ScalingStacks

Proof. [02DS]

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.

It is enough to establish ℋ⁡(α,Aα,ω){\mathcal{H}}(\alpha,A_{\alpha},\omega) for compact subsets, by regularity of μ\mu and C​a​pωCap_{\omega}. Let KK be a compact subset of XX. It follows from Hölder’s inequality that

0≤μ⁡(K)≤‖f‖Lp​(ωn)​[Volω​(K)]1/q,0\leq\mu(K)\leq||f||_{L^{p}(\omega^{n})}\left[\text{Vol}_{\omega}(K)\right]^{1/q},

where 1/p+1/q=11/p+1/q=1. Note that ‖f‖Lp​(ωn)=1||f||_{L^{p}(\omega^{n})}=1 since we assume μ\mu is a probability measure. We claim that

(4) Volω(K)≤Cωexp[−(Capω(K))−γω/n],\text{Vol}_{\omega}(K)\leq C_{\omega}\exp\left[-(Cap_{\omega}(K))^{-\gamma_{\omega}/n}\right],

for some constants Cω,γω>0C_{\omega},\gamma_{\omega}>0 that only depend on ω\omega. We will be done if we can prove (4) since we can then check by elementary computations that exp⁡(−x−δ)\exp(-x^{-\delta}) is dominated from above by Aα​xαA_{\alpha}x^{\alpha}, for all x∈[0,1]x\in[0,1].

The set of functions ℱ0:={φ∈PSH(X,ω)/supXφ=0}{\mathcal{F}}_{0}:=\{\varphi\in PSH(X,\omega)\,/\,\sup_{X}\varphi=0\} is compact in L1​(X)L^{1}(X) (see proposition 2.7, [GZ 1]). These functions have Lelong numbers ν⁡(φ,x)≤νω\nu(\varphi,x)\leq\nu_{\omega} bounded from above by a uniform constant. It follows therefore from Skoda’s uniform integrability theorem [Z], that

supφ∈ℱ0∫exp⁡[−2​φνω+1]​ωn≤C2<+∞.\sup_{\varphi\in{\mathcal{F}}_{0}}\int\exp\left[-\frac{2\varphi}{\nu_{\omega}+1}\right]\omega^{n}\leq C_{2}<+\infty.

Set γω:=2/(νω+1)>0\gamma_{\omega}:=2/(\nu_{\omega}+1)>0 and let

VK,ω∗(x):=(sup{φ(x)/φ∈PSH(X,ω),φ≤0 on K})∗V_{K,\omega}^{*}(x):=\left(\sup\{\varphi(x)\,/\,\varphi\in PSH(X,\omega),\,\varphi\leq 0\text{ on }K\}\right)^{*}

denote the Siciak extremal function of KK (see section 5.1 in [GZ 1]). Then

V​o​lω​(K)≤∫Xexp⁡(−γω​VK,ω∗)​ωn≤C2​Tω​(K)γω,Vol_{\omega}(K)\leq\int_{X}\exp\left(-\gamma_{\omega}V_{K,\omega}^{*}\right)\omega^{n}\leq C_{2}T_{\omega}(K)^{\gamma_{\omega}},

where Tω(K):=exp(−supXVK,ω∗)T_{\omega}(K):=\exp(-\sup_{X}V_{K,\omega}^{*}) denote the Alexander capacity of KK (see section 5.2 in [GZ 2]). It follows now from theorem 7.1 in [GZ 1] that

Tω(K)≤eexp[−Capω(K)−1/n],T_{\omega}(K)\leq e\exp\left[-Cap_{\omega}(K)^{-1/n}\right],

which yields (4). ∎

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