An obstacle to populating the string theory landscape

TL;DR

This paper investigates domain walls and instantons in coupled scalar field models, revealing that many solutions contain naked singularities which hinder the process of eternal inflation in populating the string theory landscape.

Contribution

It establishes a criterion for potentials to avoid singularities and demonstrates that many Type IIB string theory solutions are singular, impacting eternal inflation models.

Findings

Many solutions contain naked timelike singularities.

Vacuum bubble solutions lack true vacuum regions.

Singularities obstruct eternal inflation in string landscape.

Abstract

We construct domain walls and instantons in a class of models with coupled scalar fields, determining, in agreement with previous studies, that many such solutions contain naked timelike singularities. Vacuum bubble solutions of this type do not contain a region of true vacuum, obstructing the ability of eternal inflation to populate other vacua. We determine a criterion that potentials must satisfy to avoid the existence of such singularities, and show that many domain wall solutions in Type IIB string theory are singular. This has profound implications for applying the program of eternal inflation to making predictions in the string theory landscape.