Talk:Anti-de Sitter space

message: I substituted saddle and trumpet bell as examples of surfaces with hyperbolic or negative curvature.  A bowl, being spherical, is not such a good example because it has positive curvature whether viewed from the inside or outside.  Similarly in the following section on the rubber-sheet analogy I pointed out the trumpet-bell-shaped (rather than bowl-shaped) nature of the depression, responsible for the inward deviation of trajectories passing nearby.CharlesHBennett (talk) 05:04, 8 May 2010 (UTC)
thread_title: Introduction for non-expert

message: This article should probably be split:
# n-dimensional AdS, with better explanation of important work in math and non-gtr theories, with some interesting general coordinate charts such as Hopf charts,
# the four dimensional example, with discussion of nice coordinate charts as in Hawking and Ellis
Both revised articles should begin with much simpler intros for laypersons, and should have better citations.  The second should have citations in WikiProject GTR format.---CH  (talk) 01:54, 15 September 2005 (UTC)
thread_title:  Article needs much work 

message: Is it the y coordinate which is bounded from one side? --MarSch 17:43, 1 November 2005 (UTC)
replies: text: Hi, MarSch, in the given chart y > 0 , as for upper half space model of Hn.  Yes, anyone typing in a line element should always repeat  always  add the intended ranges of the coordinates.  Few simple actions can be as helpful in avoiding potential confusion in this subject!---CH 20:06, 5 February 2006 (UTC)
thread_title:  half-space chart 

message: It would be very nice with some references to some expository article (or book?).  (unsigned comment by 130.238.149.247)
:Indeed yes.  Someone removed the expert flag I am now restoring.  I am adding a short todo list which will include your request. ---CH 19:46, 5 February 2006 (UTC)
thread_title:  References 

message: The "picture" on the page is completely blank. It presumably should be removed or replaced. Gene Ward Smith 21:52, 4 May 2006 (UTC)
replies: text: Picture works OK for me.  A red cylinder sliced at two green ellipses.  Maybe it's your browser?  You might consider switching to a more PNG friendly browser if you haven't already.  PNG has been a W3C standard for a decade and it's the recommended format on Wikipedia, after all. -lethe talk [ +] 22:05, 4 May 2006 (UTC)
thread_title:  Blank image 

message: I deleted the last paragraph, starting with "To simplify the AdSCFT correspondence it is like...", which was a very bad analogy. Dan Gluck 06:29, 15 September 2006 (UTC)
thread_title:  Deleted from to-do list 

message: The article states that AdS space has O(2,n-1) as automorphism group.
The article should specify which kind of automorphisms (i.e. automorphisms = isometries of a pseudo-Riemannian manifold). Pierreback 19:15, 25 February 2007 (UTC)
replies: text: Should be clear now, I think. User:Linas (talk) 03:56, 3 November 2013 (UTC)
thread_title:  Automorphism group O(2,n-1) 

message: The definition now says that '\alpha' should be a negative constant, but we have '\alpha^2' in the equation? 
This is wrong. Pierreback 16:27, 28 February 2007 (UTC)
thread_title:  Wrong def 

message: The sentence "Anti de Sitter spacetime has closed time-like loops" uses the term "anti de siter spacetime" for the first time in the article. I guess it should be changed to "anti de sitter space". Also, an explanation of "closed time-like loops" should be added. 83.253.30.214 11:27, 21 July 2007 (UTC)
replies: text: Ok; I've added some info about closed timelike loops, and some more links. Ben Standeven 17:09, 23 July 2007 (UTC)
thread_title:  Sentence 

message: Does anybody have some good mathematical definition concerning the conformal boundary? This should be added.
"In the limit as y = 0, this reduces to a Minkowski metric dy^2=\left(dt^2-\sum_idx_i^2\right); thus, the anti-de Sitter space contains a conformal Minkowski space at infinity ("infinity" having y-coordinate zero in this patch)."
83.253.30.214 11:34, 21 July 2007 (UTC)
thread_title:  Conformal boundary 

message: Can someone write what that notation means? Because here the anti de Sitter space have two parameters. 200.145.112.189 (talk) 22:45, 18 November 2009 (UTC)
thread_title: AdS_n

message: "...is a maximally symmetric Lorentzian manifold with constant negative scalar curvature. It is the Lorentzian analogue of n-dimensional hyperbolic space, just as Minkowski space and de Sitter space are the analogues of Euclidean and elliptical spaces respectively."
did you write this in some weird language by mistake, because I CANNOT MAKE HEADS OR TAILS OF WTF YOUR TALKING ABOUT!!!!  —Preceding unsigned comment added by 96.231.28.194 (talk) 01:17, 2 November 2010 (UTC)
thread_title:  what the hell does this mean? 

message: I know mid-sentence this is "anti de Sitter space" and not "Anti de Sitter space", but surely the usual laws of grammar apply, and when it's the first word in a sentence, or subheading, it should get a capital "A"? -- Dr Greg  talk  19:47, 9 February 2013 (UTC)
replies: text: Yes. And there should be a hyphen too: anti-de Sitter space.  User:Linas (talk) 04:44, 3 November 2013 (UTC)
thread_title:  Capitalisation 

message: A large part of the "non-technical" section of this article deals with AdS/CFT ... but we already have a lengthly non-technical article on that. Could someone please cut this section, here? 99.153.64.179 (talk) 04:42, 3 November 2013 (UTC)
thread_title:  remove material on AdS/CFT 

message: I would urge the editors NOT to take out the non-technical section.  Most mathematics articles in Wikipedia are USELESS unless you already know the material.  This is one of the rare exceptions that offers some non-technical explanations, which are extremely helpful to the non-expert trying to make sense of the more arcane sections.98.170.198.158 (talk) 17:38, 3 April 2014 (UTC)
replies: text: The tone of the non tech exp is puffy and wordy, yet patronizing. Keep, but rewrite and shorten. 2001:62A:4:41C:B580:3333:57FA:52FB (talk) 14:03, 24 August 2017 (UTC)
replies: text: Puffy and wordy, a bit, but very helpful. Please don't shorten. RobLandau (talk) 22:31, 8 August 2018 (UTC)
thread_title:  Non-technical explanation 

message: The 5d interpretation is not quite clear to me. Curvature is an intrinsic property of a manifold. Thus, it appears that the 5d interpretation is not really necessary for anti de Sitter space. The 4d manifold can be embedded in 5d but it seems not necessary and there are many possible embeddings. Is this correct? Should that be mentioned?  — Preceding unsigned comment added by 152.3.73.36 (talk) 17:37, 8 December 2014 (UTC)
replies: text: I agree that it is not entirely clear.  As I understand it, Anti-deSitter space of any dimension can be embedded in a vector of one extra space-like dimension (but this is not a homogeneous space, since it has a unique origin), where the metric tensor is inherited via the embedding from a Lorentzian quadratic form on the vector space.  Because this is an embedding in a flat space, such an interpretation seems to be a reasonable way to make it understandable.  I do find the wording of the section confusing and possibly not accurate, though, so it could do with some attention. —Quondum 22:14, 8 December 2014 (UTC)

text: I reworded this earlier to at least refer to it as an embedding rather than as a 5-d space, so hopefully at least improved. —Quondum 14:57, 7 July 2016 (UTC)
replies: text: The embedding is total explicit -- it's just the solution of a quadratic equation -- and it gives the metric, not just the topology. See the section above called "Best definition of AdS space?". 2001:62A:4:418:E898:CDB4:21AB:526E (talk) 14:17, 24 August 2017 (UTC)
thread_title:  5d interpretation 

message: The introduction is so complicated, so full of terminology specific to the subject, that it would only make sense to someone who already knows the subject - which makes it worthless to someone trying to learn the subject - which means it is a waste of time in a reference work.  At the very least, there needs to be a non-technical thesis statement at the beginning. Pb8bije6a7b6a3w (talk) 17:51, 16 November 2015 (UTC)
thread_title:  Simplify intro 

message: There is an implicit convention being adopted when calling the curvature of AdS negative.  Specifically, the sign of the curvature flips with that of the metric tensor, or (from a physicist's perspective), with which dimensions are labelled spacelike.  To refer to the sign of the curvature without stating the convention, or calling out that the sign is not an absolute, is therefore misleading.  Surely should be mentioned and if possible sourced?
To make it clearer: AdS2 and dS2 are the same two-dimensional space; they differ only in which dimension is labelled "time" and which is "space".  Yet, the curvature is considered to be negative and positive respectively.  This ambiguity of convention occurs with all of the spaces AdSp,q.  —Quondum 14:54, 7 July 2016 (UTC)
thread_title:  "negative" curvature 

message: The sentence "For example, in general relativity, objects in motion have a slightly different gravitation effect than objects at rest." is rubbish. There is no such thing like an "object in motion" or an "object at rest" in general relativity. These notions related to Newtonian absolute space and thus are incorrect ontologies.
: I agree with this. Even though some (correct) meaning shines through for someone in the know, this sentence is extremely misleading for anybody who reads this for actually seeking information. I'll take it out. WikiPidi (talk) 11:45, 18 November 2019 (UTC)
thread_title:  Incorrect 

message: In the article it is stated  S^2  = \frac{O(3)}{O(2)}, but it's not at all clear what this means.  Clearly it's not a statement about groups because  S^2  is not a group, so it must be a statement about diffeomorphisms between topological spaces.  But modding manifolds by submanifolds never changes dimensions and as it stands this would say a 3-dimensional thing is homeomorphic to a 2-dimensional thing which is also nonsense.  I think the intention is maybe something along the lines of the Hopf map  S^1 \hookrightarrow S^3 \twoheadrightarrow S^2.  I assume something similar holds in the other cases but I have no idea.  — Preceding unsigned comment added by INLegred (talk • contribs) 19:46, 27 March 2020 (UTC)
replies: text: O(2) is a subgroup of O(3) and hence acts on it by left (right) multiplication. I read  S^2  = \frac{O(3)}{O(2)} as referring to the quotient space O(3)/O(2) of the action of O(2) on O(3). Shmuel (Seymour J.) Metz Username:Chatul (talk) 06:42, 1 May 2020 (UTC)
thread_title:  Nonsense definiton 

message: There is no absolute parallelism in GR, only parallel transport along a curve. The phrase parallel geodesic only has meaning when the manifold is parallelizable and a parallelization is specified. I realize that this is a common error in popularizations, but it is still wrong. Shmuel (Seymour J.) Metz Username:Chatul (talk) 06:04, 1 May 2020 (UTC)
thread_title:  Parallel geodesics! 

message: :The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review after discussing it on the closer's talk page. No further edits should be made to this discussion. 
The result of the move request was: not moved. (non-admin closure)  ModernDayTrilobite (talk • contribs) 17:42, 11 January 2023 (UTC)
replies: text: Anti-de Sitter space →  – It is impossible to tell from search whether this is usually spelled with a hyphen or an en dash, but MOS:PREFIXDASH calls for an en dash since  is one name. –LaundryPizza03 (dc̄) 10:28, 1 January 2023 (UTC)

text: In the instance "anti-de Sitter space", there is no ambiguity for the average reader, since "anti-de" does not parse.  To use an en dash on something that does not need an additional cue then suggests that it may need to be interpreted as a symmetric coupling rather than "anti" being a modifier.  This takes a bit more thinking by the reader to rule out.  Basically, IMO it is less cognitive load to read with a hyphen than with an en dash (it looks odd).  My suggestion would be to make no change, especially as the case to change it is unclear, with any real need for an en dash being removed by there being another cue.  Blindly applying MoS guidelines can produce odd constructions.  —Quondum 19:48, 1 January 2023 (UTC)
replies: text: I browsed through article titles in Physical Review D, and found that of the first 100 search results at , about 3/4 use the en dash when spelling out AdS the title. I could reproduce this fraction for slight variations in the search. –LaundryPizza03 (dc̄) 05:29, 2 January 2023 (UTC)
replies: text: I think what you're seeing is just APS house style. I checked the references that the Wikipedia article is using, and only one used an en-dash instead of an hyphen: the one published by APS. Tercer (talk) 11:22, 2 January 2023 (UTC)
thread_title:  Requested move 1 January 2023 

message: "Some authors define anti-de Sitter space as equivalent to the embedded quasi-sphere itself, while others define it as equivalent to the universal cover of the embedding." This seems very important and should not be buried. --99.238.150.103 (talk) 18:08, 10 September 2023 (UTC)
thread_title:  rolled vs unrolled