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The goal is to show that $\sup{|u|} \leq C|\Omega|^{\frac{1}{n} - \frac{1}{p}}||Du||_p$ in the case $p>n$.

There is a point in the proof that I just am not getting. First, the notation:
Let $n' = \frac{n}{n-1}, p' = \frac{p}{p-1}, \delta = \frac{n'}{p'}$ It is shown in the proof that if $\tilde{u} = \frac{\sqrt{n}|u|}{||Du||_p}$ that

$$||\tilde{u}||_{n'\delta^v} \leq \delta^{v\delta^{-v}}||\tilde{u}||_{n'\delta^{v-1}}^{1-\delta^{-v}} $$

This part I'm ok with. Then the book makes the statement "Iterating from $v=1$ ,we get for any $v$"

$$||\tilde{u}||_{\delta^v} \leq \delta^{\sum{v\delta^{-v}}}.$$

I don't see how this follows. Could you maybe give some insight?

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    Could you write the indexes in the sum?2012-09-29
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    Write down the inequality when $\nu=1$, then $\nu=2$, then $\nu=3$. Can you plug the first case into the second, then nto the third, and so on?2012-09-29
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    The book doesn't give indices in the sum. Presumably it's a sum over positive integers $v$. @Siminore I'm not sure exactly what you mean?2012-09-30
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    Probably $$\|\tilde{u}\|_{\delta^\nu} \leq \delta^{\nu \delta^{-\nu}}\delta^{(\nu -1)\delta^{-\nu+1}} \delta^{(\nu -2)\delta^{-\nu+2}}\cdots$$2012-09-30
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    @Siminore Yes, but what happened to the $n'$? The statement just has $\delta^v$2012-10-01
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    I did not write down the computation, but I guess $n'$ is irrelevant since it appears in both sides. Probably you can absorb it as a factor, somewhere.2012-10-02

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