Bubbles of cosmology in AdS/CFT

TL;DR

This paper investigates large cosmological bubbles within asymptotically AdS spacetimes and explores their potential dual descriptions in conformal field theories, revealing conditions under which a consistent CFT dual may exist.

Contribution

It demonstrates how arbitrarily large cosmological bubbles can be embedded in AdS spacetimes with Schwarzschild-AdS exterior and analyzes their possible dual CFT states.

Findings

Large bubbles can be embedded with a Schwarzschild-AdS exterior.

Black hole entropy can exceed the bubble's radiation entropy.

Euclidean solutions suggest a well-defined CFT dual construction.

Abstract

Gravitational effective theories associated with holographic CFTs have cosmological solutions, which are typically big-bang / big-crunch cosmologies. These solutions are not asymptotically AdS, so they are not dual to finite-energy states of the CFT. However, we can find solutions with arbitrarily large spherical bubbles of such cosmologies embedded in asymptotically AdS spacetimes where the exterior of the bubble is Schwarzschild-AdS. In this paper, we explore such solutions and their possible CFT dual descriptions. Starting with a cosmological solution with $\Lambda < 0$ plus arbitrary matter density, radiation density, and spatial curvature, we show that a comoving bubble of arbitrary size can be embedded in a geometry with AdS-Schwarzschild exterior across a thin-shell domain wall comprised of pressureless matter. We show that in most cases (in particular, for arbitrarily large bubbles with an arbitrarily small negative spatial curvature) the entropy of the black hole exceeds the (radiation) entropy in the cosmological bubble, suggesting that a faithful CFT description is possible. We show that unlike the case of a de Sitter bubble, the Euclidean continuation of these cosmological solutions is sensible and suggests a specific construction of CFT states dual to the cosmological solutions via Euclidean path integral.