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Timeline for Lipschitz smooth convex extension

Current License: CC BY-SA 4.0

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Nov 17, 2023 at 9:13 vote accept Dmitry Vilensky
Nov 17, 2023 at 8:48 answer added gerw timeline score: 2
Oct 21, 2023 at 18:38 comment added Piotr Hajlasz As far as I am aware, the answer to the question is not known.
Oct 21, 2023 at 7:29 comment added Dmitry Vilensky @DustinG.Mixon, I was thinking about this function too, but I was not able to show that its gradient has the same Lipschitz constant. I stuck at the moment of proving non-expansiveness of $y^* =\arg\max_y\{\dotsi\}$ operator, which differs from projection in that it satisfies $\langle \nabla^2 f(y^*)[x-y^*],z-y^*\rangle \leq 0$, and non-expansiveness holds in some specific local norm associated with x,y, which has spectrum proportional to Hessian, so Lipschitz constant scales as well. I don't see how to avoid this :(
Oct 21, 2023 at 1:48 comment added Dustin G. Mixon I would assume the "right" choice is something like $F(x) := \sup_{y \in S}\big( f(y) + \langle \nabla f(y),x-y \rangle\big)$.
Oct 20, 2023 at 20:32 history asked Dmitry Vilensky CC BY-SA 4.0