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Timeline for Can a 2-sphere be squashed flat?

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Aug 29 at 19:05 comment added tomasz I think this should probably follow also from the remarks in the lecture notes linked in the other answer. Specifically, they provide an argument that a length-preserving function cannot be injective on any open set, which for $C^1$ functions implies that the differential is singular everywhere, which should contradict preserving lengths (but my differential geometry is a bit rusty, so don't quote me on that).
Aug 27 at 20:35 comment added Denis T By the way, is it true that if a Finsler sphere was not already conformally (Alexandrov) flat, then it cannot be $C^1$ squashed?
Aug 27 at 18:40 history edited Amir Sagiv CC BY-SA 4.0
Extremely minor tex edits
Aug 27 at 18:24 comment added Graham Smith That's an interesting complement. Thankyou very much!
Aug 27 at 17:28 history edited Guido De Philippis CC BY-SA 4.0
Updated according to the new references.
Aug 27 at 16:34 history edited Guido De Philippis CC BY-SA 4.0
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Aug 27 at 16:22 history answered Guido De Philippis CC BY-SA 4.0