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Russian Academy of Sciences. Sbornik. Mathematics, 1995, Volume 82, Issue 2, Pages 425–440
DOI: https://doi.org/10.1070/SM1995v082n02ABEH003573
(Mi sm918)
 

This article is cited in 20 scientific papers (total in 20 papers)

Estimates of the distances from the poles of logarithmic derivatives of polynomials to lines and circles

V. I. Danchenko
References:
Abstract: Estimates are obtained for the distances $d(Q,\Gamma)$ from poles of the logarithmic derivative $\theta_Q=Q'/Q$ of a polynomial $Q$ to lines $\Gamma$ of the extended complex plane in dependence on the degree $\deg Q$ of the polynomial $Q$ and the norm of $\theta_Q$ in a certain metric on $\Gamma$. The smallest deviations are defined to be
$$ d_n(\Gamma )=\inf \{d(Q,\Gamma ):\|\theta _Q\|_{C(\Gamma )}\leqslant 1, \deg Q\le n\},\qquad n=1,2,\dotsc . $$
In this case if $\Gamma_1$ is the real axis, then $d_n(\Gamma_1)\asymp\ln\ln n/\ln n$, and if $\Gamma_2$ is the unit circle $\vert z\vert=1$, then $d_n(\Gamma_2)\asymp\ln n/n$. When the derivative $\theta'_Q$ is normalized in the metric of $C(\Gamma_1)$, $d_n'(\Gamma_1)\asymp\ln n/\sqrt{n}$ for the corresponding smallest deviation. When $\theta_Q$ is normalized in the metric of $L_p(\Gamma_1)$, $1<p<\infty$, the corresponding smallest deviations do not decrease to zero as $n$ increases, and are bounded below by the quantity $1/p(\sin\pi/p)^{p/(p-1)}$.
Received: 28.09.1993
Bibliographic databases:
UDC: 517.53
MSC: 30C10, 30C15
Language: English
Original paper language: Russian
Citation: V. I. Danchenko, “Estimates of the distances from the poles of logarithmic derivatives of polynomials to lines and circles”, Russian Acad. Sci. Sb. Math., 82:2 (1995), 425–440
Citation in format AMSBIB
\Bibitem{Dan94}
\by V.~I.~Danchenko
\paper Estimates of the distances from the~poles of logarithmic derivatives of polynomials to lines and circles
\jour Russian Acad. Sci. Sb. Math.
\yr 1995
\vol 82
\issue 2
\pages 425--440
\mathnet{http://mi.mathnet.ru//eng/sm918}
\crossref{https://doi.org/10.1070/SM1995v082n02ABEH003573}
\mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=1302623}
\zmath{https://zbmath.org/?q=an:0864.30003}
\isi{https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=Publons&SrcAuth=Publons_CEL&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=A1995RV83000011}
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  • https://doi.org/10.1070/SM1995v082n02ABEH003573
  • https://www.mathnet.ru/eng/sm/v185/i8/p63
  • This publication is cited in the following 20 articles:
    Citing articles in Google Scholar: Russian citations, English citations
    Related articles in Google Scholar: Russian articles, English articles
    Математический сборник - 1992–2005 Sbornik: Mathematics
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    Abstract page:559
    Russian version PDF:197
    English version PDF:10
    References:79
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