6,899 research outputs found

    Fermion Helicity Flip in Weak Gravitational Fields

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    The helicity flip of a spin-12{\textstyle \frac{1}{2}} Dirac particle interacting gravitationally with a scalar field is analyzed in the context of linearized quantum gravity. It is shown that massive fermions may have their helicity flipped by gravity, in opposition to massless fermions which preserve their helicity.Comment: RevTeX 3.0, 8 pages, 3 figures (available upon request), Preprint IFT-P.013/9

    Irrigated rice area estimation using remote sensing techniques: Project's proposal and preliminary results

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    The development of a methodology for annual estimates of irrigated rice crop in the State of Rio Grande do Sul, Brazil, using remote sensing techniques is proposed. The project involves interpretation, digital analysis, and sampling techniques of LANDSAT imagery. Results are discussed from a preliminary phase for identifying and evaluating irrigated rice crop areas in four counties of the State, for the crop year 1982/1983. This first phase involved just visual interpretation techniques of MSS/LANDSAT images

    Semiclassical approach to universality in quantum chaotic transport

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    The statistics of quantum transport through chaotic cavities with two leads is encoded in transport moments Mm=Tr[(tt)m]M_m={\rm Tr}[(t^\dag t)^m], where tt is the transmission matrix, which have a known universal expression for systems without time-reversal symmetry. We present a semiclassical derivation of this universality, based on action correlations that exist between sets of long scattering trajectories. Our semiclassical formula for MmM_m holds for all values of mm and arbitrary number of open channels. This is achieved by mapping the problem into two independent combinatorial problems, one involving pairs of set partitions and the other involving factorizations in the symmetric group.Comment: Published version. Changes in presentatio

    Avaliação do efeito cicatrizante da quitosana por aplicação tópica em ratos.

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    bitstream/CNPDIA-2009-09/11045/1/DOC29_2007.pd

    Executive report: Results of the IRGA-CNPq/INPE experimental project

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    A methodology for identifying and evaluating crop area with irrigated rice is described, using MSS-LANDSAT data. The maps of the spatial rice crop areas in the studied region are presented. The calculation of rice growing area from the LANDSAT images are included

    Multi Matrix Vector Coherent States

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    A class of vector coherent states is derived with multiple of matrices as vectors in a Hilbert space, where the Hilbert space is taken to be the tensor product of several other Hilbert spaces. As examples vector coherent states with multiple of quaternions and octonions are given. The resulting generalized oscillator algebra is briefly discussed. Further, vector coherent states for a tensored Hamiltonian system are obtained by the same method. As particular cases, coherent states are obtained for tensored Jaynes-Cummings type Hamiltonians and for a two-level two-mode generalization of the Jaynes-Cummings model.Comment: 24 page
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