5 – Aut | $\text{Nef}(X)\cap {\mathcal{P}}_S$

There is a natural chamber sub-structure over $\text{Nef}(X)\cap {\mathcal{P}}_S$,
bounded by $(-2)$-walls. That is,

$$\text{Nef}(X)\cap {\mathcal{P}}_S=\bigcup _{D\in \mathcal{C}}D$$ for a sub-collection $\mathcal{C}\subset {\mathcal{C}}_S$ of the ${\mathcal{P}}_S$-chamber structure.

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