ScalingStacks

Exercise 8.3 . [0307]

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Exercise 8.3.

Show that in Example 8.2, (5), ℳ¯X,x=P\overline{\mathcal{M}}_{X,x}=P if dimσ=dimMℝ\dim\sigma=\dim M_{\mathbb{R}} and xx is the unique zero-dimensional torus orbit of XX. More generally,

ℳ¯X,x=τ∨∩Nτ⟂∩N=Homm​o​n​o​i​d⁡(τ∩M,ℕ),\overline{\mathcal{M}}_{X,x}={{\tau}^{\scriptscriptstyle\vee}\cap N\over\tau^{\perp}\cap N}=\operatorname{Hom}_{monoid}(\tau\cap M,\mathbb{N}),

when x∈Xx\in X is in the torus orbit corresponding to a face τ\tau of σ\sigma. In particular, τ\tau can be recovered as Homm​o​n​o​i​d⁡(ℳ¯X,x,ℝ≥0)\operatorname{Hom}_{monoid}(\overline{\mathcal{M}}_{X,x},\mathbb{R}_{\geq 0}), where ℝ≥0\mathbb{R}_{\geq 0} is the additive monoid of non-negative real numbers. ∎

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