Método exploratório de indicadores de adoção de variedades melhoradas.

Neste boletim de pesquisa, é proposto um método exploratório para calcular os indicadores de adoção de variedades melhoradas, especialmente recomendado em caso de ausência de séries históricas acerca do processo de adoção. A quase ausência desses dados constitui o principal obstáculo à realização de estudos de adoção de variedades melhoradas na Embrapa. Portanto, o método proposto contribui ao tornar possível estudo dessa natureza a partir da coleta, em campo, de um conjunto mínimo de dados acerca do processo de adoção de variedades melhoradas. O método é composto por 12 indicadores de adoção, agrupados em três categorias principais: alcance, velocidade e eficiência. Embora o método proposto possa ser utilizado para lavouras temporárias e permanentes, a título de exemplo, e unicamente com este propósito, são calculados os indicadores de adoção de duas variedades de mandioca lançadas pela Embrapa: BRS Formosa e BRS Kiriris. Os indicadores foram elaborados por ocasião da submissão do projeto ?Impacto da pesquisa participativa do melhoramento genético da mandioca no bioma caatinga?, ao macroprograma 4 da Embrapa, sob a liderança da Embrapa Mandioca e Fruticultura.bitstream/item/100889/1/boletim-59-Finalizado-novamente-alterado.pd

Replica-symmetric solutions of a dilute Ising ferromagnet in a random field

We use the replica method in order to obtain an expression for the variational free energy of an Ising ferromagnet on a Viana-Bray lattice in the presence of random external fields. Introducing a global order parameter, in the replica-symmetric context, the problem is reduced to the analysis of the solutions of a nonlinear integral equation. At zero temperature, and under some restrictions on the form of the random fields, we are able to perform a detailed analysis of stability of the replica-symmetric solutions. In contrast to the behaviour of the Sherrington-Kirkpatrick model for a spin glass in a uniform field, the paramagnetic solution is fully stable in a sufficiently large random field

A method for evaluating models that use galaxy rotation curves to derive the density profiles

There are some approaches, either based on General Relativity (GR) or modified gravity, that use galaxy rotation curves to derive the matter density of the corresponding galaxy, and this procedure would either indicate a partial or a complete elimination of dark matter in galaxies. Here we review these approaches, clarify the difficulties on this inverted procedure, present a method for evaluating them, and use it to test two specific approaches that are based on GR: the Cooperstock-Tieu (CT) and the Balasin-Grumiller (BG) approaches. Using this new method, we find that neither of the tested approaches can satisfactorily fit the observational data without dark matter. The CT approach results can be significantly improved if some dark matter is considered, while for the BG approach no usual dark matter halo can improve its results.Comment: 11 pages, 2 figures, 4 tables. v2: diverse text improvements, no changes in the conclusions. Version accepted in MNRA

Quantum Baker Maps for Spiraling Chaotic Motion

We define a coupling of two baker maps through a pi/2 rotation both in position and in momentum. The classical trajectories thus exhibit spiraling, or loxodromic motion, which is only possible for conservative maps of at least two degrees of freedom. This loxodromic baker map is still hyperbolic, that is, fully chaotic. Quantization of this map follows on similar lines to other generalized baker maps. It is found that the eigenvalue spectrum for quantum loxodromic baker map is far removed from those of the canonical random matrix ensembles. An investigation of the symmetries of the loxodromic baker map reveals the cause of this deviation from the Bohigas-Giannoni-Schmit conjecture

Quantum revival patterns from classical phase-space trajectories

A general semiclassical method in phase space based on the final value representation of the Wigner function is considered that bypasses caustics and the need to root-search for classical trajectories. We demonstrate its potential by applying the method to the Kerr Hamiltonian, for which the exact quantum evolution is punctuated by a sequence of intricate revival patterns. The structure of such revival patterns, lying far beyond the Ehrenfest time, is semiclassically reproduced and revealed as a consequence of constructive and destructive interferences of classical trajectories.Comment: 7 pages, 6 figure