ScalingStacks

Proposition 7.3 . [02X4]

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Proposition 7.3.

Let Δ⊂ℝn\Delta\subset\mathbb{R}^{n} be a polytope of dimension nn and u∈ℝnu\in\mathbb{R}^{n}. Then, for any f∈𝒞n​(ℝ)f\in\mathscr{C}^{n}(\mathbb{R}),

∫Δf(n)​(⟨u,x⟩)​d​voln\displaystyle\int_{\Delta}f^{(n)}(\langle u,x\rangle)\,\text{\rm d}\operatorname{vol}_{n} =∑V∈Δ⁡(u)(C⁡(Δ,u,V)​(z)⋅f⁡(z+⟨u,V⟩))(dim(V))​(0)\displaystyle=\sum_{V\in\Delta(u)}\big(C(\Delta,u,V)(z)\cdot f(z+\langle u,V\rangle)\big)^{(\dim(V))}(0)
(7.4) =∑V∈Δ⁡(u)∑k≥0Ck​(Δ,u,V)​f(k)​(⟨u,V⟩).\displaystyle=\sum_{V\in\Delta(u)}\sum_{k\geq 0}C_{k}(\Delta,u,V)f^{(k)}(\langle u,V\rangle).

The coefficients Ck​(Δ,u,V)C_{k}(\Delta,u,V) are uniquely determined by this identity.

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