Higgs bundles, abelian gerbes and cameral data

We study the Hitchin map for $G_{\mathbb{R}}$-Higgs bundles on a smooth curve, where $G_{\mathbb{R}}$ is a quasi-split real form of a complex reductive algebraic group $G$. By looking at the moduli stack of regular $G_{\mathbb{R}}$-Higgs bundles, we prove it induces a banded gerbe structure on a slightly larger stack, whose band is given by sheaves of tori. This characterization yields a cocyclic description of the fibres of the corresponding Hitchin map by means of cameral data. According to this, fibres of the Hitchin map are categories of principal torus bundles on the cameral cover. The corresponding points inside the stack of $G$-Higgs bundles are contained in the substack of points fixed by an involution induced by the Cartan involution of $G_{\mathbb{R}}$. We determine this substack of fixed points and prove that stable points are in correspondence with stable $G_{\mathbb{R}}$-Higgs bundles.Comment: 34 page

Influence of OH- concentration on the illitization of kaolinite at high pressure

The products of hydrothermal reactions of kaolinite at 300°C and 1000 bars were studied in KOH solutions covering an OH- concentration, [OH-], of 1M to 3.5M. XRD patterns indicated a notable influence of the [OH-] on the reaction. At [OH]≥3M, the only stable phase was muscovite/illite. The content of muscovite/illite was calculated from the analysis of the diagnostic 060 reflections of kaolinite and muscovite/illite. The results showed a linear dependence of kaolinite and muscovite/illite contents with [OH-]. 27Al MAS NMR spectroscopy revealed the formation of small nuclei of K-F zeolite at high [OH-]. Finally, modelling of the 29Si MAS NMR spectra indicated that the Si/Al ratio of the muscovite/illite formed was very close to that of muscovite, at least in the mineral formed at low [OH-]. In good agreement with the XRD data, the quantification of the reaction products by 29Si MAS NMR indicated a linear decrease of the kaolinite content with increasing OH- concentration.Dirección General de Investigación Científica y Técnica CTQ2007-63297Junta de Andalucía P06-FQM-0217

El realismo del texto en los estudios sociales de la ciencia

Alter the relativization of science carried out through the sociology of scientific knowledge, the demand of avoid self-refutation has led some authors to extend this program of relativization of knowledge to the sociology of knowledge. This supposes omitting in writing all kinds of realist representational practice. This article proposes a critical analysis of the scope and feasibility of this project in the framework of social studies of science.Tras la relativización de la ciencia llevada a cabo por la sociología del conocimiento científico, la exigencia de evitar la auto-refutación ha conducido a algunos autores a extender este programa de relativización del conocimiento a la propia sociología del conocimiento, lo cual supone omitir en la escritura todo tipo de práctica representacional de carácter realista. Este artículo se propone analizar críticamente el alcance y la viabilidad de esta empresa en el marco de los estudios sociales de la ciencia

Del cel a la Terra.b L'astronomia dels segles XVII i XVIII i les seues conseqüències epistemològiques

From Heaven to Earth. Astronomy in the Seventeenth and Eighteenth Centuries and its Epistemological Outcome.The growth of astronomy in the seventeenth and eighteenth centuries was the culmination of a mathematization process of planetary motions. In the transition from the eighteenth to the nineteenth centuries, it was to become a model applied to terrestrial phenomena (light, electricity, magnetism, etc.) with vital consequences for all science thereafter

Towards What University Model Is Europe Converging?

En este artículo se analiza críticamente la construcción de un Espacio de Educación Superior en cuanto reorganización de la universidad europea con criterios ajenos a los objetivos que le son propios, a saber, la enseñanza concebida como vía de acceso de los estudiantes al conocimiento y, por otro, la investigación en cuanto actividad intelectual y experimental independiente destinada al aumento y generación del mismo.This article analyzes from a critical viewpoint the construction of a Higher Education Space as regards the reorganization of European universities using criteria far-removed from its proper objectives; that is, teaching seen as a channel through which students can have access to knowledge, and, on the other hand, research concerning independent intellectual and experimental activity keyed to increasing and generating knowledge