Lemma 2.3.1. [04NU]

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Lemma 2.3.1.

The restrictions of $s^{\sigma}_{j}$ and $s^{\sigma}_{i}$ to $\mathfrak{X}_{\sigma}$ are equations for $D_{j}$ and $D_{i}$ , and thus

w_{\sigma}\coloneqq t\cdot\prod_{j\in J}(s_{j}^{\sigma})^{-1}\cdot\prod_{i\in L_{\sigma}}(s_{i}^{\sigma})^{-1}

is an invertible function on $\mathfrak{X}_{\sigma}$ .