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Sándor Kovács
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Effective versus movable cones of curves

Let $\overline{NE}(X)$ be the closure of the cone generated by the numerical classes of effective curves and $\overline{\mathrm{Mov}}(X)$ the closure of the cone of moving curves.

(Q1) Is there an example of a smooth projective variety $X$ such that

  • $\overline{NE}(X)$ is (finite) polyhedral, but
  • $\overline{\mathrm{Mov}}(X)$ is not?

Here are some trivial observation:

1

If $X$ is a surface then the two cones are dual to each other and hence they are either both polyhedral or not.

2

If $X$ is a Fano variety then

  • $\overline{NE}(X)$ is polyhedral by the Cone Theorem, and
  • $\overline{\mathrm{Mov}}(X)$ is polyhedral if $\dim \leq4$ by a result of Barkowski (see here).

So, perhaps I should really ask:

(Q2) Is it true that $\overline{NE}(X)$ is polyhedral if and only if $\overline{\mathrm{Mov}}(X)$ is polyhedral?

If true, this would (for example) provide a proof of Barkowski's result in all dimensions.

Sándor Kovács
  • 42.9k
  • 2
  • 109
  • 155