Talk:Decoupling (cosmology)

Article expansion

I have expanded this article and added quite a bit more detail, references and links to other articles - hopefully this qualifies it to be upgraded from Stub-class! If not, I would be happy to know why and keep working on it. HannahFord428 (talk) 14:31, 23 July 2014 (UTC)

GA Review

This review is transcluded from Talk:Decoupling (cosmology)/GA1. The edit link for this section can be used to add comments to the review.

Reviewer: Ulflund (talk · contribs) 20:48, 1 September 2014 (UTC)

I'll review this article. I'll go through it more carefully later on, but here are a few initial comments.

• Decoupling is not defined. It is explained so that one gets an understanding of approximately what it is, but there is no exact definition given. It is common to start articles like "In field, topic is...". Maybe the start could be "In cosmology, decoupling refers to the period in the development of the universe when a type of particle ...". If you can find a definition in one of the references that could probably be used without to much changes.
• All variables used should be defined.

Done! HannahFord428 (talk) 08:23, 4 September 2014 (UTC)

• If photon and neutrino decoupling are the only verified decoupling events, I think this is worth stating in the lead section.

They are not the only verified decoupling events, but they are the most commonly discussed due to their production of the CMB (which is well-documented) and CNB (which we know must exist but is still being searched for). I have changed the lead-in to include this. HannahFord428 (talk) 10:01, 19 September 2014 (UTC)

• What if the WIMPs are relativistic?

WIMPs are what are known as "cold relics", meaning they decoupled after they became non-relativistic (neutrinos on the other hand are "hot relics", meaning they decoupled while still relativistic). I will add this to the article to clarify. HannahFord428 (talk) 10:01, 19 September 2014 (UTC)

Ulflund (talk) 20:48, 1 September 2014 (UTC)

I have rewritten the lead-in to hopefully clear up the precise definition of decoupling, and also include a comment about photon and neutrino decoupling specifically. I believe that all particles underwent a decoupling at some point in the early universe, but these two are the most relevant to us today and hence the most discussed. I will check this with an expert in the field though (an astrophysics lecturer at the University of Manchester) to make sure it's absolutely correct. I will also check with that same lecturer what exactly would happen if the WIMPs are relativistic, and whether that's worth mentioning on this page. HannahFord428 (talk) 08:23, 4 September 2014 (UTC)

Done! All issues with the article should now have been cleared up, and I apologise again for the delay. HannahFord428 (talk) 10:01, 19 September 2014 (UTC)

Rate	Attribute	Review Comment
1. Well-written:
	1a. the prose is clear, concise, and understandable to an appropriately broad audience; spelling and grammar are correct.	Equations are not well explained. See other comments. Done.
	1b. it complies with the Manual of Style guidelines for lead sections, layout, words to watch, fiction, and list incorporation.	Lead does not summarize article fully. Photons and neutrinos should be mentioned. Clear definition should be given. Done.
2. Verifiable with no original research:
	2a. it contains a list of all references (sources of information), presented in accordance with the layout style guideline.	Minor things to fix in reference list. Done.
	2b. reliable sources are cited inline. All content that could reasonably be challenged, except for plot summaries and that which summarizes cited content elsewhere in the article, must be cited no later than the end of the paragraph (or line if the content is not in prose).
	2c. it contains no original research.
3. Broad in its coverage:
	3a. it addresses the main aspects of the topic.	The existence of other decoupling events are mentioned in the discussion, but not in the article. No answer to the question which these might be.
	3b. it stays focused on the topic without going into unnecessary detail (see summary style).
	4. Neutral: it represents viewpoints fairly and without editorial bias, giving due weight to each.
	5. Stable: it does not change significantly from day to day because of an ongoing edit war or content dispute.
6. Illustrated, if possible, by media such as images, video, or audio:
	6a. media are tagged with their copyright statuses, and valid non-free use rationales are provided for non-free content.
	6b. media are relevant to the topic, and have suitable captions.	There is only one image, but I cannot think of any other that would be appropriate.
	7. Overall assessment.

The format in reference list should be made more consistent. Here are a few things I think are wrong:

• Ref 7. double punctuation
• Ref 7. what is n. pag. supposed to mean?
• ref 6. Table and page number usually goes after the name of the paper
• ref 6. (PDF) seems to imply that there should be a link to the pdf here.
• It would be nice with links to the papers.

Ulflund (talk) 23:50, 1 September 2014 (UTC)

I have reworked the references using the proper Wikipedia templates - I had originally done them using an external citation generator, which was a mistake. Fixed now! HannahFord428 (talk) 08:23, 4 September 2014 (UTC)

The equations seems to take focus away from the important factor for finding the time of decoupling, namely the electron density. I think these equations need to be reworked to be clearer and focus on the important things (probably by following the sources closer, but I haven't read them) or be removed. Since the recombination article gives a derivation for estimating the time of recombination, these estimates might not be needed here

I have simplified these by removing the mean free path equation (which wasn't really necessary), to focus on the interaction rate and expansion rate of the universe, which are the key factors in any derivation. HannahFord428 (talk) 08:23, 4 September 2014 (UTC)

Although I find things to correct I should say that I find the article overall to be well written. Good work HannahFord428. Ulflund (talk) 04:06, 2 September 2014 (UTC)

Thank you so much for your comments and critiques, I will clear up the last couple of points that need to be fixed in the next few days. HannahFord428 (talk) 08:23, 4 September 2014 (UTC)

Looking at it again, I cannot see how

$\Gamma \varpropto a^{-3}$

can be correct when there is an abrupt reduction in the free-electron density. Ulflund (talk) 15:46, 5 September 2014 (UTC)

You're absolutely right, this was a mistake on my part. That relation is true in the matter-dominated era before recombination, but the dependence on the scale factor $a$ is a lot more complicated after recombination takes place (and is too complex for the scope of this article). I have edited the equations to reflect this. HannahFord428 (talk) 10:01, 19 September 2014 (UTC)

Good. It looks much better now. Just one more thing: You write that photon and neutrino decoupling are not the only verified decoupling events. If so, why aren't the others mentioned in this article?

Page numbers in the books you refer to would be nice (but not required for GA). Ulflund (talk) 16:31, 19 September 2014 (UTC)

There is a small question. The "Recombination" is term, which often appear in reliable sources. And "Neutrino decoupling" is often appear too. But is there a "Decoupling"? What sources is includes Recombination and Neutrino decoupling to one term - "Decoupling"? In article there is : "occurred within one second of the Big Bang" and recombination is in "380,000 years after the Big Bang". Why we are merging this very different epochs? --Рулин (talk) 14:05, 9 October 2014 (UTC)

I'm failing this good article nomination because I don't get any answer to whether there are other decoupling events. Please renominate when this question can be answered. Ulflund (talk) 05:04, 24 October 2014 (UTC)