No abstract

The stability of the cosmological event horizons found recently by Gregory [Phys. Rev. D54, 4955 (1996)] for a class of non-static global cosmic strings is studied. It is shown that they are not stable to both test particles and physical perturbations. In particular, the back reaction of the perturbations of null dust fluids will turn them into spacetime singularities. The resulted singularities are strong in the sense that the distortion of test particles diverges logarithmically when these singular hypersurfaces are approaching.PACS numbers: 98.80.Cq, 04.20Jb, 04.40.+c.

La figura del entrenador es clave en el entrenamiento deportivo con jóvenes. Este estudio tuvo como objetivos establecer el perfil del entrenador de fútbol en las etapas de formación de los jóvenes jugadores de la región de Beja (Portugal), identificar la concepción sobre la enseñanza del fútbol que tienen, y conocer la forma de planificar y programar de los mismos. Con este fin se encuestaron a 124 entrenadores de fútbol base de la mencionada región portuguesa. Los datos mostraron que el perfil del entrenador de fútbol base de Beja se correspondió al siguiente: hombre de entre 31 y 40 años, con el duodécimo año de escolaridad completo, trabajando por cuenta ajena, sin curso de entrenador o con apenas el Grado I o nivel básico de la titulación de entrenador de fútbol. También destacó el hecho de que la mayoría de los entrenadores consideraran el fútbol un medio para educar a los jugadores, siendo los entrenadores más jóvenes los que más creían en el fútbol como medio transmisor de valores. Cabe destacar que los entrenadores manifestaron tener bastante claro los contenidos a trabajar en estas edades y que solían utilizar tanto métodos de enseñanza directivos como basados en el descubrimiento. Los entrenadores afirmaron que solían dar más prioridad a los aspectos técnico-tácticos con respecto al trabajo físico. Por último, gran parte de los entrenadores mostraron intención de entrenar en un futuro en categorías superiores. Abstract: The figure of the coach is key in sports training with young people. The aims of this study were to establish the profile of the football coach in the training stages of young players in the region of Beja (Portugal), to identify their conception of football teaching, and to know how to plan and programme them. To this end, 124 grassroots football coaches in the aforementioned Portuguese region were surveyed. The data showed that the profile of the base football coach in Beja corresponded to the following: a man between 31 and 40 years old, with the twelfth year of schooling complete, working as an employee, without a course of coaching or with only Grade I or basic level of the qualification of football coach. It was also highlighted the fact that most coaches considered football as a means of educating players, with younger coaches believing most in football as a means of transmitting values. It should be noted that the coaches said they were quite clear about the content to be worked on in these ages and that they used both managerial and discovery-based teaching methods. Coaches said they tended to give more priority to technical and tactical aspects over physical work. Finally, a large number of coaches showed their intention to train at higher levels in the future.

An intriguing question related to black hole thermodynamics is that the entropy of a region shall scale as the area rather than the volume. In this essay we propose that the microscopical degrees of freedom contained in a given region of space, are statistically related in such a way that obey a non-standard statistics, in which case an holographic hypothesis would be not needed. This could provide us with some insight about the nature of degrees of freedom of the geometry and/or the way in which gravitation plays a role in the statistic correlation between the degrees of freedom of a system. 1 botta@cbpf.br 2