Talk:Cosmic inflation

"after the Big Bang" ?

This article states that cosmic inflation happened after the Big Bang, but the Big Bang Wikipedia article states that inflation was part of the Big Bang and happened at the initial moments of the Big Bang. I think this contradiction arose because scientists use "Big Bang" to mean the expansion of the universe from the initial moments until now, or at least until long after inflation, but the general public conflates "Big Bang" with "inflation", or thinks "Big Bang" refers to the very first moment in time of the universe. I think it's best to stick to the scientific definition and I have changed the article accordingly. It's jarring to a reader to read "inflation happened after the Big Bang" in this article and then get curious and click on the Big Bang link which takes them to the associated Wikipedia article which then tells them that inflation was the initial part of the Big Bang. — Preceding unsigned comment added by 69.110.37.194 (talk) 04:01, 14 August 2024 (UTC)

Well it seems that sources do not agree with your claim:

• https://www.jpl.nasa.gov/news/nasa-technology-views-birth-of-the-universe
  • "Our universe burst into existence in an event known as the Big Bang 13.8 billion years ago."
• Kragh, Helge (1996). Cosmology and Controversy: The Historical Development of Two Theories of the Universe. Princeton, NJ: Princeton University Press. ISBN 978-0-691-02623-7. LCCN 96005612. OCLC 906709898.
  • "The idea of the universe originating in a singular event some finite time ago, that is, the big-bang idea..."

I think scientists refer to the 'idea' as the Big Bang theory and go on to discuss its implications, including inflation. But a finite timeline has a start and that start is called the Big Bang. Johnjbarton (talk) 14:47, 14 August 2024 (UTC)

Usage of "Big Bang" in cosmology is terribly inconsistent. Sometimes Big Bang means the initial singularity, sometimes it means the very early universe (e.g. Big Bang nucleosynthesis), and sometimes it means the Big Bang cosmological model (e.g. Big_Bang#Timeline), which describes the expansion history of the universe until now. Often it refers specifically to a cosmological model without inflation. This is usually the case when extrapolating back to define a zero time coordinate, so that we talk about time "after the Big Bang" even when describing models that don't have an initial singularity. I have heard scientific talks refer to inflation as happening "before the Big Bang" as well as "after the Big Bang" depending on which sense is meant. See [1] for some related discussion. It's often possible to reduce the ambiguity by using "Big Bang model" and "Big Bang singularity", but sometimes it's best just to avoid the term "Big Bang". --Amble (talk) 15:32, 14 August 2024 (UTC)

• If the Big Bang article actually says inflation is part of the Big Bang, then it is wrong, so that article should be fixed. Where does it say inflation is part of the Big Bang, though? (This might be better on that article's talk page, as well.) Banedon (talk) 02:37, 15 August 2024 (UTC)

Duration

The section on Duration has indirect citation to

• Liddle, Andrew; David Lyth (2000). Cosmological Inflation and Large-Scale Structure. Cambridge. ISBN 978-0-521-57598-0.

but the section of that book that discusses the 60-e-fold factor is about a model BGT that is not considered viable. The other ref in the footnote is incorrect. Johnjbarton (talk) 15:39, 16 August 2024 (UTC)

The Causal Universe of Brout Englert and Gunzig

Hi @Smassar. The priority claim added in the section "The Causal Universe of Brout Englert and Gunzig" needs a secondary, historical reference. Simply citing the primary work amounts to original research because you are asserting their priority without providing evidence of an analysis other than your post. Thanks in advance. Johnjbarton (talk) 16:44, 23 October 2024 (UTC)

Hello Johnjbarton. Thanks for your comment. How do I address your concern? (The problem is that the work of Brout, Englert and Gunzig has been largely ignored in the history of this topic).

- I can cite specific paragraphs and phrases in the two papers of Brout, Englert and Gunzig. Should I do this in the comments section? Or in the wikipedia article itself?

-A few scientists have acknowledged their contribution. For instance Brandenberger, R. (2017). Initial conditions for inflation—A short review. International Journal of Modern Physics D, 26(01), 1740002. https://arxiv.org/pdf/1601.01918 cites their work in its Ref 1. Another example is Mukhanov, V. (2013). Quantum cosmological perturbations: predictions and observations. The European Physical Journal C, 73, 1-6, see Ref 5 in this work. Both these authors are very well known in the field. Smassar (talk) 09:57, 24 October 2024 (UTC)

-Here is a history of science article that discusses their contribution SMEENK, Chris. False vacuum: Early universe cosmology and the development of inflation. In : The universe of general relativity. Boston, MA : Birkhäuser Boston, 2005. p. 223-257. Smassar (talk) 10:08, 24 October 2024 (UTC)

Discovery priority is not solely a matter of timeline. For a discovery to be important it has to have impact. If the work of Brout, Englert and Gunzig was not read by other scientists and used in follow-on work, then their priority is not significant. A secondary reference can establish the influence. The most interesting and compelling references are historical analysis, but scientific reviews or even other primary scientific works are sources establishing impact.

However now I see that my claim about your edit was incorrect. You only mentioned the priority issue in the edit summary. The Brout, Englert and Gunzig paper has 500 references so it's not ignored.

What would really make an improvement would be to add a review reference to the paragraph and, even better, find a review that positions the work in the field. The Smeenk work might be good for this. A scientific and a historical review ref would be great. The Brandenberger work clearly cites the 1978 work as "inflation". You can say as much, The section title "Early inflation models" should be changed, eg to "Guth model". Johnjbarton (talk) 15:11, 24 October 2024 (UTC)

I have added Smeenk's article to the section "Sources". Smassar (talk) 11:32, 25 October 2024 (UTC)