El Salvador: A Central American Tiger?

El Salvador is becoming an economic success story in Central America. Since the end of the civil conflict in 1992, which left the country in ruins, El Salvador has transformed its economy by implementing a far-reaching liberalization process undertaken by democratic governments, which has included the privatization of state enterprises, deregulation, trade and financial liberalization, privatization of the pension system, and the adoption of the U.S. dollar as its official currency. According to the Fraser Institute's Economic Freedom of the World Report, El Salvador ranks among the top 25 freest economies in the world. The results of the market reforms are notable: between 1991 and 2007, the percentage of households below the poverty line fell from 60 percent to 34.6 percent. However, official figures point to mediocre average annual per capita growth during the period 1992 -- 2007 -- only 1.9 percent -- which is very similar to Latin America's average of 1.6 percent in the same period. But official figures grossly underestimate the performance of the economy because of flawed measurement. In fact, the economy is probably more than 30 percent larger than indicated by the official data. Accordingly, the average per capita growth rate since 1992 has been approximately 5.2 percent per year. El Salvador still has much to do on its policy agenda. In particular, high crime rates constitute a major hindrance to further growth. This lack of security represents the greatest threat to sustained growth and liberal policies. Nonetheless, the country is showing the rest of the region how economic freedom can pave the way for development and how globalization offers great opportunities for developing countries that are willing to implement a coherent set of mutually supportive market reforms

Mixing across fluid interfaces compressed by convective flow in porous media

We study the mixing in the presence of convective flow in a porous medium. Convection is characterized by the formation of vortices and stagnation points, where the fluid interface is stretched and compressed enhancing mixing. We analyze the behavior of the mixing dynamics in different scenarios using an interface deformation model. We show that the scalar dissipation rate, which is related to the dissolution fluxes, is controlled by interfacial processes, specifically the equilibrium between interface compression and diffusion, which depends on the flow field configuration. We consider different scenarios of increasing complexity. First, we analyze a double-gyre synthetic velocity field. Second, a Rayleigh-B\'enard instability (the Horton-Rogers-Lapwood problem), in which stagnation points are located at a fixed interface. This system experiences a transition from a diffusion controlled mixing to a chaotic convection as the Rayleigh number increases. Finally, a Rayleigh-Taylor instability with a moving interface, in which mixing undergoes three different regimes: diffusive, convection dominated, and convection shutdown. The interface compression model correctly predicts the behavior of the systems. It shows how the dependency of the compression rate on diffusion explains the change in the scaling behavior of the scalar dissipation rate. The model indicates that the interaction between stagnation points and the correlation structure of the velocity field is also responsible for the transition between regimes. We also show the difference in behavior between the dissolution fluxes and the mixing state of the systems. We observe that while the dissolution flux decreases with the Rayleigh number, the system becomes more homogeneous. That is, mixing is enhanced by reducing diffusion. This observation is explained by the effect of the instability patterns

Non-comoving baryons and cold dark matter in cosmic voids

We examine the fully relativistic evolution of cosmic voids constituted by baryons and cold dark matter (CDM), represented by two non-comoving dust sources in a $\Lambda$CDM background. For this purpose, we consider numerical solutions of Einstein's field equations in a fluid-flow representation adapted to spherical symmetry and multiple components. We present a simple example that explores the frame-dependence of the local expansion and the Hubble flow for this mixture of two dusts, revealing that the relative velocity between the sources yields a significantly different evolution in comparison with that of the two sources in a common 4-velocity (which reduces to a Lemaitre-Tolman-Bondi model). In particular, significant modifications arise for the density contrast depth and void size, as well as in the amplitude of the surrounding over-densities. We show that an adequate model of a frame-dependent evolution that incorporates initial conditions from peculiar velocities and large-scale density contrast observations may contribute to understand the discrepancy between the local value of $H_0$ and that inferred from the CMB.Comment: Discussion of the evolution of baryon-CDM relative velocity added. Other minor but important corrections were incorporated. Version accepted for publication in EPJ

Formas de prescripción en la Ortografía de la RAE. De la prescripción a la descripción: la nueva tendencia

Comparative study of the norms about the use of capital letters in the Ortografía of the Spanish Royal Academy 1974 and 1999: inventory and statistics. Evolution of patterns of prescription and description. Trends in norms

Primordial Black Holes in non-linear perturbation theory

This thesis begins with a study of the origin of cosmological fluctuations with special attention to those cases in which the non-Gaussian correlation functions are large. The analysis shows that perturbations from an almost massless auxiliary field generically produce large values of the non-linear parameter f_NL. The effects of including non-Gaussian correlation functions in the statistics of cosmological structure are explored by constructing a non-Gaussian probability distribution function (PDF). Such PDF is derived for the comoving curvature perturbation from first principles in the context of quantum field theory, with n-point correlation functions as the only input. The non-Gaussian PDF is then used to explore two important problems in the physics of primordial black holes (PBHs): First, to compute non-Gaussian corrections to the number of PBHs generated from the primordial curvature fluctuations. The second application concerns new cosmological observables. The formation of PBHs is known to depend on two main physical characteristics: the strength of the gravitational field produced by the initial curvature inhomogeneity and the pressure gradient at the edge of the curvature configuration. We account for the probability of finding these configurations by using two parameters: The amplitude of the inhomogeneity and its second radial derivative, evaluated at the centre of the configuration. The implications of the derived probability for the fraction of mass in the universe in the form of PBHs are discussed.Comment: PhD Thesis, Queen Mary, U. of London, Supervisor: Bernard J Carr. (134 pages and 9 figures

The concept of finite limit of a function at one point as explained by students of non-compulsory secondary education

We review various educational studies of the mathematical concept of limit of a function at a point that indicate how colloquial uses of the terms “to approach,” “to tend toward,” “to reach,” “to exceed” and “limit” influence students’ conceptions of these terms. We then present the results of an exploratory study of this question performed with Spanish students in non-compulsory secondary education and analyze the responses they provide to justify the truth or falsity of statements related to the different characteristics of the concept of finite limit of a function at a point when they use these terms. Finally, we organize their answers according to the kinds of arguments made. Using the response profiles detected, we discuss the influence of everyday usage on the students’ arguments

Zc(3900)Z_c(3900): what has been really seen?

The $Z^\pm_c(3900)/Z^\pm_c(3885)$ resonant structure has been experimentally observed in the $Y(4260) \to J/\psi \pi\pi$ and $Y(4260) \to \bar{D}^\ast D \pi$ decays. This structure is intriguing since it is a prominent candidate of an exotic hadron. Yet, its nature is unclear so far. In this work, we simultaneously describe the $\bar{D}^\ast D$ and $J/\psi \pi$ invariant mass distributions in which the $Z_c$ peak is seen using amplitudes with exact unitarity. Two different scenarios are statistically acceptable, where the origin of the $Z_c$ state is different. They correspond to using energy dependent or independent $\bar D^* D$ $S$-wave interaction. In the first one, the $Z_c$ peak is due to a resonance with a mass around the $D\bar D^*$ threshold. In the second one, the $Z_c$ peak is produced by a virtual state which must have a hadronic molecular nature. In both cases the two observations, $Z^\pm_c(3900)$ and $Z^\pm_c(3885)$, are shown to have the same common origin, and a $\bar D^* D$ bound state solution is not allowed. Precise measurements of the line shapes around the $D\bar D^*$ threshold are called for in order to understand the nature of this state.Comment: 6 pages, 6 figure

Enseñanza y aprendizaje de las matemáticas en educación infantil, de Encarnación Castro y Enrique Castro

Recensión del libro "Enseñanza y aprendizaje de las matemáticas en educación infantil", de Encarnación Castro y Enrique Castro

Queer Identities in a Commodified World: Mark Ravenhill’s Mother Clap’s Molly House and the Rise of the (New)

[Abstract] Ravenhill’s theatre insists on the contemporary commodification of not only sex, but the whole realm of human feelings and social interactions, a preoccupation that appeared in his frequentlydiscussed Shopping and Fucking (1996) and returns, as a kind of leitmotiv, in Mother Clap’s Molly House (2001). In the latter play, the body becomes a battleground (to use Barbara Kruger’s slogan) where one can read all kinds of sexual practises, identifications and even identities in the form of transvestism, transsexuality, homosexuality, heterosexuality and bisexuality. This profusion of ‘deviated’ bodies (all of them engaged in carnal business and trade) resists any notion of stability and normalisation precisely in a moment (the eighteenth century) when reason and order were imposed by the emerging bourgeoisie on both individual and social bodies. The play, then, makes use of a historical setting in order to problematize any totalizing understanding of the modern individual and to celebrate the freedom provided by contemporary queer sexualities. The frequent changes of gender behaviour and sexual partners present in this work break any attempt to control the individual through norms and laws and function as a liberatory practise in which the usual expectations are never accomplished, but, on the contrary, are continuously turned upside down and presented in a rather unfamiliar way