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The following is an archived discussion of a featured article nomination. Please do not modify it. Subsequent comments should be made on the article's talk page or in Wikipedia talk:Featured article candidates. No further edits should be made to this page.

The article was promoted by Ian Rose 10:01, 17 November 2013 (UTC) [1].[reply]

AdS/CFT correspondence

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AdS/CFT correspondence (edit | talk | history | protect | delete | links | watch | logs | views)

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Nominator(s): Polytope24 (talk) 23:25, 5 October 2013 (UTC)[reply]

I am nominating this for featured article because... I believe it meets the FA criteria. I've been working on this article for months now, and it was recently promoted to good article status. Since then, I've significantly expanded the article to make it more comprehensive. Polytope24 (talk) 23:25, 5 October 2013 (UTC)[reply]

Comments by Chris857
There are two images here, File:Escher Circle Limit III.jpg and File:AdS3.png. Circle Limit is non-free, and AdS3 is a derivative work of it. Is there any necessity to use Circle Limit when File:Uniform tiling 433-t0.png is the same pattern, but freely licensed? File:AdS3.png should be modified to use the free pattern. Chris857 (talk) 18:31, 6 October 2013 (UTC)[reply]
Are there any other thoughts about this? I explained my rationale for using the Escher image over at File:Escher Circle Limit III.jpg. I can change the images if the community deems it necessary, but the Escher image is prettier, and I think I'm justified in using it… Polytope24 (talk) 21:23, 6 October 2013 (UTC)[reply]
Is the suggested replacement sufficient for the same encyclopedic purpose? I.e. does it convey the same information needed to understand the article or section? If yes, the non-free image and its derivative should be replaced. Being more famous or prettier is no valid rationale to prefer the non-free version. (Off-topic for this FA: Usage in Möbius transformation is also questionable. Other usages in the remaining articles appear to have stronger rationales, as the woodcut is either the focus of those articles or is discussed in more detail.) GermanJoe (talk) 09:12, 8 October 2013 (UTC)[reply]
Okay, I changed the images. Polytope24 (talk) 16:53, 8 October 2013 (UTC)[reply]

Comment: I am concerned about this article. The topic of the article is very complex physics, and the subject is accessible to a very small number of people. Because of this, there are very few Wikipedia editors capable of usefully editing the content (as opposed to the formatting) of this article, and of critiquing the article as a whole. Indeed, almost all recent edits (from mid-August) have been by Polytope24, and it seems to me that the GA review was carried out with input only from one other editor, SPat. I would feel more comfortable about granting this article "featured" status if we were able to find a few more appropriately-qualified editors to review it. None of this is meant to disparage the article as it currently stands, or Polytope24's hard work; I'd simply like to confirm that adequate reviews have been performed. RomanSpa (talk) 22:36, 9 October 2013 (UTC)[reply]

Thanks for your comments. It's true that the subject of this article is very technical, but I've tried to write the article in such a way that even non-experts can understand and verify its content. If you look at the references, you'll notice that much of the article is based on a popular article by Juan Maldacena in Scientific American. I would love to have more non-experts weigh in on this article and tell me if they find it accessible.
That said, I understand that it's difficult for a non-expert to support or oppose this nomination. If you like, I can look for people to review the article. I could probably find someone over at Wikipedia:WikiProject Physics. Polytope24 (talk) 23:19, 9 October 2013 (UTC)[reply]
I think that would be an excellent course of action. Thank you. RomanSpa (talk) 12:28, 10 October 2013 (UTC)[reply]

Comment I came here from a request at WT:Physics as a physicist, but don't claim to know anything about FA criteria or judging process. I'll stick to content. I've worked through the article up to but not including the Applications to quantum field theory section.

Overall I'd say that given the difficulty of the material, the article is well written and neutral. AdS/CFT is somewhat controversial in some parts of the physics community and the article is correct to have a criticism section (Disclaimer: I have a connection to P.W. Anderson, who is one of those critics). I don't see any undue biases in the presentation of subtopics. One subtopic I don't see mentioned is the correspondence with a particular tpye of viscous fluid dynamics, e.g., [2] and [3]. But perhaps this is discussed in the Sachdev article; I don't have access to that at the moment.

Here are some particular things that could be improved in the article. I'm being intentionally picky here. Compared to most physics article, this one is well referenced.

  1. conformal field theory is a scale invariant quantum field theory -- Not all scale invariant QFTs are automatically conformally invariant.
  2. The surface of this cylinder is called the conformal boundary of three-dimensional anti-de Sitter space. -- This needs a reference; the SciAm article referenced in the same para does not mention conformal boundary.
  3. It may also be good to explain what is meant by a conformal boundary, since it is such a core concept in the correspondence. A naive reader might say 'You just told me that AdS has a metric, a definite measure of distance. How is the boundary of that space now magically scale invariant?'
  4. Here the gravitational theory has four noncompact dimensions, so this version of the correspondence provides a somewhat more realistic description of gravity. -- Probably needs a ref--who says this theory is a more realistic description of gravity? It is a reasonable statement, but we cannot draw our own conclusions here.

Hope this is helpful and apologies for anything irrelevant to FAC. --Mark viking (talk) 22:14, 11 October 2013 (UTC)[reply]

Thank you - this looks very good. I hope that we can find someone to perform a similar review on the second half of the article. RomanSpa (talk) 23:01, 11 October 2013 (UTC)[reply]
Thank you Mark viking for this helpful review. I've made the following changes in response to your comments:
1. I've changed every instance of the term "conformal boundary" to "boundary" as in the SciAm article by Maldacena. The precise definition of conformal boundary is rather technical, and it seems unnecessary to include it in this article, which is supposed to provide a nontechnical overview. Besides, the article already makes it clear that the boundary we're talking about is infinitely far from any point in the interior.
2. I made some changes to the section on quantum field theory to emphasize that a conformal field theory is a special type of highly symmetric theory, not just a scale invariant one.
3. I added a more specific citation for the claim that the AdS4/CFT3 correspondence provides a more realistic description of gravity.
4. I had originally decided not to discuss applications to fluid dynamics in this article because it's not clear to me that there are any really serious applications to fluid dynamics. Since you noticed this omission, I have added a sentence to the end of the history section noting that this is a topic of current research.
Please let me know if I've failed to address any of your concerns. Thanks again. Polytope24 (talk) 01:20, 12 October 2013 (UTC)[reply]
Thanks for addressing these points. I agree with your decision to drop the 'conformal' from conformal boundary for the sake accessibility. All your other changes look good. I agree that the fluid dynamics connection warrants no more than a sentence. You've addressed all my points. --Mark viking (talk) 05:04, 12 October 2013 (UTC)[reply]

Comment on the second half of the article (see the comments on the first half above). I also found this half to be well written and well referenced. As above, here are some picky criticisms:

  1. fluid is viewed as a field theoretic analog of a black hole. -- as written, I cannot tell what this means. What is the field theoretic analog of a black hole? I can make some guess, but best to provide a little more descritpion here.
  2. In 1999, after taking a job at Columbia University, nuclear physicist Đàm Thanh Sơn paid a visit to Andrei Starinets, a friend from Sơn's undergraduate days who happened to be doing a Ph.D. in string theory at New York University. -- This level of detail on undergraduate friendships is a nice story, but is a trivial detail in a broad summary of the whole topic. Perhaps best to reduce to excise it.
  3. Such a duality is interesting from the point of view of cosmology since many cosmologists believe that the very early universe was close to being de Sitter space. -- citation needed for many cosmologists believing this.
  4. In the Black hole information paradox section you alluded to the Bekenstein bound for black hole information and in the later Black holes and holography section, you mentioned the holographic principle Both these concepts are closely related, as mentioned in both articles. There should be some mention of the connection of these in this article. Although Black hole information paradox and Black holes and holography are split into two sections, they are fairly closely related.

I'm not qualified to judge whether this meets FAC, but I must say, well done! --Mark viking (talk) 04:58, 12 October 2013 (UTC)[reply]

Thanks for these comments. Here's a summary of what I did:
1. I clarified the sentence on "field theoretic analog of a black hole".
2. For now, I'm leaving the story about Son and Starinets as it is. During the GA review of this article, I was encouraged to add lots of details and trivia to the history section since this is the section that lay readers will focus on. The thinking was that such readers will be most interested in historical details, anecdotes, and personal relationships of the scientists involved in AdS/CFT. I would like to hear what other reviewers think about this decision. If others agree that there's too much trivial information, then I'll go ahead and change it.
3. I added a citation on the early universe being close to de Sitter space.
4. It seems there was some confusion about my reference to Jacob Bekenstein in the section "Black hole information paradox". It was not my intention to say anything about the Bekenstein bound. In fact, the reference in that section was unnecessary and works much better in the history section, so I moved it. I hope this helps to streamline the article a bit.
Thanks again, and please let me know if there are any other issues. Polytope24 (talk) 06:22, 12 October 2013 (UTC)[reply]
Thanks for addressing my points. I wasn't aware of the GA discussion about the history section. If adding details and trivia is what is wanted there, that's OK by me; I have a tendency to just concentrate on the physics. I agree that the Bekenstein info makes more sense in the history section. You have addressed all my points.
I cropped the Susskind photo to emphasize the man, rather than his table, and pointed the article to the cropped version. Feel free to revert if you don't think it is an improvement. --Mark viking (talk) 10:26, 12 October 2013 (UTC)[reply]
No, that looks great. Thank you. Polytope24 (talk) 15:22, 12 October 2013 (UTC)[reply]

Support Based on the content of the article and having all my concerns addressed, I support this article for FA status. --Mark viking (talk) 18:30, 28 October 2013 (UTC)[reply]

Comment: I like how this article manages to find a nice balance between being technical and accessible. While some may ding you on accessibility, on my read-through, even with no understanding of the math behind string theory and its extensions, I was still able to understand what it meant, but not at the expense of technical details. Nonetheless, there are a few things that I think could use some work:

  • I think it would be nice to have some more consistency in using "we" versus "one" when describing things.
  • How does this theory solve the black hole information paradox? I was not quite clear on this while reading the article?
  • "Some condensed matter theorists hope that the AdS/CFT correspondence will make it possible to describe these systems in the language of string theory and learn more about their behavior.[48]" Any examples of who?
  • "During the transition, the atoms behave in an unusual way," in what way is their behavior unusual?
  • In the criticism section, refs need to go at the end of the quote, as well as where they are now.
  • I think the history section goes a little too in-depth about Hawking's black hole work.

Other than these, the article looks good to me, and I'd support after these issues are resolved. StringTheory11 (t • c) 17:22, 13 October 2013 (UTC)[reply]

Thanks for your comments. I'll make changes as soon as possible, hopefully later today. Polytope24 (talk) 18:25, 13 October 2013 (UTC)[reply]
Okay, I just finished making some changes. Rather than remove anything in response to your last comment, I actually added some language to explain why Hawking's work is very important in the history of AdS/CFT. In the previous version, I think maybe it wasn't clear why explained his work in depth.
Thanks for helping out with the review, and let me know if you have any further comments. Polytope24 (talk) 05:02, 14 October 2013 (UTC)[reply]

Support, content concerns addressed. StringTheory11 (t • c) 03:16, 22 October 2013 (UTC)[reply]

Comment At this point I've received some excellent feedback by several other editors, but I'm concerned that the FAC coordinators may close the nomination if there are no other reviews. I would appreciate any suggestions from editors who have more experience with the review process. (RomanSpa may have something to say about this.)

I would also like to make a couple of observations related to WP:FA Criteria:

  • In his review, Mark viking stated that the article was "well written", "neutral", and "well referenced".
  • The only comment about comprehensiveness was that the article should mention applications to fluid dynamics, and this point has now been addressed.
  • Chris857 and GermanJoe had some concerns about pictures which have now been addressed.
  • The article was recently reviewed by SPat and promoted to GA status. This means that it is well written, well referenced, neutral, stable, and illustrated by appropriate images.

Since there don't seem to be any concerns about adherence to WP:MOS, I'm inlined to say that this article meets all the criteria. I would support it myself, but I'm not sure if that's acceptable considering that I nominated the article. I would appreciate any advice people have. Polytope24 (talk) 19:44, 24 October 2013 (UTC)[reply]

Comment

  • I am coming here as a mathematician familiar with AdS/CFT (although not an expert on the physics) because of a request from the principal editor at WT:WPM. In my corner of the world, the AdS/CFT correspondence is typically associated with the names of Charles Fefferman (of Princeton University) and Robin Graham (of the University of Washington) owing to a paper on the subject that they published in a special issue of the journal Asterisque some time in the 1980s (a more detailed and quite recent paper by these authors is available on the arxiv [4]). A reference to this work is conspicuously missing from the article. Sławomir Biały (talk) 00:11, 27 October 2013 (UTC)[reply]
Thanks for the suggestion. The work that you mention is the subject of one of the links in the "See also" section. I also went ahead and added a footnote and reference. Polytope24 (talk) 01:05, 27 October 2013 (UTC)[reply]

Comment

  • I was solicited by the principal editor. I am a theoretical physicist and I am aware of Maldacena's conjecture mostly from works in AdS/QCD. As far as I can tell, there has been some effort by Cumrun Vafa to move this to the status of a theorem. How far is this situation now? Is there something certain that could be stated about? Besides, there also should be numerical attempts in the direction to confirm the conjecture. What is the literature about, if any? This conjecture is something like an important pillar of string theory, much like supersymmetry. If this is the situation (a failure in Maldacena's conjecture is a failure of string theory) then it should be properly emphasized. Finally, I would support this FA nomination as this is becoming a key aspect in a large part of physics and this is properly pointed out in the article. It is possible that all this matter will end up like the bootstrap model in the sixties, I do not know, but due to the relevant role it has now, an article like this is overdue. Better if so well written and presented.--Pra1998 (talk) 17:10, 28 October 2013 (UTC)[reply]
Thanks for your comments. I added a couple of lines explaining that, while there is considerable evidence for AdS/CFT coming from calculations in field theory and string theory, it has not been proved in any generality. I also did a Google search on numerical checks of AdS/CFT, but I wasn't able to find anything significant. If you have a specific article in mind, I'd be glad to mention it.
If you'd like to support the nomination, please remember to post the word "Support" on this page, in bold. Thanks again for your help. Polytope24 (talk) 17:51, 28 October 2013 (UTC)[reply]

Support, satisfactory article, to be promoted.--Pra1998 (talk) 22:19, 28 October 2013 (UTC)[reply]

Comment: coming here at request from Polytope24. I think this article is darn close to the FA criteria, but not quite yet. (The GA status is well deserved, and the recent editors are to be applauded.) I agree with other commenters who note that the article is now comprehensive, well researched, and neutral. I also think the overall structure/style is fine. Things that I think should be fixed up:

  • Criteria 1a: there are scattered first-person pronouns ("we" and "our") in the form of the polite construction which includes the reader. WP:MOS allows these despite their non-encyclopedic style, but indicates that alternative sentence structures are preferred if possible. I think that most (not all) of the occurrences here can be fixed up quite easily without using "we" or "our".
  • Criteria 4: I'm sorry to say that the absolutely lovely level of detail, which appears to have been encouraged in previous edits, leaves the article too long. Perhaps I'm wrong. However, I do believe that the well-written "History and Development" section gets off topic, and is more like a history of holography in general than a history of AdS/CFT specifically.

Spatrick99 (talk) 17:13, 28 October 2013 (UTC)[reply]

Thanks for your comments. I have now removed every instance of the word "we" except in quotations. I also removed some sentences from the subsection on "Black holes and holography" which was a bit too long. Other than that, I'm not sure how I can shorten the article. AdS/CFT is an enormous topic (according to Google, Maldacena's original paper now has 11,557 citations!), so naturally any survey will be rather long. I welcome comments from other users on how I might improve the length. Polytope24 (talk) 18:26, 28 October 2013 (UTC)[reply]
Looks better to me now. My feeling is that that article is still long, but, yes, this is a huge (and important) subject. Moreover, looking at Wikipedia:Featured_articles/By_length, I see that there are about 1600 FAs which are longer than this article. I'm more comfortable with the length now. Support Spatrick99 (talk) 14:24, 29 October 2013 (UTC)[reply]

Comment: have the sources been spot-checked yet? doesn't look like the GA review checked them. -- Aunva6talk - contribs 22:54, 28 October 2013 (UTC)[reply]

The GA reviewer left some comments about references on this page, which I have tried to address in my revisions. Polytope24 (talk) 23:03, 28 October 2013 (UTC)[reply]

Notes -- Although we have a pretty clear consensus to promote this article, there are still some things that need addressing:

  • Sourcing -- I'd like to see a more comprehensive spotcheck of sources for accuracy and avoidance of close paraphrasing; this is normal procedure for a nominator new to FAC. I'll post a request for this at WT:FAC.
  • Citations -- As a general rule, all paragraphs should end with a citation; this is not the case with the last two paras of Quantum gravity and strings. Pls check for other cases as well.
  • Overlinking -- While linking spacetime makes perfect sense to me, linking space and time seems a bit much; suggest you re-check the article for similar instances of possible overlinking.
  • Duplicate links -- Beyond whether something should be linked at all, there are numerous instances where links are repeated; you can check for the repeated links with this script. Note that in a detailed article you might be justified in re-linking items that appear several sections apart, but pls review in any case.

Cheers, Ian Rose (talk) 04:17, 9 November 2013 (UTC)[reply]

Okay, everything except the spotcheck should be taken care of now. Polytope24 (talk) 04:13, 10 November 2013 (UTC)[reply]
Almost... Appears that everything above has been actioned now except that the last sentence of Three-dimensional gravity is not cited. Also I'm a bit unsure of the wording in a sentence in that subsection: "Another conjecture due to Edward Witten states..." -- "due to" reads oddly to me, do we mean "Another conjecture made by [or attributed to or credited to] Edward Witten, or do we mean "Another conjecture that has arisen owing to the work of Edward Witten, or something else again? Cheers, Ian Rose (talk) 13:18, 16 November 2013 (UTC)[reply]
Fixed. Polytope24 (talk) 22:56, 16 November 2013 (UTC)[reply]
Comments from Quadell

I'll admit up front that I am only able to understand this article in a superficial way, and I am thoroughly unable to follow most of the sources. Despite this, my experience with featured articles on Wikipedia allows me to make a few intelligent comments, at least.

First off, per WP:LEAD, a lead should summarize all sections of the article without containing information not present in other sections. For this reason, most leads do not need citations at all, unless a particular statements is controversial or contains a direct quote. This lead has ten citations; although some are for statements that could be seen as contentious (e.g. "represents a major advance in our understanding"), others are utterly uncontroversial (e.g. "first proposed by Juan Maldacena in late 1997"), and are restated and sourced in the body. I (along with many other reviewers) find most citations in the lead to be an unnecessary distraction.

What is particularly troubling in this instance is that, often, the citations for statements in the lead are not used to support those same statements in the body. For instance, reference 2 sources the lead's statement that AdS/CFT correspondence "represents a major advance in our understanding of string theory and quantum gravity", but the only other place the reference is used says that the work "provided a concrete realization of the holographic principle with important implications for quantum gravity and black hole physics", which isn't really the same thing. If the citation were omitted from the lead, would the lead's claim be supported by citations in the body? I can't tell. Similarly, citation 5 supports the possibly contentious "provides a powerful toolkit" statement in the lead, but is not used in the body. In fact, the source (Klebanov and Maldacena) is only ever used in the body in the introduction to anti-de Sitter space, which is not clearly related to the statement in the lead.

Though I don't feel comfortable supporting or opposing an article I don't fully understand, I do consider the problem with the lead's sourcing to be an impediment to FA status.

In a more minor concern, when a citation says "See the subsection below", this isn't really accurate, since the noted subsection is above the notes section.

Finally, I made a valiant but failed attempt to perform spotchecks. With great effort, I was able to determine that footnote 40 was supported by the source without plagiarism, and I'm 90% sure that the sources for footnotes 25b and 25c support their statements. I can also confirm that these, and several others, do not copy or closely parallel the wording in the sources. But I'm just not competent to analyze whether most of the statements are fully supported by the sources given (although it seems at least plausible in every check I made). – Quadell (talk) 19:53, 10 November 2013 (UTC)[reply]

Thanks for your comments. In the article by de Haro et al., the relevant sentence appears on the second page, where it says
its results are… the suggested implication, acknowledged by Hawking, that black holes do not violate quantum theory… the holographic description of gravity realized in string theory, which has led to key conceptual insights in understanding gravity and geometry…
In the lead, this is being used to justify the statement that the AdS/CFT correspondence represents a major advance in our understanding of quantum gravity. This is definitely related to the subsequent claim that AdS/CFT "provides a concrete realization of the holographic principle with important implications for quantum gravity and black hole physics". The point is that the holographic principle is a very important theoretical idea, and if you have a theory that incorporates this idea, then you can learn a lot about the quantum aspects of gravity, and in particular, how gravitational phenomena like black holes are consistent with quantum mechanics.
The article by Klebanov and Maldacena is being used in the lead to provide a quick reference for the statement that AdS/CFT "provides a powerful toolkit for studying strongly coupled quantum field theories". I would say that this also follows from the material in the body, but I think its good to err on the side of caution when making statements like this.
You're right that this Klebanov-Maldacena article serves a different function in the body of the article. Here the relevant sentence is the following:
The gravitational theory involves a dynamic spacetime fluctuating around a special curved background
The authors are implicitly referring to anti-de Sitter space in this sentence, so this citation is being used to justify the statement that "the geometry of spacetime is described in terms of a certain vacuum solution of Einstein's equation called anti-de Sitter space." Please let me know if there's any problem with this reference.
Please let me know if I should remove any citations from the lead. Thanks. Polytope24 (talk) 20:52, 10 November 2013 (UTC)[reply]
Thanks for your responses. In my interpretation of MOS:LEAD, citations are only needed in the lead if they support particularly contentious statements or direct quotes. (Some articles do make it to FA with more lead citations than necessary, but I think it's optimal to have as few as possible.) Instead, every statement in the lead should be more fully given and expounded upon in the body, and the statement should be supported there with the best source possible. (That's true whether you cite a given statement in the lead or not.) – Quadell (talk) 13:32, 11 November 2013 (UTC)[reply]
Okay, I removed the unnecessary citations in the lead. Polytope24 (talk) 06:39, 12 November 2013 (UTC)[reply]

Great! The only other problems I see are with reference formatting. (You need spaces between the "p." and the page number, and between "sec." and the section number. Page ranges should have en-dashes, rather than "--" or "-". There may be other reference formatting concerns as well.) – Quadell (talk) 12:12, 12 November 2013 (UTC)[reply]

Fixed. Polytope24 (talk) 20:39, 12 November 2013 (UTC)[reply]
I have made a few other formatting changes to the citations, plus two edits (1, 2) that I'm only 90% sure are correct. (Could someone double-check me on that last point?)
My only remaining concern about the references is that if a book has an ISBN, it needs to be included in the "References" section. (Zweibach's A First Course in String Theory, for instance, has an ISBN of 978-0521880329.) Once you add those, all reference formatting concerns should be resolved. – Quadell (talk) 21:46, 12 November 2013 (UTC)[reply]
Done. Polytope24 (talk) 01:08, 13 November 2013 (UTC)[reply]

This article conforms to our MoS, and the references are formatted correctly. I can confirm that it fulfills #2, #3, and probabaly #4 of our Wikipedia:Featured article criteria. Since I'm not qualified to confirm criterion #1, I really can't fully support or oppose in good conscience... but I can at least say that I see no reason this shouldn't be featured. – Quadell (talk) 13:10, 13 November 2013 (UTC)[reply]

Thanks for your help, Quadell! Polytope24 (talk) 13:43, 13 November 2013 (UTC)[reply]

Source spot-check

  • Ref 5, fails verification. Neither Newton nor Maxwell are mentioned in the article.
  • Ref 7, close paraphrasing.
  • Article text: "the most well studied (sic) approach to quantum gravity is string theory"
  • Source text: "string theory, the most studied approach to quantum gravity"
  • Ref 8, fails verification. The citation is preceded by several sentences explaining the four-dimensional nature of spacetime and the peculiarities of string theory and M-theory. P. 8 of Zwiebach doesn't even mention the four dimensions of spacetime. It does support your statements about string theory being ten-dimensional and M-theory being eleven-dimensional. I'm not saying that what you've written about spacetime is incorrect, I'm just saying it isn't cited here. Also, Zwiebach appears to be an undergraduate textbook. Is it considered authoritative, and are these definitions uncontroversial enough that we wouldn't prefer a peer-reviewed source?
  • Ref 16, seems OK. It's difficult to tell without fully understanding the material. The source provided does introduce and define anti-de Sitter space, and seems to include vacuum solution material (albeit without explicitly calling it a vacuum solution).
  • Ref 46, OK.
I was a bit uncomfortable with the material so I may in fact be wrong about ref 16. Polytope24, I have no doubt that you understand the material and that what you've written before ref 8 is correct. However, everything has to be verifiable and even if this is very basic physics, we need a citation supporting spacetime being four-dimensional. Judging by the scarcity of citations in some places, I'm guessing there may be other areas where you've made introductory statements that are not covered by the citation at the end of the paragraph. --Laser brain (talk) 17:59, 13 November 2013 (UTC)[reply]
Thanks for your comments.
  • Citation #5 is meant to provide a reference for the fact that general relativity is part of classical physics. The fact that classical physics was studied by Newton and Maxwell is very basic and easy to verify. I have moved the citation to emphasize that it pertains to the first statement.
  • I tweaked the language near citation #7.
  • I added a citation on the fact that spacetime is four-dimensional. It's true that Zwiebach is an undergraduate textbook, but I don't think that "undergraduate text" and "authoritative" are mutually exclusive. I can cite a more advanced text if people want, but I think that would only make the article harder to verify. Polytope24 (talk) 18:49, 13 November 2013 (UTC)[reply]
Thanks for these changes. For the record, I don't know anything about physics and I found the writing to be appropriately accessible. A novice would likely have to click off into a lot of linked articles for prerequisite information, but that's OK. --Laser brain (talk) 18:59, 13 November 2013 (UTC)[reply]

Closing comment -- It appears to me that the article has had a good mix of reviewers, ranging from those familiar with physics but not with FAC, to the exact opposite -- thanks to all of you. Most importantly the nominator has responded positively and promptly to reviewers' comments -- I hope you've found this a worthwhile experience and will return with other articles, and also take part in reviewing others' FACs, whether maths/science-based or not. Cheers, Ian Rose (talk) 23:37, 16 November 2013 (UTC)[reply]

The above discussion is preserved as an archive. Please do not modify it. No further edits should be made to this page.
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