Göttingen 2025 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

GR: Fachverband Gravitation und Relativitätstheorie

GR 5: CQG II

GR 5.1: Talk

Tuesday, April 1, 2025, 16:15–16:35, ZHG007

Circular light rays in a general-relativistic medium — •Volker Perlick — Faculty 1, University of Bremen

In the 1970s Marek Abramowicz introduced a potential on spherically symmetric and static spacetimes whose corresponding equipotential surfaces he called the ``relativistic Von Zeipel cylinders'' because they are the relativistic analogues of the Von Zeipel cylinders known from Newtonian gravity. A characteristic feature of this potential, and of its generalisation to axisymmetric and stationary spacetimes which was introduced a few years later, is in the fact that its critical points give the location of circular lightlike geodesics. In this talk I will discuss a further generalisation of this potential whose critical points are the circular light rays in an isotropic medium. The medium may be non-dispersive or dispersive. The case of a cold plasma will be treated in particular. With the help of this potential several known theorems on the existence or non-existence of circular light rays can be extended from the case of light propagation in vacuum to the case of light propagation in a medium.