On Changes of Variable Preserving the Convergence and Absolute Convergence of Fourier Series in the Haar Wavelet System

Autor: K. R. Bitsadze
Rok vydání: 2020
Předmět:
Zdroj: Mathematical Notes. 108:162-170
ISSN: 1573-8876
0001-4346
DOI: 10.1134/s0001434620070172
Popis: It is established that, among all continuously differentiable homeomorphic changes of variable, the absolute convergence of Fourier series in the Haar wavelet system is preserved by only those for which $$\varphi^{-1}(0)$$ is binary-rational and $$\varphi'(x)=\pm 2^m$$ , where $$m$$ is an integer and $$x\in\mathbb R$$ . It is also established that this condition is necessary for a continuously differentiable homeomorphic change of variable to preserve the convergence of Fourier series in the Haar wavelet system.
Databáze: OpenAIRE