ScalingStacks

Proof. [04BJ]

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Proof.

We will only sketch the modifications. The positivity conditition enters through the monotonicity claim 3.22. Once we drop this, we would allow holomophic discs u:Σ→Xu:\Sigma\to X that sweep out parts of L∪L′L\cup L^{\prime} with the reversed orientation. For such curves, claim 3.22 is modified to

Claim 3.29.

Clockwise along ∂Σ\partial\Sigma, the function Re ​F\text{Re }F is decreasing on the LL boundary portion, but increasing on the L′=L1∪L2L^{\prime}=L_{1}\cup L_{2} boundary portion. In particular,

0=Re ​F​(q)≥Re ​F≥Re ​F​(p).0=\text{Re }F(q)\geq\text{Re }F\geq\text{Re }F(p).

More intrinsically, the real part of the complex volume forms on the moduli spaces at such u:Σ→Xu:\Sigma\to X are nonpositive.

The corresponding claim 3.23 is modified to

Claim 3.30.

The image F⁡(Σ)⊂ℂF(\Sigma)\subset\mathbb{C} lies below its L′L^{\prime} boundary portion, and above its LL boundary portion.

At almost every point on L∪L′L\cup L^{\prime}, only automatically transverse holomophic curves pass through it, since by assumption the boundary evaluation of the other holomorphic curves is contained in some subset of L∪L′L\cup L^{\prime} with Hausdorff dimension ≤n−1\leq n-1. According to the ±\pm types of the automatically transverse curves, we decompose the weighted characteristic functions χAi\chi_{A_{i}} on LL into its positive and negative parts χAi+≥0\chi_{A_{i}^{+}}\geq 0 and χAi−≤0\chi_{A_{i}^{-}}\leq 0.

Then upon integration over the moduli space,

Re∫LχAi+Ω=Re∫ℳΩ~Li+≥0,Re∫LχAi−Ω=Re∫ℳΩ~Li−≤0,Im∫LχA2+Ω≤Im∫ℳΩ~L2+,Im∫LχA1+Ω≥Im∫ℳΩ~L1+,Im∫LχA2−Ω≥Im∫ℳΩ~L2−,Im∫LχA1−Ω≤Im∫ℳΩ~L1−.\begin{split}&\text{Re}\int_{L}\chi_{A_{i}^{+}}\Omega=\text{Re}\int_{\mathcal{M}}\tilde{\Omega}_{L_{i}}^{+}\geq 0,\quad\text{Re}\int_{L}\chi_{A_{i}^{-}}\Omega=\text{Re}\int_{\mathcal{M}}\tilde{\Omega}_{L_{i}}^{-}\leq 0,\\ &\text{Im}\int_{L}\chi_{A_{2}^{+}}\Omega\leq\text{Im}\int_{\mathcal{M}}\tilde{\Omega}_{L_{2}}^{+},\quad\text{Im}\int_{L}\chi_{A_{1}^{+}}\Omega\geq\text{Im}\int_{\mathcal{M}}\tilde{\Omega}_{L_{1}}^{+},\\ &\text{Im}\int_{L}\chi_{A_{2}^{-}}\Omega\geq\text{Im}\int_{\mathcal{M}}\tilde{\Omega}_{L_{2}}^{-},\quad\text{Im}\int_{L}\chi_{A_{1}^{-}}\Omega\leq\text{Im}\int_{\mathcal{M}}\tilde{\Omega}_{L_{1}}^{-}.\end{split}

In particular

arg∫LχA2+Ω≤θ^2+,arg(−∫LχA2−Ω)≤θ^2−,\arg\int_{L}\chi_{A_{2}^{+}}\Omega\leq\hat{\theta}_{2}^{+},\quad\arg(-\int_{L}\chi_{A_{2}^{-}}\Omega)\leq\hat{\theta}_{2}^{-},

and

arg∫LχA1+Ω≥θ^1+,arg(−∫LχA1−Ω)≥θ^1−.\arg\int_{L}\chi_{A_{1}^{+}}\Omega\geq\hat{\theta}_{1}^{+},\quad\arg(-\int_{L}\chi_{A_{1}^{-}}\Omega)\geq\hat{\theta}_{1}^{-}.

Now χAi+≥0\chi_{A_{i}^{+}}\geq 0 and χAi−≤0\chi_{A_{i}^{-}}\leq 0, and the special case where χAi−=0\chi_{A_{i}^{-}}=0 almost everywhere is already covered by the positivity condition. The Theorem follows. ∎

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