Publicationes Mathematicae Banner
2018/93/1-2 (14) — DOI: 10.5486/PMD.2018.8156 — pp. 189-203

A domain containing all zeros of the partial theta function

Authors: Vladimir Petrov Kostov

Abstract:

We consider the partial theta function, i.e., the sum of the bivariate series $\theta(q,z):=\sum_{j=0}^{\infty}q^{j(j+1)/2}z^j$ for $q\in(-1,1)$, $z\in\mathbb{C}$. We show that for any value of the parameter $q\in(0,1)$, all zeros of the function $\theta(q,.)$ belong to the domain $\{\operatorname{Re}~z < 0,|\operatorname{Im}~z|<132\}\cup\{\operatorname{Re}~z\geq 0,|z|<18\}$. For $q\in(-1,0)$, all zeros belong to the strip $\{|\operatorname{Im}~z|<132\}$.

Keywords: partial theta function, Jacobi theta function, Jacobi triple product

Mathematics Subject Classification: 26A06, 30C15, 11F27, 30D15