14,417 research outputs found
Valence-bond theory of highly disordered quantum antiferromagnets
We present a large-N variational approach to describe the magnetism of
insulating doped semiconductors based on a disorder-generalization of the
resonating-valence-bond theory for quantum antiferromagnets. This method
captures all the qualitative and even quantitative predictions of the
strong-disorder renormalization group approach over the entire experimentally
relevant temperature range. Finally, by mapping the problem on a hard-sphere
fluid, we could provide an essentially exact analytic solution without any
adjustable parameters.Comment: 5 pages, 3 eps figure
Factorisation properties of the strong product
We investigate a number of factorisation conditions in the frame- work of sets of probability measures, or coherent lower previsions, with finite referential spaces. We show that the so-called strong product constitutes one way to combine a number of marginal coherent lower previsions into an independent joint lower prevision, and we prove that under some conditions it is the only independent product that satisfies the factorisation conditions
Constraining nonstandard neutrino-quark interactions with solar, reactor and accelerator data
We present a reanalysis of nonstandard neutrino-down-quark interactions of
electron and tau neutrinos using solar, reactor and accelerator data. In
addition updating the analysis by including new solar data from SNO phase III
and Borexino, as well as new KamLAND data and solar fluxes, a key role is
played in our analysis by the combination of these results with the CHARM data.
The latter allows us to better constrain the axial and axial-vector electron
and tau-neutrino nonstandard interaction parameters characterizing the
deviations from the Standard Model predictions.Comment: 11 pages, 6 figures, 2 tables, typo corrected in Figure 2, version
published in Phys. Rev.
Digital image processing and enhancement of gravity data as an aid to the definition of the structural framework of the north Tucano-Jatobá basins, Northeastern Brazil
Técnicas de processamento digital de imagens foram aplicadas a dados gravimétricos visando melhorar definição das principais feições estruturais na porção norte do Rift Recôncavo-Tucano-Jatobá. Os processamentos utilizados incluíram: (a) conversão de dados Bouguer e residual-Bouguer, no formato de grids, em imagens realçadas; (b) geração de composições falsa cor híbridas e (c) geração de modelos de elevação digital com visão em perspectiva. A análise integrada desse conjunto de dados permitiu reconhecer feições lineares e sutis variações espaciais nos dados gravimétricos, as quais foram associadas a unidades tectónicas no contexto do rift, tais como: plataformas em rampa, baixos e altos estruturais, horsts, grabens e falhas de borda.Digitally processed and enhanced gravity data in raster format were used to improve the definition of the main structural features in the northern part of the Reconcavo-Tucano-Jatoba Rift. Image processing techniques included: (a) conversion of Bouguer and residual-Bouguer gridded data into contrast-enhanced gray-level images; (b) generation of enhanced hybrid pseudo-color composites; and (c) generation of a gravity digital elevation model in perspective views. The integrated analysis of this dataset permitted the recognition of subtle trends and intensity-related spatial variations in gravity data, tentatively related to the following tectonic units of the RTJ Rift: ramp platforms, structural lows and highs, along-length horsts, grabens, faulted borders and extensional faults
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