Gravitational radiation from collisions at the speed of light: a massless particle falling into a Schwarzschild black hole

We compute spectra, waveforms, angular distribution and total gravitational energy of the gravitiational radiation emitted during the radial infall of a massless particle into a Schwarzschild black hole. Our fully relativistic approach shows that (i) less than 50% of the total energy radiated to infinity is carried by quadrupole waves, (ii) the spectra is flat, and (iii) the zero frequency limit agrees extremely well with a prediction by Smarr. This process may be looked at as the limiting case of collisions between massive particles traveling at nearly the speed of light, by identifying the energy $E$ of the massless particle with $m_0 \gamma$, $m_0$ being the mass of the test particle and $\gamma$ the Lorentz boost parameter. We comment on the implications for the two black hole collision at nearly the speed of light process, where we obtain a 13.3% wave generation efficiency, and compare our results with previous results by D'Eath and Payne.Comment: 10 pages, 3 figures, published versio

New instability for rotating black branes and strings

The evolution of small perturbations around rotating black branes and strings, which are low energy solutions of string theory, are investigated. For simplicity, we concentrate on the Kerr solution times transverse flat extra dimensions, possibly compactified, but one can also treat other branes composed of any rotating black hole and extra transverse dimensions, as well as analogue black hole models and rotating bodies in fluid mechanics systems. It is shown that such a rotating black brane is unstable against any massless (scalar, vectorial, tensorial or other) field perturbation for a wide range of wavelengths and frequencies in the transverse dimensions. Since it holds for any massless field it can be considered, in this sense, a stronger instability than the one studied by Gregory and Laflamme. Accordingly, it has also a totally different physical origin. The perturbations can be stabilized if the extra dimensions are compactified to a length smaller than the minimum wavelength for which the instability settles in, resembling in this connection the Gregory-Laflamme case. Likewise, this instability will have no effect for astrophysical black holes. However, in the large extra dimensions scenario, where TeV scale black holes can be produced, this instability should be important. It seems plausible that the endpoint of this instability is a static, or very slowly rotating, black brane and some outgoing radiation at infinity.Comment: 4 pages, ReVTeX4. v2: minor improvement

Black hole thermodynamics with the cosmological constant as independent variable: Bridge between the enthalpy and the Euclidean path integral approaches

Viewing the cosmological constant Λ<0 as an independent variable, we consider the thermodynamics of the Schwarzschild black hole in an anti-de Sitter (AdS) background. For this system, there is one approach which regards the enthalpy as the master thermodynamic variable and makes sense if one considers the vacuum pressure due to the cosmological constant acting in the volume inside the horizon and the outer size of the system is not restricted. From this approach a first law of thermodynamics emerges naturally. There is yet another approach based on the Euclidean action principle and its path integral that puts the black hole inside a cavity, defines a quasilocal energy at the cavity's boundary, and from which a first law of thermodynamics in a different version also emerges naturally. The first approach has affinities with critical phenomena in condensed matter physics and the second approach is an ingredient necessary for the construction of quantum gravity. The bridge between the two approaches is carried out rigorously, putting thus the enthalpic thermodynamics with Λ as independent variable on the same footing as the quasilocal energy approach. Keywords: Euclidean action, Black holes, Enthalpy, Thermodynamic

Caracterização morfológica e química de frutos de rambutan Morphologic and chemical characterization of rambutan fruits

Com a procura de alternativas por parte dos produtores e de novas opções pelos consumidores, o mercado de frutas exóticas tem ganhado cada vez mais espaço no Brasil. O rambutan encontra-se entre as frutíferas com potencial de mercado, sendo, no entanto, necessário maior conhecimento sobre a cultura, como adequada escolha de genótipos para cada região e manejo do pomar. Diante disso, realizou-se o presente trabalho, na Faculdade de Ciências Agrárias e Veterinárias - UNESP, Câmpus de Jaboticabal-SP, que teve por objetivo as caracterizações morfológica e química de frutos de rambutan, verificando a distinção de genótipos e distância genética entre os materiais. Foram avaliados: tamanho do fruto, comprimento dos filamentos, espessura da casca, tamanho da semente, peso do fruto, peso da casca, peso da semente, porcentagem de polpa, teores de sólidos solúveis (ºBrix), ácido ascórbico e acidez titulável. Realizaram-se ainda observações quanto a: coloração da casca, filamentos e polpa, aderência da polpa à casca, aderência da polpa à semente e presença de tegumento da semente na polpa. Com base nos resultados obtidos neste trabalho, pode-se concluir que os materiais A51 e B03 apresentam maior conjunto de características desejáveis, sendo promissores aos produtores na instalação de novos plantios da cultura.<br>With the increase in the search of alternatives by the producers, and of new options for the consumers, the market of exotic fruits has been gainig more space in Brazil. The rambutan is among the fruits with market potential, however it is necessary more knowledge about the culture, appropriate genotype choice for each area and handling of the orchard. Considering that, the present research was accomplished at the Faculdade de Ciências Agrárias e Veterinárias - UNESP, Campus of Jaboticabal, São Paulo State, Brazil, aiming to study the morphologic and chemical characterization of rambutan fruits, verifying the genotype distinction and the genetic distance among the materials. It was evaluated: fruit size, filament length, peel thickness, seed size, fruit, peel and seed weight, pulp percentage, soluble solid contents (ºBrix), ascorbic acid and titrable acidity. Morever, the following observations were conducted: peel coloration, filaments and pulp, adherence of the pulp to the peel, adherence of the pulp to the seed and presence of tegument of the seed in the pulp. Based on the obtained results in this research, it can be concluded that the materials A51 and B03 present a better group of desirable characteristics, revealing to be promising for the producers in the installation of new culture plantings

Seed reserves partition and light compensation point of mahogany (Swietenia macrophylla King) seedlings growth under low photosynthetic active radiation

The aim of this study was to verify the dry mass partition of the seed reserves during the initial growth of Swietenia macrophylla seedlings, in the dark, and at low levels of photosynthetically active radiation: 0.125; 3.12 and 52 µ mol.m-2.s-1. After 50 days, the dry mass of the seed reserves did not differ with treatments, but the total dry mass and leaf area were higher in the seedlings under higher light treatment. No difference in root/shoot ratio was observed between treatments, but the leaf area ratio was lower at higher light. Only the seedlings grown at 52 µ mol.m-2.s-1 showed a positive dry mass increase in relation to the mobilized seed reserves. With the values of the net increase of the seedling mass, a linear equation was adjusted in relation to the light levels, permitting to determine 3.76 µ mol.m-2.s-1 as the seedling light compensation point. These results explain the shade tolerance of the S. macrophylla seedlings.<br>O objetivo deste estudo foi verificar a partição da massa seca das reservas das sementes durante o crescimento de plântulas de Sietenia macrophylla , no escuro e sob baixos níveis de radiação fotossintéticamente ativa: 0,125; 3,12 e 52µ mol.m-2.s-1. Após 50 dias a massa seca das reservas das sementes não diferiram com os diferentes tratamentos de luz. Não foi observado diferenças na razão raíz/parte aérea, mas a razão área foliar foi menor no maior nível de luz. Somente as plântulas crescidas a 52 µ mol.m-2.s-1 mostraram um incremento positivo na massa seca em relação às reservas mobilizadas da semente. Uma equação linear foi ajustada entre o incremento líquido de massa seca das plântulas e níveis de luz, permitindo determinar 3,76 µ mol.m-2.s-1 como ponto de compensação de luz das plântulas. Esses resultados explicam a tolerância à sombra das plântulas de S. macrophyll

Levantamento pedológico e sistema de informações geográficas naavaliação do uso das terras em sub-bacia hidrográfica de Minas Gerais Pedologic survey and geographic information system for evaluation of land use within a small watershed, Minas Gerais State, Brazil

A aptidão agrícola das terras consiste em uma classificação técnica que identifica o potencial agrícola de utilização das mesmas, considerando as limitações do solo em níveis de manejo diferenciados a partir das informações geradas em um levantamento pedológico. O cruzamento dos dados de aptidão agrícola e uso atual das terras em ambiente SIG (Sistema de Informações Geográficas) consiste numa ferramenta adequada de planejamento, pois permite determinar a inadequação entre uso e aptidão agrícola, dando bases sustentáveis à exploração. Neste estudo, foram realizadas a avaliação da aptidão agrícola das terras e seu uso atual com auxílio de imagens de satélite e observações de campo, e a identificação de Áreas de Preservação Permanente (APPs) em uma sub-bacia hidrográfica da Bacia do Alto Rio Grande, MG. Com base no levantamento de solos, a utilização do sensoriamento remoto, por meio de imagens de satélites, aliado ao ambiente SIG, constituem-se em ferramentas adequadas para avaliação da aptidão agrícola e uso atual das terras, e permitem o monitoramento das áreas da sub-bacia hidrográfica. O levantamento pedológico forneceu uma base segura e real para que, com o auxílio de ferramentas de geoprocessamento, os mapas resultantes tivessem melhor qualidade e representassem com acurácia os diferentes ambientes naturais na paisagem da sub-bacia hidrográfica. Ocorreu o predomínio de usos da terra menos intensivos que os das classes de aptidão agrícola encontradas. As Áreas de Preservação Permanente (APPs) estão recebendo os mais diferentes usos agrícolas, caracterizando uma inadequação entre a legislação ambiental e o uso atual da terra.<br>The land agricultural suitability is a technical classification that identifies the agricultural potential of land use, considering the soil limitations at differential management levels from the information generated in a pedologic survey. The cross reference of data involving land agricultural suitability and land use in Geographical Information System (GIS) is an adequate tool for planning, because it allows to determine the inadequacy between land use and land agricultural suitability, giving bases to sustainable exploration. Therefore, we evaluated in this work the land agricultural suitability and the current use of the land mediated by satellite images and field observations, for the identification of permanent preservation areas (PPAs) in a small watershed from Alto Rio Grande basin - MG. Based on soil survey, the utilization of remote sensing, by means of satellite images, in association with GIS, constitutes adequate tools to evaluate the land suitability and current use, and allows monitoring areas of the small watershed. The pedologic survey supplied a secure and real basis for this purpose and with the help of geoprocessing tools, the resulting maps had better quality and represented with accuracy the different natural environments in the landscape of the hydrographic small watershed. We observed a dominance of less intensive land use in relation to the agricultural suitability classes found here. The permanent preservation areas (PPAs) are receiving a variety of agricultural uses, which characterizes an inadequacy between the environmental legislation and the current land use