ScalingStacks

Proof. [01AX]

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Proof.

We may assume 0≤h≤10\leq h\leq 1, −M≤φ≤0-M\leq\varphi\leq 0 and −M≤φj≤0-M\leq\varphi_{j}\leq 0 for all jj, where M≥1M\geq 1. Given ε>0\varepsilon>0, let GG be an open set such that Capω⁡(G)<ε\Capa_{\omega}(G)<\varepsilon and hh is continuous on GcG^{c}, see Definition 4.4. Using the Tietze extension theorem, we extend h|Gch|_{G^{c}} to a continuous function h~\tilde{h} on all of XX such that 0≤h~≤10\leq\tilde{h}\leq 1. We then have

∫h​MA⁡(φj)−∫h​MA⁡(φ)\displaystyle\int h\MA(\varphi_{j})-\int h\MA(\varphi) =∫h~​MA⁡(φj)−∫h~​MA⁡(φ)\displaystyle=\int\tilde{h}\MA(\varphi_{j})-\int\tilde{h}\MA(\varphi)
+∫G(h−h~)MA(φj)−∫G(h−h~)MA(φ).\displaystyle+\int\limits_{G}(h-\tilde{h})\MA(\varphi_{j})-\int\limits_{G}(h-\tilde{h})\MA(\varphi).

It follows from Lemma 4.6 that

|∫h​MA⁡(φj)−∫h​MA⁡(φ)|≤|∫h~​MA⁡(φj)−∫h~​MA⁡(φ)|+2​sup|h−h~|​Mn​Capω⁡(G).\left|\int h\MA(\varphi_{j})-\int h\MA(\varphi)\right|\leq\left|\int\tilde{h}\MA(\varphi_{j})-\int\tilde{h}\MA(\varphi)\right|+2\sup|h-\tilde{h}|M^{n}\,\Capa_{\omega}(G).

Since h~\tilde{h} is continuous, ∫h~​MA⁡(φj)→∫h~​MA⁡(φ)\int\tilde{h}\MA(\varphi_{j})\to\int\tilde{h}\MA(\varphi) as j→∞j\to\infty, thus

lim supj|∫h​MA⁡(φj)−∫h​MA⁡(φ)|≤4​ε.\limsup_{j}\left|\int h\MA(\varphi_{j})-\int h\MA(\varphi)\right|\leq 4\varepsilon.

Letting ε\varepsilon tend to zero completes the proof. ∎

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