%0 Journal Article
%T Orthogonal representations of affine group schemes and twists of symmetric bundles
%A Philippe Cassou-Nogu¨¨s
%A Ted Chinburg
%A Baptiste Morin
%A Martin Taylor
%J Mathematics
%D 2011
%I arXiv
%X Following Serre's initial work, a number of authors have considered twists of quadratic forms on a scheme Y by torsors of a finite group G, together with formulas for the Hasse-Witt invariants of the twisted form. In this paper we take the base scheme Y to be affine and consider non-constant groups schemes G. There is a fundamental new feature in this case - in that the torsor may now be ramified over Y. The natural framework for handling the case of a non-constant group scheme over the affine base is provided by the quadratic theory of Hopf-algebras.
%U http://arxiv.org/abs/1111.1590v1