A group law on smooth real quartics having at least real branches
Let be a smooth real quartic curve in . Suppose that has at least real branches . Let and let . Let be the map from into the neutral component Jac of the set of real points of the jacobian of , defined by letting be the divisor class of the divisor . Then, is a bijection. We show that this allows an explicit geometric description of the group law on Jac. It generalizes the classical geometric description of the group law on the neutral component of the set of real points of...