# Counting the number of zeroes of polynomials in quadrature domains

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## Abstract

Recall that given two complex polynomials $f$ and $g$, the Bezout matrix $B(f,g) = (b_{ij})$ of $f$ and $g$ is defined by $\frac{f(t)g(s) - f(s)g(t)}{t-s} = \sum_{i,j} b_{ij} t^i s^j$. It is a classical result of Hermite that given a polynomial $p(z)$, the Bezout matrix of $p(z)$ and $p^{\tau}(z) = \overline{p(\bar{z})}$ is skew self-adjoint. The number of common zeroes of $p$ and $p^{\tau}$ is the dimension of the kernel of $-i B(p,p^{\tau})$. Additionally, $p$ has $n_+$ roots in the upper half-plane and $n_-$ in the lower half-plane. Here $n-+$ and $n_-$ stand for the number of positive and negative eigenvalues of $-i B(p,p^{\tau})$, respectively. In this talk, I will describe how one can extend the notion of the Bezout matrix to a pair of meromorphic functions on a compact Riemann surface. If the surface is real and dividing the matrix $-i B(f,f^{\tau})$ is $J$-selfadjoint, for a certain signature matrix $J$. We the study the signature of the Bezoutian and obtain an extension of HermiteÃ¢s theorem to quadrature domains. This talk is based on joint work with V. Vinnikov.Non UBCUnreviewedAuthor affiliation: University of WaterlooPostdoctora
Original language English Online 32:41 Published - 30 May 2019

## Keywords

• Mathematics
• Operations Research, Mathematical Programming, Algebraic Geometry, Control/Optimization/Operation Research

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