Speaker: Volker Perlick (University of Bremen)

Title: Influence of a plasma on gravitational lensing in stationary axisymmetric spacetimes

Abstract: I review the known results on how a (cold, nonmagnetised, electron-ion) plasma influences the lensing features of a compact object modelled by a stationary axisymmetric metric. Among other things, I will give necessary and sufficient conditions for complete integrability of the ray equations, i.e., for the existence of a generalised Carter constant which allows to analytically calculate the shadow of such a compact object. The Kerr spacetime is treated as a particular example. - This talk is largely based on joint papers with Oleg Tsupko, Gennady Bisnovatyi-Kogan, Barbora Bezdekova and Jiri Bicak.