ScalingStacks

Theorem 3.11 . [01EZ]

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Theorem 3.11.

Let 𝒳\mathcal{X} be an SNC model of XX and let Δ′\Delta^{\prime} be a simplicial projective subdivision of Δ𝒳\Delta_{\mathcal{X}}. Then there exists a vertical blow-up π:𝒳′→𝒳\pi:\mathcal{X}^{\prime}\to\mathcal{X} with the following properties:

  • (i)

    𝒳′\mathcal{X}^{\prime} is normal and vertically 𝐐\mathbf{Q}-factorial.

  • (ii)

    The vertices (ei′)i∈I′(e^{\prime}_{i})_{i\in I^{\prime}} of Δ′\Delta^{\prime} are in bijection with the irreducible components (Ei′)i∈I′(E^{\prime}_{i})_{i\in I^{\prime}} of 𝒳0′\mathcal{X}^{\prime}_{0}, in such a way that c𝒳′​(emb𝒳⁡(ei′))c_{\mathcal{X}^{\prime}}(\emb_{\mathcal{X}}(e^{\prime}_{i})) is the generic point of Ei′E^{\prime}_{i} for each i∈I′i\in I^{\prime}.

  • (iii)

    If J′⊂I′J^{\prime}\subset I^{\prime}, then EJ′′:=⋂j∈J′Ej′E^{\prime}_{J^{\prime}}:=\bigcap_{j\in J^{\prime}}E^{\prime}_{j} is normal, irreducible, and nonempty iff the corresponding vertices ej′e^{\prime}_{j}, j∈J′j\in J^{\prime} of Δ′\Delta^{\prime} span a face σJ′′\sigma^{\prime}_{J^{\prime}} of Δ′\Delta^{\prime}. In this case, EJ′′E^{\prime}_{J^{\prime}} has codimension |J′||J^{\prime}| and its generic point is the center of emb𝒳⁡(s)\emb_{\mathcal{X}}(s) on 𝒳′\mathcal{X}^{\prime} for all ss in the relative interior of σJ′′\sigma^{\prime}_{J^{\prime}}.

  • (iv)

    For each D∈Div0⁡(𝒳′)D\in\Div_{0}(\mathcal{X}^{\prime}) the function φD∘emb𝒳\varphi_{D}\circ\emb_{\mathcal{X}} is affine on the faces of Δ′\Delta^{\prime}.

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