The band gap problem: the accuracy of the Wien2k code confronted

This paper is a continuation of our detailed study [Phys. Rev. B 86, 195106 (2012)] of the performance of the recently proposed modified Becke-Jonhson potential (mBJLDA) within the known Wien2k code. From the 41 semiconductors that we have considered in our previous paper to compute the band gap value, we selected 27 for which we found low temperature experimental data in order to pinpoint the relative situation of the newly proposed Wien2k(mBJLDA) method as compared to other methods in the literature. We found that the GWA gives the most accurate predictions. The Wien2k (mBJLDA) code is slightly less precise, in general. The Hybrid functionals are less accurate, on the overall. The GWA is definitely the most precise existing method nowadays. In 88% of the semiconductors considered the error was less than 10%. Both, the GWA and the mBJLDA potential, reproduce the band gap of 15 of the 27 semiconductors considered with a 5% error or less. An extra factor to be taken into account is the computational cost. If one would seek for precision without taking this factor into account, the GWA is the method to use. If one would prefer to sacrifice a little the precision obtained against the savings in computational cost, the empirical mBJLDA potential seems to be the appropriate method. We include a graph that compares directly the performance of the best three methods, according to our analysis, for each of the 27 semiconductors studied. The situation is encouraging but the problem is not yet a closed issue.Comment: 8 pages, 1 figur

Edward W. Said: 60 años después de la Naqbah y la negación de la ciudadanía a los refugiados palestinos

El presente artículo, a partir de la obra del intelectual palestino Edward W. Said, pretende rememorar, tras sesenta años de colonización y ocupación israelí, la Naqbah palestina, es decir, indagar las verdaderas y catastróficas consecuencias de la creación de un « hogar nacional judío » en las tierras de la Palestina histórica. A su vez, se realiza un análisis de la situación de los refugiados palestinos como uno de los más esenciales y trágicos efectos de la creación del Estado de Israel. Así, se perfila la negación sistemática de la ciudadanía para con los refugiados palestinos tanto en el interior de Israel, como en el Líbano, Egipto, o Jordania.The aim of this article is to look back on the Palestinian Naqbah -after sixty years of Israelian occupation and colonization- through the works of Edward W. Said, as well as to look into the true and catastrophic consequences of the creation of a 'national Jewish home' in the land of Historic Palestine. The situation of Palestinian refugees is also analized, as one of the most tragic consequences of the creation of the State of Israel. On that account, the systematic denial of the Palestinian citizenship is portrayed, both in Israel , Lebanon , Egypt and Jorda

Little evidence of reduced global tropical cyclone activity following recent volcanic eruptions

The impact of volcanic aerosols on recent global tropical cyclone (TC) activity is examined in observations, reanalysis, and models (the Coupled Model Intercomparison Project phase 5 - CMIP5 multi-model, and one single model large ensemble). In observations, we find a reduction of TC activity only in the North Atlantic following the last three strong volcanic eruptions; that signal, however, cannot be clearly attributed to volcanoes, as all three eruptions were simultaneous with El Niño events. In reanalyses, we find no robust impact of volcanic eruptions on potential intensity (PI) and genesis indices. In models, we find a reduction in PI after volcanic eruptions in the historical simulations, but this effect is significantly reduced when differences between the model environment and observations are accounted for. Morever, the CMIP5 multi-model historical ensemble shows no effect of volcanic eruptions on a TC genesis index. Finally, there is no robust and consistent reduction in recent TC activity following recent volcanic eruptions in a large set of synthetic TCs downscaled from these simulations. Taken together, these results show that in recent eruptions volcanic aerosols did not reduce global TC activity

Tropical cyclones and climate change: recent results and uncertainties

In the first part of the talk I’ll give an overview of the current understanding and recent progress on the influence of climate changes on tropical cyclones. I’ll discuss both attribution of current trends, as well as projections for the end of the century. In the second part of the talk, I’ll describe the hazard model developed at Columbia University to study tropical cyclones risk, namely CHAZ (Columbia Hazard Model) and discuss its main properties in the current climate. Then I’ll discuss two applications of this model: first, analyzing the current risk of tropical cyclones to Mumbai; second, describing how CHAZ can be used to study the influence of climate change on tropical cyclones and our recent results on this topic. In particular, I’ll discuss the uncertainties in tropical cyclone frequency projections based on CHAZ and compare with the current state-of-the-art knowledge on this topic