Pome

Theorem 14.25.3FE27B72E2DB5

Theorem 14.25.3.FE27B72E2DB5 Condition (14.25.1) holds if and only if every pair of bounded $\omega $-plurisubharmonic functions $a,b$ satisfies

A25B3D75AF64 14.25.4
\begin{equation} \int _{\{ a<b\} }\mathrm{MA}_\omega (b) \leq \int _{\{ a<b\} }\mathrm{MA}_\omega (a). \end{equation}

For the converse implication, it suffices to require this inequality for smooth potentials.

Proof. Under (14.25.1), theorem 11.1.7 gives $\int _ X\mathrm{MA}_\omega (a)=V$ for every bounded potential $a$; for $n=1$ this is Stokes' theorem.

Set $q=\max (a,b)$. On $\{ a<b\} $, plurifine locality gives $\mathrm{MA}_\omega (q)=\mathrm{MA}_\omega (b)$. On $\{ a\geq b\} $, one has $a=q$, and $a\leq q$ everywhere, so bounded ordered contact (lemma 5.28.3) gives

\[ \mathbf1_{\{ a\geq b\} }\mathrm{MA}_\omega (a) \leq \mathbf1_{\{ a\geq b\} }\mathrm{MA}_\omega (q). \]

The total masses of $a$, $b$ and $q$ all equal $V$. Hence

\[ \int _{\{ a<b\} }\mathrm{MA}_\omega (b)=V-\int _{\{ a\geq b\} }\mathrm{MA}_\omega (q) \leq V-\int _{\{ a\geq b\} }\mathrm{MA}_\omega (a)=\int _{\{ a<b\} }\mathrm{MA}_\omega (a), \]

which is (14.25.4).

Conversely, comparison for smooth potentials implies that all smooth potentials have the same mass: given a smooth pair $a,b$, add to $b$ a constant so large that $\{ a<b\} =X$, apply (14.25.4), and then interchange the roles of $a$ and $b$. Comparison with the zero potential shows that the common mass is $V$. By theorem 11.1.7, lemma 11.1.3, this implies (14.25.1) when $n\geq 2$; for $n=1$ that condition holds for degree reasons. $\square$

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