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arXiv · 2605.09333

Integral elements of Okubo algebra and the E8-lattice

Daniele Corradetti
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Abstract

In this work we study the interplay between the Coxeter-Dickson $E_{8}$-order, the para-octonions, and the real Okubo algebra. We first explain why a usual rotation presentation of the order-three automorphism, although algebraically correct, does not preserve the classical integral orders. We then introduce an integral order-three automorphism and prove that its Petersson isotope is the compact real Okubo algebra. The four octonionic orders with lattices $C_{8}$, $A_{2}^{4}$, $D_{4}^{2}$, and $E_{8}$ are preserved by the new realisation of the Okubo product. In particular, the same Coxeter-Dickson $E_{8}$ lattice supports octonionic, para-octonionic, and Okubo integral structures, although the resulting multiplicative systems are not isomorphic.

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Daniele Corradetti. 2026-05-10. Integral elements of Okubo algebra and the E8-lattice. https://arxiv.org/abs/2605.09333

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