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A real polynomial P of degree n in one real variable is hyperbolic if its roots are all real. A real-valued function P is called a hyperbolic polynomial-like function (HPLF) of degree n if it has n real zeros and P⁽ⁿ⁾ vanishes nowhere. Denote by x_k ⁽ⁱ⁾ the roots of P⁽ⁱ⁾, k = 1, ..., n-i, i = 0, ..., n-1. Then in the absence of any equality of the form x_i ...

By Descartes’ rule of signs, a real degree $d$ polynomial $P$ with all nonvanishing coefficients with $c$ sign changes and $p$ sign preservations in the sequence of its coefficients ($c+p=d$) has $\mathrm{pos}\le c$ positive and $\neg \le p$ negative roots, where $\mathrm{pos}\equiv c(mod2)$ and $\neg \equiv p(mod2)$. For $1\le d\le 3$, for every possible choice of the sequence of signs of coefficients of $P$ (called sign pattern) and for every pair $(\mathrm{pos},\mathrm{neg})$ satisfying these conditions there exists a polynomial $P$ with exactly $\mathrm{pos}$ positive and exactly $\neg$ negative roots (all of them simple). For $d\ge 4$ this is not...

[Kostov Vladimir Petrov; Костов Владимир Петров] We consider real polynomials in one variable without root at 0 and without multiple roots. Given the numbers of the positive, negative and complex roots of two such polynomials, what can be these numbers for their composition of Schur-Szegö? We give the exhaustive answer to the question for degree 2, 3 and 4 polynomials and also in the case when the degree is arbitrary, the composed polynomials being with all roots real, and one of the...

2000 Mathematics Subject Classification: 12D10. In the present paper we consider degree 6 hyperbolic polynomials (HPs) in one variable (i.e. real and with all roots real). We are interested in such HPs whose number of equalities between roots of the polynomial and/or its derivatives is higher than expected. We give the complete study of the four families of such degree 6 even HPs and also of HPs which are primitives of degree 5 HPs. Research partially supported by research...