Sobre algunas de las posibilidades de la historia

Este texto presenta una referencia a distintos enfoques de la disciplina de la historia que se han constituido como hitos en diversos momentos de su trayectoria. El autor escoge seis de ellos para discutirlos en sus aportes y falencias respecto a temas alusivos a la cultura, la identidad y los movimientos sociales. El artículo esboza un panorama muy general que puede servir como guía para no expertos en el tema o estudiantes de historia

Doped AB_2 Hubbard Chain: Spiral, Nagaoka and RVB States, Phase Separation and Luttinger Liquid Behavior

We present an extensive numerical study of the Hubbard model on the doped AB$_2$ chain, both in the weak coupling and the infinite-U limit. Due to the special unit cell topology, this system displays a rich variety of phases as function of hole doping ($\delta$) away from half-filling. Near half-filling, spiral states develop in the weak coupling regime, while Nagaoka itinerant ferromagnetism is observed in the infinite-U limit. For higher doping the system phase-separates before reaching a Mott insulating phase of short-range RVB states at $\delta=1/3$. Moreover, for $\delta>1/3$ we observe a crossover, which anticipates the Luttinger liquid behavior for $\delta > 2/3$.Comment: 11 pages, 13 figure

Economic freedom, human rights, and the returns to human capital : an evaluation of the Schultz hypothesis

According to T.W. Schultz, the returns to human capital are highest in economic environments experiencing unexpected price, productivity, and technology shocks that create"disequilibria."In such environments, the ability of firms and individuals to adapt their resource allocations to shocksbecomes most valuable. In the case of negative shocks, government policies that mitigate the impact of the shock will also limit the returns to the skills of managing risk or adapting resources to changing market forces. In the case of positive shocks, government policies may restrict access to credit, labor, or financial markets in ways that limit reallocation of resources toward newly emerging profitable sectors. This paper tests the hypothesis that the returns to skills are highest in countries that allow individuals to respond to shocks. Using estimated returns to schooling and work experience from 122 household surveys in 86 developing countries, this paper demonstrates a strong positive correlation between the returns to human capital and economic freedom, an effect that is observed throughout the wage distribution. Economic freedom benefits those workers who have attained the most schooling as well as those who have accumulated the most work experience.Debt Markets,Political Economy,Economic Theory&Research,Labor Policies,Population Policies

Evidence for azimuthal variations of the oxygen abundance gradient tracing the spiral structure of the galaxy HCG91c

Context. The distribution of elements in galaxies forms an important diagnostic tool to characterize the system's formation and evolution. This tool is however complex to use in practice, as galaxies are subject to a range of simultaneous physical processes active from pc to kpc scales. This renders observations of the full optical extent of galaxies down to sub-kpc scales essential. Aims. Using the WiFeS integral field spectrograph, we previously detected abrupt and localized variations in the gas-phase oxygen abundance of the spiral galaxy HCG91c. Here, we follow-up on these observations to map HCG91c's disk out to ~2Re at a resolution of 600pc, and characterize the non-radial variations of the gas-phase oxygen abundance in the system. Methods. We obtained deep MUSE observations of the target under ~0.6 arcsec seeing conditions. We perform both a spaxel-based and aperture-based analysis of the data to map the spatial variations of 12+log(O/H) across the disk of the galaxy. Results. We confirm the presence of rapid variations of the oxygen abundance across the entire extent of the galaxy previously detected with WiFeS, for all azimuths and radii. The variations can be separated in two categories: a) localized and associated with individual HII regions, and b) extended over kpc scales, and occurring at the boundaries of the spiral structures in the galaxy. Conclusions. Our MUSE observations suggest that the enrichment of the interstellar medium in HGC91c has proceeded preferentially along spiral structures, and less efficiently across them. Our dataset highlights the importance of distinguishing individual star-forming regions down to scales of a few 100pc when using integral field spectrographs to spatially resolve the distribution of oxygen abundances in a given system, and accurately characterize azimuthal variations and intrinsic scatter.Comment: 12 pages, 11 figures, accepted for publication in A&A. Supplementary movie assocociated with Fig. 8 is available (until publication) at: http://www.sc.eso.org/~fvogt/supp_mat/HCG91c/O_gradient.mp