On the effective action of the vacuum photon splitting in Lorentz-violating QED

We consider one-loop radiative corrections from Lorentz- and CPT- violating extended QED to address the specific problem of finding explicitly an effective action describing amplitude of photon triple splitting. We show that it is not possible to find a nonzero photon triple splitting effective action, at least by using the derivative expansion method (at zero external momenta), up to leading order in the Lorentz- and CPT- violating parameter.Comment: 4 pages, version to appear in EP

Uso do software livre Solr para construção da camada de indexação e busca do módulo de consulta institucional do sistema Ainfo.

O mecanismo de indexação e busca textual Lucene (THE APACHE SOFTWARE FOUNDATION, 2010a) tem sido largamente utilizado em projetos open source em todo mundo. Entretanto, para o módulo de consulta do sistema Ainfo, objetivou-se encontrar soluções livres capazes de estender e melhorar os recursos originais da ferramenta Lucene, como: integração com bases de dados relacionais, recursos mais sofisticados de indexação e busca, e maior integração com a arquitetura Java EE (Java Platform, Enterprise Edition)

Shallow extra mixing in solar twins inferred from Be abundances

Lithium and beryllium are destroyed at different temperatures in stellar interiors. As such, their relative abundances offer excellent probes of the nature and extent of mixing processes within and below the convection zone. We determine Be abundances for a sample of eight solar twins for which Li abundances have previously been determined. The analyzed solar twins span a very wide range of age, 0.5-8.2 Gyr, which enables us to study secular evolution of Li and Be depletion. We gathered high-quality UVES/VLT spectra and obtained Be abundances by spectral synthesis of the Be II 313 nm doublet. The derived beryllium abundances exhibit no significant variation with age. The more fragile Li, however, exhibits a monotonically decreasing abundance with increasing age. Therefore, relatively shallow extra mixing below the convection zone is necessary to simultaneously account for the observed Li and Be behavior in the Sun and solar twins

On the stability of solutions of semilinear elliptic equations with Robin boundary conditions on Riemannian manifolds

We investigate existence and nonexistence of stationary stable nonconstant solutions, i.e. patterns, of semilinear parabolic problems in bounded domains of Riemannian manifolds satisfying Robin boundary conditions. These problems arise in several models in applications, in particular in Mathematical Biology. We point out the role both of the nonlinearity and of geometric objects such as the Ricci curvature of the manifold, the second fundamental form of the boundary of the domain and its mean curvature. Special attention is devoted to surfaces of revolution and to spherically symmetric manifolds, where we prove refined results

The solar, exoplanet and cosmological lithium problems

We review three Li problems. First, the Li problem in the Sun, for which some previous studies have argued that it may be Li-poor compared to other Suns. Second, we discuss the Li problem in planet hosting stars, which are claimed to be Li-poor when compared to field stars. Third, we discuss the cosmological Li problem, i.e. the discrepancy between the Li abundance in metal-poor stars (Spite plateau stars) and the predictions from standard Big Bang Nucleosynthesis. In all three cases we find that the "problems" are naturally explained by non-standard mixing in stars.Comment: Astrophysics and Space Science, in press. New version has one reference correcte

Instruções para a criação do besouro africano Onthophagus gazella em laboratório.

Onthophagus gazella; Besouro africano; Criação; Laboratório; Inseto; Entomologia.bitstream/item/138761/1/COT-33.pdfCNPGC

Dificuldades de professores de física em início de carreira

Neste trabalho, procuramos, através de uma pesquisa qualitativa, realizada por meio de entrevistas e narrativas, identificar as principais dificuldades encontradas por três professores de física em início de carreira. Percebemos nos casos estudados, que, ao se depararem com a realidade de sala de aula em suas primeiras experiências, os professores se chocam com questões básicas do ensino, como a indisciplina, a motivação dos estudantes, como se portar em sala e que, nos momentos iniciais, estas questões fazem parte do seu desenvolvimento profissional assim como muitas vezes determinam a continuidade ou não de alguns professores em suas carreiras. Apresentamos nossos dados, relacionando, classificando e analisando as principais dificuldades encontradas por estes professores, a luz de algumas teorias relacionadas à formação de professores