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Inequalities between height and deviation of polynomials
Open Mathematics ( IF 1.7 ) Pub Date : 2021-01-01 , DOI: 10.1515/math-2021-0055
Artūras Dubickas 1
Affiliation  

In this paper, for polynomials with real coefficients P , Q P,Q satisfying ∣ P ( x ) ∣ ≤ ∣ Q ( x ) ∣ | P\left(x)| \le | Q\left(x)| for each x x in a real interval I I , we prove the bound L ( P ) ≤ c L ( Q ) L\left(P)\le cL\left(Q) between the lengths of P P and Q Q with a constant c c , which is exponential in the degree d d of P P . An example showing that the constant c c in this bound should be at least exponential in d d is also given. Similar inequalities are obtained for the heights of P P and Q Q when the interval I I is infinite and P , Q P,Q are both of degree d d . In the proofs and in the constructions of examples, we use some translations of Chebyshev polynomials.

中文翻译:

多项式的高度和偏差之间的不等式

在本文中,对于具有实系数 P , QP,Q 的多项式满足 ∣ P ( x ) ∣ ≤ ∣ Q ( x ) ∣ | P\left(x)| \le | Q\左(x)| 对于实数区间 II 中的每个 xx,我们证明 PP 和 QQ 的长度之间的界限 L ( P ) ≤ c L ( Q ) L\left(P)\le cL\left(Q) 具有常数 cc ,其中是 PP 的 dd 度数的指数。还给出了一个示例,表明此边界中的常数 cc 在 dd 中至少应为指数。当区间 II 为无穷大且 P 、QP、Q 均为 dd 阶时,PP 和 QQ 的高度也得到了类似的不等式。在证明和例子的构造中,我们使用了切比雪夫多项式的一些翻译。
更新日期:2021-01-01
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