The Levi-Civita spacetime

We consider two exact solutions of Einstein's field equations corresponding to a cylinder of dust with net zero angular momentum. In one of the cases, the dust distribution is homogeneous, whereas in the other, the angular velocity of dust particles is constant [1]. For both solutions we studied the junction conditions to the exterior static vacuum Levi-Civita spacetime. From this study we find an upper limit for the energy density per unit length $\sigma$ of the source equal ${1\over 2}$ for the first case and ${1\over 4}$ for the second one. Thus the homogeneous cluster provides another example [2] where the range of $\sigma$ is extended beyond the limit value ${1\over 4}$ previously found in the literature [3,4]. Using the Cartan Scalars technics we show that the Levi-Civita spacetime gets an extra symmetry for $\sigma={1\over 2}$ or ${1\over 4}$. We also find that the cluster of homogeneous dust has a superior limit for its radius, depending on the constant volumetric energy density $\rho_0$

Stationary Cylindrical Anisotropic Fluid

We present the whole set of equations with regularity and matching conditions required for the description of physically meaningful stationary cylindrically symmmetric distributions of matter, smoothly matched to Lewis vacuum spacetime. A specific example is given. The electric and magnetic parts of the Weyl tensor are calculated, and it is shown that purely electric solutions are necessarily static. Then, it is shown that no conformally flat stationary cylindrical fluid exits, satisfying regularity and matching conditions.Comment: 17 pages Latex. To appear in Gen.Rel.Gra

The success forecast by means of I.V.C.

El estudio de la indecisión vocacional permite al ser humano su propio dominio acerca de sus desconfianzas y dudas con la intención de mejorar su salud mental y, en el caso de este estudio, la salud mental profesional y su desarrollo vocacional. El objetivo de nuestro estudio consiste en explicar, mediante un conjunto de variables independientes sacadas del cuestionario sobre la indecisión vocacional compleja, las posibilidades de éxito de los alumnos, constituyendo un factor previsor del mismo. Por consiguiente, elegimos un grupo de alumnos de una escuela de enseñanza superior de Portugal, aplicando como instrumento el referido cuestionario y la SPSS. Concluimos que los alumnos, en su mayoría, sí se consideran con vocación y autónomos demostrando, por lo tanto, que este instrumento es un previsor del éxito de los mismos.The study of the complex vocational indecision allows the human being his own domain about his distrusts and doubts with the intention of improving his mental health and, in the case of this study, the professional mental health and its vocational development. The purpose of our research consists on explaining, by means of a group of independent variables taken from a questionnaire about the complex vocational indecision, the possibilities of success among students, becoming this survey a farsighted factor of itself. Therefore, we choose a sample of students from a higher education school in Portugal, applying as an instrument the above mentioned questionnaire and the SPSS. We conclude that most of the students consider themselves having vocation and being autonomous, proving, as a result, that this instrument is a success forecast.peerReviewe

On a stationary spinning string spacetime

The properties of a stationary massless string endowed with intrinsic spin are discussed. The spacetime is Minkowskian geometrically but the topology is nontrivial due to the horizon located on the surface $r=0$, similar with Rindler's case. For $r$ less than the Planck length $b$, $g_{\phi\phi}$ has the same sign as $g_{tt}$ and closed timelike curves are possible. We assume an elementary particles' spin originates in the frame dragging effect produced by the rotation of the source. The Sagnac time delay is calculated and proves to be constant.Comment: revised version of hep-th/0602014 v1, 7 pages, title changed, sec.5 removed, talk given at "Recent Developments in Gravity" (NEB XII), Nafplio, Greece, 29 June 200

Effective Monopoles within Thick Branes

The monopole mass is revealed to be considerably modified in the thick braneworld paradigm, and depends on the position of the monopole in the brane as well. Accordingly, the monopole radius continuously increases, leading to an unacceptable setting that can be circumvented when the brane thickness has an upper limit. Despite such peculiar behavior, the quantum corrections accrued -- involving the classical monopole solution -- are shown to be still under control. We analyze the monopole's peculiarities also taking into account the localization of the gauge fields. Furthermore, some additional analysis in the thick braneworld context and the similar behavior evinced by the topological string are investigated.Comment: 7 pages, 1 figur

Influence of half-squat intensity and volume on the subsequent countermovement jump and frequency speed of kick test performance in taekwondo athletes

The aim of this study was to assess the effects of different postactivation potentiation conditioning activities’ volumes and intensities on countermovement jump and multiple sets of high speed kicks. Nine taekwondo athletes (M±SD; age: 20.3±5.2 years; height: 177±7.2 cm; body mass: 71.8±15.3 kg; maximum dynamic half-squat 1RM: 132.8±32.5 kg and practice time: 9.6±7.2 years) participated. One control and four experimental conditions were randomly applied. Each condition was composed of warm-up, conditioning activity (half-squat: 1x3 at 50 or 90% 1RM or 3x3 at 50 or 90% 1RM), followed by a 10-minute rest interval, a countermovement jump and five sets of Frequency Speed of Kick Test. The conditions were compared using an analysis of variance with repeated measures, followed by Bonferroni post-hoc test. The alpha level was set at 5%. The significant difference was found in the number of kicks among sets (F3,21;128,36=25.34; p<.001; η2=.388 [small]). The rating of perceived exertion before control condition was higher than in all experimental protocols (F4,32=6.64; p=.001; η2=.454 [small]). There were no effects of volume and intensity on the variables investigated (maximum countermovement jump, mean countermovement jump, kick decrement, impact and rating of perceived exertion). Our results indicate that taekwondo athletes does not improve performance after conditioning activities of different volumes and intensities