Gravitational wave recoil in Robinson-Trautman spacetimes

We consider the gravitational recoil due to non-reflection-symmetric gravitational wave emission in the context of axisymmetric Robinson-Trautman spacetimes. We show that regular initial data evolve generically into a final configuration corresponding to a Schwarzschild black-hole moving with constant speed. For the case of (reflection-)symmetric initial configurations, the mass of the remnant black-hole and the total energy radiated away are completely determined by the initial data, allowing us to obtain analytical expressions for some recent numerical results that have been appeared in the literature. Moreover, by using the Galerkin spectral method to analyze the non-linear regime of the Robinson-Trautman equations, we show that the recoil velocity can be estimated with good accuracy from some asymmetry measures (namely the first odd moments) of the initial data. The extension for the non-axisymmetric case and the implications of our results for realistic situations involving head-on collision of two black holes are also discussed.Comment: 9 pages, 6 figures, final version to appear in PR

Kinetic description of particle interaction with a gravitational wave

The interaction of charged particles, moving in a uniform magnetic field, with a plane-polarized gravitational wave is considered using the Fokker-Planck- Kolmogorov (FPK) approach. By using a stochasticity criterion, we determine the exact locations in phase space, where resonance overlapping occurs. We investigate the diffusion of orbits around each primary resonance of order (m) by deriving general analytical expressions for an effective diffusion coeficient. A solution to the corresponding diffusion equation (Fokker-Planck equation) for the static case is found. Numerical integration of the full equations of motion and subsequent calculation of the diffusion coefficient verifies the analytical results.Comment: LaTeX file, 15 page

Black-hole horizons as probes of black-hole dynamics I: post-merger recoil in head-on collisions

The understanding of strong-field dynamics near black-hole horizons is a long-standing and challenging prob- lem in general relativity. Recent advances in numerical relativity and in the geometric characterization of black- hole horizons open new avenues into the problem. In this first paper in a series of two, we focus on the analysis of the recoil occurring in the merger of binary black holes, extending the analysis initiated in [1] with Robinson- Trautman spacetimes. More specifically, we probe spacetime dynamics through the correlation of quantities defined at the black-hole horizon and at null infinity. The geometry of these hypersurfaces responds to bulk gravitational fields acting as test screens in a scattering perspective of spacetime dynamics. Within a 3 + 1 approach we build an effective-curvature vector from the intrinsic geometry of dynamical-horizon sections and correlate its evolution with the flux of Bondi linear momentum at large distances. We employ this setup to study numerically the head-on collision of nonspinning black holes and demonstrate its validity to track the qualita- tive aspects of recoil dynamics at infinity. We also make contact with the suggestion that the antikick can be described in terms of a "slowness parameter" and how this can be computed from the local properties of the horizon. In a companion paper [2] we will further elaborate on the geometric aspects of this approach and on its relation with other approaches to characterize dynamical properties of black-hole horizons.Comment: final version published on PR

Avaliação do desempenho de modelos globais na simulação de cenários de impactos das mudanças climáticas na agricultura.

As mudanças climáticas e seus possíveis impactos vêm sendo amplamente discutidos pela sociedade mundial, principalmente, a partir da divulgação do quarto relatório do IPCC (2007). Os impactos no agronegócio podem acarretar mudanças drásticas no setor econômico do país, já que este é responsável por, aproximadamente, 37% dos empregos nacionais, 23% do PIB e 42% das exportações. Com base nisso, esse trabalho teve o objetivo principal de identificar e avaliar o desempenho dos modelos HadCM3 e IPCM4, considerando sua utilidade na avaliação dos impactos das mudanças climáticas na cultura da soja de ciclo precoce no Estado de São Paulo. Além disso, o trabalho pretendeu analisar, também, as alterações possíveis nas datas de plantio da cultura devidas a esses impactos. Os resultados obtidos mostram uma diminuição no número de municípios e áreas de baixo risco climático para o plantio da soja precoce nos modelos HadCM3 e IPCM4. No entanto, comparados entre si, o modelo HadCM3 apresenta-se mais pessimista para o cultivo da soja, no Estado de São Paulo no período 2070-2099.CBA 2009

Aging of CKN:Modulus Versus Conductivity Analysis

It was recently reported that the electrical modulus peaks narrows upon annealing of the ionic system CKN [Paluch et al., Phys. Rev. Lett. 110, 015702 (2013)], which was interpreted as providing evidence of dynamic heterogeneity of this glass-forming liquid. An analysis of the same data in terms of the ac conductivity shows no shape changes, however. We discuss the relation between both findings and show further that the ac conductivity conforms to the prediction of the random barrier model (RBM) at all times during the annealing

Plantas daninhas na pós-colheita de milho nas várzeas do rio São Francisco, em Minas Gerais.

Realizou-se um estudo na região do Alto São Francisco, Minas Gerais, no final da safra agrícola 1997/1998, visando identificar as plantas daninhas que permanecem nas áreas após a colheita do milho e sua distribuição ao longo da área estudada, destacando-se as mais importantes. As observações foram realizadas em 12 municípios. Em cada local foi lançado, por cem vezes, um quadrado de 0,50 x 0,50 m, a espaços de 10 m. Dentro do quadrado foram contadas as espécies e registrado o número de indivíduos de cada uma delas. Foram encontradas 151 espécies em 35 famílias, sendo Asteraceae a mais bem representada, com 25 espécies. As espécies com maior Índice de Valor de mportância (IVI) foram: Ageratum conyzoides, Sida glaziovii, Conyza bonariensis, Gaya sp., Sida rhombifolia e Blainvillea biaristata. As plantas daninhas remanescentes nas áreas recém-colhidas são fonte de alimento para insetos polinizadores e inimigos naturais das pragas; adequadamente manejadas, elas podem favorecer a manutenção do equilíbrio nos agroecossistemas

Efeitos dos antibióticos rifampicina e cefotaxima no desenvolvimento de calos de maracuja-amarelo (Passiflora edulis f. Flavicarpa).

Este trabalho teve como objetivo verificar o efeito de antibióticos adicionados ao meio decultura ou em banho de imersão dos explantes no controle da contaminação e no desenvolvimento dos calos de maracujá-amarelo