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Abstract

We present a construction which associates an infinite sequence of Kac–Moody algebras, labeled by a positive integer n, to one single Jordan algebra. For n=1, this reduces to the well known Kantor–Koecher–Tits construction. Our generalization utilizes a new relation between different generalized Jordan triple systems, together with their known connections to Jordan and Lie algebras. Applied to the Jordan algebra of Hermitian 3×3 matrices over the division algebras [openface R], [openface C], [openface H], [openface O], the construction gives the exceptional Lie algebras [fraktur f]4, [fraktur e]6, [fraktur e]7, [fraktur e]8 for n=2. Moreover, we obtain their infinite-dimensional extensions for n>=3. In the case of 2×2 matrices, the resulting Lie algebras are of the form [fraktur s][fraktur o](p+n,q+n) and the concomitant nonlinear realization generalizes the conformal transformations in a spacetime of signature (p,q).