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This article is cited in 3 scientific papers (total in 3 papers)
Continuous extension of functions from a segment to functions in $\mathbb{R}^n$ with zero ball means
V. V. Volchkov, Vit. V. Volchkov Donetsk National University, 24 Universitetskaya str., Donetsk, 283001 Republic of Ukraine
Abstract:
Let $\mathbb{R}^n$ be an Euclidean space of dimension $n\geq 2$. For a domain $G\subset \mathbb{R}^n$, we denote by $V_r(G)$ the set of functions $f\in L_{\mathrm{loc}}(G)$ having zero integrals over all closed balls of radius $r$ contained in $G$ (if the domain $G$ does not contain such balls, then we set $V_r(G)=L_{\mathrm{loc}}(G)$). Let $E$ be a nonempty subset of $\mathbb{R}^n$. In this paper we study the following questions related to with the extension problem.
1) Under what conditions given on $E$ continuous function can be extended to the whole space $\mathbb{R}^n$ to a continuous function of class $V_r(\mathbb{R}^n)$?
2) If the above extension exists, obtain growth estimates continued function at infinity.
Theorem 1 of this paper shows that for a wide class of continuous functions on segment $E$ defined in terms of the modulus of continuity there exists extension to a bounded function of class $(V_r\cap C)(\mathbb{R}^n)$ regardless of the length of segment $E$. A similar result is not true for open sets $E$ with a diameter greater than $2r$ even without conditions for extension growth. Theorem 1 also contains an estimate of the velocity decrease of the extended function at infinity in directions orthogonal to the segment $E$.
As Theorem 2 shows, in the case of a space with odd dimension $n$ Theorem 1 holds for any function continuous on $E$ with another growth estimate. The method of proving Theorems 1 and 2 allows one to obtain similar results for functions with zero integrals over all spheres of fixed radius (in this case, an analog of Theorem 2 holds for spaces with even dimension).
Keywords:
spherical and ball means, extension problem, trigonometric series.
Received: 21.04.2020 Revised: 04.06.2020 Accepted: 29.06.2020
Citation:
V. V. Volchkov, Vit. V. Volchkov, “Continuous extension of functions from a segment to functions in $\mathbb{R}^n$ with zero ball means”, Izv. Vyssh. Uchebn. Zaved. Mat., 2021, no. 3, 3–14; Russian Math. (Iz. VUZ), 65:3 (2021), 1–11
Linking options:
https://www.mathnet.ru/eng/ivm9653 https://www.mathnet.ru/eng/ivm/y2021/i3/p3
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Abstract page: | 221 | Full-text PDF : | 63 | References: | 35 | First page: | 8 |
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