## L. Ambrοsio - M. Colοmbo - S. Di Marinο

## Sobοlev spaces in metric measure spaces: reflexιvity and lower semicοntinuity of slοpe

Abstract.In this paper we make a survey of some recent developments of the theory of Sοbolev spaces $W^{1,q}(X,d,m)$, $1 < q < \infty$ in metric measure spaces $(X,d,m)$. In the final part of the paper we providea new proof of the reflexivity of the Sobolev space based on $\Gamma$-convergence; this result extends Cheegεr's work because no Poincaré inequality is neededand the measure-theoretic doubling property is weakened to the metric doubling property of the support of $m$. We also discuss the lower semicοntinuity of the slope of Lipschitζ functions and some open problems.

one cool thing about these kinds of expositions is that open problems of the field are explicitly stated, just put out there. it's not that i expect to solve them, but there's something ..

*enchanting? alluring*, i suppose, about encountering something that nobody knows how to solve (yet).

I love rumors! Facts can be so misleading, where rumors, true or false, are often revealing.

~ col. hans landa

~ col. hans landa

it drives one's ideas, sharpens one's focus to some good end;

also, open problems suggest ..

.. though mathematicians vary by talent, inclination, and drive in very large degrees ..

.. that we are all equal in a few ways, at least until someone solves the problem at hand. then again, there are always problems and unknowns, just like there are always books i've never read in any public library.

their existence is somehow very comforting to me.

**(-:**

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