Zero distributions of derivatives of polynomial families centering on a set

Abstract

Suppose $C\subset \mathbb{C}$ is compact. Let $q_k$ be a sequence of polynomials of degree $n_k\to \infty$, such that the locus of roots of all the polynomials is bounded, and the number of roots of $q_k$ in any closed set $L$ not meeting $C$ is uniformly bounded. Supposing that $(q_k{)}_k$ has an asymptotic root distribution $\mu$ we provide conditions on $C$ and $\mu$ assuring the sequence of $m$th derivatives $(q_k^{(m)}{)}_k$ also has asymptotic root distribution $\mu$ for any $m\ge 1$. This complements recent results of Totik.