文摘
Let \(I\) be an interval contained in \({\mathbb {R}}\). For a given function \(f:I\rightarrow {\mathbb {R}}\), \(u\in I\) and any \(0<\alpha \le 1\), set $$\begin{aligned} f_\alpha ^\sharp (u)=\sup \frac{1}{|J|^{\alpha }}\left( \frac{1}{|J|}\int _J \left| f(x)-\frac{1}{|J|}\int _J f(y)\text{ d }y\right| ^2\text{ d }x\right) ^{1/2}, \end{aligned}$$where the supremum is taken over all subintervals \(J\subseteq I\) which contain \(u\). The paper contains the proofs of the estimates $$\begin{aligned} \ell (\alpha )\big |\big |f_\alpha ^\sharp \big |\big |_{L^\infty (I)}\le \big |\big |f\big |\big |_{{\text {Lip}}_\alpha (I)}\le L(\alpha )\big |\big |f_\alpha ^\sharp \big |\big |_{L^\infty (I)}, \end{aligned}$$where $$\begin{aligned} \ell (\alpha )=2\sqrt{2\alpha +1},\quad L(\alpha )=\frac{(4\alpha +4)^{(\alpha +1)/(2\alpha +1)}\sqrt{2\alpha +1}}{2\alpha } \end{aligned}$$are the best possible. The proof rests on the evaluation of Bellman functions associated with the above estimates. Keywords Sharp function Lipschitz Best constants Mathematics Subject Classification 26A16 Page %P Close Plain text Look Inside Reference tools Export citation EndNote (.ENW) JabRef (.BIB) Mendeley (.BIB) Papers (.RIS) Zotero (.RIS) BibTeX (.BIB) Add to Papers Other actions Register for Journal Updates About This Journal Reprints and Permissions Share Share this content on Facebook Share this content on Twitter Share this content on LinkedIn Related Content Supplementary Material (0) References (21) References1.Burkholder, D.L.: A nonlinear partial differential equation and the unconditional constant of the Haar system in \(L^p\). Bull. Am. Math. Soc. 7, 591–595 (1982)MathSciNetCrossRefMATH2.Burkholder, D.L.: Boundary value problems and sharp inequalities for martingale transforms. Ann. Probab. 12, 647–702 (1984)MathSciNetCrossRefMATH3.Fefferman, C.: Characterizations of bounded mean oscillation. Bull. Am. Math. Soc. 77, 587–588 (1971)MathSciNetCrossRefMATH4.Ivanishvili, P., Osipov, N.N., Stolyarov, D.M., Vasyunin, V., Zatitskiy, P.B.: On Bellman function for extremal problems in BMO. C. R. Math. Acad. Sci. Paris 350(11–12), 561–564 (2012)MathSciNetCrossRefMATH5.John, F., Nirenberg, L.: On functions of bounded mean oscillation. Commun. Pure Appl. Math. 14, 415–426 (1961)MathSciNetCrossRefMATH6.Kovač, V.: Bellman function technique for multilinear estimates and an application to generalized paraproducts. Indiana Univ. Math. J. 60(3), 813–846 (2011)MathSciNetCrossRefMATH7.Nazarov, F.L., Treil, S.R.: The hunt for a Bellman function: applications to estimates for singular integral operators and to other classical problems of harmonic analysis. St. Petersburg Math. J. 8, 721–824 (1997)MathSciNet8.Nazarov, F.L., Treil, S.R., Volberg, A.: The Bellman functions and two-weight inequalities for Haar multipliers. J. Am. Math. Soc. 12, 909–928 (1999)MathSciNetCrossRefMATH9.Osȩkowski, A.: Sharp martingale and semimartingale inequalities. Monografie Matematyczne, vol. 72. Birkhäuser, Basel (2012)CrossRefMATH10.Osȩkowski, A.: Sharp inequalities for BMO functions. Chin. Ann. Math. Ser B 36, 225–236 (2015)MathSciNetCrossRef11.Pereyra, M.C.: Haar multipliers meet Bellman functions. Rev. Mat. Iberoam. 25(3), 799–840 (2009)MathSciNetCrossRefMATH12.Petermichl, S.: The sharp bound for the Hilbert transform on weighted Lebesgue spaces in terms of the classical \(A_p\) characteristic. Am. J. Math. 129(5), 1355–1375 (2007)MathSciNetCrossRefMATH13.Petermichl, S., Wittwer, J.: A sharp estimate for the weighted Hilbert transform via Bellman functions. Michigan Math. J. 50(1), 71–87 (2002)MathSciNetCrossRefMATH14.Rey, G., Reznikov, A.: Extremizers and sharp weak-type estimates for positive dyadic shifts. Adv. Math. 254, 664–681 (2014)MathSciNetCrossRefMATH15.Slavin, L., Vasyunin, V.: Sharp results in the integral-form John-Nirenberg inequality. Trans. Am. Math. Soc. 363, 4135–4169 (2011)MathSciNetCrossRefMATH16.Slavin, L., Vasyunin, V.: Sharp \(L_p\) estimates on BMO. Indiana Univ. Math. J. 61(3), 1051–1110 (2012)MathSciNetCrossRefMATH17.Vasyunin, V.: The sharp constant in John-Nirenberg inequality, Preprint PDMI no. 20, 2003. http://www.pdmi.ras.ru/preprint/2003/index.html 18.Vasyunin, V., Volberg, A.: The Bellman function for certain two weight inequality: the case study. St. Petersburg Math. J. 18, 201–222 (2007)MathSciNetCrossRefMATH19.Vasyunin, V., Volberg, A.: Monge-Ampère equation and Bellman optimization of Carleson Embedding Theorems, Am. Math. Soc. Transl. (2), vol. 226, “Linear and Complex Analysis”, pp. 195–238 (2009)20.Vasyunin, V., Volberg, A.: Sharp constants in the classical weak form of the John-Nirenberg inequality, preprint available at arxiv.org/pdf/1204.1782 21.Wittwer, J.: A sharp estimate on the norm of the martingale transform. Math. Res. Lett. 7(1), 1–12 (2000)MathSciNetCrossRefMATH About this Article Title Sharp Estimates for Lipschitz Class Journal The Journal of Geometric Analysis Volume 26, Issue 2 , pp 1346-1369 Cover Date2016-04 DOI 10.1007/s12220-015-9593-7 Print ISSN 1050-6926 Online ISSN 1559-002X Publisher Springer US Additional Links Register for Journal Updates Editorial Board About This Journal Manuscript Submission Topics Differential Geometry Convex and Discrete Geometry Fourier Analysis Abstract Harmonic Analysis Dynamical Systems and Ergodic Theory Global Analysis and Analysis on Manifolds Keywords Sharp function Lipschitz Best constants 26A16 Authors Adam Osȩkowski (1) Author Affiliations 1. Department of Mathematics, Informatics and Mechanics, University of Warsaw, Banacha 2, 02-097, Warsaw, Poland Continue reading... To view the rest of this content please follow the download PDF link above.