On the K-theory of the coordinate axes in the plane

Let k a regular Fp-algebra, let A = k[x,y]/(xy) be the coordinate ring of the coordinate axes in the affine k-plane, and let I = (x,y) be the ideal that defines the intersection point. We evaluate the relative K-groups Kq(A,I) completely in terms of the groups of big de Rham-Witt forms of k. This generalizes a formula for K1 and K2 by Dennis and Krusemeyer.

Lars Hesselholt <larsh@math.nagoya-u.ac.jp>