The Schur functors and the resolution of determinantal varieties

Abstract

Resolutions is one of the most effective methods to obtain information about varieties in Algebraic Geometry. For many years there has been considerable efforts in finding a resolution of determinantal varieties. To put the problem plainly, assume $R=K[x_{0},...,x_{s}]$ is the polynomial ring over an algebraically closed field of characteristic zero and $\mathbb{P}^{s}$ is the projective space of dimension $s$ over $K$. Given $(r_{i,j})$ a homogeneous matrix of size $pxq$ with entries in $R$, the problem is to find an explicit minimal free resolution of the ideal $I_{t}$ defined by the $txt$ minors of this matrix. Over certain hypothesis on $I_{t}$ , this is a minimal free resolution of the variety $X={z \in\mathbb{P}s|rg((r_{i,j})(z))<t} of \mathbb{P}^s$. It provides the Hilbert polynomial of $X$, the projective dimension and the arithmetically Cohen-Macaulayness of the variety among others characteristics.