Proposition 12.10.24.62BDDC322780 Let $\psi \leq 0$ be a quasi-plurisubharmonic function with $\mathrm{dd}^{\mathrm{c}}\psi \geq -C\omega $ for some $C>0$, and let $u\in \mathrm{PSH}(X,\omega )$ satisfy, everywhere on $X$,
\[ u\geq -A(1-\psi )^\alpha -B, \qquad A>0,\quad B\in \mathbb R,\quad 0<\alpha <1. \]
Then $P_{\delta \omega }(u)$ is not identically $-\infty $ for every $0<\delta <1$, and $u$ has zero Lelong numbers.
Proof.
Choose $\alpha <\beta <1$ and $\varepsilon >0$ with $\varepsilon \beta C\leq \delta $. The number
\[ K=B+\sup _{t\geq 1}(At^\alpha -\varepsilon t^\beta ) \]
is finite, and $v_\delta =-\varepsilon (1-\psi )^\beta -K\leq u$. The function $t\mapsto -\varepsilon (1-t)^\beta $ is increasing and convex on $t\leq 0$, with derivative at most $\varepsilon \beta $. Applying the chain inequality for quasi-plurisubharmonic functions to $\max (\psi ,-j)$ and passing to the decreasing limit as $j\to \infty $, we obtain $\mathrm{dd}^{\mathrm{c}}v_\delta \geq -\varepsilon \beta C\omega \geq -\delta \omega $. The limit is not identically $-\infty $ because $\psi $ is finite almost everywhere; at the poles of $\psi $ it takes the value $-\infty $, where the comparison with $u$ still holds. Thus $v_\delta \in \mathrm{PSH}(X,\delta \omega )$ is a competitor for $P_{\delta \omega }(u)$ for each $\delta $, and the Lelong estimate preceding theorem 12.10.23 proves the last assertion.
$\square$
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