%0 Journal Article
%T The Hopf condition for bilinear forms over arbitrary fields
%A Daniel Dugger
%A Daniel C. Isaksen
%J Mathematics
%D 2003
%I arXiv
%X We settle an old question about the existence of certain "sums-of-squares" formulas over a field F (which are the simplest examples of composition formulas for quadratic forms). A classical theorem says that if such a formula exists over a field of characteristic 0, then certain binomial coefficients must be even. We use motivic cohomology to prove that the same result holds in characteristic p.
%U http://arxiv.org/abs/math/0309197v1