Some analytic properties of the partial theta function

Fuente: arXiv
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Autor principal: Kostov, Vladimir Petrov
Formato: Preprint
Publicado: 2026
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author Kostov, Vladimir Petrov
author_facet Kostov, Vladimir Petrov
contents We prove new properties of the zero set of Ramanujan's partial theta function $θ(q,x):=\sum _{j=0}^{\infty}q^{j(j+1)/2}x^j$, $q\in (-1,0)\cup (0,1)$, $x\in \mathbb{R}$. We show that for each $q\in (0,1)$, there exists a line Re$x=-a$, $a\geq 5$, such that all real zeros of $θ(q,.)$ lie to its left and all complex zeros to its right. A similar property is proved for $q\in (-1,0)$. For $q\in (0,1)$, there are no real zeros $\geq -6$. For $q\in (-1,0)$, there are no negative zeros $\geq -2.4$ and no positive zeros $\leq 2.4$, except the smallest one.
format Preprint
id arxiv_https___arxiv_org_abs_2604_05559
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Some analytic properties of the partial theta function
Kostov, Vladimir Petrov
Classical Analysis and ODEs
We prove new properties of the zero set of Ramanujan's partial theta function $θ(q,x):=\sum _{j=0}^{\infty}q^{j(j+1)/2}x^j$, $q\in (-1,0)\cup (0,1)$, $x\in \mathbb{R}$. We show that for each $q\in (0,1)$, there exists a line Re$x=-a$, $a\geq 5$, such that all real zeros of $θ(q,.)$ lie to its left and all complex zeros to its right. A similar property is proved for $q\in (-1,0)$. For $q\in (0,1)$, there are no real zeros $\geq -6$. For $q\in (-1,0)$, there are no negative zeros $\geq -2.4$ and no positive zeros $\leq 2.4$, except the smallest one.
title Some analytic properties of the partial theta function
topic Classical Analysis and ODEs
url https://arxiv.org/abs/2604.05559