Let $A$ and $B$ be two abelian varieties over any algebraically closed field. Let $A[p^n]$ and $B[p^n]$ denotes the set of $p$-power torsion points of $A$ and $B$. Assume that $A[p^n]$ and $B[p^n]$ have infinitely many points in common, that is, $A[p^{\infty}] \cap B[p^{\infty}]$ is infinite.
Do there exist some formal group laws $F_A$ and $F_B$ associated with $A$ and $B$, respectively, such that $F_A[p^n]$ and $F_B[p^n]$ also have infinitely many points in common?
I am treating formal group and formal group law as two distinct object, though in many places people simple use formal group to mean formal group law.
For abelian variety $A$ has a unique formal group $\hat{A}$ associated with its structure, but, upon choice of coordinates, one can have an isomorphic class of formal group laws $F_A$ of the underlying formal group $\hat{A}$. Similarly, the abelian variety $B$ has a unique formal group $\hat{B}$ associated with its structure, but, upon choice of coordinates, one can have an isomorphic class of formal group laws $F_B$.
The formal groups $\hat{A}, \hat{B}$ capture the local behaviour of the abelian varieties $A,B$ at the identity element and therefore the formal group laws of $F_A$ and $ F_B$ also capture the local behaviour of $A$ and $B$, respectively, near the identity.
Now the $p$-torsion points $A[p^n]$ of $A$ are the solutions of the multiplication-by-$p$ map $[p]_A(x)=0$. These points $A[p^n]$ must also appears in the formal group $\hat{A}$ and therefore solutions of the multplication-by-$p$ map $[p]_{F_A}(x)$ of some suitable formal group law (or formal power series) $F_A$ of $\hat{A}$. The upshot is that the torsion points of an abelian variety transfers (upon suitable choice of coordinates) to some formal group law associated to it.
Thus I think, if $A$ and $B$ shares infinitely many $p$-torsion points, then $F_A$ and $F_B$ will also share infinitely many points.
Elliptic curve and its formal group law can be an example, I think.
