Abstract

It is very useful to distinguish between four types of interactions in nature: gravitation, and then electromagnetism, weak interaction and strong interaction. The mathematical structure of electromagnetism but also of weak and strong interaction could be understood as induced by a local gauge group. The associated groups are the unitary group in one dimension—U—for electromagnetism, the special unitary group in two dimensions—SU—for the weak interaction, and the special unitary group in three dimensions—SU—for the strong interaction. The essence of this article is to give a “first-principles” explanation for the three gauge groups.