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Mar 17, 2013 at 7:45 answer added Daniel Spector timeline score: 0
Mar 6, 2013 at 5:40 history edited Delio Mugnolo CC BY-SA 3.0
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Mar 5, 2013 at 5:33 answer added Craig timeline score: 1
Feb 21, 2013 at 9:14 comment added Daniel Spector I guess then the first question is what do Lions-Magenes mean by $\Delta u=f$ for $f \in L^2(\Omega)$? Likely these quantities are defined almost everywhere and so it is in some integral sense. Maybe the $C^\infty$ assumption is to do the extension and use Fourier transforms or some other technique like this on the whole space? I will look for a copy of it in the library and get back to you.
Feb 21, 2013 at 8:20 comment added Delio Mugnolo I don't see how this implies $u\in H^1$ (or better) by the general PDE theory. All I am aware of is that you do have $H^1$ (indeed, usually even $H^2$) if you can apply Gauß-Green so that you can set up a variational formulation and apply Lax-Milgram. But in this case this is not possible, since we have no idea of what happens at the boundary.
Feb 21, 2013 at 8:01 comment added Daniel Spector I think it should be worded differently, because if $u \in H^\frac{1}{2}$ then $u \in L^2$, and by the PDE this implies $u \in H^1$ (or better). Do you mean the fractional semi-norm of $u$ is finite, in this case?
Feb 20, 2013 at 18:46 comment added Delio Mugnolo it is independent of the boundary condition, that is exactly the point.
Feb 20, 2013 at 18:37 comment added Daniel Spector Do you want to add a boundary condition, or is this result independent of that?
Feb 20, 2013 at 17:56 history edited Delio Mugnolo CC BY-SA 3.0
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Feb 20, 2013 at 17:18 history asked Delio Mugnolo CC BY-SA 3.0