On the transposition anti-involution in real Clifford algebras II: stabilizer groups of primitive idempotents

Abstract

In the first article [R. Abłamowicz and B. Fauser, On the transposition anti-involution in real Clifford algebras I: The transposition map, Linear Multilinear Algebra, to appear] we showed that real Clifford algebras Cℓ(V, Q) possess a unique transposition anti-involution . The map reduces to reversion (resp. conjugation) for any Euclidean (resp. anti-Euclidean) signature. When applied to a general element of the algebra, it results in transposition of associated matrix of that element in the left regular representation of the algebra. In this article we show that, depending on the value of (p − q) mod 8, where ϵ = (p, q) is the signature of Q, the anti-involution gives rise to transposition, Hermitian complex and Hermitian quaternionic conjugation of representation matrices in spinor representations. We realize spinors in minimal left ideals S = Cℓ p,q f generated by a primitive idempotent f. The map allows us to define a dual spinor space S*, and a new spinor norm on S, which is different, in general, from two spinor norms known to exist. We study a transitive action of generalized Salingaros' multiplicative vee groups G p,q on complete sets of mutually annihilating primitive idempotents. Using the normal stabilizer subgroup G p,q (f), we construct left transversals, spinor bases and maps between spinor spaces for different orthogonal idempotents f i summing up to 1. We classify the stabilizer groups according to the signature in simple and semisimple cases.