Hans Ringström: Initial data on big bang singularities

The main purpose of the talk is to introduce a geometric notion of initial data on big bang singularities. The definition generalises previous notions and, given suitable assumptions, it can be argued that the conditions of the definition are necessary. After quoting a recent result of Andrés Franco Grisales concerning existence of developments corresponding to initial data on the singularity, the talk ends with a discussion of the regularity of the map from regular initial data to data on the singularity in a symmetric setting.