Skip to main content
Log in

Problems of approximation theory in linear spaces

  • Published:
Ukrainian Mathematical Journal Aims and scope

Abstract

We present a survey of results related to the approximation characteristics of the spaces S pϕ and their generalizations. The proposed approach enables one to obtain solutions of problems of classical approximation theory in abstract linear spaces in explicit form. The results obtained yield statements that are new even in the case of approximations in the functional Hilbert spaces L 2.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Similar content being viewed by others

References

  1. K. I. Babenko, “On the approximation of periodic functions of many variables by trigonometric polynomials,” Dokl. Akad. Nauk SSSR, 132, No. 2, 247–250 (1960).

    MATH  Google Scholar 

  2. K. I. Babenko, “On the approximation of one class of periodic functions of many variables by trigonometric polynomials,” Dokl. Akad. Nauk SSSR, 132, No. 5, 982–985 (1960).

    MATH  Google Scholar 

  3. S. A. Telyakovskii, “On estimates for arbitrary trigonometric polynomials of many variables,” Sib. Mat. Zh., 4, No. 6, 1404–1411 (1963).

    Google Scholar 

  4. S. A. Telyakovskii, “Some estimates for trigonometric series with quasiconvex coefficients,” Mat. Sb., 63(105), 426–444 (1964).

    MATH  MathSciNet  Google Scholar 

  5. Ya. S. Bugrov, “Approximation of classes of functions with dominating mixed derivative,” Mat. Sb., 64(106), 410–418 (1964).

    MATH  MathSciNet  Google Scholar 

  6. N. S. Nikol’skaya, “Approximation of differentiable functions of many variables by Fourier sums in the metric of L p ,” Dokl. Akad. Nauk SSSR, 208, No. 5, 1283–1285 (1973).

    Google Scholar 

  7. N. S. Nikol’skaya, “Approximation of periodic functions of the class SH r p* by Fourier sums,” Sib. Mat. Zh., 16, No. 4, 761–780 (1975).

    MathSciNet  MATH  Google Scholar 

  8. É. M. Galeev, “Approximation of some classes of periodic functions of many variables by Fourier sums in the metric of L p ,” Usp. Mat. Nauk, 32, No. 4, 251–252 (1977).

    MATH  MathSciNet  Google Scholar 

  9. É. M. Galeev, “Approximation of classes of functions with several bounded derivatives by Fourier sums,” Mat. Zametki, 23, No. 2, 197–212 (1978).

    MATH  MathSciNet  Google Scholar 

  10. V. N. Temlyakov, “Approximation of functions with bounded mixed derivative,” Tr. Mat. Inst. Akad. Nauk SSSR, 178, 1–112 (1986).

    MATH  MathSciNet  Google Scholar 

  11. P. V. Zaderei, “Approximation of \((\bar \psi ,\bar \beta )\)-differentiable periodic functions of many variables,” Ukr. Mat. Zh., 45, No. 3, 367–377 (1993).

    MATH  MathSciNet  Google Scholar 

  12. A. S. Romanyuk, “On approximation of classes of periodic functions of many variables,” Ukr. Mat. Zh., 44, No. 5, 662–672 (1992).

    MATH  MathSciNet  Google Scholar 

  13. A. S. Romanyuk, “Approximation of Besov classes of periodic functions of many variables in the space L q ,” Ukr. Mat. Zh., 43, No. 10, 1398–1408 (1991).

    Article  MATH  MathSciNet  Google Scholar 

  14. A. I. Stepanets, Approximation Characteristics of the Spaces S pϕ [in Russian], Preprint No. 2001.2, Institute of Mathematics, Ukrainian National Academy of Sciences, Kiev (2001).

    Google Scholar 

  15. A. I. Stepanets, “Approximation characteristics of the spaces S pϕ ,” Ukr. Mat. Zh., 53, No. 3, 392–416 (2001).

    MATH  MathSciNet  Google Scholar 

  16. A. I. Stepanets, “Approximation characteristics of the spaces S pϕ in different metrics,” Ukr. Mat. Zh., 53, No. 8, 1121–1146 (2001).

    MATH  MathSciNet  Google Scholar 

  17. A. I. Stepanets and A. S. Serdyuk, “Direct and inverse theorems in the theory of approximation of functions in the space S p,” Ukr. Mat. Zh., 54, No. 1, 106–124 (2002).

    MathSciNet  MATH  Google Scholar 

  18. A. I. Stepanets, Methods of Approximation Theory [in Russian], Vol. 2, Institute of Mathematics, Ukrainian Academy of Sciences, Kiev (2002).

    Google Scholar 

  19. A. I. Stepanets, “Approximation characteristics of the spaces S p,” in: Approximation Theory and Harmonic Analysis. Proceedings of the Ukrainian Mathematical Congress-2001, Institute of Mathematics, Ukrainian Academy of Sciences, Kiev (2002), pp. 208–226.

    Google Scholar 

  20. A. I. Stepanets and V. I. Rukasov, “Spaces S p with nonsymmetric metric,” Ukr. Mat. Zh., 55, No. 2, 264–277 (2003).

    MathSciNet  MATH  Google Scholar 

  21. A. I. Stepanets and V. I. Rukasov, “Best ‘continuous’ n-term approximations in the spaces S pϕ ,” Ukr. Mat. Zh., 55, No. 5, 663–670 (2003).

    MathSciNet  MATH  Google Scholar 

  22. A. I. Stepanets and A. L. Shydlich, “Best n-term approximations by Λ-methods in the spaces S pϕ ,” Ukr. Mat. Zh., 55, No. 8, 1107–1126 (2003).

    MATH  Google Scholar 

  23. A. I. Stepanets, “Extremal problems of approximation theory in linear spaces,” Ukr. Mat. Zh., 55, No. 10, 1392–1423 (2003).

    MathSciNet  Google Scholar 

  24. A. I. Stepanets, “Best approximations of q-ellipsoids in the spaces S p,µϕ ,” Ukr. Mat. Zh., 56, No. 10, 1378–1383 (2004).

    MATH  MathSciNet  Google Scholar 

  25. A. S. Serdyuk, “Widths in the space S p of classes of functions defined by the moduli of continuity of their ψ-derivatives,” in: Extremal Problems in the Theory of Functions and Related Problems [in Ukrainian], Institute of Mathematics, Ukrainian Academy of Sciences, Kiev (2003), pp. 229–248.

    Google Scholar 

  26. V. R. Voitsekhovs’kyi, “Widths of some classes from the space S p,” in: Extremal Problems in the Theory of Functions and Related Problems [in Ukrainian], Institute of Mathematics, Ukrainian Academy of Sciences, Kiev (2003), pp. 17–26.

    Google Scholar 

  27. S. B. Vakarchuk, “Jackson-type inequalities and exact values of widths of classes of functions in the spaces S p, 1 ≤ p < ∞,” Ukr. Mat. Zh., 56, No. 5, 595–605 (2004).

    MATH  MathSciNet  Google Scholar 

  28. S. B. Vakarchuk, “On some extremal problems of approximation theory in the spaces S p (1 ≤ p < ∞),” in: Voronezh Winter Mathematical School “Contemporary Methods of the Theory of Functions and Related Problems” (Voronezh, January 26–February 2, 2003) [in Russian], Voronezh University, Voronezh (2003), pp. 47–48.

    Google Scholar 

  29. V. R. Voitsekhovs’kyi, “Jackson-type inequalities in the approximation of functions from the space S p by Zygmund sums,” in: Theory of Approximation of Functions and Related Problems [in Ukrainian], Institute of Mathematics, Ukrainian Academy of Sciences, Kiev (2002), pp. 33–46.

    Google Scholar 

  30. A. L. Shydlich, “Saturation of linear methods of summation of Fourier series in the spaces S pϕ ,” in: Theory of Approximation of Functions and Related Problems [in Ukrainian], Institute of Mathematics, Ukrainian Academy of Sciences, Kiev (2002), pp. 215–232.

    Google Scholar 

  31. A. L. Shydlich, “Best n-term approximations by Λ-methods in the spaces S pϕ ,” in: Extremal Problems in the Theory of Functions [in Ukrainian], Institute of Mathematics, Ukrainian Academy of Sciences, Kiev (2003), pp. 283–306.

    Google Scholar 

  32. V. I. Rukasov, “Best n-term approximations in spaces with nonsymmetric metric,” Ukr. Mat. Zh., 55, No. 6, 806–816 (2003).

    MATH  MathSciNet  Google Scholar 

  33. E. M. Stein and G. Weiss, Introduction to Fourier Analysis of Euclidean Spaces, Princeton University, Princeton (1971).

    Google Scholar 

  34. N. I. Akhiezer, Lectures on Approximation Theory [in Russian], Nauka, Moscow (1965).

    Google Scholar 

  35. G. H. Hardy, J. E. Littlewood, and G. Pólya, Inequalities, Cambridge University, Cambridge (1934).

    Google Scholar 

  36. N. P. Korneichuk, Extremal Problems in Approximation Theory [in Russian], Nauka, Moscow (1976).

    Google Scholar 

  37. S. B. Stechkin, “On the absolute convergence of orthogonal series,” Dokl. Akad. Nauk SSSR, 102, No. 1, 37–40 (1955).

    MATH  MathSciNet  Google Scholar 

  38. K. I. Oskolkov, “Approximation properties of summable functions on sets of full measure,” Mat. Sb., 103, No. 4, 563–589, (1977).

    MATH  MathSciNet  Google Scholar 

  39. V. E. Maiorov, “On linear widths of Sobolev classes,” Dokl. Akad. Nauk SSSR, 243, No. 5, 1127–1130 (1978).

    MathSciNet  Google Scholar 

  40. G. Y. Macovoz, “On trigonometric n-widths and their generalization,” J. Approxim. Theory, 41, No. 4, 361–366 (1984).

    Article  Google Scholar 

  41. B. S. Kashin, “On approximation properties of complete orthonormal systems,” Tr. Mat. Inst. Akad. Nauk SSSR, 172, 187–191 (1985).

    MATH  MathSciNet  Google Scholar 

  42. É. S. Belinskii, “Approximation of periodic functions of many variables by a ‘floating’ system of exponents and trigonometric widths,” Dokl. Akad. Nauk SSSR, 284, No. 6, 1294–1297 (1985).

    MATH  MathSciNet  Google Scholar 

  43. B. S. Kashin and V. N. Temlyakov, “On the best m-term approximations and entropy of sets in the space L,” Mat. Zametki, 56, No. 5, 57–86 (1994).

    MathSciNet  Google Scholar 

  44. V. N. Temlyakov, “Nonlinear Kolmogorov widths,” Mat. Zametki, 63, No. 6, 891–902 (1998).

    MATH  MathSciNet  Google Scholar 

  45. V. N. Temlyakov, “Greedy algorithm and m-term trigonometric approximation,” Constr. Approxim., 14, 569–587 (1998).

    Article  MATH  MathSciNet  Google Scholar 

  46. Dinh Dung, “Continuous algorithms in n-term approximation and non-linear-widths,” J. Approxim. Theory, 102, 217–242 (2000).

    Article  MATH  Google Scholar 

  47. A. S. Romanyuk, “Best M-term trigonometric approximations of Besov classes of periodic functions of many variables,” Izv. Ros. Akad. Nauk, Ser. Mat., 67, No. 2, 61–100 (2003).

    MATH  MathSciNet  Google Scholar 

  48. R. A. de Vore and V. N. Temlyakov, “Nonlinear approximation in finite-dimensional spaces,” J. Complexity, 13, 489–508 (1997).

    Article  MathSciNet  Google Scholar 

  49. R. A. de Vore, “Nonlinear approximation,” Acta Numerica, 51–150 (1998).

  50. V. N. Temlyakov, “Nonlinear methods of approximation,” Found. Comput. Math., 3, 33–107 (2003).

    Article  MATH  MathSciNet  Google Scholar 

  51. A. I. Stepanets, “Best n-term approximations with restrictions,” Ukr. Mat. Zh., 57, No. 4, 533–553 (2005).

    MathSciNet  MATH  Google Scholar 

  52. A. I. Stepanets, Methods of Approximation Theory [in Russian], Vol. 1, Institute of Mathematics, Ukrainian Academy of Sciences, Kiev (2002).

    Google Scholar 

  53. A. Zygmund, Trigonometric Series [Russian translation], Vol. 2, Mir, Moscow (1965).

    MATH  Google Scholar 

  54. A. N. Kolmogorov, “Über die beste Annäherung von Funktionen einer gegebenen Funktionenklass,” Ann. Math., 37, No. 1, 107–110 (1936).

    Article  MATH  MathSciNet  Google Scholar 

  55. V. M. Tikhomirov, Some Problems of Approximation Theory [in Russian], Moscow University, Moscow (1976).

    Google Scholar 

  56. A. I. Stepanets, Extremal Problems of Approximation Theory in Linear Spaces [in Russian], Preprint No. 2005.1, Institute of Mathematics, Ukrainian Academy of Sciences, Kiev (2005).

    Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Additional information

__________

Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 58, No. 1, pp. 47–92, January, 2006.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Stepanets, A.I. Problems of approximation theory in linear spaces. Ukr Math J 58, 54–102 (2006). https://doi.org/10.1007/s11253-006-0052-2

Download citation

  • Received:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11253-006-0052-2

Keywords

Navigation