20 resultados para power spectrum


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We study soft limits of correlation functions for the density and velocity fields in the theory of structure formation. First, we re-derive the (resummed) consistency conditions at unequal times using the eikonal approximation. These are solely based on symmetry arguments and are therefore universal. Then, we explore the existence of equal-time relations in the soft limit which, on the other hand, depend on the interplay between soft and hard modes. We scrutinize two approaches in the literature: the time-flow formalism, and a background method where the soft mode is absorbed into a locally curved cosmology. The latter has been recently used to set up (angular averaged) 'equal-time consistency relations'. We explicitly demonstrate that the time-flow relations and 'equal-time consistency conditions'are only fulfilled at the linear level, and fail at next-to-leading order for an Einstein de-Sitter universe. While applied to the velocities both proposals break down beyond leading order, we find that the 'equal-time consistency conditions'quantitatively approximates the perturbative results for the density contrast. Thus, we generalize the background method to properly incorporate the effect of curvature in the density and velocity fluctuations on short scales, and discuss the reasons behind this discrepancy. We conclude with a few comments on practical implementations and future directions.

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The purpose of this study is to characterize the geological subsurface structure of the diabase sill of the Paraná Magmatic Province intruded in the Itararé Group, located near the city of Limeira, in the east-central region of São Paulo state. The magnetometric method served as an important tool defining the igneous body in view of the great contrast between the physical properties of the diabase sill and the host sandstones. Previous cartographic data signaled in region a possible lateral continuity in subsurface, of the various sills that occur in the region. However, the magnetic data obtained herein indicate that the area of occurrence of this body is very restricted and independent of the others observed in the region. The analysis of the radial average power spectrum obtained allowed determine the interval of number of waves adequate for the separation of shallow and deep sources, and thus conclude that the sill of the Limeira region is located more than 100 m deep.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)