ScalingStacks

4.1. Combinatorics [03EH]

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4.1. Combinatorics

It would be interesting to know whether the subdivision of |Σ||\Sigma| given by the F×F∨F\times F^{\vee} can be realized as the boundary of a dd-dimensional polytope (as the picture suggests). The dual of the face lattice would be given by the lattice of intervals in the face lattice of Δ\Delta (or of Δ∨\Delta^{\vee}).

In fact, if there was a realization of the combinatorial type of Δ\Delta with an identification ℝd≅(ℝd)∗\mathbb{R}^{d}\cong(\mathbb{R}^{d})^{*} such that the normal cones of FF and F∨F^{\vee} intersect in their relative interiors, then the Minkowski sum Δ+Δ∨\Delta+\Delta^{\vee} would do the trick. For d=3d=3, Koebe’s Theorem [Thu80] guarantees such a realization.

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