Quantum Dissipation in a Neutrino System Propagating in Vacuum and in Matter

Considering the neutrino state like an open quantum system, we analyze its propagation in vacuum or in matter. After defining what can be called decoherence and relaxation effects, we show that in general the probabilities in vacuum and in constant matter can be written in a similar way, which is not an obvious result in this approach. From this result, we analyze the situation where neutrinos evolution satisfies the adiabatic limit and use this formalim to study solar neutrinos. We show that the decoherence effect may not be bounded by the solar neutrino data and review some results in the literature. We discuss the current results where solar neutrinos were used to put bounds on decoherence effects through a model-dependent approach. We conclude explaining how and why this models are not general and we reinterpret these constraints.Comment: new version: title was changend and was added a table. To appear at Nucl. Physic.

Comportamento silvicultural e custos de implantação de sumaúma (Ceiba penthandra (L.) Gaertn) em diferentes espaçamentos.

Os plantios homogêneos de espécies autóctones são, em geral, limitados a ensaios de pequena escala ou plantações estabelecidas em função de exigências legais, não obstante o seu potencial silvicultural. Por outro lado, observa-se, em função de características físicas, mecânicas e estéticas das madeiras tropicais, uma tendência sobretudo da indústria de compensados à utilização de poucas espécies, ocasionando uma pressão de exploração seletiva quando pouco se conhece sobre sua autoecologia e estrutura genética. Novos cenários para o setor florestal criados em decorrência da queda de incentivos fiscais à pecuária, bem como o aumento de restrições à conversão de novas áreas, de forma conjugada o mais evidente impacto ambiental sobre florestas, o fim da reposição florestal, e a diminuição dos estoques asiáticos, com crescentes exigências do mercado consumidor quanto à sustentabilidade da matéria prima, fazem com que o manejo florestal sustentado e sistemas de alta produção com espécies e métodos adequados tornem-se elementos fundamentais ao desenvolvimento do setor. Espera-se que os plantios homogêneos de espécies autóctones de rápido crescimento, por produzirem madeira em ciclos de corte menores e a custos mais baixos, reduzam a pressão de exploração seletiva sobre florestas primárias. Neste contexto, a Embrapa-Acre vem desenvolvendo, em parceria com o setor privado, ensaios silviculturais, visando avaliar o comportamento silvicultural da espécie em diferentes espaçamentos, a viabilidade econômica dos plantios e estudar a sua biologia reprodutiva em plantios homogêneos.bitstream/item/117390/1/1007.pd

Forest growth dynamics of managed forests in the Southwestern Brazilian Amazon.

The objective of this work was to present the growth forest dynamics results obtained in two sites located in Acre and Amazonas states in the southwestern Brazilian Amazon.Abstracts of the XXV IUFRO World Congress

Natural regeneration of trees in selectively logged forest in western Amazonia.

We evaluated the impacts of selective logging on tree regeneration one, four, and eight years after harvests in Antimary State Forest in the State of Acre, Brazil. We inventoried tree seedlings, saplings, and poles (>50 cm tall to <10 cm DBH) on secondary roads, log landing, and skid trails, as well as in the bole and crown zones of canopy gaps created by felling; for comparison we also sampled areas not affected directly by logging. We compared these habitats on the basis soil (physical) characteristics, canopy cover, and floristic composition. For areas one and four years after logging, we supplemented the ground-based information with aerial LiDAR data. By eight years post-logging the size class distributions of tree regeneration in all habitat types resembled those in unlogged areas, and densities were only lower in crown gaps. Eight years after logging, relative densities of pioneer trees were highest on secondary roads and log landings; no among habitat differences were observed in the relative densities of non-pioneer species at any time along the chronosequence. Tree species diversity (Fisher's alpha) converged on unlogged values on skid trails, bole gaps, and crown gaps at 8-years post-logging, but values remained lower on secondary roads and log landings. Canopy openness was greatest one year after logging, especially in log landings (mean 45.4 ± SE 4.5%) whereas four and eight years post-logging it did not exceed 10% and no differences were found among habitats. Soil bulk density was elevated relative to un-logged areas only on log landings one and four years after logging, and this difference disappeared by eight years postlogging. The total area disturbed by logging varied from 7.0% to 8.6% with nearly half of the totals in felling gaps (3.0-3.7%)

Multimode Hong-Ou-Mandel interference

We consider multimode two-photon interference at a beam splitter by photons created by spontaneous parametric down-conversion. The resulting interference pattern is shown to depend upon the transverse spatial symmetry of the pump beam. In an experiment, we employ the first-order Hermite-Gaussian modes in order to show that, by manipulating the pump beam, one can control the resulting two-photon interference behavior. We expect these results to play an important role in the engineering of quantum states of light for use in quantum information processing and quantum imaging.Comment: 4 pages, 6 figures, submitted to PR