ScalingStacks

Proof. [01GS]

Original official author HTML, exact retained edition. Historical TeX conversion verdicts remain unchanged. Cited-edition alignment and mathematical self-containment are not assessed.

Complete original source context · Original author HTML

Proof.

Let 𝒳′≥𝒳\mathcal{X}^{\prime}\geq\mathcal{X} be two SNC models on which θ\theta is determined. Then p𝒳∘p𝒳′=p𝒳p_{\mathcal{X}}\circ p_{\mathcal{X}^{\prime}}=p_{\mathcal{X}}. By Proposition 7.5 (ii) this implies φ≤φ∘p𝒳′≤φ∘p𝒳∘p𝒳′=φ∘p𝒳\varphi\leq\varphi\circ p_{\mathcal{X}^{\prime}}\leq\varphi\circ p_{\mathcal{X}}\circ p_{\mathcal{X}^{\prime}}=\varphi\circ p_{\mathcal{X}}, with equality on emb𝒳⁡(Δ𝒳)\emb_{\mathcal{X}}(\Delta_{\mathcal{X}}). Set φ~:=lim𝒳φ∘p𝒳\tilde{\varphi}:=\lim_{\mathcal{X}}\varphi\circ p_{\mathcal{X}}. Then φ~≥φ\tilde{\varphi}\geq\varphi. On the other hand, it follows from Corollary 3.2 that p𝒳p_{\mathcal{X}} converges to the identity on XX, so by upper semicontinuity of φ\varphi we have φ≥φ~\varphi\geq\tilde{\varphi}. ∎

Original mathematics by the credited authors. Source-backed reader collection; mathematical self-containment is not assessed.