A Horrocks-Type Theorem for Even Orthogonal (ext{K}_2)

摘要

We prove the Horrocks theorem for unstable even-dimensional orthogonal Steinberg groups. The Horrocks theorem for Steinberg groups is one of the principal ingredients needed for the proof of the (ext{K}_2)-analogue of Serre's problem, positive solution of which currently is only known in the linear case.