Global aspects of gravitomagnetism

We consider global properties of gravitomagnetism by investigating the gravitomagnetic field of a rotating cosmic string. We show that although the gravitomagnetic field produced by such a configuration of matter vanishes locally, it can be detected globally. In this context we discuss the gravitational analogue of the Aharonov-Bohm effect.Comment: 10 pages - Typeset using REVTE

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

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

Vacuum polarization for neutral particles in 2+1 dimensions

In 2+1 dimensions there exists a duality between a charged Dirac particle coupled minimally to a background vector potential and a neutral one coupled nonminimally to a background electromagnetic field strength. A constant uniform background electric current induces in the vacuum of the neutral particle a fermion current which is proportional to the background one. A background electromagnetic plane wave induces no current in the vacuum. For constant but nonuniform background electric charge, known results for charged particles can be translated to give the induced fermion number. Some new examples with infinite background electric charge are presented. The induced spin and total angular momentum are also discussed.Comment: REVTeX, 7 pages, no figur

Diagnóstico socioeconômico do Projeto de Reflorestamento Econômico Consorciado e Adensado - RECA.

Este trabalho visa analisar as variáveis que influenciam no modelo atual de exploração utilizado no Reca, tais como: origem, experiência dos produtores, crédito financeiro, documentação das propriedades, caracterização e disponibilidade de mão-de-obra na propriedade.bitstream/CPAF-AC/1555/1/cirtec20.pd

Sistemas de manejo de solo litorâneo cultivado com cajueiro anão precoce.

O cultivo do cajueiro (Anacardium occidentale L.) e bastante expressivo nos solos dos tabuleiros costeiros da regiao Nordeste Ocidental, em face da sua rusticidade e adaptabilidade as condicoes edafoclimaticas locais. A regiao litoranea do Ceara e constituida, igualmente, de solos arenosos com problemas de deficiencia hidrica e baixa fertilidade natural, exigindo o conhecimento detalhado de suas caracteristicas para o desenvolvimento das tecnicas de manejo mais apropriadas. Nestas areas, verifica-se uma exploracao continua para atender a demanda de alimentos e de materia-prima para a agroindustria do caju, intensificada pelo uso crescente de mecanizacao em substituicao ao trabalho humano.bitstream/CNPAT-2010/2157/1/Pa-009.pd

Occurrence of geminivirus in tomato-producing areas in Submedio Sao Francisco.

This is the first report of geminivirus in Submedio Sao Francisco and reveals a wide dispersal of this virus that was previously described in the Federal District (1994) and state of Sao Paulo (1997), Minas Gerais (1996) and Bahia (1996).Suplemento. Edição dos Resumos do 30 Congresso Brasileiro de Fitopatologia, Poços de Caldas, 1997