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<div class="gmail_quote">My understanding of the story is like this:
we start with a spacetime manifold which is curled up in a complex
way, on which various fields slosh around. One of them undergoes a
false vaccum phase transition that makes some of the directions of
the manifold unfold a lot very fast, producing a big spacetime.
However, this unfolding happens differently in different patches,
producing big spacetimes separated from each other and potentially
with different dimensionality or physics (due to local symmetry
breaking of what dimensions unfolded or the values of the
parameters set by the fields).<br>
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Note that spacetime expansion is allowed to be arbitrary, but
fields on it can only change with signals moving at the speed of
light on the spacetime. So vacuum decay can only spread at
lightspeed in the surrounding manifold, although the internal
spacetime metric of the decyed region might have turned all weird.<br>
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On 2016-05-19 22:03, Rafal Smigrodzki wrote:<br>
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Superluminal? I though all vacuum decay models had it
spreading merely at lightspeed?<br>
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<div>### This is one (of many) things I don't quite get: Inflation
was superluminal and occurred after the false vacuum decay that
generated our spacetime, so you would think the change would
propagate superluminally.</div>
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<div>Now that I think about it, maybe it went like this: vacuum
decay generated new dimensions and inflation occurred in these
new dimensions, not in the parent universe. Linde's eternal
inflation does not blow up the non-inflating domains, it keeps
happening between them.<br>
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