Entire slice regular functions

TL;DR

This paper develops the theory of entire slice regular functions in the quaternionic setting, including new growth estimates, zero counting, and analogs of classical complex analysis theorems, extending the understanding of quaternionic analysis.

Contribution

It introduces new results on growth, zero distribution, and classical theorems for entire slice regular functions, advancing quaternionic analysis.

Findings

Established growth relations with power series coefficients

Proved quaternionic analogs of Jensen and Carathéodory theorems

Analyzed zeros, including spherical zeros with infinite cardinality

Abstract

Entire functions in one complex variable are extremely relevant in several areas ranging from the study of convolution equations to special functions. An analog of entire functions in the quaternionic setting can be defined in the slice regular setting, a framework which includes polynomials and power series of the quaternionic variable. In the first chapters of this work we introduce and discuss the algebra and the analysis of slice regular functions. In addition to offering a self-contained introduction to the theory of slice-regular functions, these chapters also contain a few new results (for example we complete the discussion on lower bounds for slice regular functions initiated with the Ehrenpreis-Malgrange, by adding a brand new Cartan-type theorem). The core of the work is Chapter 5, where we study the growth of entire slice regular functions, and we show how such growth is related to the coefficients of the power series expansions that these functions have. It should be noted that the proofs we offer are not simple reconstructions of the holomorphic case. Indeed, the non-commutative setting creates a series of non-trivial problems. Also the counting of the zeros is not trivial because of the presence of spherical zeros which have infinite cardinality. We prove the analog of Jensen and Carath\'eodory theorems in this setting.