Fano Schemes of Complete Intersections in Toric Varieties

Abstract

We study Fano schemes $F_k(X)$ for complete intersections $X$ in a projective toric variety $Y\subset {\mathbb{P}}^n$. Our strategy is to decompose $F_k(X)$ into closed subschemes based on the irreducible decomposition of $F_k(Y)$ as studied by Ilten and Zotine. We define the expected dimension for these subschemes, which always gives a lower bound on the actual dimension. Under additional assumptions, we show that these subschemes are non-empty and smooth of the expected dimension. Using tools from intersection theory, we can apply these results to count the number of linear subspaces in $X$ when the expected dimension of $F_k(X)$ is zero.

arXiv comment28 pages, minor revision, to appear in Math Z