6 – Proj | PModChecker 1/2 Let D∈S be an ample class. If D2=2 and there does not exist a class F∈S such thatF2=0 and F⋅D=1, then φD:X⟶P2 is a double cover. If D2=4 and there does not exist a class F∈S such that F2=0 and F⋅D∈{1,2} then φD:X⟶P3 embeds X as a quartic surface. Previous Next