Hilbert scheme of a pair of codimension two linear subspaces

摘要

We study the component H_n of the Hilbert scheme whose general point parameterizes a pair of codimension two linear subspaces in Pn for n ≥ 3. We show that H_n is smooth and isomorphic to the blow-up of the symmetric square of G_((n-2, n)) along the diagonal. Further H_n intersects only one other component in the full Hilbert scheme, transversely. We determine the stable base locus decomposition of its effective cone and give modular interpretations of the corresponding models, hence conclude that H_n is a Mori dream space.