Gravity Seminar: Mikolaj Korzynski

Title: Optical Drift Effects In General Relativity

Abstract: I will discuss the redshift and the position drifts in general relativity, i.e. the temporal variations of the redshift and the position on the sky of a light source, as registered by an arbitrary observer. I will present the derivation of exact relativistic formulas for the drifts, in which they are expressed in terms of the kinematical variables characterising the motions of the source and the observer, i.e. their momentary 4-velocities and 4-accelerations, as well as the spacetime curvature along the line of sight. The formulas we derive are completely general and involve automatically all possible GR effects. They may be regarded as the counterpart of the Sachs optical equations for temporal variations of the standard observables. I will discuss their physical consequences, especially interesting in spacetimes with caustics, and their possible applications to the gravitational lensing theory, astrometry and cosmology. The talk should be accessible to anyone with a background in general relativity.