Realisierung formaler Gruppen durch Kohomologiefunktoren

To any multiplicative cohomology theory h with the property that complex line bundles are h-oriented corresponds a formal group law F(X,Y) over the ring h(pt) which describes the Euler class of a tensor product of line bundles by means of the Euler classes of its factors. We consider this formal group as an invariant of h and give sufficient conditions under which a morphism between formal groups of cohomology theories h,k can be extended in one and only one way to a transformation of theories hk. Some typical applications will be discussed.