The Arason invariant of orthogonal involutions of degree 12 and 8, and quaternionic subgroups of the Brauer group
The Arason invariant of orthogonal involutions of degree 12 and 8, and quaternionic subgroups of the Brauer group
Using the Rost invariant for torsors under Spin groups one may define an analogue of the Arason invariant for certain hermitian forms and orthogonal involutions.We calculate this invariant explicitly in various cases, and use it to associate to every orthogonal involution σ with trivial discriminant and trivial Clifford invariant over …