Pome

Proposition 21.12.2911748980D2DF

Proposition 21.12.29.11748980D2DF Let $\varphi \in \mathrm{PSH}_{\mathrm{tor}}(X,\omega )$. Then $P_{\omega }[\varphi ]\in \mathrm{PSH}_{\mathrm{tor}}(X,\omega )$ and

F8C4AC16B8F2 21.12.30
\begin{equation} G_{P_{\omega }[\varphi ]}(x)= \begin{cases} G_0(x),& \textup{if } x\in \Delta (\omega ,\varphi );\\ \infty ,& \textup{otherwise}. \end{cases} \end{equation}

Proof. By (16.3.7), we have

\[ P_{\omega }[\varphi ]=\operatorname *{sup}_{C\in \mathbb {R}}{}\! {}^{*}\bigl ((\varphi +C)\land 0\bigr ). \]

It follows from proposition 21.12.20, proposition 21.12.21 and proposition 21.12.23 that $P_{\omega }[\varphi ]\in \mathrm{PSH}_{\mathrm{tor}}(X,\omega )$. Moreover, by the same propositions, we have

\[ G_{P_{\omega }[\varphi ]}=\operatorname{cl}\inf _{C\in \mathbb {R}} \left( G_{0}\lor (G_{\varphi }-C) \right). \]

We spell out the last closure. Set

\[ K=\inf _{C\in \mathbb {R}} \left( G_{0}\lor (G_{\varphi }-C) \right). \]

If $x\in \operatorname{Dom}G_{\varphi }$, then $G_{\varphi }(x)-C\leq G_0(x)$ for $C$ large enough, hence $K(x)=G_0(x)$. If $x\notin \operatorname{Dom}G_{\varphi }$, then $K(x)=\infty $. Since $\Delta (\omega ,\varphi )=\overline{\operatorname{Dom}G_{\varphi }}$ and $G_0$ is continuous on $P$, the lower semicontinuous regularization $\operatorname{cl}K$ is equal to $G_0$ on $\Delta (\omega ,\varphi )$ and equal to $\infty $ outside $\Delta (\omega ,\varphi )$. This is exactly (21.12.30). $\square$

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