Jean-Baptiste Cadart: Initial data on the Big Bang singularity in the polarized T^2 and U(1)-symmetric vacuum cases.

Quiescent spacetimes are spacetimes for which the leading order asymptotes near the Big Bang singularity are converging. They are important examples in the search for understanding the nature of Big Bang singularities. Several notions of singular data determining specific quiescent spacetimes have already been provided in the literature. In the recent years though, Hans Ringström introduced the notion of initial data on the singularity, which has the purpose to unify these notions of data on the singularity found in the literature. After a presentation of these notions, I show that two notions of data on the singularity in the polarized \(T^2\)-symmetric vacuum and the polarized \(U(1)\)-symmetric vacuum cases are in fact initial data on the singularity.