A universal linear algebraic model for conformal geometries

TL;DR

This paper introduces a universal algebraic framework for conformal geometries, unifying Euclidean, spherical, and hyperbolic models through a generalized linear algebraic approach that applies over various fields.

Contribution

It presents a novel algebraic construction that unifies different conformal geometries via a generalized Lie sphere geometry, applicable over any field of odd characteristic.

Findings

Measurement of distances and angles is intrinsic to the model.

Models are classified over real, complex, and finite fields.

Reveals similarities between real and finite geometries.

Abstract

This article describes an entirely algebraic construction for developing conformal geometries, which provide models for, among others, the Euclidean, spherical and hyperbolic geometries. On one hand, their relationship is usually shown analytically, through a framework comparing the measurement of distances and angles in Cayley-Klein geometries, including Lorentzian geometries, as done by F. Bachmann and later R. Struve. On the other hand, such a relationship may also be expressed in a purely linear algebraic manner, as explained by D. Hestens, H. Li and A. Rockwood. The model described in this article unifies these approaches via a generalization of Lie sphere geometry. Like the work of N. Wildberger, it is a purely algebraic construction, and as such it works over any field of odd characteristic. It is shown that measurement of distances and angles is an inherent property of the model that is easy to identify, and the possible models are classified over the real, complex and finite fields, and partially in characteristic $2$, revealing a striking analogy between the real and finite geometries.