Arason invariant

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In mathematics, the Arason invariant is a cohomological invariant associated to a quadratic form of even rank and trivial discriminant and Clifford invariant over a field k of characteristic not 2, taking values in H³(k,Z/2Z). It was introduced by (Arason 1975, Theorem 5.7).

The Rost invariant is a generalization of the Arason invariant to other algebraic groups.