Abstract. Our article contributes to the classification of dissident maps on R 7 , which in turn contributes to the classification of 8-dimensional real division algebras.We study two large classes of dissident maps on R 7 . The first class is formed by all composed dissident maps, obtained from a vector product on R 7 by composition with a definite endomorphism. The second class is formed by all doubled dissident maps, obtained as the purely imaginary parts of the structures of those 8-dimensional real quadratic division algebras which arise from a 4-dimensional real quadratic division algebra by doubling. For each of these two classes we exhibit a complete (but redundant) classification, given by a 49-parameter family of composed dissident maps and a 9-parameter family of doubled dissident maps respectively. The intersection of these two classes forms one isoclass of dissident maps only, namely the isoclass consisting of all vector products on R 7 .
Introduction.A dissident map on a finite-dimensional Euclidean vector space V is understood to be a linear map η : V ∧ V → V such that v, w, η(v ∧ w) are linearly independent whenever v, w ∈ V are. The notion of a dissident map provides a link between seemingly diverse aspects of real geometric algebra, thereby revealing its shifting significance. While it generalizes on the one hand the classical notion of a vector product, it specializes on the other hand the structure of a real division algebra. Moreover it yields naturally a large class of selfbijections of the projective space P(V ), many of which are collineations, but some of which, surprisingly, are not.Dissident maps are known to exist in dimensions 0, 1, 3 and 7 only. In dimensions 0 and 1 they are trivial. In dimension 3 they are classified completely and irredundantly. But in dimension 7 they are still far from fully understood.Our article investigates dissident maps on a 7-dimensional Euclidean space by studying and separating two classes of them, namely the composed dissident maps and the doubled dissident maps. Once an exhaustive 49-parameter family of composed dissident maps on R 7 and an exhaustive 9-parameter family of doubled dissident maps on R 7 are obtained, the problem