Lemma 10.31.34.68A4962EA99D Let $a_ j\in \mathrm{PSH}(X,\theta )$ have a common upper bound and converge in $L^1(X)$ to $a\in \mathrm{PSH}(X,\theta )$ with $a\preceq \varphi $. Suppose there is $h\in \mathcal E_\varphi $ such that $h\leq a_ j$ for every $j$. If, for some $\lambda >0$,
\[ \int _ X|a_ j-a|\mathrm{e}^{\lambda a}\, \mu _{a_ j}\longrightarrow 0, \]
then $a\in \mathcal E_\varphi $ and $a_ j\to a$ in capacity.
Proof.
By lemma 5.24.3, the lower bound passes to the limit, so $h\leq a\preceq \varphi $, and upward stability gives $a\in \mathcal E_\varphi $. Start with any subsequence and extract a further one along which the integrals in the hypothesis are at most $2^{-j}$ and $a_ j\to a$ almost everywhere for smooth volume. The finite rooftops
\[ p_{j,N}=P_\theta (a_ j,\ldots ,a_ N) \]
are not identically $-\infty $ because $h$ is a competitor. Partitioning their contact sets according to the first obstacle touched gives
\[ \int _ X\min (1,|p_{j,N}-a|)\mathrm{e}^{\lambda a}\, \mu _{p_{j,N}} \leq \sum _{k=j}^ N\int _ X|a_ k-a|\mathrm{e}^{\lambda a}\, \mu _{a_ k} \leq 2^{1-j}. \]
No relative-class assertion about these finite rooftops is needed. Their decreasing limits $p_ j=P_\theta (\inf _{k\geq j}a_ k)$ are at least $h$, and the almost-everywhere convergence gives $p_ j\leq a$. Hence the $p_ j$ and their increasing regularized limit $p$ lie in $\mathcal E_\varphi $.
The limits in $N$ and then in $j$ hold in capacity by lemma 5.29.19, since $h$ is a common lower bound. Apply the weighted lower semicontinuity lemma 13.14.8 twice, to the bounded weights $\min (1,|p_{j,N}-a|)\mathrm{e}^{\lambda a}$ and their limits. These weights converge in capacity: discard deep sublevel sets of $h$ and $a$, and use continuity on the remaining finite ranges. We obtain
\[ \int _ X\min (1,|p-a|)\mathrm{e}^{\lambda a}\, \mu _ p=0. \]
The exponential is positive off a pluripolar set, which $\mu _ p$ does not charge. Hence $\mu _ p(\{ p<a\} )=0$, and zero domination gives $p=a$. The upper envelopes $(\sup _{k\geq j}a_ k)^*$ decrease to $a$, and squeezing proves convergence in capacity along this subsequence. Since the initial subsequence was arbitrary, the convergence holds for the original sequence.
$\square$
Comments
Corrections, questions, and mathematical discussion are welcome. Sign in with GitHub to comment. Comments are public.