ScalingStacks

Remark 1.6 . [03YT]

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Remark 1.6.

If ∂∂θj\frac{\partial}{\partial\theta_{j}} are the Hamiltonian vector fields dual to ϑi\vartheta_{i}, namely ϑi​(∂∂θj)=δi​j\vartheta_{i}(\frac{\partial}{\partial\theta_{j}})=\delta_{ij}, then d​μi=−ι∂∂θi​ωd\mu_{i}=-\iota_{\frac{\partial}{\partial\theta_{i}}}\omega, namely μi\mu_{i} are the symplectic moment coordinates up to sign. When N−𝔫=1N-\mathfrak{n}=1, namely there is only one η\eta coordinate, then dη=Ω(∂∂θ1,…,∂∂θ𝔫,⋅)d\eta=\Omega(\frac{\partial}{\partial\theta_{1}},\ldots,\frac{\partial}{\partial\theta_{\mathfrak{n}}},\cdot), and accordingly we refer to η\eta as the holomorphic moment coordinate. In this situation MM admits a fibration

M→(μ1,…,μ𝔫,Im​(η))𝔱∗×ℝ,M\xrightarrow{(\mu_{1},\ldots,\mu_{\mathfrak{n}},\text{Im}(\eta))}\mathfrak{t}^{*}\times\mathbb{R},

where fibres are special Lagrangians with phase zero: the Lagrangian condition follows from d​μi=−ι∂∂θi​ω=0d\mu_{i}=-\iota_{\frac{\partial}{\partial\theta_{i}}}\omega=0 on fibres, while the special condition is equivalent to ImΩ(∂∂θ1,…∂∂θ𝔫,⋅)=dImη=0\text{Im}\Omega(\frac{\partial}{\partial\theta_{1}},\ldots\frac{\partial}{\partial\theta_{\mathfrak{n}}},\cdot)=d\text{Im}\eta=0.

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