ScalingStacks

Proof. [01BE]

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Proof.

We may assume supX|f|=1\sup_{X}|f|=1. Pick s≥ts\geq t. The probability measures μt:=MA⁡(φ⟨t⟩)\mu_{t}:=\MA(\varphi^{\langle t\rangle}) and μs\mu_{s} agree on {φ>−t}\{\varphi>-t\}. Hence

|∫fμt−∫fμs|≤(μt+μs){φ≤−t}≤1t(∫−φ⟨t⟩μt+∫−φ⟨s⟩μs)≤n+1t​(|Eω​(φ⟨t⟩)|+|Eω​(φ⟨s⟩)|)≤2​(n+1)t​|Eω​(φ)|.\left|\int f\mu_{t}-\int f\mu_{s}\right|\leq(\mu_{t}+\mu_{s})\{\varphi\leq-t\}\leq\frac{1}{t}\left(\int-\varphi^{\langle t\rangle}\mu_{t}+\int-\varphi^{\langle s\rangle}\mu_{s}\right)\\ \leq\frac{n+1}{t}(|E_{\omega}(\varphi^{\langle t\rangle})|+|E_{\omega}(\varphi^{\langle s\rangle})|)\leq\frac{2(n+1)}{t}|E_{\omega}(\varphi)|.

The result follows by letting s→∞s\to\infty. ∎

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