Manifestation of chaotic behavior is found in an intrinsically quantum property. The entanglement process, quantitatively expressed in terms of the reduced density linear entropy, is studied for the N-atom Jaynes-Cummings model. For a given energy, initial conditions are prepared as minimum uncertainty wave packets centered at regular and chaotic regions of the classical phase space. We find for short times a faster increase in decoherence for the chaotic initial conditions as compared to regular ones, which have oscillatory increase. [S0031-9007(98)

Resumo A concentração de gases de efeito estufa (GEE) na atmosfera tem aumentado acentuadamente desde a revolução industrial, o que levou a intensificação do efeito estufa e consequentemente vem causando o aquecimento global. A análise espacial de tendências permite observar as mudanças no comportamento e determinar em quais regiões uma determinada variável vem sofrendo mudanças ao longo do tempo. Diante disso, o objetivo do presente trabalho foi analisar as tendências temporais da precipitação e da temperatura média no Brasil, utilizando o método Contextual Mann-Kendall (CMK), utilizando dados espacialmente distribuídos elaborados pelo Climatic Research Unit (CRU), entre os anos 1961 e 2011. A umidade relativa e a evapotranspiração foram analisadas no intuito de auxiliar na interpretação dos resultados da precipitação e temperatura. Os resultados mostraram tendências não significativas em mais de 70% do território brasileiro em todos os meses na precipitação, porém a temperatura média apresentou tendência positiva significativa em grande parte do Brasil ao longo de todo ano. Em geral, a evapotranspiração apresentou um comportamento diretamente proporcional à temperatura, enquanto que a umidade relativa apresentou comportamento inversamente proporcional. A continuidade dessas tendências poderá resultar em impactos na agricultura e no ciclo hidrológico, e consequentemente para a fauna e flora e para a população.

This study evaluated the effects of climate change on sugarcane yield, water use efficiency, and irrigation needs in southern Brazil, based on downscaled outputs of two general circulation models (PRECIS and CSIRO) and a sugarcane growth model. For three harvest cycles every year, the DSSAT/CANEGRO model was used to simulate the baseline and four future climate scenarios for stalk yield for the 2050s. The model was calibrated for the main cultivar currently grown in Brazil based on five field experiments under several soil and climate conditions. The sensitivity of simulated stalk fresh mass (SFM) to air temperature, CO 2 concentration [CO 2 ] and rainfall was also analyzed. Simulated SFM responses to [CO 2 ], air temperature and rainfall variations were consistent with the literature. There were increases in simulated SFM and water usage efficiency (WUE) for all scenarios. On average, for the current sugarcane area in the State of São Paulo, SFM would increase 24 % and WUE 34 % for rainfed sugarcane. The WUE rise is relevant because of the current concern about water supply in southern Brazil. Considering the current technological improvement rate, projected yields for 2050 ranged from 96 to 129 tha −1 , which are respectively 15 and 59 % higher than the current state average yield.Climatic Change (2013) 117:227-239 DOI 10.1007/s10584-012-0561-

The rise in linear entropy of a subsystem in the N -atom JaynesCummings model is shown to be strongly influenced by the shape of the classical orbits of the underlying classical phase space: we find a one-to-one correspondence between maxima (minima) of the linear entropy and maxima (minima) of the expectation value of atomic excitation J z . Since the expectation value of this operator can be viewed as related to the orbit radius in the classical phase space projection associated to the atomic degree of freedom, the proximity of the quantum wave packet to this atomic phase space borderline produces a maximum rate of entanglement. The consequence of this fact for initial conditions centered at periodic orbits in regular regions is a clear periodic recoherence. For chaotic situations the same phenomenon (proximity of the atomic phase space borderline) is in general responsible for oscillations in the entanglement properties. PACS numbers: 05.45.Mt, 32.80.Qk 1 I INTRODUCTIONThe importance of studying in detail the decoherence process is twofold. Firstly it may be viewed as a key to the understanding of some of the striking differences between the quantum and classical description of the world such as "the non existence at the classical level of the majority of states allowed by quantum mechanics" [1]. The decoherence process is believed to be the agent which eliminates interference between two or more macroscopically separated localized states [2]. Secondly, given the impressive technological advances in several experimental areas (Quantum Optics, Condensed Matter and Atomic Physics, etc.), it is nowadays possible to realize a system of two interacting degrees of freedom and watch the time evolution of the corresponding entanglement process [3]. It is therefore also of importance to understand the entanglement process in simple Hamiltonian systems. Two degrees of freedom Hamiltonian systems often present a very rich dynamics which in many cases is not yet completely understood from a general point of view. In particular, if the interaction is nonlinear the system may present chaotic behavior in the classical limit. The consequences of this fact to the quantum dynamics is yet an unsettled issue. A step in this direction was taken a few years ago, as it was conjectured that "the rate of entropy production can be used as an intrinsically quantum test of the chaotic versus regular nature of the evolution" [4]. The idea has been tested in some models [5,6]. More specifically, in the context of the N-atom Jaynes-Cummings model, the reduced density linear entropy (or idempotency defect) has been used as a measure of the entanglement of the quantum subsystems. For a given classical energy, initial conditions for the quantum states are prepared as coherent wave packets centered at regular and chaotic regions of the classical phase space. For short times, a fast increase in decoherence for chaotic initial conditions is found when compared to regular ones. Typically the linear entropy in this model rises from zero to...

No abstract