A Framework for the Landscape

TL;DR

This paper proposes a new framework using an eternally inflating background to study metastable de Sitter vacua in string theory, enabling the definition of an S-matrix and analyzing transitions between different cosmological states.

Contribution

It introduces a classical background with bubble solutions that include metastable de Sitter spaces, allowing string theory to incorporate and analyze these vacua.

Findings

An eternally inflating background with bubble solutions is constructed.

The framework supports a well-defined S-matrix in this setting.

Evidence suggests string theory can describe metastable de Sitter states as intermediate configurations.

Abstract

It seems likely that string theory has a landscape of vacua that includes very many metastable de Sitter spaces. However, as emphasized by Banks, Dine and Gorbatov, no current framework exists for examining these metastable vacua in string theory. In this paper we attempt to correct this situation by introducing an eternally inflating background in which the entire collection of accelerating cosmologies is present as intermediate states. The background is a classical solution which consists of a bubble of zero cosmological constant inside de Sitter space, separated by a domain wall. At early and late times the flat space region becomes infinitely big, so an S-matrix can be defined. Quantum mechanically, the system can tunnel to an intermediate state which is pure de Sitter space. We present evidence that a string theory S-matrix makes sense in this background and contains metastable de Sitter space as an intermediate state.