Timeline for Why is a simply connected homology sphere a topological sphere?
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
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| Nov 30, 2021 at 20:50 | comment | added | HJRW | No: see this recent Quanta article to get an idea of how much more difficult the 4d case is. quantamagazine.org/… | |
| S Nov 30, 2021 at 17:55 | history | suggested | CommunityBot | CC BY-SA 4.0 |
The h-cobordism theorem is unknown in dimension 4, so I changed the reason to the generalized Poincaré conjecture.
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| Nov 30, 2021 at 17:54 | comment | added | user131113 | @HJRW I thought that the only difference in dimension 4 is an application of the Whitney trick. | |
| Nov 30, 2021 at 1:35 | review | Suggested edits | |||
| S Nov 30, 2021 at 17:55 | |||||
| Nov 28, 2021 at 16:49 | comment | added | HJRW | Perhaps it's worth noting that the result that "any homotopy sphere is actually a topological sphere" is often called "the generalised Poincaré conjecture" (en.wikipedia.org/wiki/Generalized_Poincaré_conjecture), and its proof in dimension 4 is quite different from the proof in dimensions $\geq 5$. | |
| Nov 28, 2021 at 2:15 | history | answered | user131113 | CC BY-SA 4.0 |