Stable base loci, movable curves, and small modifications, for toric varieties

Abstract

We show that the dual of the cone of divisors on a complete Q-factorial toric variety X whose stable base loci have dimension less than k is generated by curves on small modifications that move in families sweeping out the birational transforms of k-dimensional subvarieties of X. We give an example showing that it does not suffice to consider curves on X itself.

10 pages, 1 figure. v2: minor expository changes. To appear in Math. Z