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arXiv 2001.09791math.CV
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几类有理函数导数的界

Bounds of the Derivative of Some Classes of Rational Functions

Nuttapong Arunrat, Keaitsuda Maneeruk Nakprasit

摘要:

设$r(z)$是一个有理函数,其极点个数至多为$n$,$a_1, a_2, \ldots, a_n,$,其中$|a_j| > 1,$ $1\leq j\leq n.$本文研究了有理函数$r(z)$在单位圆上导数模的估计.当$r(z)$的所有零点都在$|z|\geq k\geq 1$中时,我们建立了一个上界,当$r(z)$的所有零点都在$|z|\leq k \leq 1.$中时,我们建立了一个下界。特别地,当$k=1$和$r(z)$恰好有$n$零点时,我们得到了A.阿齐兹和W. M. Shah [有理函数的Bernstein型不等式的一些改进,Glas.材料、{ \bf 32}(52)(1997),29- 37.]。

英文摘要:

Let $r(z)$ be a rational function with at most $n$ poles, $a_1, a_2, \ldots, a_n,$ where $|a_j| > 1,$ $1\leq j\leq n.$ This paper investigates the estimate of the modulus of the derivative of a rational function $r(z)$ on the unit circle. We establish an upper bound when all zeros of $r(z)$ lie in $|z|\geq k\geq 1$ and a lower bound when all zeros of $r(z)$ lie in $|z|\leq k \leq 1.$ In particular, when $k=1$ and $r(z)$ has exactly $n$ zeros, we obtain a generalization of results by A. Aziz and W. M. Shah [Some refinements of Bernstein-type inequalities for rational functions, Glas. Mat., {\bf 32}(52) (1997), 29--37.].

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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