Classical diffusion in double-delta-kicked particles

We investigate the classical chaotic diffusion of atoms subjected to {\em pairs} of closely spaced pulses (`kicks) from standing waves of light (the $2\delta$-KP). Recent experimental studies with cold atoms implied an underlying classical diffusion of type very different from the well-known paradigm of Hamiltonian chaos, the Standard Map. The kicks in each pair are separated by a small time interval $\epsilon \ll 1$, which together with the kick strength $K$, characterizes the transport. Phase space for the $2\delta$-KP is partitioned into momentum `cells' partially separated by momentum-trapping regions where diffusion is slow. We present here an analytical derivation of the classical diffusion for a $2\delta$-KP including all important correlations which were used to analyze the experimental data. We find a new asymptotic ($t \to \infty$) regime of `hindered' diffusion: while for the Standard Map the diffusion rate, for $K \gg 1$, $D \sim K^2/2[1- J_2(K)..]$ oscillates about the uncorrelated, rate $D_0 =K^2/2$, we find analytically, that the $2\delta$-KP can equal, but never diffuses faster than, a random walk rate. We argue this is due to the destruction of the important classical `accelerator modes' of the Standard Map. We analyze the experimental regime $0.1\lesssim K\epsilon \lesssim 1$, where quantum localisation lengths $L \sim \hbar^{-0.75}$ are affected by fractal cell boundaries. We find an approximate asymptotic diffusion rate $D\propto K^3\epsilon$, in correspondence to a $D\propto K^3$ regime in the Standard Map associated with 'golden-ratio' cantori.Comment: 14 pages, 10 figures, error in equation in appendix correcte

Theory of 2δ\delta-kicked Quantum Rotors

We examine the quantum dynamics of cold atoms subjected to {\em pairs} of closely spaced $\delta$-kicks from standing waves of light, and find behaviour quite unlike the well-studied quantum kicked rotor (QKR). Recent experiments [Jones et al, {\em Phys. Rev. Lett. {\bf 93}, 223002 (2004)}] identified a regime of chaotic, anomalous classical diffusion. We show that the corresponding quantum phase-space has a cellular structure, arising from a unitary matrix with oscillating band-width. The corresponding eigenstates are exponentially localized, but scale with a fractional power, $L \sim \hbar^{-0.75}$, in contrast to the QKR for which $L \sim \hbar^{-1}$. The effect of inter-cell (and intra-cell) transport is investigated by studying the spectral fluctuations with both periodic as well as `open' boundary conditions.Comment: 12 pages with 14 figure

Origin of strong scarring of wavefunctions in quantum wells in a tilted magnetic field

The anomalously strong scarring of wavefunctions found in numerical studies of quantum wells in a tilted magnetic field is shown to be due to special properties of the classical dynamics of this system. A certain subset of periodic orbits are identified which are nearly stable over a very large interval of variation of the classical dynamics; only this subset are found to exhibit strong scarring. Semiclassical arguments shed further light on why these orbits dominate the experimentally observed tunneling spectra.Comment: RevTeX, 5 page

Análise multitemporal da Área de Proteção Ambiental de Belém e Parque Ambiental de Belém.

Mesmo com mecanismos legais que amparam legalmente as unidades de proteção, ainda assim, as restrições que a legislação, vigente desde julho do ano 2000, impõe através do Sistema Nacional de Unidades de Conservação SNUC, é notável a ameaça aos reservatórios de abastecimento de água do Parque Ambiental de Belém, assim como aos recursos florestais da Área de Proteção Ambiental, devido a intensa pressão exercida no entorno e no interior das unidades por meio de habitações clandestinas e atividades ilegais. Contudo, fez-se necessário a utilização de técnicas e produtos do sensoriamento remoto para que fosse possível a identificação, entre os anos de 1984 a 2008, dos efeitos da pressão urbana sobre os recursos ambientais das unidades supracitadas

Semiclassical theory of magnetotransport through a chaotic quantum well

We develop a quantitative semiclassical formula for the resonant tunneling current through a quantum well in a tilted magnetic field. It is shown that the current depends only on periodic orbits within the quantum well. The theory explains the puzzling evolution of the tunneling spectra near a tilt angle of $30^{\circ}$ as arising from an exchange bifurcation of the relevant periodic orbits.Comment: 4 pages, RevTeX, epsf, 2 PostScript Figures (1 with color

Improved sensitivity of H.E.S.S.-II through the fifth telescope focus system

The Imaging Atmospheric Cherenkov Telescope (IACT) works by imaging the very short flash of Cherenkov radiation generated by the cascade of relativistic charged particles produced when a TeV gamma ray strikes the atmosphere. This energetic air shower is initiated at an altitude of 10-30 km depending on the energy and the arrival direction of the primary gamma ray. Whether the best image of the shower is obtained by focusing the telescope at infinity and measuring the Cherenkov photon angles or focusing on the central region of the shower is a not obvious question. This is particularly true for large size IACT for which the depth of the field is much smaller. We address this issue in particular with the fifth telescope (CT5) of the High Energy Stereoscopic System (H.E.S.S.); a 28 m dish large size telescope recently entered in operation and sensitive to an energy threshold of tens of GeVs. CT5 is equipped with a focus system, its working principle and the expected effect of focusing depth on the telescope sensitivity at low energies (50-200 GeV) is discussed.Comment: In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil

Dinâmica espectro-temporal MODIS em plantios de paricá (Schizolobium parahyba var. amazonicum (Huber ex. Ducke) Barneby) associada a diferentes condições hídricas do solo na Amazônia brasileira.

As características de absorção e reflectâncias nas faixas do vermelho e infravermelho próximo em dosséis, tanto de plantios como de vegetação natural, auxiliam na identificação de respostas espectrais em diversas condições de tempo e clima. Objetivou-se avaliar o comportamento espectral em plantios de paricá (Schizolobium parahyba var. amazonicum (Huber ex Ducke) Barneby) nos períodos de maior e de menor oferta hídrica, em Dom Eliseu, Pa. Foram analisados dados meteorológicos, balanços hídricos (CAD=300 mm) e respostas em NDVI (Normalized Difference Vegetation Index) extraídos do sensor MODIS (Moderate Resolution Imaging Spectroradiometer). As imagens-índice referentes aos meses de janeiro a dezembro foram processadas no software Envi 4.5 e retiradas amostras com base em dados de verdade terrestre. Os dados foram analisados estatisticamente, aplicando-se teste de média e análise de perfil por meio de técnicas uni e multivariadas. Verificou-se que existe tendência no vigor do paricá, com decrescimento de 0,85 a 0,68, nos meses de maior deficiência hídrica, em nível de significância de 5 %. Conclui-se que o NDVI respondeu significativamente à condição hídrica do solo, em plantios de paricá, no Estado do Pará

Avaliação da produtividade de girassol semeado em janeiro em Pelotas - RS.

Com o objetivo de avaliar a produtividade de girassol foram realizados dois experimentos na safrinha, experimento 1 (2008) e experimento 2 (2009). Os experimentos foram conduzidos na área experimental da Embrapa Clima Temperado, com delineamento experimental em blocos casualizados com quatro repetições. A produtividade média do experimento 1 foi de 1190 kg.ha-1, onde foram avaliados os genótipos: Agrobel 960, Aguará 3, Embrapa 122, BRHS 01, Hélio 358 e M 733.No experimento 2, onde foram avaliados os genótipos Agrobel 962, Aguará 4, BRHS 01, Hélio 251, MG 2, Olisum 3 e Zenit, obteve-se produtividade média de 379 kg.ha-1. A diferença na produtividade média entre os experimentos, foi devida as diferentes condições climáticas ocorridas durante a execução dos dois experimentos, principalmente após a floração na fase de enchimento de aquênio, onde as precipitações ocorridas nessa fase foram diferentes, com 4,8 mm no experimento 2 ( 2009) e 135,9 mm no experimento 1 (2008)

Weight-length relationship, condition factor and blood parameters of farmed Cichla temensis Humboldt, 1821 (Cichlidae) in central Amazon.

Farming of native carnivore fish species has drawn attention due to their promising use in aquaculture. Among these species, tucunaré of the genus Cichla stand out, them being of high economical interest for sport fishing and Amazon's industry of ornamental fish. The present study describes the weight-length relationship (WLR), relative condition factor (Kn), red blood cell parameters, thrombocytes and leukocytes count of Cichla temensis Humboldt, 1821, farmed in central Amazon. Fish that underwent food training during fingerling culture received extruded ration containing 45% of crude protein during fattening, and had Kn with values from 0.925-1.199, which indicated good health condition during the culture. The equation obtained from the WLR was W = 0.0073Lt3.1435, indicating an isometric growth, which is the desirable for fish of fish farm. Red blood cell counts, total thrombocyte and leukocyte counts, hematocrit, hemoglobin concentration, mean corpuscular volume (MCV), concentration of mean corpuscular hemoglobin (MCHC), lymphocytes, monocytes and neutrophils had intra-specific variation. A significant (p<0.001) positive correlation of the red blood cells number with the hemoglobin concentration and hematocrit was found. These are the first sets of blood parameters for C. temensis and could be used as reference for comparison in further studies to evaluate the health status of this fish in different environments, because assessment of these parameters may be used as quick tool for diagnosing diseases, stress and malnutrition