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

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

Filtering the Tau method with Frobenius-Pad\'e Approximants

In this work, we use rational approximation to improve the accuracy of spectral solutions of differential equations. When working in the vicinity of solutions with singularities, spectral methods may fail their propagated spectral rate of convergence and even they may fail their convergence at all. We describe a Pad\'e approximation based method to improve the approximation in the Tau method solution of ordinary differential equations. This process is suitable to build rational approximations to solutions of differential problems when their exact solutions have singularities close to their domain