ScalingStacks

Theorem 9.4 . [030C]

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Theorem 9.4.

Let ℳ⁡(X†/S†)\mathscr{M}(X^{\dagger}/S^{\dagger}) denote the stack of basic stable log maps in X†X^{\dagger} over S†S^{\dagger}. Then:

  1. (1)

    ℳ⁡(X†/S†)\mathscr{M}(X^{\dagger}/S^{\dagger}) is a Deligne-Mumford stack.

  2. (2)

    Let β\beta denote a choice of genus gg, number of marked points kk, homology class in H2​(X,ℤ)H_{2}(X,\mathbb{Z}), along with a collection of tangency data for the marked points (this notion can be made precise). Let ℳ⁡(X†/S†,β)\mathscr{M}(X^{\dagger}/S^{\dagger},\beta) denote the substack of ℳ⁡(X†/S†)\mathscr{M}(X^{\dagger}/S^{\dagger}) of basic stable log maps of curves of genus gg and kk marked points, representing the given homology class, and satisfying the given tangency conditions. Then modulo some technical hypotheses on X†X^{\dagger}, ℳ⁡(X†/S†,β)\mathscr{M}(X^{\dagger}/S^{\dagger},\beta) is proper over SS if XX is proper over SS.

  3. (3)

    Assuming further that X†→S†X^{\dagger}\rightarrow S^{\dagger} is log smooth, ℳ⁡(X†/S†,β)\mathscr{M}(X^{\dagger}/S^{\dagger},\beta) carries a virtual fundamental class, allowing for the definition of logarithmic Gromov-Witten invariants.

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