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)[reply]

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)[reply]

Three spatial dimensions implied

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"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

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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)[reply]

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Relation to dust

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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)[reply]

Mechanism of inflaton is not important

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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).

Merge into Cosmic inflation

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This article is not notable independent of cosmic inflation and that article has no section on the epoch. Content here overlaps content in the main article.

None of the 13 references here are directly about the epoch as an era. In fact they all seem to be about a result that eventually was attributed to dust. Johnjbarton (talk) 16:05, 16 August 2024 (UTC)[reply]

Citations need to be more specific

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Hello Wikipedians,

I think the citations need to be more specific. In this article, two books related to Inflation theory were used as references. From these books, I am only familiar with the one from Guth, Alan H.(1998). Moreover, the references I think should have the page numbers with the data and information mentioned here. If anyone can do this it will be awesome.

```` Sarandebnath (talk) 06:22, 19 March 2025 (UTC)[reply]

The "epoch" terminology is not commonly used in cosmology textbooks. There are lots of good sources on inflation theory, not very many for "inflationary epoch". Johnjbarton (talk) 02:21, 20 March 2025 (UTC)[reply]

Merge proposal

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I propose to move the figure and maybe the External links into cosmic inflation and redirect this article to Chronology_of_the_universe#Inflation. Please see other discussion in this Talk page for reasoning. Johnjbarton (talk) 17:23, 19 August 2025 (UTC)[reply]

While this article has its flaws, might merging it with Chronology produce an article that is too large? I guess that most readers will first see an article on their smartphone; if the article is too large that might be counter-productive in that they can't find the info they want without scrolling through lots of text. Breaking large articles into smaller ones can have its advantages. Richard Nowell (talk) 08:00, 22 August 2025 (UTC)[reply]
While I agree with your overall comment, I see two problems in this case. First is "epoch". This terminology is rare in modern cosmology discussions and I think we are giving it a status not reflected in sources. Cosmology texts simply call it "inflation". Second, Chronology_of_the_universe really needs to be one article to give a sense of the big picture. I have been working to change the Chronology article in to a Wikipedia:Broad-concept article with short summaries linked to main articles. The main link for Chronology_of_the_universe#Inflation would be Inflation. Thus I don't see what this article offers. It has few sources and a poor explanation of the physics. If it were improved it would simply repeat one of the main articles. To put it another way, the "epoch" part makes this essential a dictionary entry for "When cosmic inflation happened". Johnjbarton (talk) 15:00, 22 August 2025 (UTC)[reply]
  • This topic is stand-alone notable. Randy Kryn (talk) 12:28, 29 August 2025 (UTC)[reply]
    @Randy Kryn Please provide a source. No source cited here uses "Inflationary epoch". Johnjbarton (talk) 16:40, 29 August 2025 (UTC)[reply]
    When searched for the term is quite common, although not sure about which sources would be reputable. As long as the core pertinent information and links are presented in all the related articles, and the term itself is used and searchable, then this page has some merit. Randy Kryn (talk) 23:09, 29 August 2025 (UTC)[reply]
    The majority of the hits in that search are circular. I think this topic barely passes general notability guidelines, lacking significant coverage in reliable sources. That people search for it does not make it notable.
    But I am not proposing to delete the page, but simply merge it because it's only unique content is
    • It is not known exactly when the inflationary epoch ended, but it is thought to have been between 10−33 and 10−32 seconds after the Big Bang.
    Everything else is covered better in Inflation (cosmology).
    Inflation is a complex topic and this page has nothing for readers by itself. By directing readers to Chronology of the universe § Inflation they will quickly see the relation of this time to cosmology and can navigate to learn more.
    Would you reconsider? Johnjbarton (talk) 23:24, 29 August 2025 (UTC)[reply]
    Of course I would. Just offering a point of view, and you make a very good case. Inflationary epoch does, however, have sources. If the merge is a good one it should lose no encyclopedic information, and that's the goal to strive for. I've witnessed lots of "merges" where a name is just redirected and good encyclopedic information is lost (or hidden in the page history), so just coming down on the side of keeping the best data easily accessible. Thanks. Randy Kryn (talk) 23:32, 29 August 2025 (UTC)[reply]
    That's the thing. Let's look at the sources in this article:
    1. "WMAP Inflation Theory". wmap.gsfc.nasa.gov. Retrieved 2025-03-19. Does not mention "Epoch"
    2. Guth, Alan H. (1998). The inflationary universe: the quest for a new theory of cosmic origins. London: Vintage. ISBN 978-0-09-995950-2. Uses "inflationary epoch" once in 390 pages on inflation.
    3. Greene, Brian (2005). The fabric of the cosmos: space, time, and the texture of reality. London: Penguin Books. ISBN 978-0-14-101111-0. Uses "epoch" 6 times, never "inflationary epoch"
    The only potential reliable source I've found is
    • Liddle, A. R. (1998). An introduction to cosmological inflation. High energy physics and cosmology, 260.
    which uses the term a couple of times and does not define it.
    Based on this we can't even say what the "inflationary epoch" is. We can guess: the epoch of when cosmological inflation was active. But a reader's guess is as good as our guess. My personal guess is that using "epoch" was more common 20 or 30 years ago but modern writers stopped using the term, perhaps because so many theories gave indeterminate and overlapping timelines. Johnjbarton (talk) 00:43, 30 August 2025 (UTC)[reply]
This article should be merged with cosmic inflation (and/or chronology of the universe as appropriate). It is standard to use "inflation" to refer both to the theory and to the event or time period (see for example the first sentence of the abstract of this review [1]). The inflation era can't really be discussed independently of the theory anyway. Too little is experimentally confirmed to give precise numbers about when inflation took place, except when discussing specific inflation models. Aseyhe (talk) 17:25, 3 November 2025 (UTC)[reply]
That will be a good idea to merge DJ Crimson Oracle (talk) 16:42, 7 November 2025 (UTC)[reply]