Evento
Descrizione:
Abstract:
The irreducibility of the punctual Hilbert scheme in the plane Hilb^n_0(A^2) has been first proved by Briançon. An alternative proof relies on the geometry of the variety parametrizing pairs ofcommuting nilpotent matrices. We extend this circle of ideas to describe the geometry of nested Hilbert schemes Hilb^{n,m}_0 (A^2) parametrizing pairs (z_n; z_m) of punctual subschemes with z_n \subset z_m. As an application, we construct creation operators on the equivariant Chow ring A*_K(Hilb^n(A^2)) of the Hilbert scheme Hilb^n(A^2) with equivariant coefficients inverted. We compute base change formulas in A*_K(Hilb^n(A^2)) between the natural bases introduced by Nakajima, Ellingsrud and Strømme, and the classical basis associated with the fixed points.