Abstract:
A study is made of the natural action of the group of biregular automorphisms of the affine plane on pairs of square matrices and pairs of symmetric square matrices. It is proved that in the open set of pairs $(A,B)$ such that $A$ is semisimple and $A$ and $B$ have no common invariant subspaces, the commutator $[A,B]=AB-BA$ is the unique invariant in both cases.
Bibliography: 3 titles.