Seminário com o Gena S. Bisnovatyi-Kogan- 26 de junho de 2015 – 10h15min
O PROGRAMA DE PÓS-GRADUAÇÃO EM FÍSICA convida para o seminário:
Gravitational lensing*
Gena S. Bisnovatyi-Kogan
Space Research Institute, Russian Academy of Sciences
Russia and National Research Nuclear University MEPhI, Moscow, Russia
*Presença obrigatória para os alunos matriculados na disciplina seminários
Resumo:
After some historical remarks, we consider observational data on the gravitational lensing, different types of lensing: strong, weak, and microlensing, discovery of planets around distant stars by microlensing. We consider lensing with large deviation angles, when light passes close to the gravitational radius of the lens, and formation of weak relativistic rings. In the last part we consideran influence of plasma on the gravitational lensing. When a gravitating body is surrounded by a plasma, the lensing angle depends on the frequency of the electromagnetic wave, due to dispersion properties of plasma, in presence of a plasma inhomogeneity, and due to a gravity. The second effect leads, even in a uniform plasma, to a difference of the gravitational photon deflection angle from the vacuum case, and to its dependence on the photon frequency. Both effects are taken into account. Dependence of the lensing angle on the photon frequency in a homogeneous plasma resembles the properties of a refractive prism spectrometer, which strongest action is for longest radio waves. We have shown that the gravitational effect could be detected in the case of a hot gas in the gravitational field of a galaxy cluster.
Comments