English

Distances between zeroes and critical points for random polynomials with i.i.d. zeroes

Probability 2018-07-09 v1

Abstract

Consider a random polynomial QnQ_n of degree n+1n+1 whose zeroes are i.i.d. random variables ξ0,ξ1,,ξn\xi_0,\xi_1,\ldots,\xi_n in the complex plane. We study the pairing between the zeroes of QnQ_n and its critical points, i.e. the zeroes of its derivative QnQ_n'. In the asymptotic regime when nn\to\infty, with high probability there is a critical point of QnQ_n which is very close to ξ0\xi_0. We localize the position of this critical point by proving that the difference between ξ0\xi_0 and the critical point has approximately complex Gaussian distribution with mean 1/(nf(ξ0))1/(nf(\xi_0)) and variance of order lognn3\log n \cdot n^{-3}. Here, f(z)=E[1/(zξk)]f(z)= \mathbb E[1/(z-\xi_k)] is the Cauchy-Stieltjes transform of the ξk\xi_k's. We also state some conjectures on critical points of polynomials with dependent zeroes, for example the Weyl polynomials and characteristic polynomials of random matrices.

Keywords

Cite

@article{arxiv.1807.02140,
  title  = {Distances between zeroes and critical points for random polynomials with i.i.d. zeroes},
  author = {Zakhar Kabluchko and Hauke Seidel},
  journal= {arXiv preprint arXiv:1807.02140},
  year   = {2018}
}

Comments

28 pages, 4 figures

R2 v1 2026-06-23T02:52:16.499Z