Quadratic Hyperbolicity Preservers & Multiplier Sequences

R. Bates, R. Yoshida

It is known (see \cite[Brändén, Lemma 2.7]{B10}) that a necessary condition for $T:=\sum Q_k(x)D^k$ to be hyperbolicity preserving is that $Q_k(x)$ and $Q_{k-1}(x)$ have interlaci…