English

Pairing between zeros and critical points of random polynomials with independent roots

Probability 2017-07-31 v3

Abstract

Let pnp_n be a random, degree nn polynomial whose roots are chosen independently according to the probability measure μ\mu on the complex plane. For a deterministic point ξ\xi lying outside the support of μ\mu, we show that almost surely the polynomial qn(z):=pn(z)(zξ)q_n(z):=p_n(z)(z - \xi) has a critical point at distance O(1/n)O(1/n) from ξ\xi. In other words, conditioning the random polynomials pnp_n to have a root at ξ\xi, almost surely forces a critical point near ξ\xi. More generally, we prove an analogous result for the critical points of qn(z):=pn(z)(zξ1)(zξk)q_n(z):=p_n(z)(z - \xi_1)\cdots (z - \xi_k), where ξ1,,ξk\xi_1, \ldots, \xi_k are deterministic. In addition, when k=o(n)k=o(n), we show that the empirical distribution constructed from the critical points of qnq_n converges to μ\mu in probability as the degree tends to infinity, extending a recent result of Kabluchko.

Keywords

Cite

@article{arxiv.1610.06248,
  title  = {Pairing between zeros and critical points of random polynomials with independent roots},
  author = {Sean O'Rourke and Noah Williams},
  journal= {arXiv preprint arXiv:1610.06248},
  year   = {2017}
}

Comments

39 pages, 5 figures; incorporated comments and suggestions from Boris Hanin