Instantons, euclidean wormholes and AdS/CFT

Abstract

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 AdS5 ×S5/Zk and allows for smooth Euclidean wormholes. For the supersymmetric D-instanton-like solutions we seem to find a match with the instantons in the dual N = 2 quivers. This match even extends a bit further to self-dual instantons without supersymmetry.