Complete intersections and movable curves on the moduli space of six-pointed rational curves

Research paper by Paul L. Larsen

Indexed on: 21 Mar '12Published on: 21 Mar '12Published in: Mathematics - Algebraic Geometry


A curve on a projective variety is called movable if it belongs to an algebraic family of curves covering the variety. We consider when the cone of movable curves can be characterized without existence statements of covering families by studying the complete intersection cone on a family of blow-ups of complex projective space, including the moduli space of stable six-pointed rational curves, $\bar{M}_{0,6}$, and the permutohedral or Losev-Manin moduli space of four-pointed rational curves. Our main result is that the movable and complete intersection cones coincide for the toric members of this family, but differ for the non-toric member, $\bar{M}_{0,6}$. The proof is via an algorithm that applies in greater generality. We also give an example of a projective toric threefold for which these two cones differ.