Proposition 5.27.31.026A64B7A5A2 Let $\Omega \subset \mathbb C^ n$, $n\geq 2$, be a bounded domain and $a\in \Omega $. For every $c>0$, there are smooth bounded plurisubharmonic functions $u_ j\leq 0$ on $\Omega $ such that
\[ \| u_ j\| _{L^ p(\Omega )}\longrightarrow 0\quad (1\leq p<\infty ), \qquad (\mathrm{dd}^{\mathrm{c}}u_ j)^ n\longrightarrow c\delta _ a \quad \text{vaguely}. \]
The same sequence tends to zero in local capacity. Here the norms are taken with respect to Lebesgue measure, and vague convergence means convergence against every compactly supported continuous test function.
Proof.
Translate $a$ to the origin and write $z=(\zeta ,z')\in \mathbb C\times \mathbb C^ m$, $m=n-1$. It suffices to construct measures of mass one and then multiply the potentials by $c^{1/n}$. For $\delta >0$, put $H_\delta (z')=\log (|z'|^2+\delta ^2)$. With $s=|z'|^2$, the complex Hessian of $H_\delta $ has the eigenvalue $(s+\delta ^2)^{-1}$ with multiplicity $m-1$ in the directions orthogonal to $z'$ and the eigenvalue $\delta ^2(s+\delta ^2)^{-2}$ in the radial direction. Taking the determinant and integrating in polar coordinates gives
\[ (\mathrm{dd}^{\mathrm{c}}H_\delta )^ m= \frac{m!}{\pi ^ m}\frac{\delta ^2}{(|z'|^2+\delta ^2)^{m+1}} \, \mathrm d\lambda _{2m}, \qquad \int _{|z'|<b}(\mathrm{dd}^{\mathrm{c}}H_\delta )^ m =\left(\frac{b^2}{b^2+\delta ^2}\right)^ m, \]
where $\lambda _{2m}$ is Lebesgue measure. These probability measures tend to $\delta _0$ as $\delta \downarrow 0$, since their mass outside each ball about the origin tends to zero.
Choose $R>\max (1,\sup _\Omega |\zeta |)$ and a ball $P\subset \mathbb C^ m$ containing the projection of $\Omega $ to the $z'$ variables. Set
\[ \begin{gathered} \delta _ j=\varepsilon _ j=j^{-1},\qquad \eta _ j=j^{-2}, \qquad v_ j=\varepsilon _ j^{-1/m}H_{\delta _ j},\\ A_ j=\sup _ Pv_ j+2\varepsilon _ j\log (Rj). \end{gathered} \]
Apply lemma 5.27.29 on $\mathbb C\times \mathbb C^ m$ to these data, and let $u_ j=h_ j-\eta _ j$, where $h_ j$ is the resulting function. The convolution satisfies $0\leq \chi _{\eta _ j}(t)-\max (t,0)\leq \eta _ j$, and $q+\max (T,0)=\max (q,v_ j-A_ j)$. Both branches of this maximum are negative on $\Omega $, so
\[ \varepsilon _ j\log (|\zeta |^2/R^2)-\eta _ j \leq u_ j\leq 0. \]
Each $u_ j$ is smooth and bounded on $\Omega $, since the second branch $v_ j-A_ j$ is bounded below on the bounded set $P$. The logarithm has finite $L^ p(\Omega )$ norm for every finite $p$, by polar integration on a fixed polydisk containing $\Omega $. Hence $u_ j\to 0$ in all these norms.
Let $B'\Subset B\Subset \Omega $ be concentric balls, and let $w\in \mathrm{PSH}(B)$ with $0\leq w\leq 1$. Since $|u_ j|\leq \varepsilon _ j|\log (|\zeta |^2/R^2)|+\eta _ j$, the weighted Chern–Levine–Nirenberg estimate applied to $\log (|\zeta |^2/R^2)$, together with the range estimate (5.27.3) for the constant term, gives
\[ \int _{B'}|u_ j|(\mathrm{dd}^{\mathrm{c}}w)^ n\leq C_ B(\varepsilon _ j+\eta _ j), \]
where $C_ B$ depends on the fixed balls and the logarithm but not on $j$ or $w$. Restricting the integral to $B'\cap \{ |u_ j|>t\} $, dividing by $t>0$ and taking the supremum over $w$ shows that the capacity of $B'\cap \{ |u_ j|>t\} $ relative to $B$ tends to zero.
In (5.27.30), the factor $\varepsilon _ j(\mathrm{dd}^{\mathrm{c}}v_ j)^ m$ equals $(\mathrm{dd}^{\mathrm{c}}H_{\delta _ j})^ m$. For $z'\in P$ and $|t|\leq \eta _ j$, the radii satisfy
\[ r_ t(z')\leq j^{-1}\exp (\eta _ j/(2\varepsilon _ j)) \leq \mathrm e^{1/2}/j. \]
Extend $f\in C_ c(\Omega )$ by zero to $\mathbb C^ n$. Outside the projection of $\operatorname {supp}f$ to the $z'$ variables, both $f(r_ t\mathrm e^{\mathrm i\vartheta },z')$ and $f(0,z')$ vanish. On this projection, the uniform continuity of $f$ and the bound on the radii make their difference tend to zero uniformly. Since the weights $w_{\eta _ j}(t)\, \mathrm dt$ and $\mathrm d\vartheta /(2\pi )$ and the measures $(\mathrm{dd}^{\mathrm{c}}H_{\delta _ j})^ m$ all have total mass one, it follows that
\[ \int _\Omega f(\mathrm{dd}^{\mathrm{c}}u_ j)^ n -\int _{\mathbb C^ m}f(0,z')(\mathrm{dd}^{\mathrm{c}}H_{\delta _ j})^ m \longrightarrow 0. \]
The second integral tends to $f(0)$, which proves the asserted vague limit.
$\square$
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