Two Notes on Flatness.
The purpose of this paper is to study the connectedness of the Hilbert scheme H(d,g) of degree d and genus g curves (locally Cohen-Macaulay) in P3. Thanks to the method of triads, we show that a large class of curves (the curves whose Rao-module is Koszul, i.e. a complete intersection) are in the connected component of extremal curves. This generalizes widely several recent results.
Here we give conditions and examples for the surjectivity or injectivity of the restriction map , where is a projective variety, is a vector bundle on and is a “general” -dimensional subscheme of , union of general “fat points”.