Symmetry of the triple octonionic product

Abstract: The Hermitian decomposition of a linear operator is generalized to the case of two or more operations. An additive expansion of the product of three octonions into three parts is constructed, wherein each part either preserve or change the sign under the action of the Hermitian conjugation and operation of inversion of the multiplicative order of three hypercomplex numbers, as well as under the composition of specified operations. The product of three octonions, in particular quaternions, with conjugate central factor is presented as the sum of mutually orthogonal triple anticommutator, triple commutator and associator that vanishes in the case of associative quaternions. The triple commutator is treated as a generalization of the cross product to the case of three arguments both for quaternions and octonions. A generalized cross product is introduced as an antisymmetric component of the triple octonionic product that changes sign both for inversion of the multiplicative order of three arguments, and for the Hermitian conjugation of the product considered respectively to the central argument. The definition of the cross product of three hypercomplex numbers deduced from symmetry considerations is compared with the solution of S. Okubo (1993) and the modern solution of T. Dray and M.A. Corinne (2015). It is shown that the derived definition is equivalent to the first solution presented by S.Okubo in an insufficiently perfect form.