Vacuum polarization by topological defects in de Sitter spacetime

In this paper we investigate the vacuum polarization effects associated with a massive quantum scalar field in de Sitter spacetime in the presence of gravitational topological defects. Specifically we calculate the vacuum expectation value of the field square, $$. Because this investigation has been developed in a pure de Sitter space, here we are mainly interested on the effects induced by the presence of the defects.Comment: Talk presented at the 1st. Mediterranean Conference on Classical and Quantum Gravity (MCCQG

Observações preliminares sobre a transmissão de oncocercose no rio Toototobi, Amazonas, Brasil

Em dezembro de 1975 os autores estudaram vários fatores que influenciam a transmissão de Onchocerca volvulus ao norte do Amazonas, no rio Toototobi. Observaram que a densidade de microfilarias de O. volvulus era maior no tronco do que nos membros de dois índios Yanomama examinados. Foram capturados três espécies antropófilas de Simuliidae, provisoriamente denominados Simulium sp. A, S.sp. B e S.sp. C. A primeira espécie foi coletada em grande número no começo da tarde, atacando o homem. O encontro de larvas salsichóides em espécimes naturalmente infetados e o sucesso da infecção experimental de espécimes selvagens com microfilarias de O. volvulus que desenvolveram até o final do estágio salsichóide, sugerem que o provável vetor de oncocercose nesta área é o Simulium sp. A.Preliminary studies on various factors influencing the transmission of onchocerciasis were made in December 1975 on the river Toototobi in northern Amazonas. Microfilariae of O. volvulus were more abundant in the trunk than in the limbs of two Yanomama indian volunteers. Three anthrophilic species of Simuliidae were captured and have been temporarily nemaed as Simulium sp.A., sp.B., sp.C. until a definitive identification is made. Only the former species was abundant biting mainly in the early afternoon. The finding of sausage larva in a naturally infected fly and the successful experimental infection of wild flies with microfilariae of O. volvulus, which subsequently developed to the late sausage stage, suggest that Simulium sp.A is a probable vector of onchocerciasis in the area

Nonrelativistic Quantum Analysis of the Charged Particle-Dyon System on a Conical Spacetime

In this paper we develop the nonrelativistic quantum analysis of the charged particle-dyon system in the spacetime produced by an idealized cosmic string. In order to do that, we assume that the dyon is superposed to the cosmic string. Considering this peculiar configuration {\it conical} monopole harmonics are constructed, which are a generalizations of previous monopole harmonics obtained by Wu and Yang(1976 {\it Nucl. Phys. B} {\bf 107} 365) defined on a conical three-geometry. Bound and scattering wave functions are explicitly derived. As to bound states, we present the energy spectrum of the system, and analyze how the presence of the topological defect modifies obtained result. We also analyze this system admitting the presence of an extra isotropic harmonic potential acting on the particle. We show that the presence of this potential produces significant changes in the energy spectrum of the system.Comment: Paper accepted for publication in Classical and Quantum Gravit

Electrostatic in Reissner-Nordstrom space-time with a conical defect

We calculate the electrostatic potential generated by a point charge in the space-time of Reissner-Nordstrom with a conical defect. An expression for the self-energy is also presented.Comment: 7 pages, LATEX fil

Análise de envoltória de dados para avaliação de eficiência e caracterização de tipologias em agricultura: um estudo de caso.

Este artigo usa Análise de Envoltória de Dados (DEA) para medir a eficiência de uma amostra de agricultores de Holambra, município do Estado de São Paulo

Olympic ranking based on a zero sum gains DEA model.

It is usual to rank the participant countries in the Olympic Games in accordance with the number of medals they have won. An alternative ranking is suggested in this paper. This ranking is based on each country's ability to win medals in relation to its available resources. This is an efficiency that can be measured with the help of data envelopment analysis (DEA) for which two models exist: the traditional DEA model, that takes into account variable returns to scale, and a DEA model based on the premise that the sum of the gains is zero (constant sum of outputs). It is the latter that is developed in this paper

Solving Four Dimensional Field Theories with the Dirichlet Fivebrane

The realization of ${\cal N}=2$ four dimensional super Yang-Mills theories in terms of a single Dirichlet fivebrane in type IIB string theory is considered. A classical brane computation reproduces the full quantum low energy effective action. This result has a simple explanation in terms of mirror symmetry.Comment: Final version to appear in Phys. Rev.

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