Isogenies of Polynomial Formal Groups

LetH = Hv(i, j) be a Greither order inKCp2and let Spec Hv(i, j) → Spec B → Spec Cbe a resolution of Spec Hv(i, j) in the flat topology which appears as μp2 → Gm × Gm → Gm × Gmover the fieldK. Under certain conditions, the formal completions ofBandCgive rise to two-dimensional polynomial formal groups and , respectively. The given resolution will then translate to an isogeny of polynomial formal groups Ψ: → with kernel Spec Hv(i, j).