Kolmogorov-type inequalities for functions with asymmetric restrictions on the highest derivative
Abstract
For $$$k, r\in {\rm \bf N}$$$, $$$k<r$$$; $$$q\ge 1$$$, $$$p>0$$$; $$$\alpha, \beta>0$$$ and for functions $$$x\in L_{\infty}^r({\rm\bf R})$$$ inequalities that estimate the norm $$$\|x_{\pm }^{(k)}\|_{L_q[a,b]}$$$ on an arbitrary segment $$$[a,b] \subset {\rm\bf R}$$$ such that $$$\;x^{(k)}(a)=x^{(k)}(b)=0$$$ via a local norm of the function $$$|||x^{\uparrow \downarrow}|||_p :=\sup \left\{ E_0(x)_{L_p[a,b]}: \; \pm x'(t) > 0 \; \forall t\in (a,b), \;\; a,b\in \rm \bf R \right\},$$$ and the asymmetric norm $$$\|\alpha^{-1}x_+^{(r)}+\beta ^{-1}x_-^{(r)}\| _{\infty}$$$ of its highest derivative are proved, where $$$E_0(x)_{L_p([a,b])}:= \inf \{\|x - c\|_{L_p([a,b])}: c \in {\rm \bf R }\}$$$.
As a consequence, generalizations of a number of well-known Kolmogorov-type inequalities are obtained.
Keywords
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Korneichuk N.P., Babenko V.F., Kofanov V.A., Pichugov S.A. Inequalities for derivatives and their applications, Nauk. dumka, Kyiv, 2003; (in Russian)
Babenko V.F. "Researches of Dnipropetrovsk mathematicians on inequalities for derivatives of periodic functions and their applications", Ukrainian Math. J., 2000, 52(1): pp. 9-29. (in Russian) doi:10.1007/BF02514133
Kwong M.K., Zettl A. "Norm inequalities for derivatives and differences", Lecture notes in mathematics, Berlin: Springer-Verlag, 1993.
Babenko V.F., Kofanov V.A., Pichugov S.A. "Comparison of exact constants in inequalities for derivatives of functions defined on the real axis and a circle", Ukrainian Math. J., 2003; 55(5): pp. 699-711. doi:10.1023/B:UKMA.0000010250.39603.d4
Kofanov V.A. "Sharp inequalities of Bernstein and Kolmogorov type", East J. Approx., 2005; 11(2): pp. 131-145.
Kofanov V.A. "On sharp inequalities of Bernstein type for splines", Ukrainian Math. J., 2006; 58(10): pp. 1357-1367. (in Russian) doi:10.1007/s11253-006-0152-z
Kofanov V.A., Miropolskiy V.E. "On the best constants in inequalilies of Kolmogorov-type", East J. Approx., 2007; 13(4): pp. 455-466.
Ligun A.A. "Inequalities for upper bounds of functionals", Analysis Math., 1976; 2(1): pp. 11-40. doi:10.1007/BF02079905
Kofanov V.A. "Inequalities for derivatives in $$$L_p$$$ spaces", Ukrainian Math. J., 2008; 60(10): pp. 1338-1349. (in Russian) doi:10.1007/s11253-009-0152-x
Kofanov V.A. "Inequalities of various metrics for differentiable periodic functions", Ukrainian Math. J., 2015; 67(2): pp. 202-212. (in Russian) doi:10.1007/s11253-015-1076-2
Kofanov V.A. "Inequalities for derivatives of functions on the axis with asymmetrically bounded higher derivatives", Ukrainian Math. J., 2012; 64(5): pp. 721-736. doi:10.1007/s11253-012-0674-5
Kofanov V.A. "Bojanov–Naidenov problem for functions with asymmetric restrictions for the higher derivative", Ukrainian Math. J., 2019; 71(3): pp. 419-434. doi:10.1007/s11253-019-01655-2
Kofanov V.A. "Inequalities for norms of derivatives of non-periodic functions with non-symmetric constraints on higher derivatives", Res. Math., 2012; 20: pp. 99-105. (in Russian) doi:10.15421/241214
Babenko V.F., Kofanov V.A. "Nonsymmetric approximation of classes of differentiable functions by algebraic polynomials in the mean", Analys. Math., 1988; 14(3): pp. 193-217. doi:10.1007/BF01906847
Kofanov V.A., Sydorovych K.D. "Strengthening the Comparison Theorem and Kolmogorov Inequality in the Asymmetric Case", Res. Math,, 2022; 30(1): pp. 30-38. doi:10.15421/242204
Kofanov V.A., Zhuravel A.V. "A sharp Remez type inequalities for the functions with asymmetric restrictions on the oldest derivative", Res. Math., 2023; 31(1): pp. 40-51. doi:10.15421/242304
Pinkus A., Shisha O. "Variations on the Chebyshev and $$$L^q$$$-Theories of Best Approximation", Journal of Approx. Theory, 1982; 35(2): pp. 148-168. doi:10.1016/0021-9045(82)90033-8
Hörmander L. "A new proof and a generalization of an inequality of Bohr", Math. Scand., 1954; 2: pp. 33-45. doi:10.7146/math.scand.a-10392
Babenko V.F. "Asymmetric extremal problems in approximation theory", Dokl. AN SSSR, 1983; 269(3): pp. 521-524. (in Russian)
Korneichuk N.P., Babenko V.F., Ligun A.A. Extremum properties of polynomials and splines, Naukova dumka, 1992; (in Russian)
Kofanov V.A. "On sharp inequalities of Kolmogorov and Bernstein type", Pratsі Ukrajins'kogo matematychnogo kongresu (Approximation theory and Fourier analysis), 2001, Kyiv, 2002; pp. 84-99. (in Russian)
Ligun A.A. "On inequalities between norms of derivatives of periodic functions", Mat. zametki, 1983; 33(3): pp. 385-391. (in Russian) doi:10.1007/BF01686326
DOI: https://doi.org/10.15421/242421
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