Vacuum Polarization for a Massless Spin-1/2 Field in the Global Monopole Spacetime at Nonzero Temperature

In this paper we present the effects produced by the temperature in the renormalized vacuum expectation value of the zero-zero component of the energy-momentum tensor associated with massless left-handed spinor field in the pointlike global monopole spacetime. In order to develop this calculation we had to obtain the Euclidean thermal Green function in this background. Because the expression obtained for the thermal energy density cannot be expressed in a closed form, its explicit dependence on the temperature is not completely evident. So, in order to obtain concrete information about its thermal behavior, we develop a numerical analysis of our result in the high-temperature limit for specific values of the parameter $\alpha$ which codify the presence of the monopole.Comment: 22 pages, LaTex format, 5 figure

Dilaton Gravity with a Non-minmally Coupled Scalar Field

We discuss the two-dimensional dilaton gravity with a scalar field as the source matter. The coupling between the gravity and the scalar, massless, field is presented in an unusual form. We work out two examples of these couplings and solutions with black-hole behaviour are discussed and compared with those found in the literature

Vacuum Polarization by a Magnetic Flux Tube at Finite Temperature in the Cosmic String Spacetime

In this paper we analyse the effect produced by the temperature in the vacuum polarization associated with charged massless scalar field in the presence of magnetic flux tube in the cosmic string spacetime. Three different configurations of magnetic fields are taken into account: $(i)$ a homogeneous field inside the tube, $(ii)$ a field proportional to $1/r$ and $(iii)$ a cylindrical shell with $\delta$-function. In these three cases, the axis of the infinitely long tube of radius $R$ coincides with the cosmic string. Because the complexity of this analysis in the region inside the tube, we consider the thermal effect in the region outside. In order to develop this analysis, we construct the thermal Green function associated with this system for the three above mentioned situations considering points in the region outside the tube. We explicitly calculate in the high-temperature limit, the thermal average of the field square and the energy-momentum tensor.Comment: 16 pages, 1 figur

Crescimento, desenvolvimento e rentabilidade do algodoeiro BRS 200 - marrom, irrigado.

Tendo como objetivo principal a avaliação dos efeitos de diferentes lâminas de irrigação sobre o algodoeiro BRS 200 - Marrom, no seu primeiro ano de ciclo, realizou-se este trabalho na Estação Experimental da Embrapa em Barbalha, CE, (latitude: 07?19?S, longitude: 39?18? W e altitude: 415,74 m). Os tratamentos testados foram T1 = 0,8; T2 = 1,0 e T3 = 1,2 da evapotranspiração da cultura, estimada através do balanço de energia baseado na razão de Bowen, correspondendo a lâminas de irrigação de 411,6; 514,5 e 617,4 mm, tendo-se avaliado o rendimento, alguns componentes de produção (percentagem de fibra, peso do capulho e peso de 100 sementes) e as características tecnológicas da fibra. Por fim, determinou-se a eficiência de uso de água e a eficiência econômica do sistema de produção. Foram estudadas as seguintes variáveis de crescimento (altura média de plantas, diâmetro caulinar, área foliar e a fitomassa da planta). O rendimento do algodão em caroço aumentou com o incremento da lâmina de irrigação, tendo a maior lâmina (617,4 mm) produzido 3.289,5 kg.ha-1 de algodão em rama. Os tratamentos aplicados não afetaram os componentes de produção (percentagem de fibra, massa média do capulho, massa de 100 sementes) e as características tecnológicas da fibra da cultivar BRS 200 ? Marrom. A eficiência de uso de água decresceu com o aumento da lâmina de irrigação, apresentando valores de 0,60; 0,55 e 0,53 kg.mm-3, para a aplicação de 411,6; 515,5 e 617,4 mm, respectivamente. Todos os tratamentos apresentaram resposta econômica positiva, com receita líquida por hectare de R$386,99; 732,89 e R$ 1.140,37 para os tratamentos que receberam as lâminas de 411,6; 515,5 e 617,4 mm, respectivamente, com uma relação benefício/custo de 1,59; 1,83 e 2,12, com base nos preços praticados. Observou-se diferenças significativa para todas as variáveis de crescimento estudadas, tendo o tratamento que recebeu lâmina de 617,4 mm apresentado uma maior resposta ao longo de todo o ciclo da cultura.Tese (Doutorado em Recursos Naturais) - Universidade Federal de Campina Grande, Centro de Tecnologia e Recursos Naturais, Campina Grande, PB. Orientador: Pedro Vieira de Azevedo; Orientador: Bernardo Barbosa da Silva

Aplicação fracionada de nitrogênio no algodoeiro irrigado.

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Yield of cotton cultivars under different irrigation depths in the Brazilian semi-arid region.

The objective of this study was to evaluate the effect of irrigation depths on seed cotton yield and water-use efficiency of cotton cultivars in the Brazilian semi-arid region. Field experiment was conducted during two consecutive years in the Apodi region, RN, using sprinkler irrigation. The experiment consisted of factorial combination in split-plots, composed of four irrigation depths (130; 100; 70 and 40% ETc and four cotton cultivars - FiberMax 993, BRS 286, BRS 336 and BRS 335), in randomized block design with 4 replicates. Data were evaluated by mean test (Tukey) and regression analysis. Considering the irrigation depths of 40% ETc, cotton yield was 48% lower compared to the higher irrigation depth (130% ETc). The higher water-use efficiency (0.69 kg m-3) was obtained with 70% ETc irrigation depth. The highest seed cotton yield was achieved with the higher water depth for all evaluated cultivars. Yield response factor (Ky) was equal to 0.632, 0.711, 0.784 and 0.858, for FiberMax 993, BRS 286, BRS 335 and BRS 336 cultivars, respectively. FiberMax 993 and BRS 286 cultivars presented the best performance, showing that they are more suitable for irrigated farming in the semi-arid region

Gravitation: Global Formulation and Quantum Effects

A nonintegrable phase-factor global approach to gravitation is developed by using the similarity of teleparallel gravity with electromagnetism. The phase shifts of both the COW and the gravitational Aharonov-Bohm effects are obtained. It is then shown, by considering a simple slit experiment, that in the classical limit the global approach yields the same result as the gravitational Lorentz force equation of teleparallel gravity. It represents, therefore, the quantum mechanical version of the classical description provided by the gravitational Lorentz force equation. As teleparallel gravity can be formulated independently of the equivalence principle, it will consequently require no generalization of this principle at the quantum level.Comment: Latex (IOP style), 14 pages, 3 figures. To appear in Classical and Quantum Gravit