Title: Probing the Big Bang with Quantum Fields

Abstract: Singularity theorems of Penrose and Hawking are based on geodesic incompleteness. Physically, this criterion refers to the fate of classical test particles. What if one uses quantum fields instead? They would be more fundamental probes. We will see that in the Friedmann-Lemaître, Roberson-Walker cosmologies, one can unambiguously evolve quantum fields across the Big Bang in a rigorous sense. The expectation values of renormalized products of fields is also finite across the big-bang. Thus the Big Bang singularity is much tamer when seen from a quantum perspective, and quantum considerations provide more refined tools to probe its nature. This work is based on joint work with Tommaso De Lorenzo, Adriane del Rio and Marc Schneider