On certain quartic forms for affine surfaces
The authors introduce some interesting new invariants in equiaffine hypersurface theory, namely some quadratic and quartic forms. They apply these results to characterize certain classes of nondegenerate surfaces in affine 3-space by the vanishing of such an invariant; as an example: they characterize all flat affine spheres by the vanishing of a qudratic form. -- A final chapter is devoted to the characterization of hyperquadrics in \({\mathbb{R}}P^{n+1}\) using tools of affine differential geometry.
scientific article; zbMATH DE number 570300