Fourier Eigenfunctions, Uncertainty Gabor Principle and Isoresolution Wavelets

Shape-invariant signals under Fourier transform are investigated leading to a class of eigenfunctions for the Fourier operator. The classical uncertainty Gabor-Heisenberg principle is revisited and the concept of isoresolution in joint time-frequency analysis is introduced. It is shown that any Fourier eigenfunction achieve isoresolution. It is shown that an isoresolution wavelet can be derived from each known wavelet family by a suitable scaling.Comment: 6 pages, XX Simp\'osio Bras. de Telecomunica\c{c}\~oes, Rio de Janeiro, Brazil, 2003. Fixed typo

Chaos and a Resonance Mechanism for Structure Formation in Inflationary Models

We exhibit a resonance mechanism of amplification of density perturbations in inflationary mo-dels, using a minimal set of ingredients (an effective cosmological constant, a scalar field minimally coupled to the gravitational field and matter), common to most models in the literature of inflation. This mechanism is based on the structure of homoclinic cylinders, emanating from an unstable periodic orbit in the neighborhood of a saddle-center critical point, present in the phase space of the model. The cylindrical structure induces oscillatory motions of the scales of the universe whenever the orbit visits the neighborhood of the saddle-center, before the universe enters a period of exponential expansion. The oscillations of the scale functions produce, by a resonance mechanism, the amplification of a selected wave number spectrum of density perturbations, and can explain the hierarchy of scales observed in the actual universe. The transversal crossings of the homoclinic cylinders induce chaos in the dynamics of the model, a fact intimately connected to the resonance mechanism occuring immediately before the exit to inflation.Comment: 4 pages. This essay received an Honorable Mention from the Gravity Research Foundation, 1998-Ed. To appear in Mod. Phys. Lett.

Cenários de desenvolvimento sustentável no Pantanal em função de tendências hidroclimáticas.

Nesta feita uma análise prospectiva do futuro hidrológico do Pantanal sob a perspectiva de dados pretéritos, da mudança do clima com base em relações entre o nível máximo do Rio Paraguai, interação oceano-atmosfera e precipitação na América do Sul. A cenarização hidroclimática, incluindo a componente humana, permite ainda identificar adaptações e oportunidades para as próximas décadas, também em função de mudanças e tendências da economia mundial.bitstream/CPAP-2009-09/56873/1/DOC98.pd

Rotation intrinsic spin coupling--the parallelism description

For the Dirac particle in the rotational system, the rotation induced inertia effect is analogously treated as the modification of the "spin connection" on the Dirac equation in the flat spacetime, which is determined by the equivalent tetrad. From the point of view of parallelism description of spacetime, the obtained torsion axial-vector is just the rotational angular velocity, which is included in the "spin connection". Furthermore the axial-vector spin coupling induced spin precession is just the rotation-spin(1/2) interaction predicted by Mashhoon. Our derivation treatment is straightforward and simplified in the geometrical meaning and physical conception, however the obtained conclusions are consistent with that of the other previous work.Comment: 10 pages, no figur

Silvicultura de cinco espécies arbóreas da Amazônia: indicações de usos de seus produtos madeireiros e não-madeireiros.

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Informações básicas sobre ecologia e silvicultura de cinco espécies arbóreas da Amazônia brasileira.

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Water productivity in function of the regulated deficit of irrigation in the phase of maturation of grape Apirênica in the Valley of the San Francisco.

The aim of this work was to evaluate the effects o f irrigation water depths and cut-off timing in the maturation stage of Superior Seedles s grape grown in the of the San Francisco River region , to obtain simultaneously maximum yields and water use efficiency

Teste de inibição da enzima acetilcolinesterase de compostos organofosforados com potencial ação fungicida na cultura de mamão (Carica papaya L.).

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