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Let $f_n : U \rightarrow \mathbb R$ be a given sequence of functions of class $C^\infty$ on open subsets $U \subset \mathbb R^n$. Does there exist a function $F:\mathbb R \times U \rightarrow \mathbb R$ of class $C^\infty$ such that $$ \frac{\partial^n f}{\partial t^n}(0, x)=f_n(x) $$ for $n=0,1,2,\ldots $ and all $x \in U ?$

flag	asked Oct 8 at 10:17 user 12345 11●1

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en.wikipedia.org/wiki/Borel%27s_lemma – Willie Wong Oct 8 at 10:33

This looks to me like a parametrised version of Borel's theorem. Am I interpreting it correctly? – Andrew Stacey Oct 8 at 10:34

Thanks for help. I did not know earlier that it is Borel's lemma. – user 12345 Oct 8 at 10:49

Alexandre Eremenko · Answer 1 · 2012-10-08 18:45:25Z UTC

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This is Theorem 1.2.6 in L. Hormander, Analysis of linear partial differential operators, vol. I.

edited Oct 8 at 18:45

answered Oct 8 at 13:11

Alexandre Eremenko
10.6k●1●24●39

	Yes, but in Hormander books is assumed additionally that each $f_n$ has compact support. – user 12345 Oct 8 at 19:14
	This is not important. Using the standard technique, partition of unity, (Hormander, section I.1.4) one gets rid of the assumption of compact support. – Alexandre Eremenko Oct 9 at 14:20

Question about existence of function with given derivatives

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