Probing cosmological singularities with quantum fields

Singularity theorems indicate that a large family of solutions of Einstein’s equations are singular when probed with classical test particles. As a result, the big bang singularity is often interpreted as an absolute barrier beyond which physical theories cannot be extended beyond. In this talk we will show that a quantum scalar field and physical observables constructed from it can be formulated as well-defined distributions in a wide family of cosmological spacetimes even when the metric is enlarged to include the curvature singularity. In contrast to test particles, the evolution of quantum fields can be traced back across the big bang.