ScalingStacks

Proof [03Q0]

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Proof

Take z∈(M∖E)∩Bj.z\in(M\setminus E)\cap B_{j}. Then

(uj,δ−u)​(z)≤(χ⁡(δ)3−2)​δα(u_{j,\delta}-u)(z)\leq(\frac{\chi(\delta)}{3}-2)\delta^{\alpha}

and therefore, by 2.5

(uj,δ−v)​(z)≤(χ⁡(δ)3−1)​δα.(u_{j,\delta}-v)(z)\leq(\frac{\chi(\delta)}{3}-1)\delta^{\alpha}.

Since u>1u>1 we get from this

(uδ−v)(z)≤maxj:z∈Bj(uj,δ−v)(z)≤(χ⁡(δ)3−1)δα.(u_{\delta}-v)(z)\leq\max_{j:z\in B_{j}}(u_{j,\delta}-v)(z)\leq(\frac{\chi(\delta)}{3}-1)\delta^{\alpha}. 2.6

Again, by 2.5

(uj0,δ−v)​(z0)≥(χ⁡(δ)−1)​δα.(u_{j_{0},\delta}-v)(z_{0})\geq(\chi(\delta)-1)\delta^{\alpha}.

Therefore the definition of uδu_{\delta} yields

(uδ−v)​(z0)≥(χ⁡(δ)−1)​δα−η⁡(δ)​(2​c1​‖u‖∞+1).(u_{\delta}-v)(z_{0})\geq(\chi(\delta)-1)\delta^{\alpha}-\eta(\delta)(2c_{1}||u||_{\infty}+1). 2.7

The Three Circles Theorem gives for δ\delta small enough

(uj,N​δ−uj,δ)≥log⁡Nlog⁡C​(uj,C​δ−uj,δ).(u_{j,N\delta}-u_{j,\delta})\geq\frac{\log N}{\log C}(u_{j,C\delta}-u_{j,\delta}).

It follows that, choosing jj so that

η⁡(δ)=maxz∈Bj⁡(uj,C​δ−uj,δ)​(z)\eta(\delta)=\max_{z\in B_{j}}(u_{j,C\delta}-u_{j,\delta})(z)

we obtain

(N​δ)α​χ​(N​δ)≥log⁡Nlog⁡C​η​(δ).(N\delta)^{\alpha}\chi(N\delta)\geq\frac{\log N}{\log C}\eta(\delta).

Further, since χ⁡(δ)≥χ⁡(N​δ)\chi(\delta)\geq\chi(N\delta), we get from 2.2 that

δα​χ​(δ)≥log⁡Nlog⁡C​η​(δ)​N−α>2​η​(δ)​(2​c1​‖u‖∞+1).\delta^{\alpha}\chi(\delta)\geq\frac{\log N}{\log C}\eta(\delta)N^{-\alpha}>2\eta(\delta)(2c_{1}||u||_{\infty}+1).

Inserting this into 2.7 we finally arrive at

(uδ−v)​(z0)>(χ⁡(δ)/2−1)​δα.(u_{\delta}-v)(z_{0})>(\chi(\delta)/2-1)\delta^{\alpha}.

The proposition follows by comparing this inequality with 2.6.

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