Universe Is Infinite: Mathematical Proofs

[Ontoplankton]

It was some time ago when I read the paper, but IIRC their main claim is that you get an infinite universe with infinitely many Hubble-sized regions within every one (no longer inflating) bubble. Whether there are many such bubbles shouldn't matter. I encountered this through Tegmark's paper "Parallel Universes" (Tegmark seems to agree with Garriga and Vilenkin's claim that inflation generically leads to an infinite universe).

You've mentioned a counterexample, so it can't be true that this sort of eternal inflation happens in all kinds of inflation. But do you think there are many such counterexamples? Would it be right to say that most, but not all, types of inflation that are being seriously considered are like Garriga and Vilenkin descibe (with inflation that never ends, but not necessarily with more than one infinite bubble-universe)? Or would it be more correct to say that it applies only in one specific example of inflation?

Edit: I had already read your previous post; one thing you said was that of the two types of eternal inflation you mentioned, the one they mean is the first one. I suppose that is what I mean by eternal inflation, too, though I don't understand enough to mean anything exact. (This just for general clarification.)

 

[marcus]

Originally posted by Ontoplankton
... I encountered this through Tegmark's paper "Parallel Universes" (Tegmark seems to agree with Garriga and Vilenkin's claim that inflation generically leads to an infinite universe)...

was that the SciAm article on Multiverses? I haven't seen his paper "Parallel Universes" do you have a link or some such handle on it.

Are you comfortable with the idea that in our own universe (the one we see) inflation stopped.

that is, the inflation people usually mean when they talk about the "inflationary scenario" around the time of the big bang, was not eternal but was very brief

 

[Ontoplankton]

Originally posted by marcus
was that the SciAm article on Multiverses? I haven't seen his paper "Parallel Universes" do you have a link or some such handle on it.

http://arxiv.org/abs/astro-ph/0302131

It's a watered-up version of the SciAm article.

Are you comfortable with the idea that in our own universe (the one we see) inflation stopped.

that is, the inflation people usually mean when they talk about the "inflationary scenario" around the time of the big bang, was not eternal but was very brief

Right, but, as I understand it, in "eternal inflation" the rest of the universe outside of our thermalized bubble is supposed to still be inflating, even though our bubble itself is not. IIRC Tegmark/Garriga/Vilenkin claim that in nicer coordinates, such a thermalized bubble is actually infinite instead of always growing.

(By the way, I haven't looked at Lineweaver's tutorial just now, but I think I did back when you first posted it here; I agree it's very good and remember especially liking the explanations of event/particle horizons, etc.)