Talk:Inflationary epoch

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08/15/20 - How long would this epoch have lasted? (PS: An epoch is after all a time unit.) — Preceding unsigned comment added by Ivowelch (talk • contribs) 17:00, 16 August 2020 (UTC)

22/04/07 - Anyone else noticed some quite extraordinary typos in the referenced link? Hardly desirable in an article entitled 'inflation for beginners'

4/15/12- shouldn't it be the 'inflaton' field below (not inflation)? "However, the huge potential energy of the inflation field was released at the end of the inflationary epoch, .." — Preceding unsigned comment added by 74.242.215.246 (talk) 02:47, 16 April 2012 (UTC)

Three spatial dimensions implied

"rapid expansion increased the linear dimensions of the early universe by a factor of at least 10²⁶ (and possibly a much larger factor), and so increased its volume by a factor of at least 10⁷⁸." implies three (spatial) dimensions. My naïve question (not a physisist..), does the theory/recent data have anything to say about string theory? That theory says there are more dimensions but that only three are spatial (or the other compactified). I wander would they have been compactified at some point? During, after, before that epoch? comp.arch (talk)

Strong Evidence - BICEP2

In mid-May, 2014 some information came to light which indicates significant problems with the data analysis of the BICEP2 team. See this reference:http://www.math.columbia.edu/~woit/wordpress/?p=6865. I note that the talk by Ralphael Flauger at Princeton was not formally peer reviewed (similar to the BICEP2 news conference). AFAIK, the systematics paper by the BICEP2 team isn't even "in press" yet! The general consensus of the responses to the Flauger talk seems to be that until we have information at more than one frequency, and especially at higher frequencies, we should not accept the idea that the results are definitely from the Big Bang. Planck data will probably NOT answer this, as the BICEP2 study was done in an area of sky where Planck hasn't separated signal from noise. Anyway, the claim that the BICEP2 study is "strong" evidence is, I believe, an exaggeration. What is needed is multifrequency data with a clear measurement (and subtraction) of the 'noise' caused by galactic dust (as well as lensing). This may take a few years to resolve. Until then, I am changing "strong" to "the first clear experimental" (I think 'clear' is better than 'direct' as the B-mode frequency power spectrum is hardly what most would consider 'direct', imho). I am going to make the same change in the identical paragraph in the Wikipedia article "Inflation (cosmological).Abitslow (talk) 21:12, 1 June 2014 (UTC)

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Relation to dust

How does the paragraph about interstellar dust (which turned out to be in the Milky Way only) and the “tensor-to-scalar ratio” relate to inflation? --PointedEars (talk) 13:30, 25 January 2019 (UTC)

Mechanism of inflaton is not important

Currently the article contains the phrase: "The expansion is thought to have been triggered by the phase transition that marked the end of the preceding grand unification epoch at approximately 10−36 seconds after the Big Bang. One of the theoretical products of this phase transition was a scalar field called the inflaton field."

It should not be there. Even existence on grand unification per se is not a necessary part of inflationary models.

ANY vacuum state ("vacuum state" is a configuration of quantum fields which is a local minimum of potential energy) with large energy density automatically satisfies the necessary conditions for inflation to occur. And it must not be stable (the field configuration must not be the *global* minimum), or else inflation would not ever end.

Now, we know from observed Universe around us that it is not inflating. This is the reason why inflationary models posit that there is (possibly yet unknown) field, "inflaton", which is currently in low energy minimum, but used to be in a high-energy one.

Why "possibly yet unknown"? Because Standard Model, for all its successes, has one major flaw: it can not calculate vacuum energy densities. (Well, it can, but results do not make much sense: they are divergent when taken to limit of scale -> 0, and even with EFT approach, they are finite but HUGE, which clearly is not supported by observations). Because of this, currently we can't rule out that in fact, SM fields may already have all necessary ingredients. E.g. the Higgs field may have a high-energy minimum (in addition to observed current minimum of 246 GeV). We just don't know. Thus, inflaton may be just the Higgs field. (Why not any other SM field? Well, all other fields are not scalars, and a vacuum condensate of a non-scalar field would break Lorentz invariance of vacuum - vaccum would have preferred directions. This is not what we observe. A non-scalar condensate needs to be composite, like pion condensate in QCD).

I'm going to edit the article to make the explanation more generic (e.g. remove the reference to GUTs).