2020/96/1-2 (13)
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DOI: 10.5486/PMD.2020.8640
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pp. 161-184
Descartes' rule of signs and moduli of roots
Abstract:
A hyperbolic polynomial (HP) is a real univariate polynomial with all roots real. By Descartes' rule of signs, an HP with all coefficients nonvanishing has exactly $c$ positive and exactly $p$ negative roots counted with multiplicity, where $c$ and $p$ are the numbers of sign changes and sign preservations in the sequence of its coefficients. For $c=1$ and $2$, we discuss the question: When the moduli of all the roots of an HP are arranged in the increasing order on the real half-line, at which positions can be the moduli of its positive roots depending on the positions of the sign changes in the sequence of coefficients?
Keywords: real polynomial in one variable, hyperbolic polynomial, sign pattern, Descartes' rule of signs
Mathematics Subject Classification: 26C10, 30C15
