Normal forms for the G_2-action on the real symmetric 7x7-matrices by conjugation
arXiv:math/0703321 · doi:10.1016/j.jalgebra.2007.03.007
Abstract
The exceptional Lie group G_2 acts on the set of real symmetric 7x7-matrices by conjugation. We solve the normal form problem for this group action. In view of earlier results, this gives rise to a classification of all finite-dimensional real flexible division algebras. By a classification is meant a list of pairwise non-isomorphic algebras, exhausting all isomorphism classes. We also give a parametrisation of the set of all real symmetric matrices, based on eigenvalues.
23 pages. Made typographical update in accordance with the final, published version