Generation of jets and Fujita's jet ampleness conjecture on toric varieties

Abstract

Jet ampleness of line bundles generalizes very ampleness by requiring the existence of enough global sections to separate not just points and tangent vectors, but also their higher order analogues called jets. We give sharp bounds guaranteeing that a line bundle on a projective toric variety is $k$-jet ample in terms of its intersection numbers with the invariant curves, in terms of the lattice lengths of the edges of its polytope, in terms of the higher concavity of its piecewise linear function and in terms of its Seshadri constant. For example, the tensor power $k+n-2$ of an ample line bundle on a projective toric variety of dimension $n \geq 2$ always generates all $k$-jets, but might not generate all $(k+1)$-jets. As an application, we prove the $k$-jet generalizations of Fujita's conjectures on toric varieties with arbitrary singularities.