Axion Electrodynamics from Infeld-van der Waerden formalisms

In this article we will explore the spacetime phase structure inside the Infeld-van der Waerden formalisms, showing that Maxwell's theory in this scenario leads to an axion-like phase electrodynamics, which suggests that this phase may originate the axion field.Comment: 15 page

Conducción y valor empresarial en Brasil (y Chile)

(Disponible en idioma inglés únicamente) En este trabajo se elabora un índice de prácticas de conducción empresarial (CGI, por sus siglas en inglés) basándose en un conjunto de 24 preguntas que se pueden responder objetivamente a partir de información disponible públicamente. El objetivo es cuantificar la calidad general de las prácticas de conducción empresarial del mayor número posible de compañías. Los niveles del CGI en Brasil han venido mejorando con el tiempo, y un análisis de sus componentes indica que las compañías brasileñas tienen un desempeño mucho mejor en cuanto a la información que suministran que en cuanto a otros aspectos de la gestión empresarial. En este trabajo se hallan niveles sumamente elevados de concentración de derechos de voto, apalancados por el uso generalizado de estructuras de control indirecto y acciones sin derecho a voto. No se hallan indicios ni de afianzamiento firme ni de incentivos en cuanto al uso de porcentajes de propiedad en Brasil, pero sí se hallan indicios de que la separación del control de los derechos sobre el flujo de caja destruye el valor. El CGI mantiene una relación positiva, significativa y robusta con el valor de la empresa. Una mejora de peor a mejor en el CGI en 2002 conduciría a un aumento de 0,38 del coeficiente de Tobin, lo cual representa un aumento de 95% del valor de la acción de una compañía con apalancamiento promedio y las proporciones del coeficiente de Tobin. Tomando en cuenta nuestro coeficiente CGI más bajo, un aumento de un punto del CGI conduciría a un aumento de 6,8% del precio de la acción de la compañía promedio en 2002. No se halló relación significativa alguna entre la conducción empresarial y el pago de dividendos. Los resultados se ponen en contexto mediante un análisis comparativo con Chile.

Photospheric parameters and C abundances in solar-like stars with and without planets

We have been analyzing a large sample of solar-like stars with and without planets in order to homogeneously measure their photospheric parameters and Carbon abundances. Our sample contains around 200 stars in the solar neighborhood observed with the ELODIE spectrograph, for which the observational data are publicly available. We performed spectral synthesis of prominent bands of C$_{2}$ and C I lines, aiming to accurately obtain the C abundances. We intend to contribute homogeneous results to studies that compare elemental abundances in stars with and without known planets. New arguments will be brought forward to the discussion of possible chemical anomalies that have been suggested in the literature, leading us to a better understanding of the planetary formation process. In this work we focus on the C abundances in both stellar groups of our sample.Comment: 2 pages, 2 figures, to be published in the proceedings of the IAU Symposium No. 265, 200

Diversity of the arthropod fauna in organically grown garlic intercropped with fodder radish.

The cultivation of garlic faces several problems, which include pest attack, and the diversification of habitat through intercropping with attractive plants comes up as a method to pest management. The objective of this research was to verify the effect of the association of garlic with fodder radish on richness, abundance and diversity of arthropods under organic production system in Lavras, MG, Brazil. The treatments were composed of garlic in monoculture and garlic in association with fodder radish, in plots of 40 garlic plants, intercropped or not with two lines of fodder radish. Weekly, 25 samples were collected for a period of 10 weeks (n=250). Species accumulation curves, species richness, abundance, and diversity index were determined, and T or Mann-Whitney tests were used for analysis. The 250 samples collected were sufficient to register the majority of species present in garlic. Richness and abundance were higher in diversified garlic whereas diversity was higher in monoculture. Diversified system increased the overall richness of phytophagous species and parasitoids. The abundance of T. tabaci decreased, while increased the presence of A. fabae, demonstrating that the association was potentially beneficent to the culture. The possible reasons for these results are discussed, and future works should focus in the ecological mechanisms involved in crop diversification of organic garlic

Replicator Dynamics and Evolutionary Stable Strategies in Heterogeneous Games

We generalise and extend the work of Inarra and Laruelle (2011) by studying two person symmetric evolutionary games with two strategies, a heterogeneous population with two possible types of individuals and incomplete information. Comparing such games with their classic homogeneous version with complete information found in the literature, we show that for the class of anti-coordination games the only evolutionarily stable strategy vanishes. Instead, we find infinite neutrally stable strategies. We also model the evolutionary process using two different replicator dynamics setups, each with a different inheritance rule, and we show that both lead to the same results with respect to stability.

Replicator Dynamics and Evolutionary Stable Strategies in Heterogeneous Games

We generalise and extend the work of Inarra and Laruelle (2011) by studying two person symmetric evolutionary games with two strategies, a heterogeneous population with two possible types of individuals and incomplete information. Comparing such games with their classic homogeneous version with complete information found in the literature, we show that for the class of anti-coordination games the only evolutionarily stable strategy vanishes. Instead, we find infinite neutrally stable strategies. We also model the evolutionary process using two different replicator dynamics setups, each with a different inheritance rule, and we show that both lead to the same results with respect to stability.