Two dimensional Nearly de Sitter gravity

TL;DR

This paper explores the properties of two-dimensional nearly de Sitter gravity, analyzing boundary modes, wavefunctions, topology effects, and implications for cosmological observables and black hole physics.

Contribution

It provides a detailed study of boundary modes, perturbative wavefunctions, and topological contributions in nearly de Sitter gravity, connecting 2D models to 4D cosmological and black hole phenomena.

Findings

Boundary mode induces gravitational corrections to cosmological observables.

All-order perturbative wavefunctions and probability measures are computed.

Topological contributions influence the gravitational dynamics in de Sitter space.

Abstract

We study some aspects of the de Sitter version of Jackiw-Teitelboim gravity. Though we do not have propagating gravitons, we have a boundary mode when we compute observables with a fixed dilaton and metric at the boundary. We compute the no-boundary wavefunctions and probability measures to all orders in perturbation theory. We also discuss contributions from different topologies, borrowing recent results by Saad, Shenker and Stanford. We discuss how the boundary mode leads to gravitational corrections to cosmological observables when we add matter. Finally, starting from a four dimensional gravity theory with a positive cosmological constant, we consider a nearly extremal black hole and argue that some observables are dominated by the two dimensional nearly de Sitter gravity dynamics.