A menagerie of Euclidean constructions for 3D holographic cosmologies

Abstract: In this talk, I will introduce a large family of solutions of Euclidean three-dimensional gravity coupled to heavy matter particles that, upon continuation to Lorentzian signature, contain a closed big-bang / big-crunch cosmology entangled with additional asymptotically AdS regions. The construction generalizes the one introduced by Antonini-Sasieta-Swingle (AS^2), but the extra analytic control available in three dimensions makes it possible to embed more general cosmologies (e.g., approximately homogeneous and isotropic ones) in a relatively conventional AdS/CFT setup. I will then discuss to what extent these saddles containing a closed universe can dominate the path integral, introducing possible competing geometries, and comment on a general necessary condition for the dominance of the cosmological saddle points.