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

Relativistic Quantum Scattering on a Cone

We study the relativistic quantum mechanical scattering of a bosonic particle by an infinite straight cosmic string, considering the non-minimal coupling between the bosonic field and the scalar curvature. In this case, an effective two-dimensional delta-function interaction takes place besides the usual topological scattering and a renormalization procedure is necessary in order to treat the problem that appears in connection with the delta-function.Comment: 22 pages, LATEX fil

Black hole formation in bidimensional dilaton gravity coupled to scalar matter systems

This work deals with the formation of black hole in bidimensional dilaton gravity coupled to scalar matter fields. We investigate two scalar matter systems, one described by a sixth power potential and the other defined with two scalar fields containing up to the fourth power in the fields. The topological solutions that appear in these cases allow the formation of black holes in the corresponding dilaton gravity models.Comment: Latex, 9 pages. Published in Mod. Phys. Lett. A14 (1999) 268

Self-Forces on Electric and Magnetic Linear Sources in the Space-Time of a Cosmic String

In this paper we calculate the magnetic and electric self-forces, induced by the conical structure of a cosmic string space-time, on a long straight wire which presents either a constant current or a linear charge density. We also show how these self-forces are related by a Lorentz tranformation and, in this way, explain what two different inertial observers detect in their respective frames.Comment: 10 pages, LaTeX, to be published in Phys. Rev. D

Vacuum Polarization of Massless Spinor Field in Global Monopole Spacetime

We calculate the renormalized vacuum average of the energy-momentum tensor of massless left-handed spinor field in the pointlike global monopole spacetime using point-separation approach. The general structure of the vacuum average of the energy-momentum tensor is obtained and expressed in terms of $^{ren}$ component, explicit form of which is analyzed in great details for arbitrary solid angle deficit.Comment: 12 pages, REVTEX, print error was correcte

Produção de biomassa e CO2 equivalente em sistema agrossilvipastoril: uma aplicação da dinâmica de sistema.

Resumo: Os Sistemas Agroflorestais (SAFs) mostram-se como uma alternativa social e econômica às consequências da ação antrópica sobre o meio ambiente. Buscou-se verificar a dinâmica da produção de biomassa e o estoque de CO2 equivalente no SAF, em área de caatinga no estado do Ceará. A área de estudo compreendeu o SAF localizado na Fazenda Crioula, pertencente ao Centro Nacional de Pesquisa de Caprinos da Embrapa, estando situada no município de Sobral, CE. Utilizou-se como ferramenta de elaboração do modelo o software Vensim®. As simulações basearam-se na determinação de cenários para uso da terra (culturas agrícolas) e manejo da caatinga. Os resultados demonstraram que o sistema foi capaz agregar renda por meio da venda dos produtos agrícolas e a comercialização do CO2 equivalente caso existisse um mercado específico para o produtor. O modelo desenvolvido para SAF oriundo desta pesquisa mostrou-se capaz de contribuir com as pesquisas já desenvolvidas atualmente, bem como para a sustentabilidade e viabilidade desse modelo de produção, por meio da diversificação de atividades e produtos, favorecendo uma geração de renda mais harmônica no tempo. [Estimated of biomass and CO2 equivalent by an agrosilvopastoral system: through the system dynamics]. Abstract: Agroforestry Systems (SAF) are shown as an alternative to social and economic consequences of human action on the environment. We sought to determine the dynamics of biomass production and the stock of CO2 equivalent in the SAF, in an area of "caatinga" biome in the state of Ceará. The study area comprised the SAF in Crioula farm, belonging to the National Research Center of Embrapa Goats, being situated in the municipality of Sobral - CE. It was used as a tool for developing the model the software Vensim. The simulations were based on the determination of option settings land uses (agricultural crops) and management of ?caatinga?. The results showed that the system was able to add income by selling agricultural products and the commercialization of CO2 equivalent if there were a specific market for this producer. The model developed for this research come from SAF was able to contribute to the research already carried out today as well as to the sustainability and viability of this model of production through diversification of activities and products, promoting a more harmonious income generation in time.Edição dos Resumos do VII Congresso Brasileiro de Agroecologia, Fortaleza, CE, 12 a 16 dez. 2011