Gravitational Lensing by Vector Perturbations

Perturbation theory is a useful tool used in cosmology to describe fluctuations in an almost-uniform universe. We focus on vector-type perturbations, and investigate their gravitational lensing effects. To begin, we study gravitational lensing by the Kerr metric, which we show can be seen as a vector+scalar perturbation of the Schwarzschild metric. We use our results to assess the E- and B- modes of rotating galaxies, and argue whether the perturbative contribution generated by the rotation may be measurable.