RECENTLY, a characterization of the larger exceptional Lie groups has been obtained which throws considerable light on what their role may be in physical theory1. They are, namely, automorphisms of Clifford algebras of the special form Γ(m,n) = Qm × Qn; that is, tensor products of normed division algebras Qn of 2n ⩽ 8 elements. If m = 3, the groups are F4, E6, E7, E8 for n = 0, 1, 2, 3.
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