Abstract
We study Jackson’s inequality between the best approximation of a function f ∈ L2(ℝ3) by entire functions of exponential spherical type and its generalized modulus of continuity. We prove Jackson’s inequality with the exact constant and the optimal argument in the modulus of continuity. In particular, Jackson’s inequality with the optimal parameters is obtained for classical modulus of continuity of order r and Thue–Morse modulus of continuity of order r ∈ ℕ. These results are based on the solution of the generalized Logan problem for entire functions of exponential type. For it we construct a new quadrature formulas for entire functions of exponential type.
Similar content being viewed by others
References
Abramowitz, M., Stegun, I. A.: Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, Applied Mathematics Series 55, National Bureau of Standards, Washington, 1972
Arestov, V. V., Babenko, A. G.: On the optimal point in Jackson’s inequality in L 2(−∞,∞) with the second modulus of continuity. East J. Approximation, 10(1–2), 201–214 (2004)
Arestov, V. V., Popov, V. Yu.: Jackson inequalities on a sphere in L 2. Russian Math. (Iz. VUZ Mat.), 39(8), 11–18 (1995)
Babenko, A. G.: Exact Jackson–Stechkin inequality in the space L 2(ℝm) (in Russian). Trudy Inst. Mat. i Mekh UrO RAN, 5, 182–198 (1998)
Bateman, H., Erdélyi, A.: Tables of Integral Transforms II, McGraw-Hill Book Company, Inc., New York, Toronto, London, 1954
Berdysheva, E. E.: Two related extremal problems for entire functions of several variables. Math. Notes, 66(3), 271–282 (1999)
Bogachev, V. I.: Measure Theory I, Springer, Berlin, Heidelberg, New York, 2007
De Jeu, M.: Paley–Wiener theorems for the Dunkl transform. Trans. Amer. Math. Soc., 358(10), 4225–4250 (2006)
Frappier, C., Oliver, P.: A quadrature formula involving zeros of Bessel functions. Math. of Comp., 60(6), 303–313 (1993)
Ghobber, S., Jaming, P.: Strong annihilating pairs for the Fourier–Bessel transform. J. Math. Anal. Appl., 377(2), 501–515 (2011)
Gorbachev, D. V.: Extremum problems for entire functions of exponential spherical type. Math. Notes, 68(2), 159–166 (2000)
Gorbachev, D. V.: Estimate of optimal argument in exact multidimensional L 2-inequality of Jackson–Stechkin (in Russian). Trudy Inst. Mat. i Mekh UrO RAN, 20(1), 83–91 (2014)
Gorbachev, D. V., Strankovskii, S. F.: An extremal problem for even positive definite entire functions of exponential type. Math. Notes, 80(5–6), 673–678 (2006)
Grozev, G. R., Rahman, Q. I.: A quadrature formulae with zeros of Bessel functions as nodes. Math. of Comp., 84(6), 715–725 (1995)
Hue, H. T. M.: About the connection of multidimensional and one-dimensional Jackson constants in L 2- spaces with power weights (in Russian). Izv. TulGU. Estestv. Nauki, 2, 114–123 (2012)
Hue, H. T. M.: Generalized Jackson–Stechkin inequality in the space L 2(ℝd) with Dunkl weight (in Russian). Izv. TulGU. Estestv. Nauki, 1, 63–82 (2014)
Ivanov, A. V.: Some extremal problems for entire functions in weighted spaces (in Russian). Izv. TulGU. Estestv. Nauki, 1, 26–44 (2010)
Ivanov, A. V.: Logan problem for multivariate entire functions and Jackson constants in weighted spaces (in Russian). Izv. TulGU. Estestv. Nauki, 2, 29–58 (2011)
Ivanov, A. V., Ivanov, V. I., Hue, H. T. M.: Generalized Jackson constant in L 2(ℝd)-space with Dunkl weight (in Russian). Izv. TulGU. Estestv. Nauki, 3, 74–90 (2013)
Ivanov, A. V., Ivanov, V. I.: Optimal arguments in Jacksons inequality in the power-weighted space L 2(ℝd). Math. Notes, 94(3–4), 320–329 (2013)
Ivanov, A. V., Ivanov, V. I.: Optimal argument in generalized Jackson inequality in L 2(ℝd)-space with Dunkl weight and generalized Logan problem (in Russian). Izv. TulGU. Estestv. Nauki, 1, 22–36 (2014)
Ivanov, V. I., Ivanov, A. V.: Optimal Arguments in the Jackson–Stechkin Inequality in L 2(ℝd) with Dunkl Weight. Math. Notes, 96(5–6), 674–686 (2014)
Kozko, A. I., Rozhdestvenskii, A. V.: On Jackson’s inequality for a generalized modulus of continuity in L 2. Sbornic Math., 195(8), 1073–1115 (2004)
Levitan, B. M., Sargsian, I. S.: Introduction to Spectral Theory (in Russian), Self-adjoint Ordinary Differential Operators, Nauka, Moscow, 1970
Logan, B. F.: Extremal problems for positive-definite bandlimited functions I. Eventually positive functions with zero integral. SIAM J. Math. Anal., 14(2), 249–252 (1983)
Logan, B. F.: Extremal problems for positive-definite bandlimited functions II. Eventually negative function. SIAM J. Math. Anal., 14(2), 253–257 (1983)
Moskovskii, A. V.: Jackson theorems in the spaces L p(ℝn) and L p,λ(ℝ+) (in Russian). Izv. TulGU. Ser. Math. Mekh. Inform., 3(1), 44–70 (2013)
Plancherel, M., Pólya G.: Fonctions entiéres et intégrales de Fourier multiples. Comment. Math. Helv., 9(6), 224–248 (1937)
Vasil’ev, S. N.: Jackson inequality in L 2(ℝn) with generalized modulus of continuity. Proc. of the Steklov Inst. of Math., 273(1S), 163–170 (2011)
Watson, G. N.: A Treatise on the Theory of Bessel Functions, Cambridge University Press, Cambridge, 1944
Author information
Authors and Affiliations
Corresponding author
Additional information
Supported by the Russian Foundation for Basic Research (Grant No. 16-01-00308)
Rights and permissions
About this article
Cite this article
Ivanov, V., Ivanov, A. Generalized Logan’s Problem for Entire Functions of Exponential Type and Optimal Argument in Jackson’s Inequality in L2(ℝ3). Acta. Math. Sin.-English Ser. 34, 1563–1577 (2018). https://doi.org/10.1007/s10114-018-4437-6
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10114-018-4437-6
Keywords
- Best approximation
- generalized modulus of continuity
- Jackson’s inequality
- optimal argument
- Logan’s problem
- quadrature formula