Conformal Kaehler submanifolds

This paper presents two results in the realm of conformal Kaehler submanifolds. These are conformal immersions of Kaehler manifolds into the standard flat Euclidean space. The proofs are obtained by making a rather strong use of several facts and techniques developed by S. Chion and M. Dajczer for the study of isometric immersions of Kaehler manifolds into the standard hyperbolic space

The Dirac operator on untrapped surfaces

We establish a sharp extrinsic lower bound for the first eigenvalue of the Dirac operator of an untrapped surface in initial data sets without apparent horizon in terms of the norm of its mean curvature vector. The equality case leads to rigidity results for the constraint equations with spherical boundary as well as uniqueness results for constant mean curvature surfaces in Minkowski space.Comment: 16 page

The mean curvature of cylindrically bounded submanifolds

We give an estimate of the mean curvature of a complete submanifold lying inside a closed cylinder $B(r)\times\R^{\ell}$ in a product Riemannian manifold $N^{n-\ell}\times\R^{\ell}$. It follows that a complete hypersurface of given constant mean curvature lying inside a closed circular cylinder in Euclidean space cannot be proper if the circular base is of sufficiently small radius. In particular, any possible counterexample to a conjecture of Calabion complete minimal hypersurfaces cannot be proper. As another application of our method, we derive a result about the stochastic incompleteness of submanifolds with sufficiently small mean curvature.Comment: First version (December 2008). Final version, including new title (February 2009). To appear in Mathematische Annale

CARACTERÍSTICAS BIOCLIMÁTICAS DE INTERÉS EDAFOLÓGICO DE LA SIERRA DEL MAIGMÓ (ALICANTE, S.E. ESPAÑA)

In this work, the authors give account on the bioclimatic characteristics of pedological interest in the «Sierra del Maigmó » (Alicante, S.E. Spain): topography, litology, climate, and vegetation. The «Sierra del Maigmó» (Alicante province) is characterised by a mediterranean climate ranging from arid, with a warm winter, to semiarid, with a cool winter. Depending on the altitude and exposure, the soil moisture regime is aridic or xeric. The temperature regime can be considered mesic. The vegetation is mainly made up by xerophytic plants; the Bupleruro-Quercetum rotundifoliae climax forest can still be observed, being largely degraded to shrubs, pine wood and arable land.Como resultado de un profundo estudio realizado en la Sierra del Maigmó (Alicante), se sintetizan los resultados bioclimáticos que guardan estrecha relación con los procesos de edafogénesis, es decir, topografía, litología, clima y vegetación. La Sierra del Maigmó está caracterizada por un clima mediterráneo árido, con invierno cálido, en transición a semiárido con invierno frío. El régimen de humedad de los suelos va de arídico a xérico, dependiendo de la altitud y la exposición. El régimen de temperatura es mésico. La vegetación está constituida por biotipos xerofíticos, pudiendo observarse restos de la climax (Bupleuro- Quercetum rotundifolirie) generalmente degradada por etapas arbustivas, repoblaciones de pinos y cultivos

Spacelike surfaces with free boundary in the Lorentz-Minkowski space

We investigate a variational problem in the Lorentz-Minkowski space \l^3 whose critical points are spacelike surfaces with constant mean curvature and making constant contact angle with a given support surface along its common boundary. We show that if the support surface is a pseudosphere, then the surface is a planar disc or a hyperbolic cap. We also study the problem of spacelike hypersurfaces with free boundary in the higher dimensional Lorentz-Minkowski space \l^{n+1}.Comment: 16 pages. Accepted in Classical and Quantum Gravit

Marginally Trapped Surfaces in the Nonsymmetric Gravitational Theory

We consider a simple, physical approach to the problem of marginally trapped surfaces in the Nonsymmetric Gravitational Theory (NGT). We apply this approach to a particular spherically symmetric, Wyman sector gravitational field, consisting of a pulse in the antisymmetric field variable. We demonstrate that marginally trapped surfaces do exist for this choice of initial data.Comment: REVTeX 3.0 with epsf macros and AMS symbols, 3 pages, 1 figur

Los depósitos de ceniza volcánica del Pleistoceno Superior-Holoceno de la región de Tafí del Valle-Cafayate, noroeste de Argentina

[EN]We identified volcanic ash deposits, whose thickness can exceed sometimes the 4 m, in the southeastern margin of La Puna and neighbouring areas (Provinces of Tucuman and Salta, Argentina). These Late Pleistocene and Holocene deposits show the existence of a highly explosive volcanism only some few thousand years ago, without comparison with any historical volcanic episode in northwestern Argentina. We have characterized the size distribution of ash (laser diffraction), morphology of particles (SEM), mineralogy (XRD) and the geochemistry of major and trace elements in bulk sample using mass spectrometry (HR-ICP-MS). The information provided by these deposits is of great interest to size adequately the geochemical impact models of ashfall in future volcanic eruptions in the Central Volcanic Zone of the Andes, quantifying the contribution of volcanic ash to the regional geochemical balances, both with respect to nutrients (e.g., Ca and Fe) and potentially toxic elements (e.g., As and F), among other elements of interest.[ES] Se han localizado diversos depósitos de ceniza volcánica, cuyos espesores llegan a superar en ocasiones los 4 m al suroeste de La Puna y áreas limítrofes (Provincias de Tucumán y Salta, Argentina). Estos depósitos son de edad Pleistoceno Superior y Holoceno y muestran la existencia hace pocos miles de años de volcanismo altamente explosivo, sin comparación con ningún episodio volcánico histórico en el noroeste de Argentina. Se han caracterizado la distribución granulométrica de la ceniza (difracción laser), la morfología de las partículas (microscopía electrónica de barrido), mineralogía (difracción de rayos X) y la geoquímica de elementos mayores y trazas en muestra total mediante espectrometría de masas (HR-ICP-MS). La información suministrada por estos depósitos tiene gran interés a la hora de dimensionar los modelos de impacto geoquímico de la caída de ceniza de futuras erupciones volcánicas en la Zona Volcánica Central de los Andes, cuantificando la contribución de la ceniza volcánica a los balances geoquímicos regionales, tanto por lo que respecta a nutrientes (p. ej., Ca y Fe), como de elementos potencialmente tóxicos (p. ej., As y F), entre otros elementos de interés.Agradecemos el apoyo técnico del labGEOTOP (infraestructura cofinanciada por FEDER, CSIC08-4E-001) del ICTJA-CSIC; de los Grupos PEGEFA (2009-SGR-972) y GEOVOL y fue financiado por el Proyecto QUECA (CGL2011-23307).Peer reviewe

The Dirichlet problem for constant mean curvature surfaces in Heisenberg space

We study constant mean curvature graphs in the Riemannian 3-dimensional Heisenberg spaces ${\cal H}={\cal H}(\tau)$. Each such ${\cal H}$ is the total space of a Riemannian submersion onto the Euclidean plane $\mathbb{R}^2$ with geodesic fibers the orbits of a Killing field. We prove the existence and uniqueness of CMC graphs in ${\cal H}$ with respect to the Riemannian submersion over certain domains $\Omega\subset\mathbb{R}^2$ taking on prescribed boundary values

Classification of spacelike surfaces in spacetime

A classification of 2-dimensional surfaces imbedded in spacetime is presented, according to the algebraic properties of their shape tensor. The classification has five levels, and provides among other things a refinement of the concepts of trapped, umbilical and extremal surfaces, which split into several different classes. The classification raises new important questions and opens many possible new lines of research. These, together with some applications and examples, are briefly considered.Comment: 42 pages, 10 tables, many diagram

BCN Rocks: aprendiendo geología urbana a través de una aplicación App interactiva

BCN Rocks is an application (App) for personal mobile devices (Android and iOS versions) suitable for secondary and high school students as well as people without background in Earth Sciences. The main objective of this App is to learn geology using the city facades and pavements of two emblematic spaces of the city of Barcelona, the Passeig de Gràcia and the Barri Gòtic. The application has three main sections (ELEMENTS, EXPLORE, and LABORATORY) that are intended to satisfy the different needs of users. In the first section, Elements, the user will find all the information about rocks forming the selected buildings as well as a brief explanation about the history and architecture of each edifice. The second section, Explore, aims to arise the curiosity of users. In this sense, several routes are proposed according to different criteria including geographic position and age of the edifices. Finally, the third section, Laboratory, allows all users to investigate several geological aspects by means of interactive experiments.Este trabajo se enmarca en un proyecto financiado por la Fundación Española para la Ciencia y la Tecnología, FECYT (ref. 8524) en el que ha participado la Universitat de Barcelona, el Instituto de Ciencias de la Tierra Jaume Almera del Consejo Superior de Investigaciones Científicas (ICTJA-CSIC) y la empresa FUSTA. AG agradece su contrato Ramón y Cajal (RYC-2012-11024).Peer Reviewe