On the Terwilliger algebra of the group association scheme of Cn⋊C2

Abstract

In 1992, Terwilliger introduced the notion of the Terwilliger algebra in order to study association schemes. The Terwilliger algebra of an association scheme A is the subalgebra of the complex matrix algebra, generated by the Bose-Mesner algebra of A and its dual idempotents with respect to a point x.In Bannai and Munemasa (1995) [3] determined the dimension of the Terwilliger algebra of abelian groups and dihedral groups, by showing that they are triply transitive (i.e., triply regular and dually triply regular). In this paper, we give a generalization of their results to the group association scheme of semidirect products of the form Cn⋊C2, where Cm is a cyclic group of order m≥2. Moreover, we will give the complete characterization of the Wedderburn components of the Terwilliger algebra of these groups.