Integrality of height-one formal groups

Abstract

Let $K$ be a finite extension of ${\mathbb{Q}}_p$. We prove that a one-dimensional formal group law over $K$ has integral coefficients if and only if its multiplication-by-$n$ endomorphisms have integral coefficients for all integers $n$, in the height-one case, i.e. when the multiplication by $p$ has Weierstrass degree $p$. The proof uses some $p$-adic Hodge theory.

7 pages, 1 figure