Grothendieck topologies from unique factorisation systems

This article presents a way to associate a Grothendieck site structure to a category endowed with a unique factorisation system of its arrows. In particular this recovers the Zariski and Etale topologies and others related to Voevodsky's cd-structures. As unique factorisation systems are also frequent outside algebraic geometry, the same construction applies to some new contexts, where it is related with known structures dened otherwise. The paper details algebraic geometrical situations and sketches only the other contexts.

The Political cost of reforms

This paper formalizes in a fully-rational model the popular idea that politicians perceive an electoral cost in adopting costly reforms with future benefits and reconciles it with the evidence that reformist governments are not punished by voters. To do so, it proposes a model of elections where political ability is ex-ante unknown and investment in reforms is unobservable. On the one hand, elections improve accountability and allow to keep well-performing incumbents. On the other, politicians make too little reforms in an attempt to signal high ability and increase their reappointment probability. Although in a rational expectation equilibrium voters cannot be fooled and hence reelection does not depend on reforms, the strategy of underinvesting in reforms is nonetheless sustained by out-of-equilibrium beliefs. Contrary to the conventional wisdom, uncertainty makes reforms more politically viable and may, under some conditions, increase social welfare. The model is then used to study how political rewards can be set so as to maximize social welfare and the desirability of imposing a one-term limit to governments. The predictions of this theory are consistent with a number of empirical regularities on the determinants of reforms and reelection. They are also consistent with a new stylized fact documented in this paper: economic uncertainty is associated to more reforms in a panel of 20 OECD countries.

Implementació d'un sistema per al control de la qualitat d'imatges JPEG (III)

Aquest TFC vol desenvolupar una aplicació gràfica per a treballar amb imatges i convertir-les al format JPEG.

Trade, markup heterogeneity and misallocations

We argue that the procompetitive effect of international trade may bring about significant welfare costs that have not been recognized. We formulate a stylized general equilibrium model with a continuum of imperfectly competitive industries to show that, under plausible conditions, a trade-induced increase in competition can actually amplify monopoly distortions. This happens because trade, while lowering the average level of market power, may increase its cross-sectoral dispersion. Using data on US industries, we document a dramatic increase in the dispersion of market power overtime. We also show evidence thattrade might be responsible for it and provide some quantifications of the induced welfare cost. Our results suggest that, to avoid some unpleasant effects of globalization, trade integration should be accompanied by procompetitive reforms (i.e., deregulation) in the nontraded sectors.

Equivalent roughness of gravel-bed rivers

The relation between the equivalent roughness and different grain size percentiles of the sediment in gravel-bed rivers was determined under the hypothesis that the vertical distribution of the flow velocity follows a logarithmic law. A set of 954 data points was selected from rivers with gravel size sediment or larger, with a non-sinuous alignment and free of vegetation or obstacles. According to the results, the ks roughness is equivalent to approximately 2.4D90, 2.8D84, and 6.1D50. No correlation was detected between the sediment sorting and the sediment mobility index on one hand, and, on the other, the coefficient of proportionality of each grain size percentile.