Hello! I've found this paper, wherein page 33 states that the reverse PoincarĂ© inequality gives(adsbygoogle = window.adsbygoogle || []).push({});

[tex]\forall v \in H^1_0(\Omega) , \|v\|_{L^2(\Omega)} \leq C(\Omega) \|\nabla v\|_{L^2(\Omega)} [/tex]

This I can follow - it gives a norm equivalence between the norm of a vector and the gradient of its gradient (clumsily expressed, I know). However, just a little bit later the paper states that

[tex]\|u\|_{H_0^1(\Omega)} = \|\nabla u\|_{L^2(\Omega)}[/tex]

That is, those two norms are equivalent. This is what I don't understand - I don't understand the jump from the L^2-norms in the first statement to the Sobolev norm in the second. Any help in understanding this would be helpful.

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# Norm equivalence between Sobolev space and L_2

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