Convergence of distributional approximate identities

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Let the function g∈L1(R)g \in L_{1}(\mathbb {R}) and ∫Rgdx=1\int_{\mathbb {R}} g d x = 1. Let Fn∈D′F_{n} \in \mathcal{D}^{\prime } be the regular generalized functions generated by the functions ng(nx)n g(n x). Prove that Fn∗φ→φF_{n} * \varphi \rightarrow \varphi in D\mathcal{D} for every function φ∈D\varphi \in \mathcal{D} (cf. problems 16.20 and 18.31 а)).

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Suppose {fi}\left\{ f_{i}\right\} is a sequence of locally integrable functions in Rn\mathbb {R}^{n}, such that

lim⁡i→∞(fi∗ϕ)(x) \lim _{i \rightarrow \infty }\left(f_{i} * \phi \right)(x)

exists, for each ϕ∈D(Rn)\phi \in \mathscr {D}\left(\mathbb {R}^{n}\right) and each x∈Rnx \in \mathbb {R}^{n}. Prove that then {Da(fi∗ϕ)}\left\{ D^{a}\left(f_{i} * \phi \right)\right\} converges uniformly on compact sets, for each multi-index α\alpha.

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If {hj}\left\{ h_{j}\right\} is an approximate identity, as in Definition 6.31, and u∈Sn′u \in \mathscr {S}_{n}^{\prime }, does it follow that u∗hj→uu * h_{j} \rightarrow u as j→∞j \rightarrow \infty, in the weak*-topology of Sn′\mathscr {S}_{n}^{\prime }?

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References

[БСШ17] Бородин П.А., Савчук А.М., Шейпак И.А. Задачи по функциональному анализу. МЦНМО, 2017.
[Rud91] Rudin W. Functional Analysis. 2nd ed., McGraw-Hill, 1991.