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Mar 9, 2023 at 10:57 comment added Hyperbolic PDE friend I see, thanks a lot!
Mar 9, 2023 at 10:20 comment added cs89 The supremum with $v \in C^1$ or $v \in C^\infty$ is the same. You only need to change the construction of the sequence $v_n$. With my notations, you want to construct $v_n \in C^\infty([0,1])$ with $v_n(x) = 1$ for $x \in [1/n,1]$, $v_n(0) = \sigma$, and $\sigma \leq v_n(x) \leq 1$ on $[0,1/n]$. Making a $C^\infty$ junction at $x =1/n$ is rather standard. You can choose $v_n(x) = 1+(\sigma-1) \exp(1-1/s^2)$ where $s = n(x-1/n)$.
Mar 9, 2023 at 9:12 comment added Hyperbolic PDE friend and $o \in C^\infty(\mathbb{R})$ for that matter.
Mar 9, 2023 at 8:54 comment added Hyperbolic PDE friend This is a great answer, thank you! Do you have any idea what happens when we additionaly demand $u \in W^{\infty, \infty}([a, b])$?
Mar 9, 2023 at 8:54 vote accept Hyperbolic PDE friend
Mar 9, 2023 at 8:46 comment added cs89 The same argument also works for the maximization version. I edited my answer.
Mar 9, 2023 at 8:45 history edited cs89 CC BY-SA 4.0
Changed minimization problem to maximization as asked by @Meowdog
Mar 9, 2023 at 8:18 comment added Hyperbolic PDE friend This is a very good answer, thank you! But I made a mistake myself... I wanted the problem to be a maximum problem and I wrote minimum. Still, I hope that I can maybe rewrite your argument... I would still be happy if you could provide some insight
Mar 9, 2023 at 0:19 history answered cs89 CC BY-SA 4.0