906 research outputs found

    Complete loop quantization of a dimension 1+2 Lorentzian gravity theory

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    De Sitter Chern-Simons gravity in D = 1 + 2 spacetime is known to possess an extension with a Barbero-Immirzi like parameter. We find a partial gauge fixing which leaves a compact residual gauge group, namely SU(2). The compacticity of the residual gauge group opens the way to the usual LQG quantization techniques. We recall the exemple of the LQG quantization of SU(2) CS theory with cylindrical space topology, which thus provides a complete LQG of a Lorentzian gravity model in 3-dimensional space-time.Comment: Loops11 - Madrid - 2011 (4 pages, Latex

    Six new species of the widespread Brazilian millipede genus Eucampesmella (Polydesmida: Chelodesmidae)

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    This study concerns the diplopod genus Eucampesmella Schubart, 1955, widespread in Brazil. After this work, the genus includes 12 valid species, and three incertae sedis: E. pugiuncula (Schubart, 1946), E. brunnea Kraus, 1959 and E. schubarti Kraus, 1957. The type-species, Eucampesmella tricuspis (Attems, 1931), is redescribed based on the holotype, and the following six new Brazilian species are added: Eucampesmella macunaima sp. nov. from the states of Rondônia, Pará, and Piauí; E. capitu sp. nov. from the states of Piauí and Paraíba; E. brascubas sp. nov. from the state of Sergipe; E. iracema sp. nov. from the state of Pernambuco; E. pedrobala sp. nov. from the state of Ceará; and E. lalla sp. nov. from the state of Rio Grande do Norte. Furthermore, E. lartiguei ferrii (Schubart, 1956) is recognized as a junior synonym of E. lartiguei lartiguei (Silvestri, 1897), which also had its status changed, and E. sulcata (Attems, 1898) is revalidated, prevailing under the name Leptodesmus tuberculiporus Attems, 1898. In addition, drawings, diagnoses, and distribution maps for all species of the genus are provided

    Brazilian Agroforestry Systems for Cattle and Sheep

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    Agroforestry systems for animal husbandry, including integrated crop-livestock-forest systems (ICLF) are rather diversified in the five Brazilian regions. They present several technical, environmental and socioeconomic benefits. However they are not broadly adopted, mainly because of their higher complexity compared with traditional systems as well as a certain lack of understanding by farmers regarding their benefits. To change this situation, in the last five years, the Brazilian government has directed financial resources for credit as well as for research and technology transfer addressing ICLF systems, including good agricultural practices and mitigation of greenhouse gases emissions. The goal is to improve competitiveness of the Brazilian agribusiness sector

    Quantization of Lorentzian 3d Gravity by Partial Gauge Fixing

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    D = 2+1 gravity with a cosmological constant has been shown by Bonzom and Livine to present a Barbero-Immirzi like ambiguity depending on a parameter. We make use of this fact to show that, for positive cosmological constant, the Lorentzian theory can be partially gauge fixed and reduced to an SU(2) Chern-Simons theory. We then review the already known quantization of the latter in the framework of Loop Quantization for the case of space being topogically a cylinder. We finally construct, in the same setting, a quantum observable which, although non-trivial at the quantum level, corresponds to a null classical quantity.Comment: Notation defect fixed on pages 5 (bottom) and 6 (around Eqs. 3.1)-- 19 pages, Late
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