Actions of finite hypergroups

Abstract

This paper is concerned with actions of finite hypergroups on sets. After introducing the definitions in the first section, we use the notion of 'maximal actions' to characterise those hypergroups which arise from association schemes, introduce the natural sub-class of *-actions of a hypergroup and introduce a geometric condition for the existence of *-actions of a Hermitian hypergroup. Following an insightful suggestion of Eiichi Bannai we obtain an example of the surprising phenomenon of a 3-element hypergroup with infinitely many pairwise inequivalent irreducible *-actions.