28,408 research outputs found
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 . 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 and within,
respectively, and 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
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
Nova metodologia e procedimentos para criação da joaninha predadora exótica Cryptolaemus montrouzieri.
A espécie predadora exótica Cryptolaemus montrouzieri Mulsant (Col.: Coccinellidae) é multiplicada em escala massal nos Estados Unidos por empresas de base tecnológica que comercializam esse inseto benéfico visando ao controle biológico de cochonilhas. No Brasil, C. montrouzieri foi introduzido pelo Laboratório de Entomologia da Embrapa Mandioca e Fruticultura Tropical (Processo MA nº 21052.007104/97-33) e apoio do Laboratório Costa Lima da Embrapa Meio Ambiente, proveniente do Instituto de Investigaciones Agricolas - Centro de Entomologia La Cruz- INIA, Chile, com a finalidade de ser utilizada em programas de controle biológico de cochonilhas e pulgões. Adicionalmente, a Embrapa Mandioca e Fruticultura Tropical está atuando, estrategicamente, de forma proativa visando ao controle biológico clássico da cochonilha rosada Maconellicoccus hirsutus Green (Hemiptera: Pseudococcidae), praga quarentenária A1, caso esta seja introduzida no território nacional.pdf 246
Procedimentos para manejo da criação e multiplicação do predador exótico Cryptolaemus montrouzieri.
No Brasil, a joaninha predadora Cryptolaemus montrouzieri Mulsant (Coleoptera:Coccinellidae) (Figura 1) foi introduzida pelo Laboratório de Entomologia da Embrapa Mandioca e Fruticultura (processo Ministério da Agricultura nº 21052.007104/97-33) com apoio do Laboratório Costa Lima da Embrapa Meio Ambiente, proveniente do Instituto de Investigaciones Agricolas ? Centro de Entomologia La Cruz- INIA, Chile, como alternativa para o controle biológico de cochonilhas sem carapaça e pulgões (afídeos) em cultivos de importância econômica e, adicionalmente, como forma estratégica e proativa de controle biológico clássico da cochonilha rosada Maconellicoccus hirsutus Green (Hemiptera: Pseudococcidae), caso esta praga quarentenária tipo A1 seja introduzida no território nacional.bitstream/item/29720/1/circular-99ID27552.pd
Correlations around an interface
We compute one-loop correlation functions for the fluctuations of an
interface using a field theory model. We obtain them from Feynman diagrams
drawn with a propagator which is the inverse of the Hamiltonian of a
Poschl-Teller problem. We derive an expression for the propagator in terms of
elementary functions, show that it corresponds to the usual spectral sum, and
use it to calculate quantities such as the surface tension and interface
profile in two and three spatial dimensions. The three-dimensional quantities
are rederived in a simple, unified manner, whereas those in two dimensions
extend the existing literature, and are applicable to thin films. In addition,
we compute the one-loop self-energy, which may be extracted from experiment, or
from Monte Carlo simulations. Our results may be applied in various scenarios,
which include fluctuations around topological defects in cosmology,
supersymmetric domain walls, Z(N) bubbles in QCD, domain walls in magnetic
systems, interfaces separating Bose-Einstein condensates, and interfaces in
binary liquid mixtures.Comment: RevTeX, 13 pages, 6 figure
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