Abstract
In this paper, we construct a two-variable integrable function \(U\) whose Fourier coefficients by the double Walsh system are positive on the spectrum and arranged in decreasing order in all directions. For each almost everywhere finite measurable function \(f(x,y)\), \((x,y)\in[0,1)^{2}\), and for any \(\delta>0\) it is possible to find a bounded function \(g(x,y)\) such that
and \(|c_{k,s}(g)|=c_{k,s}(U)\) on the spectrum of the function \(g\), and its spherical partial sums of the Fourier series by the double Walsh system converge uniformly on \([0,1)^{2}.\)
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REFERENCES
B. Golubov, A. Efimov, and V. Skvortsov, Walsh Series and Transforms, Mathematics and Its Applications, Vol. 64 (Springer, Dordrecht, 1991). https://doi.org/10.1007/978-94-011-3288-6
I. P. Natanson, Theory of Functions of Real Variable (Nauka, Moscow, 1974).
C. Watari, ‘‘Mean convergence of Walsh-Fourier series,’’ Tohoku Math. J. 16, 183–188 (1964). https://doi.org/10.2748/tmj/1178243704
M. G. Grigoryan, ‘‘On the universal and strong \((L^{1},L^{\infty})\)-property related to Fourier–Walsh series,’’ Banach J. Math. Anal. 11, 698–712 (2017). https://doi.org/10.1215/17358787-2017-0012
M. G. Grigorian, ‘‘Uniform convergence of the greedy algorithm with respect to the Walsh system,’’ Stud. Math. 198 (2), 197–206 (2010). https://doi.org/10.4064/sm198-2-6
N. N. Luzin, ‘‘On the main theorem of integral calculus,’’ Mat. Sb. 28 (2), 266–294 (1912).
D. E. Men’shov, ‘‘On the uniform convergence of Fourier series,’’ Mat. Sb. 53 (2), 67–96 (1942).
M. G. Grigoryan and A. A. Sargsyan, ‘‘On the universal function for the class \(L^{p}[0,1],p\in(0,1)\),’’ J. Funct. Anal. 270, 3111–3133 (2016). https://doi.org/10.1016/j.jfa.2016.02.021
M. G. Grigoryan and L. N. Galoyan, ‘‘On the universal functions,’’ J. Approximation Theory 225, 191–208 (2018). https://doi.org/10.1016/j.jat.2017.08.003
M. G. Grigoryan, ‘‘Universal Fourier series,’’ Math. Notes 108, 282–285 (2020). https://doi.org/10.1134/S0001434620070299
M. G. Grigoryan, ‘‘Functions with universal Fourier–Walsh series,’’ Sb.: Math. 211, 850–874 (2020). https://doi.org/10.1070/sm9302
M. G. Grigoryan and L. N. Galoyan, ‘‘Functions universal with respect to the trigonometric system,’’ Izv.: Math. 85, 241–261 (2021). https://doi.org/10.1070/im8964
A. Kolmogoroff, ‘‘Sur les fonctions harmoniques conjuguées et les séries de Fourier,’’ Fundamenta Math. 7, 24–29 (1925). https://doi.org/10.4064/fm-7-1-24-29
M. Riss, ‘‘Sur les fonctions conjugees,’’ Math. Z. 27, 214–244 (1927).
L. Carleson, ‘‘On convergence and growth of partial sums of Fourier series,’’ Acta Math. 116, 135–157 (1966). https://doi.org/10.1007/bf02392815
C. Fefferman, ‘‘The multiplier problem for the ball,’’ Ann. Math. 94, 330–336 (1971). https://doi.org/10.2307/1970864
D. C. Harris, ‘‘Almost everywhere divergence of multiple Walsh–Fourier series,’’ Proc. Am. Math. Soc. 101, 637–643 (1987). https://doi.org/10.1090/s0002-9939-1987-0911024-3
M. G. Grigoryan, ‘‘Convergence in the metric of \(L^{p}\), \(o<p<1\), of spherical partial sums of double Fourier series,’’ Math. Notes Acad. Sci. USSR 33, 264–270 (1983). https://doi.org/10.1007/BF01157057
R. D. Getsadze, ‘‘A continuous function with multiple Fourier series in the Walsh–Paley system that diverges almost everywhere,’’ Math. USSR Sb. 56, 262–286 (1987). https://doi.org/10.1070/SM1987v056n01ABEH003035
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The work is supported by the Science Committee of the Republic of Armenia, project no. 21AG-1A066.
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Translated by E. Oborin
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Sargsyan, S.A., Galoyan, L.N. On the Uniform Convergence of Spherical Partial Sums of Fourier Series by the Double Walsh System. J. Contemp. Mathemat. Anal. 58, 370–383 (2023). https://doi.org/10.3103/S1068362323050072
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DOI: https://doi.org/10.3103/S1068362323050072