The properties of general Fourier partial sums of functions $f \in C_L$

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Hauptverfasser: Tutberidze, Giorgi, Tsagareishvili, Vakhtang, Cagareishvili, Giorgi
Format: Preprint
Veröffentlicht: 2025
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author Tutberidze, Giorgi
Tsagareishvili, Vakhtang
Cagareishvili, Giorgi
author_facet Tutberidze, Giorgi
Tsagareishvili, Vakhtang
Cagareishvili, Giorgi
contents In this paper, we investigate the convergence properties of Fourier partial sums associated with general orthonormal systems, focusing on functions that belong to specific differentiable function classes. While classical Fourier analysis has extensively studied trigonometric systems, our approach considers a broader class of orthonormal systems, including those adapted to weighted function spaces or arising from orthogonal polynomials. The primary objective is to analyze how the smoothness and differentiability of the function \( f \) affect the rate and nature of convergence of its Fourier partial sums. We derive estimates for the approximation error in various norms and establish sufficient conditions under which uniform or pointwise convergence occurs. In particular, we highlight how differentiability constraints on \( f \) can lead to sharper convergence results than those available for general \( L^2 \)-functions. Furthermore, we explore the impact of specific system properties, such as localization and boundedness, on the summation behavior. Several illustrative examples are provided, demonstrating the theoretical findings for commonly used orthonormal systems. Our results contribute to the deeper understanding of spectral approximations and have potential applications in numerical analysis, signal processing, and the theory of function spaces.
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id arxiv_https___arxiv_org_abs_2509_19311
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publishDate 2025
record_format arxiv
spellingShingle The properties of general Fourier partial sums of functions $f \in C_L$
Tutberidze, Giorgi
Tsagareishvili, Vakhtang
Cagareishvili, Giorgi
General Mathematics
In this paper, we investigate the convergence properties of Fourier partial sums associated with general orthonormal systems, focusing on functions that belong to specific differentiable function classes. While classical Fourier analysis has extensively studied trigonometric systems, our approach considers a broader class of orthonormal systems, including those adapted to weighted function spaces or arising from orthogonal polynomials. The primary objective is to analyze how the smoothness and differentiability of the function \( f \) affect the rate and nature of convergence of its Fourier partial sums. We derive estimates for the approximation error in various norms and establish sufficient conditions under which uniform or pointwise convergence occurs. In particular, we highlight how differentiability constraints on \( f \) can lead to sharper convergence results than those available for general \( L^2 \)-functions. Furthermore, we explore the impact of specific system properties, such as localization and boundedness, on the summation behavior. Several illustrative examples are provided, demonstrating the theoretical findings for commonly used orthonormal systems. Our results contribute to the deeper understanding of spectral approximations and have potential applications in numerical analysis, signal processing, and the theory of function spaces.
title The properties of general Fourier partial sums of functions $f \in C_L$
topic General Mathematics
url https://arxiv.org/abs/2509.19311