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A tempered function on $\mathbb{R}^n$ is a locally integrable function that is tempered as a distribution, i.e. $L^1_{loc}\cap\mathcal{S}'$ is the space of tempered functions.

This MSE question asked for a characterization of tempered functions.

Not every tempered function has a tempered function as its Fourier transform, e.g. the constant function $1$ has the delta distribution $\delta_0$ as its Fourier transform.

My question is, is there a nice characterization of tempered functions whose Fourier transforms are also tempered functions, i.e.

$$ \{ f \in L^1_{loc}\cap\mathcal{S}' : \hat{f} \in L^1_{loc}\cap\mathcal{S}' \} \quad \text{?}$$

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  • $\begingroup$ I would try using the fact that Fourier gives a ¨duality" between multiplication by a coordinate ad derivation with respect to that coordinate. $\endgroup$
    – NameNo
    Commented Jan 15, 2022 at 13:38

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