The γ-filtration on the Witt ring of a scheme

The K-ring of symmetric vector bundles over a scheme X, the so-called Grothendieck–Witt ring of X, can be endowed with the structure of a (special) λ-ring. The associated γ-filtration generalizes the fundamental filtration on the (Grothendieck–)Witt ring of a field and is closely related to the ‘classical’ filtration by the kernels of the first two Stiefel–Whitney classes.