Eternal Inflation

As I read a few articles on Stephen Hawking's final paper, and investigate eternal inflation and infinite universes, I see authors stating eternal inflation 'implies' infinite universes, or that it 'leads to' infinite universes, as space expands and breaks apart into discrete bubbles. But no one explains how a single, inflationary universe seemingly spontaneously breaks up into parts. I can't figure out how the one causes or implies the next, when the only thing I imagine happening is space/time spreading out and taking objects with it. I have a fairly good amateur understanding of cosmology, but I'm missing some essential piece here. Can you explain the connection?Thank you!
- Heather Brutosky (age 43)
Helena MT USA

Great question!

The missing piece is that the inflation is supposed to be driven by some vacuum field being temporarily stuck in un unstable high-energy state. If you've ever seen a bottle of supercooled water (https://van.physics.illinois.edu/qa/listing.php?id=1618), cold enough that it should be ice, that's an example of such an unstable state. It takes some sort of local accident to trigger the formation of the lower-energy state (ice, for the water case), a non-inflating universe in the cosmic case). 

But why doesn't the whole universe leave the rapidly inflating state once the new state gets triggered somewhere? The inflation is so fast that it beats the formation of the new type of space. The old inflating one is growing faster than the rate at which it's losing parts to the new states, for example states like the type we live in. This feature is quite unlike the behavior of supercooled water!

Mike W.

(published on 05/03/2018)