A solution for galactic disks with Yukawian gravitational potential

We present a new solution for the rotation curves of galactic disks with gravitational potential of the Yukawa type. We follow the technique employed by Toomre in 1963 in the study of galactic disks in the Newtonian theory. This new solution allows an easy comparison between the Newtonian solution and the Yukawian one. Therefore, constraints on the parameters of theories of gravitation can be imposed, which in the weak field limit reduce to Yukawian potentials. We then apply our formulae to the study of rotation curves for a zero-thickness exponential disk and compare it with the Newtonian case studied by Freeman in 1970. As an application of the mathematical tool developed here, we show that in any theory of gravity with a massive graviton (this means a gravitational potential of the Yukawa type), a strong limit can be imposed on the mass (m_g) of this particle. For example, in order to obtain a galactic disk with a scale length of b ~ 10 kpc, we should have a massive graviton of m_g << 10^{-59} g. This result is much more restrictive than those inferred from solar system observations.Comment: 7 pages; 1 eps figure; to appear in General Relativity and Gravitatio

High-contrast observations of brown dwarf companion HR 2562 B with the vector Apodizing Phase Plate coronagraph

InstrumentationStars and planetary system

On-sky Performance Analysis of the Vector Apodizing Phase Plate Coronagraph on MagAO/Clio2

Stars and planetary systemsInstrumentatio

The Mass Profile and Shape of Bars in the Spitzer Survey of Stellar Structure in Galaxies (S4G): Search for an Age Indicator for Bars

Galaxie

Search for B^0 -> l^+ l^- at Belle

We report the results of a search for the decay B^0 -> e^+ e^-, mu^+ mu^- and e^{+-} mu^{-+} based on an analysis of 78 fb^{-1} of data collected by the Belle detector at KEKB. No candidate events have been found. Upper limits on the branching fractions are calculated at the 90% confidence level: B(B^0 -> e^+ e^-) mu^+ mu^-) e^{+-} mu^{-+})< 1.7 x 10^{-7}. A limit on the Pati-Salam leptoquark mass M_{LQ}> 46 TeV/c^2 is obtained at the 90% confidence level.Comment: 8 pages, 1 figure, submitted to Phys. Rev. D (RC

Vector-apodizing phase plate coronagraph: design, current performance, and future development [Invited]

Instrumentatio

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema