Universes out of almost empty space

Understand

Baby universes (inflationary or non--inflationary) are regions of spacetime that disconnect from the original ambient spacetime, which we take to be asymptotically flat spacetime.

• A particular kind of baby universe solution, involving string--like matter, is studied to show that it can be formed by ``investing'' an arbitrarily small amount of energy, i.e.
• it can appear from an almost flat space at the classical level.
• Since this possibility has not yet been clearly recognized in the literature, we then discuss in detail its properties, relevance and possible generalizations.