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Dec 31, 2022 at 13:43 history edited Anton Petrunin
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Apr 20, 2011 at 18:21 comment added Igor Belegradek A most recent discussion of these issues is the following paper [Taylor, Trans. Amer. Math. Soc. 358 (2006), 2415-2423] avaialble at ams.org/journals/tran/2006-358-06/S0002-9947-06-04090-6/…
Apr 20, 2011 at 17:38 comment added Andrew @Deane Yang Thank you for DeTurck and Yang reference! I've read their later work, but didn'ty knew this one. Sorry, instead of global coordinates I should say a smooth atlas.
Apr 20, 2011 at 17:34 comment added Willie Wong @Igor: you posted a link to the Georgia Tech proxy, which most of us cannot go through :-p. The link Igor meant to post is MR: ams.org/mathscinet-getitem?mr=MR2204038 article: dx.doi.org/10.1090/S0002-9947-06-04090-6
Apr 20, 2011 at 17:17 vote accept Andrew
Apr 20, 2011 at 16:53 history edited George Lowther CC BY-SA 3.0
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Apr 20, 2011 at 16:46 comment added Willie Wong On #2: if you believe that the best coordinates one can use is the harmonic ones, then in fact on any compact, closed manifold, you will not be able to extend the coordinates globally...
Apr 20, 2011 at 16:21 comment added Willie Wong In fact, for #1, in the DeTurck-Kazdan paper you find a counterexample in the first paragraph. Note that in this case "changing coordinates" actually corresponds to changing atlas (as noted by Anton below). I wonder if for #1 you intend them to be Einstein manifolds? In which case the result is true using elliptic regularity.
Apr 20, 2011 at 16:20 answer added Deane Yang timeline score: 7
Apr 20, 2011 at 16:18 answer added Vladimir S Matveev timeline score: 8
Apr 20, 2011 at 15:16 answer added Anton Petrunin timeline score: 14
Apr 20, 2011 at 14:07 comment added Deane Yang For #1, see: DeTurck, Dennis M.; Kazdan, Jerry L. Some regularity theorems in Riemannian geometry. Ann. Sci. École Norm. Sup. (4) 14 (1981), no. 3, 249–260. You need assumptions on the curvature tensor (and its covariant derivatives) if you want higher regularity. I don't know what you mean by #2. Could you explain why the three-dimensional sphere has global co-ordinates?
Apr 20, 2011 at 11:01 history asked Andrew CC BY-SA 3.0