Initial Conditions for Bubble Universes

Understand

The "bubble universes" of Coleman and De Luccia play a crucial role in string cosmology.

• Since our own Universe is supposed to be of this kind, bubble cosmology should supply definite answers to the long-standing questions regarding cosmological initial conditions.
• In particular, it must explain how an initial singularity is avoided, and also how the initial conditions for Inflation were established.
• We argue that the simplest non-anthropic approach to these problems involves a requirement that the spatial sections defined by distinguished bubble observers should not be allowed to have arbitrarily small volumes.