1
$\begingroup$

I refer to the paper "Normal Subgroups in the Cremona Group". In the last paragraph of the proof of proposition 5.13, the author wrote the following: "Assume now that $h\in \text{Bir}(X)$ preserves the axis of $g_\ast$. Then $h_\ast [D']$ is an ample class." Here $[D']$ is an ample class in $N^1(X)\cap V_g$. May I ask how is the ampleness of $h_\ast[D']$ deduced?

$\endgroup$

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Browse other questions tagged or ask your own question.