Abstract:
Let $f$ be a function holomorphic in the upper half-plane and belonging to the Nevanlinna class $N(\mathbb{C}_+)$. Assume that
$$
\varlimsup_{y\to+\infty}\frac{\ln|f(iy)|}{y}\le 0
$$
and that the boundary values of $f$ on the real axis lie in $L^1(\mathbb{R})$. It is shown that if $\vert\widehat{f}(x)\vert\le\frac{1}{\lambda(|x|)}$, $x\in{\mathbb{R}_-}$, where $\widehat{f}$ is the Fourier transform of $f$ and $\lambda$ is a logarithmically convex positive function on ${\mathbb{R}_+}$, then the condition $\int_{1}^{+\infty}\frac{\ln \lambda(x)}{x^{3/2}}\,dx=+\infty$ implies that $\widehat{f}(x)=0$ for all $x\in{\mathbb{R}_-}$. Conversely, if one of the conditions listed above fails, then there exists $f\in N(\mathbb{C}_+) \cap L^1(\mathbb{R})$ with $\widehat{f}(x)\ne 0$, $x\in{\mathbb{R}_-}$.
Keywords:
Function of bounded characteristic, Fourier transform.
Citation:
F. A. Shamoyan, “On Fourier transforms of functions of Nevanlinna class in a half-plane”, Algebra i Analiz, 20:4 (2008), 218–240; St. Petersburg Math. J., 20:4 (2009), 665–680
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\by F.~A.~Shamoyan
\paper On Fourier transforms of functions of Nevanlinna class in a half-plane
\jour Algebra i Analiz
\yr 2008
\vol 20
\issue 4
\pages 218--240
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\transl
\jour St. Petersburg Math. J.
\yr 2009
\vol 20
\issue 4
\pages 665--680
\crossref{https://doi.org/10.1090/S1061-0022-09-01066-8}
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Linking options:
https://www.mathnet.ru/eng/aa527
https://www.mathnet.ru/eng/aa/v20/i4/p218
This publication is cited in the following 3 articles:
F. A. Shamoyan, “Boundary quasianalyticity and a Phragmén–Lindelöf type theorem in classes of functions of bounded type in tubular domains”, St. Petersburg Math. J., 33:6 (2022), 1035–1046
F. A. Shamoyan, “Fourier transform and quasi-analytic classes of functions of bounded type on tubular domains”, Funct. Anal. Appl., 51:2 (2017), 157–160
F. A. Shamoyan, “On Fourier transforms of functions of bounded type in tubular domains”, Siberian Math. J., 57:6 (2016), 1100–1116