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Lemma 18.39.1246F892FF98FE

Lemma 18.39.12.46F892FF98FE Let $M$ be a compact complex manifold of dimension $d\geq 0$, and let $E,F_1,\ldots ,F_ N$ be holomorphic line bundles on $M$. For each $C_0>0$ there is a constant $C_1$ such that

\[ h^0\left(M,E^ m\otimes \bigotimes _{i=1}^ NF_ i^{j_ i}\right)\leq C_1m^ d \qquad (m\geq 1,\ j_ i\in \mathbb Z,\ |j_ i|\leq C_0m). \]

Proof. For $d=0$ the dimension is at most the number of points of $M$. For $d\geq 1$, use fixed smooth metrics, a smooth positive volume form and finitely many framed charts as in the proof of lemma 18.39.1. The local weight of the metric is $m\phi _ E+\sum _ i j_ i\phi _{F_ i}$, whose second derivatives are bounded by $Cm$ uniformly over the stated range. After its constant and real-linear terms at a point have been removed by a holomorphic affine change of frame, it is bounded by a fixed constant on a ball of radius $\varepsilon m^{-1/2}$ about that point. The submean inequality then gives $|s(x)|^2\leq Cm^ d\| s\| _{L^2}^2$, uniformly in $x$, $m$ and the integers $j_ i$. Since evaluation has a one-dimensional target, an orthonormal basis satisfies $\sum _\ell |s_\ell (x)|^2\leq Cm^ d$, and integration gives the estimate. The constants depend only on the fixed bundles, metrics, charts, volume and $C_0$. $\square$

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