Vacuum fluctuations of a scalar field near a reflecting boundary and their effects on the motion of a test particle

The contribution from quantum vacuum fluctuations of a real massless scalar field to the motion of a test particle that interacts with the field in the presence of a perfectly reflecting flat boundary is here investigated. There is no quantum induced dispersions on the motion of the particle when it is alone in the empty space. However, when a reflecting wall is introduced, dispersions occur with magnitude dependent on how fast the system evolves between the two scenarios. A possible way of implementing this process would be by means of an idealized sudden switching, for which the transition occurs instantaneously. Although the sudden process is a simple and mathematically convenient idealization it brings some divergences to the results, particularly at a time corresponding to a round trip of a light signal between the particle and the wall. It is shown that the use of smooth switching functions, besides regularizing such divergences, enables us to better understand the behavior of the quantum dispersions induced on the motion of the particle. Furthermore, the action of modifying the vacuum state of the system leads to a change in the particle energy that depends on how fast the transition between these states is implemented. Possible implications of these results to the similar case of an electric charge near a perfectly conducting wall are discussed.Comment: 17 pages, 8 figure

Polpas branqueadas de misturas de madeiras da Amazônia.

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Rural establishments environmental management and insertion in production chains of oleaginous crops for biofuels.

Building upon a set of socio-environmental impact assessments carried out in five rural territories across the country, regarding the context of increasing demand for oleaginous crops for biofuels production, this study presents the sustainability assessment of rural establishments in those territories, aiming at checking the impact results against current local agricultural settings. The main results point out that, in general, the ecological dimensions of sustainability, such as Landscape Ecology and Atmosphere, Water, and Soil quality indicators, show adequate field conditions, seemingly not yet negatively affected by inputs and natural resources pressure increases, predicted as important potential impacts. On the other hand, most valuable positive consequences expected from the socio-environmental impact assessments, such as improved Socio-cultural Values and Management & Administration indicators, are still opportunities to be realized, if sustainable local rural development is to occur under the emerging agro-energy scenario

Conservação e melhoramento genético da pimenteira-do-reino (Piper nigrum L.) em associação com as técnicas de biotecnologia.

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