Source: Proc. Japan Acad. Ser. A Math. Sci. Volume 80, Number 3
(2004), 15-17.
Pour-El and Richards [5] discussed computable smooth functions
with non-computable first derivatives. We show that a similar
result holds in the case of Sobolev spaces by giving a non-computable
$\mathcal{H}^1(0,1)$-element which, however, is computable
in any of larger Sobolev spaces $\mathcal{H}^s(0,1)$ for any
computable $s$, $0 \le s < 1$.
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