Vacuum spacetimes with a spacelike, hypersurface-orthogonal Killing vector: reduced equations in a canonical frame

The Newman-Penrose equations for spacetimes having one spacelike Killing vector are reduced -- in a geometrically defined "canonical frame'' -- to a minimal set, and its differential structure is studied. Expressions for the frame vectors in an arbitrary coordinate basis are given, and coordinate-independent choices of the metric functions are suggested which make the components of the Ricci tensor in the direction of the Killing vector vanish.Comment: 13 pages, no figures, LaTeX, to be published in Class. Quantum Gravity; v2: added/rephrased content, corrected typos, changed 1 referenc

On the Papapetrou field in vacuum

In this paper we study the electromagnetic fields generated by a Killing vector field in vacuum space-times (Papapetrou fields). The motivation of this work is to provide new tools for the resolution of Maxwell's equations as well as for the search, characterization, and study of exact solutions of Einstein's equations. The first part of this paper is devoted to an algebraic study in which we give an explicit and covariant procedure to construct the principal null directions of a Papapetrou field. In the second part, we focus on the main differential properties of the principal directions, studying when they are geodesic, and in that case we compute their associated optical scalars. With this information we get the conditions that a principal direction of the Papapetrou field must satisfy in order to be aligned with a multiple principal direction of the Weyl tensor in the case of algebraically special vacuum space-times. Finally, we illustrate this study using the Kerr, Kasner and pp waves space-times.Comment: 24 pages, LaTeX2e, IOP style. To appear in Classical and Quantum Gravit

Test particle motion in a gravitational plane wave collision background

Test particle geodesic motion is analysed in detail for the background spacetimes of the degenerate Ferrari-Ibanez colliding gravitational wave solutions. Killing vectors have been used to reduce the equations of motion to a first order system of differential equations which have been integrated numerically. The associated constants of the motion have also been used to match the geodesics as they cross over the boundary between the single plane wave and interaction zones.Comment: 11 pages, 6 Postscript figure

General approach to the study of vacuum space-times with an isometry

In vacuum space-times the exterior derivative of a Killing vector field is a 2-form (named here as the Papapetrou field) that satisfies Maxwell's equations without electromagnetic sources. In this paper, using the algebraic structure of the Papapetrou field, we will set up a new formalism for the study of vacuum space-times with an isometry, which is suitable to investigate the connections between the isometry and the Petrov type of the space-time. This approach has some advantages, among them, it leads to a new classification of these space-times and the integrability conditions provide expressions that determine completely the Weyl curvature. These facts make the formalism useful for application to any problem or situation with an isometry and requiring the knowledge of the curvature.Comment: 24 pages, LaTeX2e, IOP style. To appear in Classical and Quantum Gravit

Consequences of a Killing symmetry in spacetime's local structure

In this paper we discuss the consequences of a Killing symmetry on the local geometrical structure of four-dimensional spacetimes. We have adopted the point of view introduced in recent works where the exterior derivative of the Killing plays a fundamental role. Then, we study some issues related with this approach and clarify why in many circumstances its use has advantages with respect to other approaches. We also extend the formalism developed in the case of vacuum spacetimes to the general case of an arbitrary energy-momentum content. Finally, we illustrate our framework with the case of spacetimes with a gravitating electromagnetic field.Comment: 20 pages, LaTeX2e, IOP style. Revised version accepted for publication in Classical and Quantum Gravit

Seed germination and seedling allogamy in Rosmarinus officinalis: the costs of inbreeding

1) Self-pollination by geitonogamy is likely in self-compatible plants that simultaneously expose large numbers of flowers to pollinators. However, the progeny of these plants is often highly allogamous. Although mechanisms to increase cross-pollination have been identified and studied, their relative importance has rarely been addressed simultaneously in plant populations. (2) We used Rosmarinus officinalis to explore the factors that influence the probability of self-fertilization due to geitonogamy or that purge its consequences, focusing on their effect on seed germination and allogamy rate. For doing this, we experimentally tested the effects of geitonogamy on the proportion of filled seeds and how it influences germination rates. Then during two field seasons, we studied how life-history and flowering traits of individuals influence seed germination and allogamy rates of their progeny in wild populations at the extremes of the altitudinal range. The traits considered were plant size, population density, duration of the flowering season, number of open flowers, flowering synchrony among individuals within populations, and the proportion of male-sterile flowers. (3) We found that most seeds obtained experimentally from self-pollinations were apparently healthy but in fact empty, and that the presence of filled seeds drove the differences in germination rates between self- and cross-pollination experiments. Plants from wild populations consistently showed low germination rates and high rates of allogamy as determined with microsatellites. Germination rates related positively to the length of the flowering season, flowering synchrony and the rate of male-sterile flowers whereas the rate of allogamous seedlings was positively related only to the rate of male-sterile flowers. (4) Rosemary plants purge most of the inbreeding caused by its pollination system by aborting seeds. This study showed that the rates of seed germination and of the resulting allogamy are a function of a complex combination of factors that vary in space and time. Male sterility of flowers, length of the flowering season and flowering synchrony of individuals within populations all favor high rates of cross-pollination, therefore increasing germination and allogamy rates. These flowering traits appear to be highly plastic and respond to local and seasonal environmental conditions

El cese de la motivación: el síndrome del burnout en deportistas

Partiendo del análisis conceptual del papel de las variables moduladoras cognitivas en los procesos emocionales y motivacionales, en la aparición del síndrome del burnout y su relación con el estrés, se analiza este fenómeno en el contexto deportivo. Tras un breve repaso de su origen en la literatura científica (fundamentalmente sustentada en el ámbito organizacional), nos detenemos en aquellos trabajos e investigaciones que se han centrado en el estudio del síndrome en deportistas, para plantear finalmente la incidencia que la estructura social del deporte puede tener en el proceso motivacional del deportista, siguiendo el planteamiento propuesto por Coakley (1992), para intentar comprender mejor cómo puede aparecer el burnout en los deportistas y cuál puede ser su relación con la ausencia de motivación en este contextoOnce we are studying the conceptual analysis of modulate and cognitive variables in emotional and motivational appearance process of burnout syndrome and its link with the stress, we analyse this phenomenon in the sports context. After a brief review about, its origin in the cientific literature (mainly based in the organizational's field), we have stopped in those works and investigations that have been developed in the study of this syndrome in athletes to pose, finally, the effects that the sport's social structure could have in the process of the motivation about athletes, following Coakley's theory (1992), trying to get more knowledge about how could the burnout appears in athletes and which can be the link between the burnout and the absence of motivation in this contex

La hipnosis en psicología del deporte

En este trabajo efectuamos un encuadre de la intervención hipnosugestiva en el ámbito de la psicología del deporte, a través de una revisión crítica de trabajos representativos en distintas facetas de la disciplina. Se hace énfasis en la necesidad de consensuar algunas premisas teóricas que permitan un entendimiento y una aplicación de la hipnosis al deporte de manera justa y objetiva. Finalmente, partiendo de una propuesta conceptual sobre la hipnosis, se apuntan algunas ideas básicas sobre el manejo de la sugestión en el entrenamiento de las principales variables psicológicas relevantes para la ejecución deportivaIn this work, hypnosuggestive intervention will be delt with within the frame of sports psychology. A critical revision of some representative works in the different aspects of this discipline will be used to achieve this goal. We will emphasize the need for a consensus in some thoretical premises that could lead us to a better understanding of hypnosis in sports and allow us to use it in a fair and objective way. Finally, from a conceptual proposal about hypnosis, some new basic ideas about how to use suggestion in the training of the most important psychological variables which are relevant to sports performance will be put forwar

Aproximación teórico-descriptiva de la violencia de género: propuestas para la prevención

Los graves episodios de violencia que transcurren en numerosas familias a diario, es uno de los temas que mayor protagonismo ha ido adquiriendo en las noticias de sucesos. La violencia de género es una consecuencia más de un comportamiento violento que recae sobre una víctima, en este caso la mujer. En este trabajo se presenta el desarrollo de una aproximación teórico-descriptiva de la violencia de género en un intento de aclarar qué variables podrían estar asociadas a su manifestación dentro del contexto familiar. Así, en primer lugar, se hace una breve introducción del concepto de agresión y de los posibles factores que predisponen a su desarrollo y manifestación. A continuación, se describen algunas características que pueden estar relacionadas con el perfil de personalidad del maltratador y las consecuencias tanto físicas como psicológicas que dicha violencia puede ocasionar en la víctima. Finalmente, proponemos algunas de las líneas esenciales a desarrollar en un programa de intervención para maltratadores.Serious successes from gender violence and alarming social oppinion, are probably taking outstanding places in reports. Gender violence is one more consequence from the violent behavior on women. This work aims a theorist and descriptive nearing of gender violence; and it is sustained that many variables can be associated with a violent behavior in family context. The author introduces a brief concept of aggression, as so as possible factors that predispose to its development and manifestation. Then, some characteristics probably connected to aggressor's fuss and their physical and psychological consequences in victims, are described. Finally, we purpose many essential lines in a programme of intervention with aggressors