Instantons, Euclidean wormholes and AdS/CFT

Understand

I present an informal overview of several recent results about Euclidean saddle points sourced by axion fields in quantum gravity (AdS/CFT), such as wormholes, their extremal "D-instanton" limits and their under-extremal singular counterparts.

• Concerning wormholes we argue they cannot contribute to the path integral because a stability analysis suggests they fragment like other super-extremal objects.
• For concrete AdS/CFT embeddings the Euclidean saddle point solutions are neatly described by geodesic curves living inside moduli spaces and can typically be solved for using group theory.
• Our working example is $AdS_5\times S^5/\mathbb{Z}_k$ and allows for smooth Euclidean wormholes.