Abstract:
Consider the Sobolev space Wn2(R+) on the semiaxis with norm of general form defined by a quadratic polynomial in derivatives with nonnegative coefficients. We study the problem of exact constants An,k in inequalities of Kolmogorov type for the values of intermediate derivatives |f(k)(0)|⩽An,k‖f‖. In the general case, the expression for the constants An,k is obtained as the ratio of two determinants. Using a general formula, we obtain an explicit expression for the constants An,k in the case of the following norms:
‖f‖21=‖f‖2L2+‖f(n)‖2L2and‖f‖22=n∑l=0‖f(l)‖2L2.
In the case of the norm ‖⋅‖1, formulas for the constants An,k were obtained earlier by another method due to Kalyabin. The asymptotic behavior of the constants An,k is also studied in the case of the norm ‖⋅‖2. In addition, we prove a symmetry property of the constants An,k in the general case.
Keywords:
Sobolev space, Kolmogorov-type inequalities, intermediate derivative, linear functional in Hilbert space, Vandermonde matrix, Cramer's rule.
Citation:
A. A. Lunev, L. L. Oridoroga, “Exact Constants in Generalized Inequalities for Intermediate Derivatives”, Mat. Zametki, 85:5 (2009), 737–744; Math. Notes, 85:5 (2009), 703–711
This publication is cited in the following 3 articles:
Dmytro Skorokhodov, “The Landau–Kolmogorov problem on a finite interval in the Taikov case”, Journal of Approximation Theory, 280 (2022), 105771
Babenko V. Babenko Yu. Kriachko N. Skorokhodov D., “On Hardy-Littlewood-Polya and Taikov Type Inequalities For Multiple Operators in Hilbert Spaces”, Anal. Math., 47:4 (2021), 709–745
Osipenko K.Yu., “Recovery of Derivatives For Functions Defined on the Semiaxis”, J. Complex., 48 (2018), 111–118