Charged Rotating Black Hole Formation from Thin Shell Collapse in Three Dimensions

The thin shell collapse leading to the formation of charged rotating black holes in three dimensions is analyzed in the light of a recently developed Hamiltonian formalism for these systems. It is proposed to demand, as a way to reconcile the properties of an infinitely extended solenoid in flat space with a magnetic black hole in three dimensions, that the magnetic field should vanish just outside the shell. The adoption of this boundary condition results in an exterior solution with a magnetic field different from zero at a finite distance from the shell. The interior solution is also found and assigns another interpretation, in a different context, to the magnetic solution previously obtained by Cl\'{e}ment and by Hirschmann and Welch.Comment: 15 pages, no figures. Discussion on junction conditions and conclusions enlarged. Few references added. Final version for MPL

Fungos e micotoxinas em castanha do Brasil: manejo e alternativas de controle.

bitstream/item/83115/1/2012-307.pd

Noncommutative Black Holes and the Singularity Problem

A phase-space noncommutativity in the context of a Kantowski-Sachs cosmological model is considered to study the interior of a Schwarzschild black hole. Due to the divergence of the probability of finding the black hole at the singularity from a canonical noncommutativity, one considers a non-canonical noncommutativity. It is shown that this more involved type of noncommutativity removes the problem of the singularity in a Schwarzschild black hole.Comment: Based on a talk by CB at ERE2010, Granada, Spain, 6th-10th September 201

Entropic Gravity, Phase-Space Noncommutativity and the Equivalence Principle

We generalize E. Verlinde's entropic gravity reasoning to a phase-space noncommutativity set-up. This allow us to impose a bound on the product of the noncommutative parameters based on the Equivalence Principle. The key feature of our analysis is an effective Planck's constant that naturally arises when accounting for the noncommutative features of the phase-space.Comment: 12 pages. Version to appear at the Classical and Quantum Gravit

Rotating Dilaton Solutions in 2+1 Dimensions

We report a three parameter family of solutions for dilaton gravity in 2+1 dimensions with finite mass and finite angular momentum. These solutions are obtained by a compactification of vacuum solutions in 3+1 dimensions with cylindrical symmetry. One class of solutions corresponds to conical singularities and the other leads to curvature singularities.Comment: Accepted to be published in Gen. Rel. Grav., added reference

NSM CFRP laminates for the shear strengthening of high strength concrete beams

The effectiveness of the Near Surface Mounted (NSM) shear strengthening technique with Carbon Fiber Reinforced Polymer (CFRP) laminates applied in relatively high-strength concrete beams was assessed by experimental research. Six NSM shear strengthening configurations (three CFRP orientations and two levels of CFRP percentage) were applied in T cross section Reinforced Concrete (RC) beams with a steel stirrups percentage of 0.10% (ρsw = 0.10%). Four of these NSM configurations were also applied in beams with ρsw = 0.16%. The concrete of the beams had a compressive strength of 59.4 MPa at the age of beam tests. The main results of this experimental research are presented and analyzed in terms of the structural behaviour of the beams, failure modes and performance of the NSM technique with CFRP laminates. The results showed that NSM shear strengthening technique with CFRP laminates has a high performance in RC beams with high-strength concrete, not only in terms of increasing the load carrying capacity of the beams but also in mobilizing more effectively the tensile properties of the CFRP

Proposta de uma técnica de reforço ao corte com CFRP

As mais recentes técnicas de reforço ao corte de vigas de betão armado com materiais compósitos são apresentadas no presente trabalho, tomando como base alguns dos trabalhos experimentais efectuados até ao momento. Uma nova técnica de reforço ao corte baseada na inserção de laminados de CFRP no betão de recobrimento das faces laterais de vigas de betão armado é proposta. O desempenho desta técnica de reforço foi avaliado por intermédio de uma campanha de ensaios em vigas de betão armado. Os resultados obtidos nos ensaios realizados são analisados e interpretados

Assessment of the effectiveness of the NSM shear strengthening technique for deep T cross section RC beams

The effectiveness of the near surface mounted (NSM) technique with carbon fibre reinforced polymer (CFRP) laminates for the shear strengthening of reinforced concrete (RC) beams has been demonstrated during the last decade. Analytical and numerical research indicate that the NSM technique for the shear strengthening of RC beams can be more effective if the CFRP laminates are deeper installed into the slits. However, the depth of the slits is conditioned by the thickness of concrete cover of the lateral faces of the beam. Furthermore, relatively deep slits can only be executed, by maintaining an effective bond transfer length for the CFRP laminates crossing the shear crack, if the beam’s cross section is relatively high. Therefore, an experimental program composed of a series of RC beams of relatively high T cross section web, shear strengthened according to the NSM technique with CFRP laminates, was carried out. The experimental program is described and the main results are presented and discussed.Fundação para a Ciência e a Tecnologia (FCT