Black holes as D3-branes on Calabi-Yau threefolds

We show how an extremal Reissner-Nordstrom black hole can be obtained by wrapping a dyonic D3-brane on a Calabi-Yau manifold. In the orbifold limit T^6/Z_3, we explicitly show the correspondence between the solution of the supergravity equations of motion and the D-brane boundary state description of such a black hole.Comment: 14 pages, LaTex, minor corrections, version to appear on Phys. Lett.

A Lata de Lixo da História: Chanchada Política

Conversa com Roberto SchwarzEsta palestra, seguida de uma conversa entre o crítico literário Roberto Schwarz e o diretor teatral Sérgio de Carvalho, discutiu a peça A Lata de Lixo da História, relançada recentemente. Ocorreu durante o I Seminário Internacional Teatro e Sociedade organizado pela Companhia do Latão em 10 de setembro de 2014 e se deu após a leitura de algumas cenas, feita por atores do grupo

Las ideas fuera de lugar: algunas aclaraciones cuatro décadas después

Las ideas fuera de lugar:algunas aclaraciones cuatro décadas despuésRoberto Schwar

Roberto Schwarz

nul

Minimum representative root distribution sampling for calculating slope stability in Pinus radiata D.Don plantations in New Zealand

Background: Rainfall-triggered shallow landslides on steep slopes cause significant soil loss and can be hazards for property and people in many parts of the world. In New Zealand’s hill country, they are the dominant erosion process and are responsible for soil loss and subsequent impacts on regional water quality. Use of wide-spaced trees and afforestation with fast growing conifers are the primary land management tools in New Zealand to help control erosion and improve water quality. To decide where to implement erosion controls in the landscape requires determining the most susceptible places to these processes and models that incorporate how trees reinforce soils to understand if, and when, such treatments become effective. Methods: This paper characterises the mechanical properties of Pinus radiata D.Don roots (the common tree species used for afforestation in New Zealand) by means of field pullout tests and by measuring the root distribution at 360 degrees around trees. The Root Bundle Model (RBM) was used to calculate the root reinforcement. Statistical analysis was carried out to assess the statistical reduction coefficients of root reinforcement that depend on the number of measurements, used in geotechnical analysis to reduce the mean value of a parameter to a so-called characteristic value. Results: We show that to reach an effective level of root reinforcement, trees of 0.5 m DBH require a density of about 300 trees per hectare. Trees of this size are about 30 years of age across many sites and have generally reached the recommended conditions for clear-fell harvesting. The analysis of variance shows that 4 trees are the minimum number to be excavated to obtain sufficient root information to obtain less than 5% of error with a 95% of probability on the estimation of a design value of root reinforcement in accord with geotechnical standards. Conclusions: We found that the variability of lateral and basal root reinforcement does not limit the implementation of vegetation in slope stability models for Pinus radiata. We adopt for the first time the concept of a minimum sampling requirement and characteristic value, similarly to what is assumed for the value of effective soil cohesion in geotechnical guidelines for slope stability calculations

Interaction of moving D-branes on orbifolds

We use the boundary state formalism to study the interaction of two moving identical D-branes in the Type II superstring theory compactified on orbifolds. By computing the velocity dependence of the amplitude in the limit of large separation we can identify the nature of the different forces between the branes. In particular, in the Z_3 orbifold case we find a boundary state which is coupled only to the N=2 graviton multiplet containing just a graviton and a vector like in the extremal Reissner-Nordstr\"{o}m configuration. We also discuss other cases including $T_4/Z_2$.Comment: 15 pages, Revtex, no figure

Efeito da Lua e da maré na captura de peixes em uma planície de maré do setor Euhalino da Baia de Paranaguá,PR

Orientador:Henry Louis SpachMonografia(Bacharelado) - Universidade Federal do Paraná. Setor de Ciencias Biológicas. Curso de Graduaçao em Ciencias Biológica