Tuesday 16 September 2025, 16:00 - 17:00 in HG00.071
Jakob Hedicke (Radboud)
On the space of light rays
The space of all light rays in a spacetime was first studied by Roger Penrose in the context of twistor theory. In many cases it has interesting geometric properties that encode the causality of the spacetime. For instance, if the spacetime is globally hyperbolic, the space of light rays naturally has the structure of a smooth manifold and it can be equipped with a certain hyperplane distribution, called a contact structure. In the first part of this talk we will review the construction of these structures on the space of light rays and their relation to the causal properties of the spacetime. Afterwards we will focus on the connections to contact geometry, particularly the question of orderability of Legendrian isotopy classes.