively to spatially extended profiles. Finally, we provide simple and accurate expressions for the gravitational drag force felt by the perturber, in both the subsonic and supersonic regime.Comment: 10 pages, 8 figure

UNION STRUCTURE AND THE INCENTIVES FOR INNOVATION IN OLIGOPOLY

In this paper we consider the effect of union structure on the adoption of innovation in the context of Cournot duopoly. With a market size large enough we show that the incentive to innovate is higher under a decentralized union structure (with each firm facing its own independent union) than under an industry-wide union. However, for a small market size (or, equivalently, for sufficiently drastic potential innovation) the new technology is more likely to be adopted in the presence of a centralized union. This result goes against the conventional view that unionization harms the incentive to innovate.Oligopoly, Unions, Innovation.

Ecological psychology is radical enough: A reply to radical enactivists

Ecological psychology is one of the most influential theories of perception in the embodied, anti-representational, and situated cognitive sciences. However, radical enactivists claim that Gibsonians tend to describe ecological information and its ‘pick up’ in ways that make ecological psychology close to representational theories of perception and cognition. Motivated by worries about the tenability of classical views of informational content and its processing, these authors claim that ecological psychology needs to be “RECtified” so as to explicitly resist representational readings. In this paper, we argue against this call for RECtification. To do so, we offer a detailed analysis of the notion of perceptual information and other related notions such as specificity and meaning, as they are presented in the specialized ecological literature. We defend that these notions, if properly understood, remain free of any representational commitment. Ecological psychology, we conclude, does not need to be RECtified

Universal Behavior of Extreme Price Movements in Stock Markets

Many studies assume stock prices follow a random process known as geometric Brownian motion. Although approximately correct, this model fails to explain the frequent occurrence of extreme price movements, such as stock market crashes. Using a large collection of data from three different stock markets, we present evidence that a modification to the random model -- adding a slow, but significant, fluctuation to the standard deviation of the process -- accurately explains the probability of different-sized price changes, including the relative high frequency of extreme movements. Furthermore, we show that this process is similar across stocks so that their price fluctuations can be characterized by a single curve. Because the behavior of price fluctuations is rooted in the characteristics of volatility, we expect our results to bring increased interest to stochastic volatility models, and especially to those that can produce the properties of volatility reported here.Comment: 4 pages, 3 figure

Presencia y funciones del discurso científico en la cobertura informativa y cinematográfica del cambio climático

Producción CientíficaLa relación entre comunidad científica y medios masivos de comunicación siempre ha resultado conflictiva. Mientras el colectivo científico considera que su presencia en los medios es insuficiente y su discurso se ve simplificado por los profesionales de la comunicación, éstos se quejan de la inaccesibilidad de los expertos y de la dificultad para que el público comprenda su lenguaje. Este artículo profundiza en el papel otorgado por los medios de comunicación a la comunidad científica tomando como objeto de estudio el cambio climático, y observándolo desde dos prismas diferentes con un propósito comparativo: noticiarios televisivos y películas de cine. Los resultados contribuyen a profundizar en el papel secundario que, mayoritariamente, recibe el discurso científico en los medios, tanto en los géneros informativos como en la ficción

Curvature(s) of a light wavefront in a weak gravitational field

The geometry of a light wavefront evolving from a flat wavefront under the action of weak gravity field in the 3-space associated to a post-Newtonian relativistic spacetime, is studied numerically by means of the ray tracing method.Comment: 3 pages, 1 fig, Talk given by JFPS at the 12th Marcel Grossmann conference (Paris, July, 2009), submitted to the Proceeding