AdS/CFT, Ultralimits and Baby universes

Abstract

We propose boundary theories, CFT${}_p$ with $p\in \beta \mathbb{N}/\mathbb{N}$, which can be interpreted as an ensemble of theories in the context of AdS/CFT duality, when the boundary spacetime dimension is more than one. These theories are only emergent in the infinite $N$ limit of the boundary CFT and depend on $p$, which corresponds to the different ways one can take a generalized form of the infinite $N$ limit, in the presence of a chaotic or an oscillatory operator. This generalized infinite $N$ limit is called an \emph{ultralimit}, and $p$ is a \emph{free ultrafilter} on $\mathbb{N}$. We propose that the gravitational path integral computes an average of CFT${}_p$ in each of its sectors; and in the appropriate cases, it produces baby universes and spacetime wormholes. We apply this proposal to the Antonini-Sasieta-Swingle (AS${}^2$) like states.

48 pages, 2 figures