polynomials;
zeros;
annular region;
laurent polynomials;
unit interval;
elliptic region;
D O I:
10.1080/17476933.2013.829462
中图分类号:
O1 [数学];
学科分类号:
0701 ;
070101 ;
摘要:
A few years ago, the second named author was asked if he knew the largest open simply connected region G(n) superset of [-1, 1] containing no zero of any polynomial p of degree n is an element of N such that 0 < m <= vertical bar p(x)vertical bar <= M for all x is an element of [-1, 1]. This question is answered in Theorem 3. This required us to first consider a related problem for polynomials on the unit circle, whose solution is given in Theorem 1. The paper contains several other results which are all sharp.