Zeros of a table of polynomials satisfying a four-term contiguous relation

Abstract

For any $A(z),B(z),C(z)\in\mathbb{C}[z]$, we study the zero distribution of a table of polynomials $\{P_{m,n}(z)\}_{m,n\in\mathbb{N}_0}$ satisfying the recurrence relation

with the initial conditions $P_{0,0}(z)=1$ and $P_{-m,-n}(z)=0$ for all $m,n\in\mathbb{N}$. We show that the zeros of $P_{m,n}(z)$ lie on a curve whose equation is given explicitly in terms of $A(z)$, $B(z)$, and $C(z)$. We also study the zero distribution of a case with a general initial condition.