Applications of Geometrical Optics to the Kerr Metric. Analytical Results

The null tetrad formalism of geometrical optics is used to analyze the optical properties of images when light travels into the field of an axisymmetric system. The method is applied to the Kerr metric and analytical results obtained in the limit of weak field or low rotation. It is shown that counterrotating trajectories are focused by a larger amount than corotating trajectories and that the rotation of the body introduces a left-right asymmetry (with respect to the rotation axis) in the orientation of images. The formalism is also used to discuss the rotation of the polarization plane. Subject headings: gravitation - relativity