Rational Curves in Projective Toric Varieties

Abstract

We study embedded rational curves in projective toric varieties. Generalizing results of the first author and Zotine for the case of lines, we show that any degree $d$ rational curve in a toric variety $X$ can be constructed from a special affine-linear map called a degree $d$ Cayley structure. We characterize when the curves coming from a degree $d$ Cayley structure are smooth and have degree $d$. We use this to establish a bijection between the set of irreducible components of the Hilbert scheme whose general element is a smooth degree $d$ curve, and so-called maximal smooth Cayley structures. Furthermore, we describe the normalization of the torus orbit closure of such rational curves in the Chow variety, and give partial results for the orbit closures in the Hilbert scheme.