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

Re-thinking feminism and democratic politics: the potential of online networks for social change and gender equality in Brazil

The relationship between women and new technologies has been an important area of research for feminist sociologists and others working with gender and cultural studies (i.e. Gill, 2012; Sassen, 2002), as well as for scholars within the GAD (Gender and Development) empowerment framework (Gajjala, 2003). A significant body of international scholarship on gender and the Internet has also developed in the last decades throughout the world (i.e. Haraway, 1991, 2000; Plant, 1995; Harcourt, 2000; Sandoval, 2000; Sutton and Pollock, 2000), including emerging research in Brazil (i.e. Ferreira, 2015; Natansohn, 2013; Matos, 2017). Many Brazilian women, who do not feel represented in the mainstream media and who struggle to have a voice, have increasingly made use of new technologies for self-expression, civic engagement and political mobilization. This article provides a critical summary of feminist theoretical perspectives on the potential of online communications for women's rights, further sketching a brief case study of contemporary Brazilian feminism and the mobilization around women's rights, particularly in the year 2015. This is done through a discussion of the discursive online practices of websites like Blogueiras Feministas and the NGO Think Olga, part of a wider project (Matos, 2017). Questions asked include how the media can better contribute to assist in gender development, and how online platforms can make a difference. I argue that despite constraints and setbacks, the seeds of a wider transformative influence in the offline world are slowly being planted in a highly fragmented, heterogenous and erratic blogosphere

Exact Solutions of G-Invariant Chiral Equations

We give a methodology for solving the chiral equations $(\alpha g_{,z} g^{-1})_{,\overline z} + (\alpha g_{,\overline z} g^{-1})_{,z} \ = \ 0$ where $g$ belongs to some Lie group $G$. The solutions are writing in terms of Harmonic maps. The method could be used even for some infinite Lie groups. (Preprint CIEA-gr-94/06)Comment: 8 TeX pages. Seminar presented at the First Mexican-Russian Meeting on Mathematical Physics, Mexico city, 199

Generalized Gross--Perry--Sorkin--Like Solitons

In this paper, we present a new solution for the effective theory of Maxwell--Einstein--Dilaton, Low energy string and Kaluza--Klein theories, which contains among other solutions the well known Kaluza--Klein monopole solution of Gross--Perry--Sorkin as special case. We show also the magnetic and electric dipole solutions contained in the general one.Comment: 10 latex pages, no figures. To appear in Class. Quant. Gravity

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

ϕ2\phi^2 as Dark Matter

In this paper we consider $\phi^2$ scalar field potential as a candidate to dark matter. If it is an ultralight boson particle, it condensates like a Bose-Einstein system at very early times and forms the basic structure of the Universe. Real scalar fields collapse in equilibrium configurations that oscillate in space-time (oscillatons).The cosmological behavior of the field equations are solved using the dynamical system formalism. We use the current cosmological parameters as constraints for the present value of the scalar field. We reproduce the cosmological predictions of the standard $\Lambda$CDM model with this model. Therefore, scalar field dark matter seems to be a good alternative to cold dark matter nature.Comment: Accepted for publication in MNRAS 11 pages, 7 figure