Cartwright-Sturmfels Hilbert Schemes

Abstract

Let S be the Cox ring of a product of r projective spaces. In this paper, we study the Cartwright-Sturmfels Hilbert schemes of S, which are multigraded Hilbert schemes that only parametrize radical ideals. Our main result shows that these Hilbert schemes are always smooth and irreducible if the Picard rank r is at most 2. This result can be seen as a multigraded analogue of the famous theorems of Fogarty and Maclagan-Smith, where the Picard rank replaces the dimension of the ambient space.