Lower bound for the best approximations of periodic summable functions of two variables and their conjugates in terms of Fourier coefficients

In terms of Fourier coefficients, we establish lower bounds for the sum of norms and the sum of the best approximations by trigonometric polynomials for functions from the space L(Q²) and functions conjugate to them with respect to each variable and with respect to both variables, provi...

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Datum:2008
Hauptverfasser: Kononovych, T. O., Кононович, Т. О.
Format: Artikel
Sprache:Ukrainisch
Englisch
Veröffentlicht: Institute of Mathematics, NAS of Ukraine 2008
Online Zugang:https://umj.imath.kiev.ua/index.php/umj/article/view/3222
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Назва журналу:Ukrains’kyi Matematychnyi Zhurnal
Завантажити файл: Pdf

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Ukrains’kyi Matematychnyi Zhurnal
Beschreibung
Zusammenfassung:In terms of Fourier coefficients, we establish lower bounds for the sum of norms and the sum of the best approximations by trigonometric polynomials for functions from the space L(Q²) and functions conjugate to them with respect to each variable and with respect to both variables, provided that these functions are summable.