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Fix $\theta\in (-\pi/2,\pi/2)$ and let $a>0$. Suppose that $f:\mathbb{C}\rightarrow \mathbb{C}$ is analytic in $S:=\{z\in \mathbb{C}: |\arg{z}|<\pi/2\}$ and $$|f(z)|\sim |z|^{-a},\qquad |z|\to \infty,\qquad z\in S.$$ Let $g(x):=f(e^{i \theta} x)$. Then $x\mapsto g(|x|)$ is obviously continuous and bounded on $\mathbb{R}^{d}$, and consequently has a Fourier transform in the sense of tempered distributions.

Is it true that

$$|\mathcal{F}\left(g(|\cdot|)\right)(\xi)|\sim |\xi|^{a-d},\qquad \text{as}\quad |\xi|\to 0$$

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    $\begingroup$ There are no such functions $f$: a bounded entire function is constant. $\endgroup$ Commented Jan 11 at 19:37
  • $\begingroup$ I corrected the question. Sorry about the multiple edits. $\endgroup$
    – Medo
    Commented Jan 11 at 20:25

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