Populating the Landscape: A Top Down Approach

TL;DR

This paper introduces a top down cosmological framework combining the string landscape with no boundary conditions, focusing on how universe histories depend on specific questions and exploring observational implications.

Contribution

It proposes a novel top down approach to cosmology that calculates universe histories with only final boundary conditions, integrating the string landscape and no boundary conditions.

Findings

A simple model landscape with multiple inflationary histories.

Certain vacua in the landscape are more likely to be populated.

The approach offers testable observational predictions.

Abstract

We put forward a framework for cosmology that combines the string landscape with no boundary initial conditions. In this framework, amplitudes for alternative histories for the universe are calculated with final boundary conditions only. This leads to a top down approach to cosmology, in which the histories of the universe depend on the precise question asked. We study the observational consequences of no boundary initial conditions on the landscape, and outline a scheme to test the theory. This is illustrated in a simple model landscape that admits several alternative inflationary histories for the universe. Only a few of the possible vacua in the landscape will be populated. We also discuss in what respect the top down approach differs from other approaches to cosmology in the string landscape, like eternal inflation.