Proving the Theorem of Wigner by an Exercise in Simple Geometry

TL;DR

This paper offers a geometric approach to prove Wigner's theorem, serving both as an educational resource and as a foundational step for a more general proof.

Contribution

It introduces a simple geometric exercise that simplifies understanding and proving Wigner's theorem, bridging pedagogy and rigorous proof.

Findings

Provides a geometric proof of Wigner's theorem

Enhances pedagogical understanding of the theorem

Lays groundwork for a more general proof

Abstract

The leading idea of the paper is to treat the theorem of Wigner with methods inspired by geometry. The exercise mentionned in the title has two functions: On the one hand it can serve as a pedagogical text in order to make the reader acquainted with the essential features of the theorem and its proof. On the other hand it will turn out to be the core of the general proof.