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Exact Values of Kolmogorov Widths for the Classes of Analytic Functions. II

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Ukrainian Mathematical Journal Aims and scope

It is shown that the lower bounds of the Kolmogorov widths d 2n in the space C established in the first part of our work for the function classes that can be represented in the form of convolutions of the kernels \( {H}_{h,\beta }(t)={\displaystyle \sum_{k=1}^{\infty}\frac{1}{ \cosh kh} \cos \left(kt-\frac{\beta \pi }{2}\right),\kern1em h>0,\kern1em \beta \in \mathbb{R},} \) with functions φ ⊥ 1 from the unit ball in the space L coincide (for all nnh) with the best uniform approximations of these classes by trigonometric polynomials whose order does not exceed n − 1. As a result, we obtain the exact values of widths for the indicated classes of convolutions. Moreover, for all nnh, we determine the exact values of the Kolmogorov widths d 2n−1 in the space L 1 of classes of the convolutions of functions φ ⊥ 1 from the unit ball in the space L 1 with the kernel H h,β .

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References

  1. A. S. Serdyuk and V. V. Bodenchuk, “Exact values of Kolmogorov widths for the classes of analytic functions. I,” Ukr. Mat. Zh., 67, No. 6, 719–738 (2015).

    MathSciNet  Google Scholar 

  2. N. I. Akhiezer, “On the best approximations of analytic functions,” Dokl. Akad. Nauk, 18, No. 4–5, 241–245 (1938).

    Google Scholar 

  3. S. M. Nikol’skii, “Approximations of functions by trigonometric polynomials in the mean,” Izv. Akad. Nauk SSSR, Ser. Mat., 10, 207–256 (1946).

  4. A. S. Serdyuk, “On the best approximations on the classes of convolutions of periodic functions,” in: Approximation Theory of Functions and Related Problems [in Ukrainian], Proc. of the Institute of Mathematics, Ukrainian National Academy of Sciences, Kyiv, 35 (2002), pp. 172–194.

  5. A. S. Serdyuk and V. V. Bodenchuk, “Exact values of Kolmogorov widths of classes of Poisson integrals,” J. Approxim. Theory, 173, No. 9, 89–109 (2013).

    Article  MathSciNet  MATH  Google Scholar 

  6. I. S. Gradshtein and I. M. Ryzhik, Tables of Integrals, Sums, Series, and Products [in Russian], Nauka, Moscow (1963).

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Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 67, No. 8, pp. 1011–1018, August, 2015.

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Bodenchuk, V.V., Serdyuk, A.S. Exact Values of Kolmogorov Widths for the Classes of Analytic Functions. II. Ukr Math J 67, 1137–1145 (2016). https://doi.org/10.1007/s11253-016-1141-5

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  • DOI: https://doi.org/10.1007/s11253-016-1141-5

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