Minimal representations and algebraic relations for single nested products

TL;DR

This paper develops a framework for representing finite sets of hypergeometric products in formal difference rings with minimal transcendental generators, and explicitly describes relations among these products.

Contribution

It introduces a new approach to minimize the number of transcendental generators in difference ring representations of hypergeometric products.

Findings

Minimal number of transcendental generators achieved

Explicit relations among input products described

Framework allows reuse of existing difference rings

Abstract

Recently, it has been shown constructively how a finite set of hypergeometric products, multibasic hypergeometric products or their mixed versions can be modeled properly in the setting of formal difference rings. Here special emphasis is put on robust constructions: whenever further products have to be considered, one can reuse --up to some mild modifications-- the already existing difference ring. In this article we relax this robustness criteria and seek for another form of optimality. We will elaborate a general framework to represent a finite set of products in a formal difference ring where the number of transcendental product generators is minimal. As a bonus we are able to describe explicitly all relations among the given input products.