Cosmological constant constraints from observation-derived energy condition bounds and their application to bimetric massive gravity

Among the various possibilities to probe the theory behind the recent accelerated expansion of the universe, the energy conditions (ECs) are of particular interest, since it is possible to confront and constrain the many models, including different theories of gravity, with observational data. In this context, we use the ECs to probe any alternative theory whose extra term acts as a cosmological constant. For this purpose, we apply a model-independent approach to reconstruct the recent expansion of the universe. Using Type Ia supernova, baryon acoustic oscillations and cosmic-chronometer data, we perform a Markov Chain Monte Carlo analysis to put constraints on the effective cosmological constant $\Omega^0_{\rm eff}$. By imposing that the cosmological constant is the only component that possibly violates the ECs, we derive lower and upper bounds for its value. For instance, we obtain that $0.59 < \Omega^0_{\rm eff} < 0.91$ and $0.40 < \Omega^0_{\rm eff} < 0.93$ within, respectively, $1\sigma$ and $3\sigma$ confidence levels. In addition, about 30\% of the posterior distribution is incompatible with a cosmological constant, showing that this method can potentially rule it out as a mechanism for the accelerated expansion. We also study the consequence of these constraints for two particular formulations of the bimetric massive gravity. Namely, we consider the Visser's theory and the Hassan and Roses's massive gravity by choosing a background metric such that both theories mimic General Relativity with a cosmological constant. Using the $\Omega^0_{\rm eff}$ observational bounds along with the upper bounds on the graviton mass we obtain constraints on the parameter spaces of both theories.Comment: 11 pages, 4 figures, 1 tabl

Produção e conservação de forragens em escala para sustentabilidade dos rebanhos caprinos e ovinos na agricultura de base familiar.

Esta revisão pretende abordar alguns aspectos sobre a produção e conservação de forragens em escala para sustentabilidade dos rebanhos caprinos e ovinos na agricultura de base familiar

Avaliação dos efeitos da adição de sal e da densidade no transporte de tambaqui.

Os objetivos deste trabalho foram testar a eficiência do sal como redutor de estresse e verificar a melhor densidade de transporte de juvenis de tambaqui em caixas de plástico adaptadas

Physical properties of single-crystalline fibers of the colossal-magnetoresistance manganite La0.7Ca0.3MnO3

We have grown high-quality single crystals of the colossal-magnetoresistance (CMR) material La0.7Ca0.3MnO3 by using the laser heated pedestal growth (LHPG) method. Samples were grown as fibers of different diameters, and with lengths of the order of centimeters. Their composition and structure were verified through X-ray diffraction, scanning electron microcopy with EDX (Energy Dispersive X-ray Analysis) and by Rietveld analysis. The quality of the crystalline fibers was confirmed by Laue and EBSD (Electron Backscatter Diffraction) patterns. Rocking curves performed along the fiber axis revealed a half-height width of 0.073 degrees. The CMR behavior was confirmed by electrical resistivity and magnetization measurements as a function of temperature.Comment: 11 pages (including 3 figures); to appear in Appl. Phys. Let

Avaliação de protocolos de extração de DNA genômico total em Cymbopogon winterianu.

Realizou-se extrações de DNA em Cymbopogon winterianus, onde avaliou-se os protocolos descritos por Doyle e Doyle (1987), Clark et al. (1989), Ferreira e Grattapaglia (1995) e Romano e Brasileiro (1998), todos baseados no detergente Brometo de Cetiltrimetilamônio (CTAB), com modificações relativas à quantidade de tecido foliar, onde padronizou-se para a quantidade de 40 mg por amostra. O objetivo do presente trabalho foi estabelecer um protocolo de extração de DNA para C. winterianus, possibilitando a obtenção de um DNA de alta qualidade, em boa quantidade, de forma rápida, eficiente e menos onerosa. Os resultados mais eficientes foram obtidos por meio do protocolo descrito por Doyle e Doyle (1987); porém, o método de Clark et al. (1989) pode ser uma boa alternativa em substituição ao protocolo de Doyle e Doyle (1987)