Formal group of an elliptic curve
= Formal group of an elliptic curve
The local parameter $z=-x/y$ at the identity of a Weierstrass curve expresses addition as a formal group law. Over a local field it describes points reducing to the identity.
= Formal group of an elliptic curve
The local parameter $z=-x/y$ at the identity of a Weierstrass curve expresses addition as a formal group law. Over a local field it describes points reducing to the identity.