Inequalities for the derivative of a polynomial with restricted zeros

被引:4
|
作者
Ahanger, Uzma Mubeen [1 ]
Shah, W. M. [1 ]
机构
[1] Cent Univ Kashmir, Dept Math, Ganderbal 191201, Jammu & Kashmir, India
来源
JOURNAL OF ANALYSIS | 2021年 / 29卷 / 04期
关键词
Inequalities; Restricted zeros; Polynomials;
D O I
10.1007/s41478-021-00316-7
中图分类号
O1 [数学];
学科分类号
0701 ; 070101 ;
摘要
For a polynomial p(z) of degree n, it is known that max|z|=1|p '(z)|<= n1+kmax|z|=1|p(z)|,\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\begin{aligned}\max _{|z|=1}|p<^>{'}(z)|\le \frac{n}{1+k}\max _{|z|=1}|p(z)|,\end{aligned}$$\end{document}if p(z)not equal 0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p(z)\ne 0$$\end{document} in |z|<k,k >= 1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$|z|<k,k \ge 1$$\end{document} and max|z|=1|p '(z)|>= n1+kmax|z|=1|p(z)|,\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\begin{aligned}\max _{|z|=1}|p<^>{'}(z)|\ge \frac{n}{1+k}\max _{|z|=1}|p(z)|,\end{aligned}$$\end{document}if p(z)not equal 0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p(z)\ne 0$$\end{document} for |z|>k,k <= 1.\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$|z|>k,k \le 1.$$\end{document} In this paper, we assume that there is a zero of multiplicity s, s<n\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$s at a point inside |z|=1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$|z|=1$$\end{document} and prove some generalizations and improvements of these inequalities.
引用
收藏
页码:1367 / 1374
页数:8
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