On involutions of type $\mathrm{O}(\mathrm{q},k)$ over a field of characteristic two

Abstract

In this article we study the involutions of $\mathrm{O}(V,\mathrm{q})$, an orthogonal group for a vector space $V$ with quadratic form $\mathrm{q}$ over a field of characteristic 2. The classification proceeds by discussing conjugacy classes of involutions arising as a product of transvections, involutions with respect to a hyperbolic space, and involutions acting nontrivially in the radical of $V$. We achieve a complete classification of the conjugacy classes of involutions when the quadratic space $(V,\mathrm{q})$ is non-defective, and conclude with a discussion of the defective case.