Caption: A cartoon of the growth of an inflation region with representative numbers.
The inflation region includes observable universe.
Features:
However, sufficiently large quantum fluctuations will lift the region over the energy threshold. So the false-vacuum universe is NOT completely stable.
Note quantum fluctuations are a fundamental feature of quantum mechanics and are NOT specfic to any particular quantum field theory.
The essential idea is that the energy becomes (perhaps NOT directly) photons, leptons, quarks, and probably dark matter particles.
The particles are created with kinetic energy which drives a super rapid expansion of the inflation region. The super rapid expansion is the inflation itself and it's duration is the inflation era which is though to be ∼ 10**(-32) s to ∼ 10**(-36) s after the time of the Big Bang singularity---which very probably did NOT happen, but is just the time zero of the Friedmann-equation (FE) models that the inflation tracks into as the inflation era ends.
For a slightly longer explication of the decay from the false-vacuum state, see Cosmology file: inflation_false_vacuum_decay.html.
Well, there are various suggested values, but for the cartoon yours truly chose expansion by a factor ∼ 10**60 which seems to be a typical value.
Particular inflation theories will give specific expansion factors and specific durations for the inflation era
So, in fact, it is a like pure cosmological constant growth (such as in the de Sitter universe), but with a much larger EFFECTIVE cosmological constant than is used to account for the accelerated expansion of the universe of the modern observable universe in the Λ-CDM model.
Of course, yours truly is NOT arguing that unbelievability is a proof of truth.
Outside it may be Hamlet's "nutshell.'' See the figure below local link / general link: hamlet_edwin_booth.html).
If this is literally true, stuff from outside could fall into our pocket universe, but CANNOT get out---but where it would arrive and how would it appear and what would it be?
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In eternal inflation, observable universe is deeply embedded in a pocket universe since we observe NO signs of the boundary of the pocket universe---whatever that is like---sharp or spread out.
Our pocket universe and other pocket universes exist in the background the false-vacuum universe. The pocket universes all arise from quantum fluctuations in the false-vacuum universe.
The pocket universe and the false-vacuum universe together constitute the whole universe.