Orbits in the anti-invariant sublattice of the K3-lattice -- Ali Sinan Sertöz

We determine the number of orbits of primitive vectors in the anti-invariant sublattice of the K3-lattice under the action of isometries. In particular when this K3 surface covers an Enriques surface we draw geometric conclusions about the orbits of curves which do not descend down to the Enriques surface.