Spacetime: Arena or Reality?

For small values of the mass (in relation to the angular momentum and electric charge), the Kerr-Newman (KN) solution of Einstein equation reduces to a naked singularity of circular shape. By considering the Hawking and Ellis extended interpretation of the KN spacetime, as well as Wheeler's idea of "charge without charge", the non-trivial topological structure of the extended KN spatial section is found to represent gravitational states with half-integral angular momentum. As a consequence, it can be consistently interpreted as a model for the electron-positron system, in which the concepts of mass, charge and spin emerge from the spacetime geometry. According to this model, therefore, instead of a simple arena, spacetime must have a concrete existence, being responsible -- through its highly non-trivial topological structures -- for the building blocks of (at least some of) the existing matter in the universe.Comment: Chapter in the book "Relativity and the Dimensionality of the World", Springer series "Fundamental Theories of Physics", Vol. 153 (2007). Volume Editor: Vesselin Petko

Kerr-Newman solution as a Dirac particle

For m^2 < a^2 + q^2, with m, a, and q respectively the source mass, angular momentum per unit mass, and electric charge, the Kerr--Newman (KN) solution of Einstein's equation reduces to a naked singularity of circular shape, enclosing a disk across which the metric components fail to be smooth. By considering the Hawking and Ellis extended interpretation of the KN spacetime, it is shown first that, similarly to the electron-positron system, this solution presents four inequivalent classical states. Next, it is shown that due to the topological structure of the extended KN spacetime it does admit states with half-integral angular momentum. This last property is corroborated by the fact that, under a rotation of the space coordinates, those inequivalent states transform into themselves only after a 4pi rotation. As a consequence, it becomes possible to naturally represent them in a Lorentz spinor basis. The state vector representing the whole KN solution is then constructed, and its evolution is shown to be governed by the Dirac equation. The KN solution can thus be consistently interpreted as a model for the electron-positron system, in which the concepts of mass, charge and spin become connected with the spacetime geometry. Some phenomenological consequences of the model are explored.Comment: 19 pages, 6 figures. References added, section 2 enhanced, an appendix and one figure adde

An alternative factorization of the quantum harmonic oscillator and two-parameter family of self-adjoint operators

We introduce an alternative factorization of the Hamiltonian of the quantum harmonic oscillator which leads to a two-parameter self-adjoint operator from which the standard harmonic oscillator, the one-parameter oscillators introduced by Mielnik, and the Hermite operator are obtained in certain limits of the parameters. In addition, a single Bernoulli-type parameter factorization which is different of the one introduced by M. A. Reyes, H. C. Rosu, and M. R. Gutierrez, Phys. Lett. A 375 (2011) 2145 is briefly discussed in the final part of this workComment: 18 pages, 7 figures, last 2 figures are not included in the version to be published, accepted by Phys. Lett.

Vibrating soap films: An analog for quantum chaos on billiards

We present an experimental setup based on the normal modes of vibrating soap films which shows quantum features of integrable and chaotic billiards. In particular, we obtain the so-called scars -narrow linear regions with high probability along classical periodic orbits- for the classically chaotic billiards. We show that these scars are also visible at low frequencies. Finally, we suggest some applications of our experimental setup in other related two-dimensional wave phenomena.Comment: 5 pages, 7 figures. Better Postscript figures available on reques

Torsion and Gravitation: A new view

According to the teleparallel equivalent of general relativity, curvature and torsion are two equivalent ways of describing the same gravitational field. Despite equivalent, however, they act differently: whereas curvature yields a geometric description, in which the concept of gravitational force is absent, torsion acts as a true gravitational force, quite similar to the Lorentz force of electrodynamics. As a consequence, the right-hand side of a spinless-particle equation of motion (which would represent a gravitational force) is always zero in the geometric description, but not in the teleparallel case. This means essentially that the gravitational coupling prescription can be minimal only in the geometric case. Relying on this property, a new gravitational coupling prescription in the presence of curvature and torsion is proposed. It is constructed in such a way to preserve the equivalence between curvature and torsion, and its basic property is to be equivalent with the usual coupling prescription of general relativity. According to this view, no new physics is connected with torsion, which appears as a mere alternative to curvature in the description of gravitation. An application of this formulation to the equations of motion of both a spinless and a spinning particle is madeComment: To appear on IJMP

Fenomenologia: uma visão para a pesquisa em enfermagem

La disciplina de enfermería necesita identificarse con una filosofía que le permita otorgar un sentido interpretativo a los fenómenos sociales o individuales; y la investigación cualitativa ofrece la metodología necesaria para llevar a cabo la interpretación de los significados bajo un análisis crítico y reflexivo. El objetivo del presente trabajo fue reflexionar sobre diferentes tradiciones filosóficas en torno a la fenomenología, al explorar los pensamientos de Edmund Husserl, Martin Heidegger y Alfred Schütz. Se realizó un ensayo teórico cuyo insumo literario se obtuvo de repositorios y fuentes de datos electrónicas, se incluyeron artículos publicados de los años 2010 al 2014, se utilizaron combinaciones de ocho palabras clave y se excluyeron aquellos artículos que no mencionaron el enfoque teórico de los filósofos de interés. Se concluye que las tres perspectivas filosóficas plantean una estrategia metodológica factible de ser utilizada dentro de la investigación cualitativa en enfermería, ya sea bajo la escuela descriptiva de Husserl, la postura interpretativa de Heidegger o la visión social de Schütz.The discipline of nursing needs to identify with a philosophy that allows give an interpretive sense of social or individual phenomena; and qualitative research provides the necessary methodology to perform the interpretation of the meanings under a critical and reflective analysis. The aim of this study was to reflect on different philosophical traditions around phenomenology, exploring the thoughts of Edmund Husserl, Martin Heidegger and Alfred Schütz. A theoretical essay whose literary input was obtained from repositories and electronic data sources was conducted, published in the years 2010 to 2014 were included combinations of eight key words were used and those items not mentioned the theoretical approach of philosophers were excluded of interest. It is concluded that the three philosophical perspectives pose a feasible methodological strategy to be used in qualitative research in nursing, either under the descriptive school of Husserl, Heidegger interpretive stance or the social vision of Schütz.A disciplina de enfermagem precisa identificar-se com uma filosofia que permite dar um sentido interpretativo dos fenômenos sociais ou individuais; e pesquisa qualitativa fornece a metodologia necessária para realizar a interpretação dos significados sob uma análise crítica e reflexiva. O objetivo deste estudo foi refletir sobre diferentes tradições filosóficas em torno de fenomenologia, explorando os pensamentos de Edmund Husserl, Heidegger e Alfred Martin Schütz. Um ensaio teórico cuja entrada literária foi obtida a partir de repositórios e fontes de dados eletrônicos foram realizadas, publicado nos anos de 2010 a 2014 foram incluídos foram utilizadas combinações de oito palavras-chave e esses itens não mencionou a abordagem teórica de filósofos foram excluídos juros. Conclui-se que as três perspectivas filosóficas representam uma estratégia metodológica viável para ser utilizado na pesquisa qualitativa em enfermagem, seja sob a escola descritiva de Husserl, Heidegger postura interpretativa ou a visão social de Schütz