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Inverse functions of polynomials and orthogonal polynomials as operator monotone functions
Authors:Mitsuru Uchiyama
Affiliation:Department of Mathematics, Fukuoka University of Education, Munakata, Fukuoka, 811-4192, Japan
Abstract:
We study the operator monotonicity of the inverse of every polynomial with a positive leading coefficient. Let ${p_n}_{n=0}^{infty}$ be a sequence of orthonormal polynomials and $p_{n+}$ the restriction of $p_n$ to $[a_n, infty)$, where $a_n$ is the maximum zero of $p_n$. Then $p_{n+}^{-1}$ and the composite $p_{n-1}circ p_{n+}^{-1}$ are operator monotone on $[0, infty)$. Furthermore, for every polynomial $p$ with a positive leading coefficient there is a real number $a$ so that the inverse function of $p(t+a)-p(a)$ defined on $[0,infty)$is semi-operator monotone, that is, for matrices $ A,B geq 0$, $(p(A+a)-p(a))^2 leq ((p(B+a)-p(a))^{2}$ implies $A^2leq B^2.$

Keywords:Positive semi-definite operator   operator monotone function   orthogonal polynomials
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