p-jets Of p-isogenies

Abstract

p-jets of finite flat maps of schemes are generally neither finite nor flat. This phenomenon can be seen already in the case of p-isogenies of group schemes. However, for p-divisible groups, this pathology tends to disappear mod p "in the limit". We illustrate this in the case of the p-divisible groups of elliptic curves and of formal groups of finite height; in the case of ordinary elliptic curves the structure in the limit depends on the Serre-Tate parameter.