The Cayley-Dickson doubling products

TL;DR

This paper systematically identifies all Cayley-Dickson doubling products, which define the algebraic structure of complex numbers, quaternions, and octonions, by characterizing the polynomial pairs that generate these algebras.

Contribution

It provides a complete classification of all Cayley-Dickson doubling products, clarifying the algebraic structures used historically for constructing complex, quaternion, and octonion algebras.

Findings

All doubling products satisfying the Cayley-Dickson construction are characterized.

The paper clarifies the historical usage of different doubling products.

A comprehensive list of doubling products for classical algebras is provided.

Abstract

The purpose of this paper is to identify all of the Cayley-Dickson doubling products. A Cayley-Dickson algebra $\mathbb{A}_{N+1}$ of dimension $2^{N+1}$ consists of all ordered pairs of elements of a Cayley-Dickson algebra $\mathbb{A}_{N}$ of dimension $2^N$ where the product $(a,b)(c,d)$ of elements of $\mathbb{A}_{N+1}$ is defined in terms of a pair of second degree binomials $\left(f(a,b,c,d),g(a,b,c,d)\right)$ satisfying certain properties. The polynomial pair$(f,g)$ is called a `doubling product.' While $\mathbb{A}_{0}$ may denote any ring, here it is taken to be the set $\mathbb{R}$ of real numbers. The binomials $f$ and $g$ should be devised such that $\mathbb{A}_{1}=\mathbb{C}$ the complex numbers, $\mathbb{A}_{2}=\mathbb{H}$ the quaternions, and $\mathbb{A}_{3}=\mathbb{O}$ the octonions . Historically, various researchers have used some but not all of these doubling products.