Thus, the code image last associatedK3surface X gives the (minimal) associated K3 surface to X. For more details and notation, see the paper Trisecant Flops, their associated K3 surfaces and the rationality of some Fano fourfolds.
i1 : X = specialCubicFourfold "quartic scroll"; o1 : ProjectiveVariety, cubic fourfold containing a surface of degree 4 and sectional genus 0 |
i2 : describe X o2 = Special cubic fourfold of discriminant 14 containing a (smooth) surface of degree 4 and sectional genus 0 cut out by 6 hypersurfaces of degree 2 |
i3 : time (mu,U,C,f) = associatedK3surface(X,Verbose=>true); -- computing the map mu from P^5 to P^5 defined by the quadrics through the surface S_14 -- computing the surface U corresponding to the fourfold X -- computing the surface U' corresponding to another fourfold X' -- computing the exceptional conic on U and U' -- computing the map f from U to the minimal K3 surface of degree 14 -- computing the image of f -- used 9.976 seconds |
i4 : ? mu o4 = multi-rational map consisting of one single rational map source variety: PP^5 target variety: PP^5 dominance: false image: hypersurface in PP^5 defined by a form of degree 2 |
i5 : ? U o5 = surface in PP^5 cut out by 7 hypersurfaces of degrees 2^1 3^6 |
i6 : first C o6 = curve in PP^5 cut out by 4 hypersurfaces of degrees 1^3 2^1 o6 : ProjectiveVariety, curve in PP^5 |
i7 : image f o7 = surface in PP^8 cut out by 15 hypersurfaces of degree 2 o7 : ProjectiveVariety, surface in PP^8 |