An obstacle to populating the string theory landscape

Understand

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.