A Jentzsch-Theorem for Kapteyn, Neumann, and General Dirichlet Series

Fuente: arXiv
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Auteur principal: Bornemann, Folkmar
Format: Preprint
Publié: 2021
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_version_ 1866909138518278144
author Bornemann, Folkmar
author_facet Bornemann, Folkmar
contents Comparing phase plots of truncated series solutions of Kepler's equation by Lagrange's power series with those by Bessel's Kapteyn series strongly suggest that a Jentzsch-type theorem holds true not only for the former but also for the latter series: each point of the boundary of the domain of convergence in the complex plane is a cluster point of zeros of sections of the series. We prove this result by studying properties of the growth function of a sequence of entire functions. For series, this growth function is computable in terms of the convergence abscissa of an associated general Dirichlet series. The proof then extends, besides including Jentzsch's classical result for power series, to general Dirichlet series, to Kapteyn, and to Neumann series of Bessel functions. Moreover, sections of Kapteyn and Neumann series generally exhibit zeros close to the real axis which can be explained, including their asymptotic linear density, by the theory of the distribution of zeros of entire functions.
format Preprint
id arxiv_https___arxiv_org_abs_2107_07207
institution arXiv
publishDate 2021
record_format arxiv
spellingShingle A Jentzsch-Theorem for Kapteyn, Neumann, and General Dirichlet Series
Bornemann, Folkmar
Complex Variables
30B50, 30C15 (Primary) 33C10, 30D20 (Secondary)
Comparing phase plots of truncated series solutions of Kepler's equation by Lagrange's power series with those by Bessel's Kapteyn series strongly suggest that a Jentzsch-type theorem holds true not only for the former but also for the latter series: each point of the boundary of the domain of convergence in the complex plane is a cluster point of zeros of sections of the series. We prove this result by studying properties of the growth function of a sequence of entire functions. For series, this growth function is computable in terms of the convergence abscissa of an associated general Dirichlet series. The proof then extends, besides including Jentzsch's classical result for power series, to general Dirichlet series, to Kapteyn, and to Neumann series of Bessel functions. Moreover, sections of Kapteyn and Neumann series generally exhibit zeros close to the real axis which can be explained, including their asymptotic linear density, by the theory of the distribution of zeros of entire functions.
title A Jentzsch-Theorem for Kapteyn, Neumann, and General Dirichlet Series
topic Complex Variables
30B50, 30C15 (Primary) 33C10, 30D20 (Secondary)
url https://arxiv.org/abs/2107.07207