Hi,
Let $k$ be a perfect field of characteristic $p > 0$. Let $A/k$ be an abelian variety. Then the first crystalline cohomology group of $A$ with respect to $W(k)$ (= Witt vectors) is canonically isomorphic to the (contravariant) Dieudonne functor of the $p$-divisible group of $A$.
This is well-known result and I am wondering if there is a simple proof of it. Specifically, I am wondering if there is a proof that doesn't require defining the Dieudonne crystal for a $p$-divisible group as an intermediary.
Thanks!