Signature change events: A challenge for quantum gravity?

Understand

Within the framework of either Euclidian (functional-integral) quantum gravity or canonical general relativity the signature of the manifold is a priori unconstrained.

• Furthermore, recent developments in the emergent spacetime programme have led to a physically feasible implementation of signature change events.
• This suggests that it is time to revisit the sometimes controversial topic of signature change in general relativity.
• Specifically, we shall focus on the behaviour of a quantum field subjected to a manifold containing regions of different signature.