We solve the following extremal problems: (i) \( {\left\Vert {s}^{(k)}\right\Vert}_{L_q\left[\alpha, \beta \right]}\to \sup \) and (ii) \( {\left\Vert {s}^{(k)}\right\Vert}_{W_q}\to \sup \) over all shifts of splines of order r with minimal defect and nodes at the points lh, l ∈ Z , such that L(s) p ≤M in the cases: (a) k =0, q ≥ p >0, (b) k =1, . . . , r −1, q ≥ 1, where [α, β] is an arbitrary interval in the real line,
and \( {\left\Vert \cdot \right\Vert}_{W_q} \) is the Weyl functional, i.e.,
As a special case, we get some generalizations of the Ligun inequality for splines.
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References
A. Pinkus and O. Shisha, “Variations on the Chebyshev and L q theories of best approximation,” J. Approxim. Theory, 35, No. 2, 148–168 (1982).
V. A. Kofanov, “Sharp upper bounds of the norms of functions and their derivatives on classes of functions with given comparison function,” Ukr. Mat. Zh., 63, No. 7, 969–984 (2011); English translation: Ukr. Math. J., 63, No. 7, 1118–1135 (2011).
B. Bojanov and N. Naidenov, “An extension of the Landau–Kolmogorov inequality. Solution of a problem of Erdos,” J. d’Anal. Math., 78, 263–280 (1999).
P. Erdös, “Open problems,” in: B. Bojanov (editor), Open Problems in Approximation Theory, SCT Publishing, Singapore (1994), pp. 238–242.
G. G. Magaril-Il’yaev, “On the best approximations by splines of functional classes on the axis,” Tr. Mat. Inst. Ros. Akad. Nauk, 194, 153–154 (1992).
B. M. Levitan, Almost Periodic Functions [in Russian], Gostekhteorizdat, Moscow (1953).
H. Weyl, “Almost periodic invariant vector sets in a metric vector space,” Amer. J. Math., 71, No. 1, 178–205 (1949).
V. F. Babenko and S. A. Selivanova, “On the Kolmogorov-type inequalities for periodic and nonperiodic functions,” in: Differential Equations and Their Application, Dnipropetrovs’k National University, Dnipropetrovs’k (1998), pp. 91–95.
V. A. Kofanov, “Some extremal problems various metrics and sharp inequalities of Nagy–Kolmogorov type,” East. J. Approxim., 16, No. 4, 313–334 (2010).
A. A. Ligun, “Sharp inequalities for spline-functions and the best quadrature formulas for some classes of functions,” Mat. Zametki, 19, No. 6, 913–926 (1976).
V. M. Tikhomirov, “Widths of the sets in functional spaces and the theory of best approximations,” Usp. Mat. Nauk, 15, No. 3, 81–120 (1960).
V. A. Kofanov, “On some extremal problems of different metrics for differentiable functions on the axis,” Ukr. Mat. Zh., 61, No. 6, 765–776 (2009); English translation: Ukr. Math. J., 61, No. 6, 908–922 (2009).
A. N. Kolmogorov, “On the inequalities between the upper bounds of successive derivatives on an infinite interval,” in: Selected Works, Mathematics and Mechanics [in Russian], Nauka, Moscow (1985), pp. 252–263.
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Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 66, No. 2, pp. 216–225, February, 2014.
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Kofanov, V.A. Inequalities for Nonperiodic Splines on the Real Axis and Their Derivatives. Ukr Math J 66, 242–252 (2014). https://doi.org/10.1007/s11253-014-0926-7
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DOI: https://doi.org/10.1007/s11253-014-0926-7