On sharp Kolmogorov-type inequalities taking into account the number of sign changes of derivatives |
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Authors: | V A Kofanov V E Miropol’skii |
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Institution: | (1) Dnepropetrovsk National University, Dnepropetrovsk, Ukraine |
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Abstract: | We obtain new sharp Kolmogorov-type inequalities, in particular the following sharp inequality for 2π-periodic functions x ∈ L
∞
r
(T):
where k, r ∈ N, k < r, r ≥ 3, p ∈ 1, ∞], α = (r – k) / (r – 1 + 1/p), φ
r
is the perfect Euler spline of order r, and ν(x′) is the number of sign changes of x′ on a period.
Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 60, No. 12, pp. 1642–1649, December, 2008. |
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Keywords: | |
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