Abstract:
We consider a problem of approximation by entire functions of exponential type of functions defined on a countable set EE of continuums GnGn, E=⋃n∈ZGn. We assume that all Gn are pairwise disjoint and are situated near the real axis. We assume too that all Gn are commensurable in a sense and have uniformly smooth boundaries. A function f is defined independantly on each Gn and is bounded on E and f(r) has a module of continuity ω which satisfies a condition ∫x0ω(t)/tdt+x∫∞xω(t)/t2dt⩽cω(x). Then we construct an entire function Fσ of exponential type ⩽σ such that we have the following estimate of approximation of the function f by functions Fσ: |f(z)−Fσ(z)|⩽cfσ−rω(σ−r),z∈Z,σ⩽1.
Keywords:
Holder classes, approximation, entire functions of exponential type.
Citation:
O. V. Silvanovich, N. A. Shirokov, “Approximation by entire functions on a countable set of continuums”, Vestnik of Saint Petersburg University. Mathematics. Mechanics. Astronomy, 7:3 (2020), 481–489; Vestn. St. Petersbg. Univ., Math., 7:3 (2020), 329–335
\Bibitem{SilShi20}
\by O.~V.~Silvanovich, N.~A.~Shirokov
\paper Approximation by entire functions on a countable set of continuums
\jour Vestnik of Saint Petersburg University. Mathematics. Mechanics. Astronomy
\yr 2020
\vol 7
\issue 3
\pages 481--489
\mathnet{http://mi.mathnet.ru/vspua171}
\crossref{https://doi.org/10.21638/spbu01.2020.310}
\transl
\jour Vestn. St. Petersbg. Univ., Math.
\yr 2020
\vol 7
\issue 3
\pages 329--335
\crossref{https://doi.org/10.1134/S1063454120030139}
Linking options:
https://www.mathnet.ru/eng/vspua171
https://www.mathnet.ru/eng/vspua/v7/i3/p481
This publication is cited in the following 1 articles:
O. V. Silvanovich, N. A. Shirokov, “Approximation by entire functions on a countable set of continua. The inverse theorem”, Vestn. St. Petersbg. Univ., Math., 8:4 (2021), 366–371