Finitely presented algebras defined by permutation relations of dihedral type

© World Scientific Publishing Company. The class of finitely presented algebras over a field K with a set of generators a1,...,an and defined by homogeneous relations of the form a1a2⋯an = aσ(1)aσ(2)⋯aσ(n), where σ runs through a subset H of the symmetric group Symn of degree n, is investigated. Groups H in which the cyclic group 〈(1, 2,...,n)〉 is a normal subgroup of index 2 are considered. Certain representations by permutations of the dihedral and semidihedral groups belong to this class of groups. A normal form for the elements of the underlying monoid Sn(H) with the same presentation as the algebra is obtained. Properties of the algebra are derived, it follows that it is an automaton algebra in the sense of Ufnarovskij. The universal group Gn of Sn(H) is a unique product group, and it is the central localization of a cancellative subsemigroup of Sn(H). This, together with previously obtained results on such semigroups and algebras, is used to show that the algebra K[Sn(H)] is semiprimitive.