Abstract:
An estimate is obtained for the derivatives of real rational functions that map a compact set on the real line to another set of the same kind. Many well-known inequalities (due to Bernstein, Bernstein—Szegö, V. S. Videnskii, V. N. Rusak, and M. Baran–V. Totik) are particular cases of this estimate. It is shown that the estimate is sharp. With the help of the solution of the fourth Zolotarev problem, a class of examples is constructed in which the estimates obtained turn into identities.
Keywords:
Estimates of derivatives, optimal filter, Zolotarev problems.
Citation:
A. L. Lukashov, “Estimates for derivatives of rational functions and the fourth Zolotarev problem”, Algebra i Analiz, 19:2 (2007), 122–130; St. Petersburg Math. J., 19:2 (2008), 253–259
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\by A.~L.~Lukashov
\paper Estimates for derivatives of rational functions and the fourth Zolotarev problem
\jour Algebra i Analiz
\yr 2007
\vol 19
\issue 2
\pages 122--130
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\transl
\jour St. Petersburg Math. J.
\yr 2008
\vol 19
\issue 2
\pages 253--259
\crossref{https://doi.org/10.1090/S1061-0022-08-00997-7}
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Linking options:
https://www.mathnet.ru/eng/aa116
https://www.mathnet.ru/eng/aa/v19/i2/p122
This publication is cited in the following 9 articles:
Lukashov A.L., Szabados J., “The order of Lebesgue constant of Lagrange interpolation on several intervals”, Period. Math. Hung., 72:2 (2016), 103–111
Totik V., “Bernstein- and Markov-Type Inequalities For Trigonometric Polynomials on General Sets”, Int. Math. Res. Notices, 2015, no. 11, 2986–3020
A. V. Olesov, “Inequalities for majorizing analytic functions and their applications to rational trigonometric functions and polynomials”, Sb. Math., 205:10 (2014), 1413–1441
V. N. Dubinin, “Methods of geometric function theory in classical and modern problems for polynomials”, Russian Math. Surveys, 67:4 (2012), 599–684
Totik V., “Bernstein-type inequalities”, J. Approx. Theory, 164:10 (2012), 1390–1401
S. I. Kalmykov, “Majoration principles and some inequalities for polynomials and rational functions with prescribed poles”, J. Math. Sci. (N. Y.), 157:4 (2009), 623–631
V. N. Dubinin, D. B. Karp, V. A. Shlyk, “Izbrannye zadachi geometricheskoi teorii funktsii i teorii potentsiala”, Dalnevost. matem. zhurn., 8:1 (2008), 46–95
V. N. Dubinin, “Emkosti kondensatorov i printsipy mazhoratsii v geometricheskoi teorii funktsii kompleksnogo peremennogo [Itogovyi nauchnyi otchet po mezhdistsiplinarnomu integratsionnomu proektu SO RAN: “Razrabotka teorii i vychislitelnoi tekhnologii resheniya obratnykh i ekstremalnykh zadach s prilozheniem v matematicheskoi fizike i gravimagnitorazvedke”]”, Sib. elektron. matem. izv., 5 (2008), 465–482
V. N. Dubinin, S. I. Kalmykov, “A majoration principle for meromorphic functions”, Sb. Math., 198:12 (2007), 1737–1745