Rotating 5D-Kaluza-Klein Space-Times from Invariant Transformations

Using invariant transformations of the five-dimensional Kaluza-Klein (KK) field equations, we find a series of formulae to derive axial symmetric stationary exact solutions of the KK theory starting from static ones. The procedure presented in this work allows to derive new exact solutions up to very simple integrations. Among other results, we find exact rotating solutions containing magnetic monopoles, dipoles, quadripoles, etc., coupled to scalar and to gravitational multipole fields.Comment: 24 pages, latex, no figures. To appear in Gen. Rel. Grav., 32, (2000), in pres

Dynamics of a Self-interacting Scalar Field Trapped in the Braneworld for a Wide Variety of Self-interaction Potentials

We apply the dynamical systems tools to study the linear dynamics of a self-interacting scalar field trapped in the braneworld, for a wide variety of self-interaction potentials. We focus on Randall-Sundrum (RS) and on Dvali-Gabadadze-Porrati (DGP) braneworld models exclusively. These models are complementary to each other: while the RS brane produces ultra-violet (UV) corrections to general relativity, the DGP braneworld modifies Einstein's theory at large scales, i. e., produces infra-red (IR) modifications of general relativity. This study of the asymptotic properties of both braneworld models, shows -- in the phase space -- the way the dynamics of a scalar field trapped in the brane departs from standard general relativity behaviour.Comment: 12 pages, 5 figures and 5 table

On the Space Time of a Galaxy

We present an exact solution of the averaged Einstein's field equations in the presence of two real scalar fields and a component of dust with spherical symmetry. We suggest that the space-time found provides the characteristics required by a galactic model that could explain the supermassive central object and the dark matter halo at once, since one of the fields constitutes a central oscillaton surrounded by the dust and the other scalar field distributes far from the coordinate center and can be interpreted as a halo. We show the behavior of the rotation curves all along the background. Thus, the solution could be a first approximation of a ``long exposition photograph'' of a galaxy.Comment: 8 pages REVTeX, 11 eps figure

Axisymmetric Stationary Solutions as Harmonic Maps

We present a method for generating exact solutions of Einstein equations in vacuum using harmonic maps, when the spacetime possesses two commutating Killing vectors. This method consists in writing the axisymmetric stationry Einstein equations in vacuum as a harmonic map which belongs to the group SL(2,R), and decomposing it in its harmonic "submaps". This method provides a natural classification of the solutions in classes (Weil's class, Lewis' class etc).Comment: 17 TeX pages, one table,( CINVESTAV- preprint 12/93

Nonequilibrium charge dynamics of light-driven rings threaded by a magnetic flux

We study theoretically the charge polarization and the charge current dynamics of a mesoscopic ring driven by short asymmetric electromagnetic pulses and threaded by an external static magnetic flux. It is shown that the pulse-induced charge polarization and the associated light-emission is controllable by tuning the external magnetic flux. Applying two mutually perpendicular pulses triggers a charge current in the ring. The interplay between this nonequilibrium and the persistent currents is investigated and the conditions under which the pulses stop the persistent current are identified.Comment: 6 pages, 2 figures; submitted to EP

Solutions in Self-Dual Gravity Constructed Via Chiral Equations

The chiral model for self-dual gravity given by Husain in the context of the chiral equations approach is discussed. A Lie algebra corresponding to a finite dimensional subgroup of the group of symplectic diffeomorphisms is found, and then use for expanding the Lie algebra valued connections associated with the chiral model. The self-dual metric can be explicitly given in terms of harmonic maps and in terms of a basis of this subalgebra.Comment: Plain Latex, 13 Pages, major revisions of style in the above proof, several Comments added. Version to appear in Physical Review

Using text mining to analyse digital transformation impact on people

Digital transformation is changing people's lives in many ways, creating competition between people and machines. All aspects of people’s lives are being influenced with global impacts for society. In this context, many problems have emerged for which there is still no clear ideas of their effects on people's lives. To study these problems, new tools and methodologies are needed in order to compare large volumes of data. The analysis of texts, using Text Mining, has been gaining prominence, among researchers, as one of the most relevant methodologies. However, methodologies using Text Mining are not robust enough to allow researchers to compare data from different sources, such as report data and text data. The main objective of this paper is to propose an innovative Text Mining methodology that allows to compare different texts. This study is exploratory, and it is supported by quantitative methodologies. Using Text Mining to explore ECIAIR 2019 proceedings and other European reputed reports about digital transformation, and comparing the opinions expressed by researchers with those manifested by other people, it is intended to understand if there are coincidences in the language used by researchers and on the reports in what concerns what people feel about the impacts of digital transformation on their lives. This paper belongs to an ongoing research aiming to develop text mining tools that consider corpora as variables with specific values, treating those variables as statistic variables, contributing to the enrichment of the statistical methodologies used to study digital transformation impacts. The results show that there is a gap between the language of the investigators and the one used on the reports. At the same time, there are also overlaps in some topics analysed in the documents. These results indicate that there are topics that concern both the scientific community and the international organisations responsible for the preparation of public policy guiding reports.info:eu-repo/semantics/acceptedVersio

Trends of intangibles and intellectual capital: State of art and research

Conference proceedings about intellectual capital and knowledge management are important sources of current ideas about intellectual capital, intangibles, knowledge management, authors, institutions, trends and how these are related. Since those meetings are periodic concentrations of the main sources - the papers' authors - of innovative ideas about those subjects, it is believed that an adequate analysis and synthesis of those documents can be useful to identify emerging concepts, topics, trends, directions and relations involving those concepts, their creators and the places where they were presented. The purpose of this paper is to provide, using as a data source the texts of conference proceedings, a comprehensive knowledge about the state of art of the research on intangibles and intellectual capital overthe last decade and to identify the trends on those issues for future research. This study consists of a review of abstracts, titles, authors' names, emails and institutions, keywords and main texts of all the papers in the Proceedings of the European Conference on Intellectual Capital, presented between 2009 and 2017. The study also involves the identification and characterization of patterns, such as the main topics subjacent to such texts, including associations of concepts, and the trends of such associations, involving concepts of intellectual capital and intangibles, throughout that period and conference locations. The innovative methodology used in this study is text mining, based on the classic bag-of-words model and in more recent natural language processing approaches, incorporated in R or Python packages. This work also highlights some needs not covered by the present packages and presents directions for future researches and software development. The paper can be classified as a pilot study to support the construction of new computational and knowledge management methodologies in this area.info:eu-repo/semantics/acceptedVersio

Quintessence and Scalar Dark Matter in the Universe

Continuing with previous works, we present a cosmological model in which dark matter and dark energy are modeled by scalar fields $\Phi$ and $\Psi$, respectively, endowed with the scalar potentials $V(\Phi)=V_{o}[ \cosh {(\lambda \sqrt{\kappa_{o}}\Phi)}-1]$ and $\tilde{V}(\Psi)=\tilde{V_{o}}[ \sinh {(\alpha \sqrt{\kappa_{o}}\Psi)}] ^{\beta}$. This model contains 95% of scalar field. We obtain that the scalar dark matter mass is $m_{\Phi}\sim 10^{-26}eV.$ The solution obtained allows us to recover the success of the standard CDM. The implications on the formation of structure are reviewed. We obtain that the minimal cutoff radio for this model is $r_{c}\sim 1.2 kpc.$Comment: 4 pages REVTeX, 3 eps color figures. Minor changes and references updated. To appear in Classical and Quantum Gravity as a Letter to the Editor. More information at http://www.fis.cinvestav.mx/~siddh/PHI