Schemes [HB 92]

New Features:

• Intrinsic ArithmeticGenus added for ordinary projective varieties.

• To work with the tangent and secant varieties of schemes, TangentVariety, SecantVariety, IsInTangentVariety and IsInSecantVariety have been added.

• Intrinsic IsomorphicProjectionToSubspace added. This finds a sequence of point projections of a projective scheme of dimension d down to a 2d + 1 linear subspace of its ambient space such that the combined projection is an isomorphism of the scheme onto its image.

• Intrinsic EmbedPlaneCurveInP3 added. This gives a non-singular projective plane or (3D-)space curve birationally equivalent to the original plane curve.
• The intrinsic IsAmbient has been provided for schemes.