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JOURNALS // Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika // Archive

Izv. Vyssh. Uchebn. Zaved. Mat., 2024 Number 11, Pages 35–50 (Mi ivm10033)

Weighted Sobolev orthogonal systems with two discrete points and Fourier series with respect to them

M. G. Magomed-Kasumovab

a Daghestan Federal Research Centre of the Russian Academy of Science, 45 M. Gadjiev str., Makhachkala, 367000 Russia
b Southern Mathematical Institute – the Affiliate of Vladikavkaz Scientific Center of Russian Academy of Science, 53 Vatutin str., Vladikavkaz, 362027 Russia

Abstract: We consider the properties of systems $\Phi_1$ orthogonal with respect to a weighted discrete-continuous Sobolev inner product of the form $\langle f,g \rangle_S = f(a)g(a)+f(b)g(b)+\displaystyle\int_a^b f'(t)g'(t)w(t)dt$. The completeness of systems $\Phi_1$ in the Sobolev space $W^1_{L^2_w}$ and the relation of $\Phi_1$ to systems orthogonal in weighted Lebesgue spaces $L^2_u$ are studied. We also analyze properties of the Fourier series with respect to systems $\Phi_1$. In particular, conditions for the uniform convergence of Fourier series to functions from $W^1_{L^2}$ are obtained.

Keywords: discrete-continuous inner product, Sobolev inner product, Fourier series, uniform convergence, coincidence at the ends of the segment, completeness of Sobolev systems.

UDC: 517.538

Received: 17.12.2023
Revised: 27.02.2024
Accepted: 20.03.2024

DOI: 10.26907/0021-3446-2024-11-35-50


 English version:
Russian Mathematics (Izvestiya VUZ. Matematika), 2024, 68:11, 29–43


© Steklov Math. Inst. of RAS, 2026