Talk:Horizon problem

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The last sentence, "According to the theory, inflation was caused by a momentarily displaced quantum potential", sounds dodgy to me. As far as I know, the term "quantum potential" is used only in the context of Bohm's interpretation of (non-relativistic) quantum mechanics. It doesn't appear in the article on quantum field theory that the term links to here, and I've never seen it used in that context, either. "momentarily displaced" is also at least unclear – displaced in what sense? But I don't know enough about inflation theory to correct it. Fpahl 00:08, 22 Sep 2004 (UTC)

You're absolutely right. The truth is this is how inflation was explained to me, and I don't know enough about quantum field theory to say any more about what exactly it means while retaining an encyclopedic tone. I can do a little better here, though. It has nothing to do with Bohmian mechanics. A primitive example of a quantum potential would be the scalar potential from electromagnetism. (I say primitive because the scalar potential turns out to not actually be a potential by itself but only a "part," in a certain loose sense, of a potential.) By saying such a potential is "displaced" I mean it is "removed from its least energy configuration." I think I'll substitute "globally excited" for "displaced." –Floorsheim 01:06, 22 Sep 2004 (UTC)

The entity that the scalar potential becomes a component of in QFT is called the photon field. You can derive an effective potential from this field, but I've never seen either the former or the latter referred to as a "quantum potential". (Just to clarify things; I'm not sure whether you were arguing for using the term or just explaining what you'd meant by it.) Fpahl 08:31, 22 Sep 2004 (UTC)

Roadrunner, your new formulation seems an improvement to me. However, I hadn't heard that this "later proved problematic". Do you have a source for this? (Both for the article and out of my personal interest). BTW, please use edit summaries; they help in interpreting the history. Fpahl 08:24, 22 Sep 2004 (UTC)

I thought about this some more and realized that you probably intended this as a summary of what it says in the cosmic inflation article. If so, I think the summary is misleading – it's the tie to specific GUT fields that became problematic, not the more general ideas related to vacuum energy. Please correct me if I'm wrong; otherwise I'll be changing the sentence to reflect this view. Fpahl 16:46, 22 Sep 2004 (UTC)

I decided to remove the sentence entirely, since any precise statement would necessarily have duplicated a lot of what can be found under inflationary theory anyway.Fpahl 16:08, 8 Oct 2004 (UTC)

I can offer an explanation to momentarily displaced quantum potential (but cannot be sure that this was meant by the perosn that explained the topic Floorsheim). It is only a rough picture of course:

Image a phi^4+a*phi^2 term for the effective Lagrangian of quantum field, starting with a>0. The vacuum state, the state of lowest energy, would be phi=0. Now through interaction with other fields the a term decreases. Once a<0, the the state of lowest energy no longer is at phi=0. Not with formula, but with more complicated ones, phi=0 may be still a local maximum and the field may stay in this local maximum for some time. But when it finally transitions to the true minimum, vast amounts of energy are set free. Pjacobi 09:59, 22 Sep 2004 (UTC)