Talk:de Sitter space

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WikiProject class rating

This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 09:47, 10 November 2007 (UTC)[reply]

AdS

Can someone please unify the notation of this article and the Anti de Sitter one.200.145.112.189 (talk) 17:16, 11 November 2009 (UTC)[reply]

Plain English Summary

It would be great if there was a plain English summary of what de-Sitter space is. Or at least a link to another website where there is an explanation of what de-Sitter space is. Is de-Sitter space space of a certain shape? After reading this article I still have no idea what de-Sitter space is. It seems to me that Wikipedia articles should be written with lay people in mind. This article seems to be highly technical. Dedwarmo (talk) 15:28, 10 April 2013 (UTC)[reply]

Its a highly technical topic. Start by reading the linked articles; they provide background. User:Linas (talk) 04:30, 3 November 2013 (UTC)[reply]

Assessment comment

The comment(s) below were originally left at Talk:De Sitter space/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Geometry guy 21:20, 1 June 2007 (UTC)[reply]

The problem I have with this article is I doubt anyone but hard core physicists can understand what is trying to be conveyed. In that this encyclopedia suppose to be for a general audience I would think a verbalized non-formulated explanation of De Sitter space would be more useful.

May I suggest the follwing link is a possible alternative: =560692

==Agreed==

User:Geometry guy, I totally agree. Dedwarmo (talk) 15:29, 10 April 2013 (UTC)[reply]

Last edited at 15:30, 10 April 2013 (UTC). Substituted at 13:03, 29 April 2016 (UTC)

Defining characteristics of a de Sitter space?

Defining a de Sitter space as a submanifold of a Minkowski space using a vector space as given in the article is unambiguous, but is not ideal as a general mathematical definition, since it relies on embedding and coordinates. If there is another definition along the lines of "a real Lorentzian manifold of dimension n that is maximally symmetric and has constant positive curvature", this would be worth giving. What I have given in quotes defines it locally, and It would be worthwhile noting in the article that other spaces (with distinct topologies) exist with the same local description. For example, in the vector space definition if we identify every point in a de Sitter space with that opposite the origin, we obtain a space with the topology of a punctured projective space (e.g. a Möbius strip for n=2). Such a space is not simply connected, and is not necessarily nonphysical as a model of the universe, notwithstanding the argument that paths exist that reverse the direction of time. Are there any references that discuss these possibilities? —Quondum 20:37, 26 May 2016 (UTC)[reply]

Metric signature

Are the definitions in terms of induced metric from ambient space with the given Miknowski metric (mostly plus convention) and the definition as a homogeneous space as the quotient $O(1; n)/O(1; n - 1)$ and the mention of the Lorentz group as being $O(1; n)$ really in compliance? YohanN7 (talk) 10:44, 9 December 2016 (UTC)[reply]

Lead paragraph

Last paragraph in lead,

More recently it has been considered as the setting for special relativity rather than using Minkowski space, since a group contraction reduces the isometry group of de Sitter space to the Poincaré group, allowing a unification of the spacetime translation subgroup and Lorentz transformation subgroup of the Poincaré group into a simple group rather than a semi-simple group. This alternate formulation of special relativity is called de Sitter relativity.

really needs a reference. Besides, the Poincare group certainly isn't semi-simple (if that is what is hinted). YohanN7 (talk) 10:55, 9 December 2016 (UTC)[reply]

Merge with De Sitter universe

I propose that De Sitter universe be merged into this article. There doesn't seem to be any reason why the two articles should be separate. Thoughts?

I oppose the suggestion. The De Sitter space article is written for scientists who (probably already) understand the mathematics of a De Sitter space. While it has issues, the De Sitter universe article is written for ordinary people who want to understand what a De Sitter space means in the context of cosmology.Work permit (talk) 17:10, 14 April 2017 (UTC)[reply]

I'm removing the banner. There was discussion of this back in 2005, and the proposal garnered no support.Work permit (talk) 20:12, 28 April 2017 (UTC)[reply]

Does anyone actually understand this subject?

Leonard Susskind on the recent Lex podcast, says that he doesn't get De Sitter spaces. And that we live in them. Avindratalk / contribs 03:26, 27 September 2019 (UTC)[reply]

This comment is mostly irrelevant here. If I understand correctly, Susskind was talking about the quantum mechanics of a De Sitter geometry, i.e. its realization in a quantum theory of gravity. This is unrelated to understanding the properties of De Sitter as pseudo-Riemannian manifold which is the main topic of this page. Virtual Neutrino (talk) 10:41, 29 May 2020 (UTC)[reply]